H 52 01 31 16 01N 31.2669444444444 130 37 57E 130.6325 Fe Ti Ibusuki Placer Fe Average grade of 22% Fe and 3.7% TiO2. Consists of a large number of placer deposits along beach. District is 60 km long on Satsuma Peninsula side, and 20 km long on Osumi Peninsula side around Kagoshima Bay. Eight subdistricts ocuur in the district. Placer Fe minerals occur in modern beach sands. Thickness of deposits are 0.05 to 0.2 m. Ore minerals are magnetite, hematite, and ilmenite. Geological Survey of Japan, 1954. Japan I 52 01 33 36 12N 33.6033333333333 131 42 37E 131.710277777778 Fe Kunisaki Placer Fe Average grade of 15% Fe. Consists of 13 main placer deposits along a beach. Main part of the district is about 30 km long in the Kunisaki Peninsula, Oita Prefecture. Major deposits are at Yasugahama and Tomiku. Placer Fe minerals occur modern beach sands. Thickness of deposits is 0.1-0.2 m. Ore minerals are magnetite and ilmenite. Geological Survey of Japan, 1954; MITI, 1959, 1959; Hasegawa, 1963. Japan I 53 01 35 41 57N 35.6991666666667 140 42 05E 140.701388888889 Fe Ti Iioka Placer Fe Average grade of 10.4% Fe and 2.4% TiO2 Consists of two major placer deposits along beach. District is about 10 km long and 1 km wide. Each body is 3 km long, 70-100 m wide, and 2-10 m thick. Four major mines are in the district. Placer Fe minerals occur in coastal plane deposits, coastal terrace deposits, and modern beach sands. Fe minerals in a coastal plane deposits is major type in the area. Sands contain magnetite, hematite, ilmenite, pyroxene, quartz, and plagioclase. Geological Survey of Japan, 1954. Japan I 53 01 35 26 51N 35.4475 133 17 30E 133.291666666667 Fe Ti Yonago Placer Fe Average grade of 24% Fe and 3.2% TiO2. Consists of a large number of placer deposits along a beach that is 80 km long from Tottori to Yonago. Major deposits are at Yonago, Takaraki, Hamamura, and Kaike. Yonago deposit is about 7 km long and 30 m wide. Thickness of the deposits is typically 0.2 m. Grade is 57.6% Fe and 10% TiO2. Ore minerals are magnetite, hematite, and ilmenite. Placer Fe minerals occur in coastal plane deposits, coastal terrace deposits, and modern beach sands. Fe minerals in the coastal plane deposits is major type. Geological Survey of Japan, 1954; MITI, 1958, 1959; Hasegawa, 1963. Japan J 51 01 39 30 00N 39.5 122 10 00E 122.166666666667 Diamond Toudaohe area, Fuxian County Placer diamond Small Average grade of 20 to 30 mg/m3 Au, ranges up to 70 mg/m3 Au. Placer diamond deposits are River valley type and are divided into 4 subtypes. The ore beds consist of of yellow-brown mild clay and/or sand and gravel beds. The total thickness of the ore beds is 5-6 m. Clay-bearing sand and gravel beds contain more placer diamond, and consist of gravel-50-80%, quartz sand-20-30% and clay-5-20%. Rounded quartz and diamonds and has a diameter of about 0.2-20 cm. The ore bodies average 13.62mg/m3 and have an variation coefficient of 114%. Placer diamond derived from the diamond-bearing kimberlite pipes. Diamond is colorless or faint yellow, and 39% contain graphite inclusions. Diamond grains are usually less than 1 mg, maximum up to 200-300 mg. Alluvial placers are limited. In alluvial placers, diamond is hosted in gravel-bearing clay, gravel-bearing mild clay, and mild clay-bearing gravel beds. The thickness of this type of ore beds is 3-4 m. The grade of diamond in this type of ores is 34.04mg/m3, maximum of 100mg/m3. The placer diamond beds at 200 m from the kimberlite pipes are most valuable. Deng Chujun and others, 1994a, b. China J 51 02 37 10 00N 37.1666666666667 121 30 00E 121.5 Au Jiaodong (East part of Shandong Province) Placer Au Moderate to small. Reserves of 6 tonnes Au. 699-999 Areas consists of low mountains, hills, and planes in that many short Rivers drain to the sea and form a dendritic water system. More than 20 placer Au deposits occur and have been mined since ancient times. The best placer Au deposits are adjacent to primary gold deposits, including ore than 10 large gold quartz vein deposits. The placer Au in the area belongs to alluvial-deluvial River valley type. The proven placer Au reserve is 6 tonnes, but the potential reserve is greater than 30 tonnes. The Xinanhe Placer Au deposit has ore bodies that are 30 km long, 40-600 m wide and 5-16 m thick. Gold grains are fine to moderate. Other heavy minerals are magnetite, garnet, zircon, ilmenite and tourmaline. Chen Jiming and others, 1997. China J 52 01 36 58'00 N 36.9666666666667 126 48'00 E 126.8 Au Hanjin Placer Au Small Average grade of 0.167gms/yd3 Au. Reserves of 191 kg Au. Placer district is underlain by mica schist, quartzite, and limestone that are intruded by biotite granite with some quartz veins. At high tide, district is covered with sea water. Generally, the deposit is low-grade placer but locally high-grade. Thickness of alluvial deposit is very irregular (max. 52 ft, mim 0.5 ft), with average thickness 15.8f t. The thickness of the pay strata ranges from 0.3 ft to 2.5 ft. In high-grade part, the alluvium formation is the pay strata. Gold content and the scope of high-grade are as follows: area-553,750 m3, average depth-4.87 ft, volume-874,500 m3, gold grade-0.1671 gms/yd3, reserves-191kg. Hanjin beach gold placer occurs along the Hanjin seashore of Asan bay, Songak-myon, Dangjin-gun, and Chungchong-namdo. Park and others, 1964. Korea J 52 02 36 45 30 N 36.7583333333333 127 14 00 E 127.233333333333 Au Sungnam Placer Au Medium Average grade of 0.077-0.184 g/yd3 Au, 1.067-5.669 g/yd3 fergusonite. Ore reserves of 3,857kg gold and 76.5 tonnes of fergusonite. Placer district is underlain by granite-gneiss intruded by two-mica granite, of probable Precambrian age. Younger diorite, quartz-veins, and pegmatites, up to one to two meters wide, occur in the area. Granite gneiss forms small hills 100 m or less high in the immediate area of the district, and higher hills (up to 400 m) farther south. The granite forms rolling ground from one to two hundred m high north of the deposit. The placer district is about 500 m wide, and extends from east to west for 10 km along the stream. Maximum thickness is 32 ft.(at hole 151) and a minimum of 8 ft. (at holes 201 and 202). Average thickness is 16.7 ft. in the western mine claim, and 23.5ft. in the eastern. Between 6 and 15 feet of clay occurs locally at the northern and southern margins of the deposit. Sandy clay occurs in the center of the district, and ranges from 3 to 34 ft thick. Ore minerals are fergusonite (3.5% U3O8 ; 1.5% ThO2) and gold. Deposit is 12 km southeast of Chonan in Sungnam and Sushin-myons, Chonan-gun, Chungchong-namdo. Hwang and Choi, 1961. Korea J 52 03 36 42' 30 N 36.7008333333333 127 03 00 E 127.05 Au Asan Bay Placer Au Medium Average grade of 0.190 to 0.253 g/yd3 Au. Reserves of 1,748 kg Au. Upper course in district contain minable gold placers with many nearby lode gold mines. Two wide alluvial basins contain mostly clay, and are very wide. Average thickness of alluvium is about 9.8 m with a sequence of surface clay 7 m, clay and sand from 7 to 8 m, sand from 8 to 9 m, and sand and pebble from 9 to 10 m. Bedrock is augen gneiss in Pyongtaik area and granite gneiss in Yesan area. Lee and Yoon, 1970. Korea J 52 04 36 38'00N 36.6333333333333 126 42'30E 126.708333333333 Au Kumma-chon Placer Au Medium Grade range of 0.05-0.27 g/yd3 Au. Reserves of 1,236 kg ore. Consists of ilmenite and gold placers that are underlain by coarse-grained granite gneiss of probable Precambrian age. Younger quartz veins and pegmatites 0.8 to 2.5 meters wide occur in this area. The granite gneiss forms small hills 120 meters or less in height in the immediate area of the deposit and higher hills farther southeast. The granite forms rolling ground from 80 to 200 meters high west of the deposit. The placer is about 800 m wide and extends from south to north 6.5 km along the stream. The maximum thickness of the alluvium are 26.4ft and minimum thickness is 12 ft. The average thickness is 18.99 ft (5.79m) in the southern area and 19.23 ft (5.86m) in the northern area. The alluvium formation includes clay between 4 and 10 ft locally at the margins of the deposit. Sandy clay in the center of the placer ranges from 5 to 15 ft thick. The alluvial placer is 3.5 km northwest Kumma-myon, Hongsoung-gun and Sapkyo-myon, Yaesan-gun, and Chunchong-namdo. C. I. Choi and K. B. Kim, written commun., 1963. Korea J 52 05 36 32 30 N 36.5416666666667 127 27 50 E 127.463888888889 Au Musim-chon Placer Au Small Average grade of 0.260g/yd3. Au. Total reserves of 1,992 kg Au District about 100m wide and extendd south to north for 11.5 km along the stream. Average thickness of alluvium is about 15.4 ft (4.8m). The deposit overlies Precambrian schist that is intruded by coarse-grained Jurassic biotite granite and lamprophyre. The alluvium formation is mostly coarse sand, and contains more conglomerate in upper part of the stream than lower part. Total area is 1,238km2; volume is 7,785,250 yd3 (5,943,000m3). Placer occurs in the western part of Chongju city, Chungchong-pukdo. J. K. Lee and B. C. Kim, written commun., 1969. Korea J 52 06 38 17'30N 38.2916666666667 128 33'30E 128.558333333333 Th REE Kosong Placer Th Medium Average grade of 2,586 g/m3 monazite and 44,100 g/m3 ilmenite. Reserves of 56,654 tonnes ore. Consists of ilmenite, monazite and zircon bearing placers that occur along the shore ine in Hyonnae-myon, Kojin-myon and Kansung-myon of Kosong-gun, and Chuckwang-myon of Yangyang-gun, Kangwon-do areas. Country rock is mostly Precambrian mica schist and injection gneiss, with younger granite. Heavy mineral sands were concentrated on the beach by wave action, and the grades of the component minerals of heavy sand are high enough for economic exploration. Grade averages 2,586 gms monazite, 9800 gms zircon, 4,119 gms magnetite, 36,400 gms garnet and 44,100 gms ilmenite per cubic meter of sand. S. K. Yoon, I. C. Hwang and Y. H. Chang, written commun., 1959. Korea J 54 01 38 32 50N 38.5472222222222 141 09 11E 141.153055555556 Au Kitakami Placer and paleoplacer Au Nishimikawa district contains historical placer deposits. Gold was discovered in 749 from this district. First placer deposit located at Koganehazama in Wakuya town, Miyagi Prefecture. Deposits were exhausted in historical time, and not much detailed information is available. Area consists of sandstone of Miocene Koganehazama Formation that may also may contain paleoplacer Au deposits. Alluvial placer deposits also occur. District covers most of southern Kitakami Mountains and western foothill of the mountains. Size of district is 60 km by 40 km, elongated NS. A large number of lode gold deposits occur in the district, and are probable source of the placer gold. Watanabe, 1939; Watanabe, 1950; Oide and others, 1989. Japan J 54 02 37 54 21N 37.9058333333333 138 19 47E 138.329722222222 Au Nishimikawa Placer and paleoplacer Au Nishimikawa district contains at least 32 alluvial placer deposits. Gold occurs as paleoplacer deposits and placer deposits. 16 paleoplacer deposits occur around Sasagawa village, and are hosted in sand and conglomerate of the lower to middle Miocene Orito Formation. Gold is concentrated in lower 23 m of a 70-m-thick conglomerate formation. Paleoplacer deposits contain average of 0.23 g/t of gold. Placer deposits occur in the lower reaches of Nishimikawa Rver flowing from the Sasagawa village area. The deposits occur in alluvial deposits and alluvial terrace deposits. The size of the district is 6 km by 5 km. Mining started at least in 1100, and likely from 1022. Several tonnes (at least 1.5 tonnes) of gold were produced form the district. Mining stopped in 1872. Kosuge, 1988; Mining and Materials Processing Institute of Japan, 1994. Japan K 48 01 42 01 20N 42.0222222222222 104 54 00E 104.9 SnO2 (Mn,Fe)WO4 Khar Morit Placer Sn Average grade of 500 g/m3 SnO2. Reserves of 7,090 tonnes SnO2. More than 10 valleys with placer deposits occur around Khar Morit Mountain in a region of moderate relief. Most placers are near-surface alluvial deposits in first-order stream valleys, forming single Holocene stratum concentrations. Multiple pay layers are rare. The cassiterite placers extend for a length of 4 km. The thick ranges from 0.5 m, and average concentration of cassiterite is 200-600 g/m3 with locally up to 1000 g/m3 cassiterite. Eluvial-talus placer deposits occur near the top of mountan where lode deposits occur. Placers are mainly monomineralic, but small admixtures of wolframite (from 10 to 30% of cassiterite), and scheelite occur. Cassiterite-silicate stockwork, streaky zones, mineralized greisens, and rare veins are the main lode sources. Cassiterite grains are coarse (80% of grain size larger than 5-8 mm). The content of Sn in lode deposits ranges from 0.5 to 1.0%. E. Iotov and others., written commun., 1972; N.A. Marinov, written commun., 1977. Mongolia K 49 01 41 30 00N 41.5 110 30 00E 110.5 Au Yinshan, Inner Mongolia Placer Au Small Occurs in Yinshan Mountains and the drainages of the branches of the Yellow River. Many placer Au deposits in the area are alluvial, alluvial-deluvial River channel, and River flat types. Scale is usually small. Together with the placer Au in the Yanshan area in K-50-01, totally gold reserves is up to 30 tonnes. Gold derived from the primary gold deposits and quartz veins in Archean metamorphic rock of the Jining Group, and from Mesozoic syenite and granite. In the area, a series of primary gold deposits occur and are mined. Jinpen placer Au deposit in the area is eluvial- drift bed type, is 1300-7293 m long, 23-24 m wide, averages 1.0m thick, and contains 1.4g/ m3. Gold grains greater than 5mm comprise 17%, 5-1mm-48%, and 1-0.4 mm-27%. Gold nuggets occur. Gold derived from the Au lodes in upper stream areas. Chen Jiming and others, 1997. China K 49 02 40 09 40N 40.1611111111111 141 42 56E 141.715555555556 Fe Ti Kuji Placer Fe Average grade of 23.0% Fe and 5.8% TiO2. Consists of Pleistocene placer and paleo-placer deposits. Main part of the district is about 16 km long and 4 km wide, and is in western part of Kuji city, Iwate Prefecture. The Pleistocene Formation consists of sandstone, is about 30 m thick, and forms a 200-300 m high terrace. Thickness of placer deposits is 2 to 4 m. Average grade is about 22.5% Fe and about 7% TiO2. Sands include magnetite, hematite, ilmenite, limonite, pyroxene, hornblende, quartz, and plagioclase. Historical records indicate extensive mining operation between 1660 and 1760. Japanese traditional Nambu Ironware used iron from this deposits. Geological Survey of Japan, 1954; MITI, 1959, 1959; Hasegawa, 1963. Japan K 50 01 41 10 00N 41.1666666666667 118 30 00E 118.5 Pt Gaositai Placer PGE Small District located in the Damiao V-Ti-Fe-bearing mafic-ultramafic rock belt in Hebei Province. Placer Pt occurs in Quaternary River channel and placer terrain deposits. Conglomerate beds of the terrain deposits consist of Ti-magnetite, galena, chromite, and mafic-ultramafic rock debris. Placer Pt accompanied by placer gold and is concentrated at the base of the conglomerate. In the concave sites of the weathered surface of the basement rock, placer Pt and Au are enriched. 80% of placer Pt minerals are the alloys of Pt, Ir and Os, and 20% are PGE. Xu Enrong and others, 1994. China K 50 02 40 30 00N 40.5 119 30 00E 119.5 Au Yanliao Placer Au Small Occurs in mild to low hills of the Yanshan Mountains. The main River systems are the Laohahe, Dalinghe, Luanhe, and Shangganhe Rivers. Placer Au deposits are widely distributed in the area, and are deluvial, alluvial-deluvial River channel, River flat, and first order terrain types. All are small. Gold derived mainly from the gold-bearing quartz veins in Archean metamorphic rock of the Jianping and Jianxi Groups and from various Mesozoic granites. Total of 30 tonnes gold has been proven combined with the placer Au deposits in Yinshan area in K-49-01. Chen Jiming and others, 1997. China K 51 01 40 54 08N 40.9022222222222 141 23 08E 141.385555555556 Fe Ti Kamikita Placer Fe Average grade of 17.3% Fe and 3.0% TiO2. Consists of a large number of placer deposits in eastern Aomori along the Pacific Ocean. Main part of the district is about 40 km long and 0.5 to 1 km wide, and occurs between Sabishiro and Tomari. Placer Fe had been mined in five locations in the district. Sabishiro and Misawa mines are in the district. Placer Fe minerals occur in the coastal plane deposits, coastal terrace deposits, and modern beach sands. Thickness of deposits is about 1.5-2 m, and consists of a large number of magnetite-rich horizons that range up to 5 cm thick. Average grade is about 17.3% Fe and 3.0% TiO2. Sands include magnetite, hematite, ilmenite, limonite, pyroxene, hornblende, quartz, and plagioclase. Geological Survey of Japan, 1954. Japan K 51 02 40 30 00N 40.5 123 25 00E 123.416666666667 Au Liaodong (Eastern Liaoning Province) Placer Au Small 590-877 Deposits are scarcely distributed in the tributaries of the Liaohe, Taizhihe, and Yalujiang Rivers. The Zhongtanghe area along the Zhongtang River, that belongs to the second tributary of the Taizhi River, contains several small-moderate Quaternary alluvial placer Au deposits. Au mainly derived from the base metal sulphide veins and gold quartz veins in metamorphic rock of the Early Proterozoic Liaohe Group. The Zhongtang River placer Au body is 6.0 km long, 50-250 m wide, and occurs along the valley of the Zhongtang River along a NNE direction. Au grains are 0.3-1.0 mm in diameter. Feng Xishan, 1991. China K 52 01 43 15 00N 43.25 130 17 00E 130.283333333333 Au Hunchun-Huadian, Jilin Province Placer Au and paleoplacer Au Small 843-872 Occurs in Changbaishan Mountains in eastern Jilin province with three large water systems-Yalujiang, Tumenjiang, and Songhuajiang Rivers. In 2nd to 4th order subbranches, placer Au deposits are widespread and have been mined for a long time. These include the Hunchun, Hunjiang, and Jiapigou areas, where some large primary gold deposits occur. At the Hunchun area, mining started 1000 years ago. The area occurs in Hunchun near the border between Russia and China, and belongs to drainage of the Tumen River, a first order of tributary of the upper Hunchun River. The placers are alluvial valley channel and valley terrace types. Au derived from gold lodes (Xiaoxinancha gold deposit), base metal veins and Tertiary paleo-placers in basal conglomerate (Chunhua deposit). The Hunchun River Placer Au is relatively large, and gold is coase-grained and platy, and generally averages 1.0 mm, locally up to 2 mm in diameter. The Hunchun-Huadian district also contains a group of Miocene paleoplacer Au deposit in the Huangsongdingzi area. The paleoplacer deposits occur in basal conglomerate of the Tertiary Tuchengzhi Formation. Two placer Au horizons are identified. One horizon is 2,600 m long, 1,000 m wide, and 1.87 m thick. The horizons vary from massive to bedded. More than 30 heavy minerals occur in the horizons. Besides gold, common heavy minerals are ilmenite, pyrite, magnetite, arsenopyrite, and limonite. Other minerals include feldspar, quartz, amphibole, sericite, biotite, chlorite, garnet, andalusite, pyroxene, spinel, sillimanite, zircon, sphene, apatite, rutile, corundum, and others. The source for the horizons are intermediate to siliceous intrusive rock and associated hydrothermal gold veins. Liu Baocheng and Yuan Li, 1994; Chen Jiming and others, 1997. China K 54 01 43 54 45N 43.9125 142 05 58E 142.099444444444 Pt, Cr, Au Horokanai Placer PGE District consists of alluvial PGE and Au placer deposits. The size of the district is 45 km by 30 km, elongated to NS. The deposits are underlain mainly by serpentinite of Kamuikotan belt. The placer deposits occur in Uryu River and Inushibetu River, a tributary of Teshio River. Main deposits in the district are at Takadomari and Horokanai. Heavy metals of deposits contain 20-30% of Au. Average grade is 0.4g/m2. The grade increase to 4 g/m2 ilocally. Ore minerals are rutheniridosmine, osmium, and ruthenium. Geological Survey of Japan, 1955; Saito and others, 1967. Japan K 54 02 43 02 35N 43.0430555555556 142 09 38E 142.160555555556 Pt, Au Shirokingawa Placer PGE District contains alluvial PGE and Au placer deposits. Size of the district is 70 km by 40 km, elongated to NS. The deposits are underlain mainly by serpentinite of Kamuikotan belt. The placer deposits occur in Shirokingawa, a tributary of Yubari, Sorachigawa, Mukawa, and Niseu Rivers, a tributary of Sarugawa River. Main deposits in the district are at Shirokinzawa and Numanosawa. The Shirokinzawa deposit occurs for 12 km along the River. PGE minerals occurr in terrace deposits around the River. The grade ranges up to 0.1 g/m2. Ore minerals are mostly Os-minerals. Heavy metals in deposits also contain 20-30% of Au. Suzuki, 1950; Geological Survey of Japan, 1955; Saito and others, 1967; Nakagawa, 1994. Japan K 54 03 42 33 21N 42.5558333333333 140 09 43E 140.161944444444 Au Imagane Placer and paleoplacer Au District contains alluvial placer deposits. Dstrict is 25 km by 20 km. Deposits occur along Toshibetu River. Two main deposits occur at Meppugawa and Toshibetugawa. Placer gold occurs in alluvial deposits in the River. The deposits are underlain by Paleozoic to Mesozoic sedimentary and granitic rock. Placer gold has been mined since 1804 at the Toshibetsugawa deposit. This deposit produced 12 kg of gold from 1934 to 1943. Saito and others, 1967; Kato and others, 1990. Japan K 54 04 42 26 55N 42.4486111111111 140 19 43E 140.328611111111 Fe Ti Funkawan Placer Fe Average grade of 24% Fe and 3.2% TiO2. Consists of a large number of beach placer deposits. Main part of the district is about 18 km long and 0.5 to 1 km wide, and occurs between Oshamanbe and Kuroiwa. More than 20 deposits have been mined. Major deposits are at Kunnui, Oshamanbe, Nakanosawa, Hanaoka, Toyono, and Toyotu. Placer Fe minerals occur in coastal plane deposits, coastal terrace deposits, and modern beach sands. Fe minerals in the coastal plane deposits is major type. Most of deposits occur from several hundreds m to 600 m above present shore line. Thickness of deposits ranges from 5 to 1m. Average grade is about 15-30% Fe and 4% TiO2, with maximum grade of 60% Fe and 6.5% TiO2. Sands include magnetite, hematite, ilmenite, limonite, pyroxene, chlorite, quartz, and plagioclase. Geological Survey of Japan, 1954; Saito, 1967. Japan K 54 05 41 33 34N 41.5594444444444 140 12 45E 140.2125 Au Matsumae Placer and paleoplacer Au District consists of alluvial placer deposits. District is 25 km by 25 km. Placer deposits occur in Rivers around Daisengendake Mountain. The main deposits occur along Shiriushi River. Placer gold occurs in alluvial deposits in river and alluvial terrace deposits. Deposits are underlain by Paleozoic and Mesozoic sedimentary rock. Quartz veins in sedimentary rock are likely the source of placer gold. Saito and others, 1967; Kato and others, 1990. Japan L 45 01 47 30 00N 47.5 89 20 00E 89 Au Altai, Xinjiang Placer Au Moderate 10 tonnes of gold produced in 1951-1942, and 33.9 tonnes of gold produced since 1980. Predicted gold reserves are greater than 30 tonnes. 997 Six mines are in operation. First order drainage systems are the EW Erqisi and Wuluohe Rivers. Third to fifth order branches usually have placer gold. Moraine placer Au deposits are several tens of km long, 40 to 120 m wide, and 3 to 15m thick. Grade ranges from 0.38 g/m3 to 2.2 g/t. Glaciofluvial and alluvial-deluvial River valley placer deposits range up to several tens of km long, 5 to 20m wide, and range from 0.15-0.25 to 23.5 g/m3. Alluvial-deluvial River flat deposits range up to several tens of km long, 100-500 m wide, 5 to 10 m thick, and range from 0.1-0.15 to 3.5 g/m3. Gold is derived from quartz veins in Hercynian granite and from metamorphosed Ordovician through Carboniferous strata. The typical Xichahe placer Au deposit is moderate size and is a glaciofluvial River valley type. The ore bodies are usually 3 to 4 km long, 80 m wide, 6 to 10 m thick, and with an average grade of 0.37 g/m3. Diameter of gold grains is 0.3-1.0 mm with a maximum of 2.48 mm. Heavy minerals in the ores include zircon, magnetite, garnet, pyrite, and cinnabar. 10 tonnes of gold produced in 1951-1942, and 33.9 tonnes of gold produced since 1980. Lu Yingjie and others, 1992; Chen Jiming and Others, 1997. China L 47 01 46 25 00N 46.4166666666667 100 07 00E 100.116666666667 Au Dovont Placer Au Average grade of 580 mg/m3 to 1015 mg/m3 Au. Production: 0.02 tonnes Au in 1992, 0.117 tonnes in 1993, 0.131 tonnes in 1994, and 0.147 tonnes in 1995. Proven reserves of 6.2 tonnes Au. 887 - 943 Occurs in the middle part of the Bayankhongor metallogenic belt, in the Dovont Mountains. Most placer Au deposits are alluvial-proluvial type, and minor alluvial type. There also are several manmade placers. Alluvial deposits are older than the alluvial-proluvial type. Main placer Au deposits are the Sairan-hudag, Mukkharereg, Ovorchuluut, Jargalant, Archuluut, Khooloi-khudag, and Dalt.Most deposits were partly mined out in 1939-1953. Presently, deposits and other small placer Au deposits of the Bayankhongor belt are being mined intensively. Deposits vary from 0.4 km to 6.6 km long, 30 m to 220 m wide, and from 0.6-1.8 m thick. Proven reserves range from 0.082 to 1.55 tonnes Au. Some deposits, for-example the Archuluut and the Buht located in NE foothills of the Dovont Mountains, occur in approximately 100-m-thick sediments, and have Au-rich several stratas from 8.5 m to 48.5 m depth. The Archuluut deposit was partly mined in 1939-1953 with production of 680 kg Au. Placer Au deposits in SW slope of the mountain range are covered with up to 3.2 m of barren sediments. Some placers, for-example, the Sairan-khudag alluvial deposit, has two Au-rich strata. Primary source of gold is not known. Bedrock consists mostly of late Riphean to Early Cambrian greenschist and a Vendian to Early Cambrian ophiolite complex. D. Andreas and others, written commun., 1970; Mormily and Tegshil, 1971; Blagonravov and Shavolovskyi, 1977; B. Bat-Oroom and others, written commun., 1980. Mongolia L 48 01 46 27 05N 46.4513888888889 102 22 05E 102.368055555556 Au Uyanga-Taragt Placer Au Average grade of 845 to 1100mg/m3 Au. Production of 0.6 tonnes Au in 1993-1995. Reserves of 4.5 tonnes Au. 840 - 860 (average 853 ) Occurs in the middle part of the East-Khangai metallogenic belt in northern valleys of the upper part of the Ongiin-gol River. District strikes NW-SE, is approximately 40 km long, and 30 km wide. Bedrock is mainly Early to Middle Devonian volcanic, sedimentary, and siliceous rock in the Erdenetsogt Formation that is intruded by Late Permian granodiorite to granite small stocks of the Khangai Complex. District divided into the Uyanga, the Taragt, and Zuunbayan-Ulaan subdistricts. Placer Au is derived from nearby quartz vein and replacement Au and probably from Early to Middle Jurassic conglomerate. Known placer deposits and prospects occur mainly in N-S striking valleys. Known placers belong to alluvial and alluvial-proluvial types. Valleys of main rivers are well developed, and have few terraces. The Uyanga subdistrict occurs in the NW part of the district, approximately 5 km in north of the Uyanga village. Main placer Au deposits occur in the Olt River valley and tributaries. Estimated reserve is approximately 3.0 tonnes Au. The largest placer deposit is the Olt placer that is 3.5 km long, averages 187 m wide, and ranges from 0.6 m to 3.6 m thick (average 1.44 m). The Au rich strata are covered by from 0.8 m to 2.4 m thick, barren sediments. The proven reserve is 0.85 tonnes Au at average grade 872 mg/m3 (from 167 mg/m3 to 2747 mg/m3). Most Au grains are from 3.0 to 40.0 mm Placer Au deposits in the subdistrict were mined out from 1994 by the private Erel Mongolian company. The Taragt subdistrict occurs in southern part of the district, occurs approximately 3-5 km north to northeast of the Taragt village. Placer Au deposits, as at Khuree-sair, Sort-am and Olziim-bulag occur in proluvial-alluvial valleys that drain from Early to Middle Jurassic conglomerate. Placers of the subdistrict have been known since 1940. The Zuunbayan-Ulaan sundistrict occurs in northern part of the district, approximately 10 km NW of the Zuunbayan-Ulaan village. Known small (0.1-0.2 tonnes Au) placer Au deposits and prospects occur in proluvial-alluvial valleys draining Early to Middle Devonian volcanic and sedimentary rock. Placer Au deposits and prospects of the subdistrict were discovered in 1995. D. Urtnasan and others, written commun., 1970; Blagonravov and Shavolovskyi, 1977; Ch. Baadai and others, written commun., 1992. Mongolia L 48 02 47 07 05N 47.1180555555556 107 17 05E 107.284722222222 Au Baruun -Urt Placer Au Average grade of 1.0 g/m3 Au. Production of 0.5 tonnes in 1994 and 1995. Reserves of 1.5 tonnes Au. Occurs in SW part of the South Khentii metallogenic belt, strikes NE, and is along the North Govi fault zone. District is approximately 50 km long and 30 km wide. Bedrock is mainly early Paleozoic clastic rock intruded by small early Mesozoic granotoids. Primary source of placer Au not defined. Placer Au deposits are small and proluvial-alluvial type. Main deposits are at Baruun-Uurt, Western Baruun-Urt, Khushuu-Uul, and Salkhitai. Largest is the Baruun-Urt deposit that is 7 km long, 40 to 400 m wide, and approximately 1 m thick. Grade of Au ranges from a few grains to 49,20 mg/m3. Deposit was mined out in 1994. Sanjsugar, written commun., 1988. Mongolia L 48 03 47 42 30N 47.7083333333333 107 35 00E 107.583333333333 SnO2 (Mn,Fe)WO4 Janchivlan Placer Sn Averade grade of 500g/m3 SnO2. Reserves of 7,090 tonnes SnO2. More than ten Sn placer deposits, such as the Janchivlan, Baatar, Bayandavaa, Elstei, Zuun Elstei, and Avdrant deposits, occur in the Janchivlan district. The placer deposits occur in first-to third-order stream valleys. Pay zones of late Pleistocene to Holocene placers range up to 7 km long and are generally simple single-layered deposits. These placers occur in gravel deposits. Heavy minerals are cassiterite, scheelite, wolframite, monozite, berill, ilmenite, fluorspar, molybdenite, gold, magnetite, and pyrite. All the deposits and small eluvial-talus placers are associated with quartz-cassiterite veins and greisens of the Janchivlan, Urt Gozgor, and other lode deposits. Lode deposits contain cassiterite and quartz. M.G. Korolev and others, written commun., 1955; G.Y. Borodyev and others., written commun., 1960; E.N. Chetverikov and others, written commun., 1975; Bykovsky and others, 1977a, b; B. Baasan, written commun., 1988. Mongolia L 48 04 46 15 00N 46.25 106 01 30E 106.025 SnO2 Baga Gazar Placer Sn Averade grade of 500 g/m3 SnO2. Reserves of 7,090 tonnes SnO2. District contains at least three placer deposits. Main resources occur in valley bottoms of first-to second-order streams, mainly in Recent alluvial material. Thickness of ore stratum ranges from 2.5 to 6.5 m. Width of alluvial placers ranges up to 130 m. Pay zones of placers range up to 5 km long and are generally simple single-layered deposits. Most cassiterite grains average less than 7 mm diameter. Tuviin deposit is richest and contains up to 370 g/m3 tin. Main placer minerals are quartz, topaz, cassiterite, and biotite. Topaz-cassiterite greisen (zivettery) is the main lode sources of metals. Zivettery occurs mainly along inside boundaries of silicate masses with coarse-grain topaz. G.Y. Borodyev and others, written commun., 1962; N.M. Zasimovskii and others, written commun., 1955; B. Baasan, written commun., 1969; N. Buyan., written commun., 1969; Khasin and Zakhai., 1977. Mongolia L 49 01 47 46 30N 47.775 109 07 45E 109.129166666667 SnO2 (Mn,Fe)WO4 Modot Placer Sn Reserves of 7,012 tonnes SnO2. Averade grade of 320g/m3 SnO2. Placer tin mined from modern streams and benches. Khyjikhan area and Bayan Mod basin are most productive. Heavy minerals include cassiterite, wolframite, fluorspar, molybdenite, gold, magnetite, scheelite, and pyrite. Placers range from 5-7 km long and are generally simple single-layered deposits. Placer deposits at Khujikhan contain maximum up to 1000g/m3 tin, locally more (4500g/m3 tin; 1500 g/m3 wolframite). Tin probably derived from quartz-cassiterite-wolframite vein and greisen lode deposits in contact zones in Neoproterozoic schist that is intruded by Mesozoic hypabyssal granitic plutons. Local bedrock is metamorphosed Neoproterozoic sedimentary and volcanic rock, and late Mesozoic granitic plutons. Bykovsky and others, 1977a, b; L.E. Esipov and others, written commun., 1978; E. Jadambaa and others, written commun., 1989; D. Erdene, written commun., 1990. Mongolia L 52 01 47 10 00N 47.1666666666667 130 30 00E 130.5 Au Jiayin Placer Au Large Production of 80 tonnes Au from 1920-1995. 877 The placer district covers 26,000 sq.km. and belongs to the systems of Heilongjiang River (including tributaries of Sunhe and Jiayin Rivers), and the Songhuajiang River (including tributaries of Dulu, Wutong, and Tangwang Rivers). Placer Au deposits are mainly alluvial valley type, and partly alluvial valley terrace type. Au mainly derived from gold lodes in metamorphic rock and granite (including the large Tuanjiegou gold deposit). The Jiulizhuangh River placer Au deposit is representative of the placer Au deposits in the area. The ore bodies occur along the river valley in single layers and in lenses. Au is tabular and layered. Associated minerals are magnetite, pyrite, garnet, and tourmaline. Lu Yingjie and others, 1988; Chen Jiming and others, 1977. China L 52 02 46 20 00N 46.3333333333333 130 55 00E 130.916666666667 Au Huanan Placer Au Large Reserves of up to 80 tonnes Au. 820 District covers 28,000 km2 and belongs to the drainage area of Mudanjiang and Weikenhe Rivers and their tributaries (these rivers are also the tributaries of the Songhuajiang River), and to the drainage area of Mulinghe River and related branches of the Wusulijiang River. Placers are mainly are alluvial, slope wash-proluvial valley flat, and valley channel deposits. Au mainly derived from gold quartz veins in Paleoproterozoic metamorphic rock and the Jurassic and Tertiary gold-bearing conglomerate. Typical placer Au is the Shitouhezhi placer Au deposit, that contains ore in beds or in lenses along the rivers in alluvial and alluvial-proluvial sediments, basal conglomerate beds, and in residual rock debris. The grain size of gold is 0.2-0.4mm. Lu Yingjie and others, 1988; Chen Jiming and others, 1997. China L 52 03 44 30 00N 44.5 131 00 00E 131 Au Dongning Placer Au 775-920 District overs 1,100 sq.km. and belongs to the water systems of the Wusulijiang and Shuifenhe Rivers and their tributaires. The deposits are alluvial, alluvial-proluvial valley flat and valley terrace types. Au mainly derived from gold occurrence in metamorphic rock, Mesozoic granite, and altered volcanic belts. Typical is the Jinchangtui placer Au deposit in that gold ore bodies occur as bands or lenses. The grade is relatively high. Associated minerals are galena and cassiterite. The diameter of Au grains is usually less than 0.5mm. Lu Yingjie and others, 1988. China L 54 01 45 02 03N 45.0341666666667 142 05 11E 142.086388888889 PGE, Cr, Au Teshio Placer PGE District consists of alluvial PGE and Au placer deposits. The size of the district is 60 km by 20 km, and is elongated NS. The deposits are underlain mainly by serpentinite of Kamuikotan belt. The placer deposits occur along the Makanbetu River. Main deposits in the district is at Makanbetu-Hoshin. Heavy metals of deposits also contains 20-30% of Au. Average grade is 0.4g / m2. Suzuki, 1950; Geological Survey of Japan, 1955; Saito and others, 1967. Japan L 54 02 45 02 16N 45.0377777777778 142 26 34E 142.442777777778 Au PGE Esashi Placer and paleoplacer Au District consists of alluvial placer deposits. The size of the district is 25 km by 25 km. The placer deposits occur along Usotan, Tonbetu, Peichan, and Horobetsu Rivers. Alluvial terrace deposits also contain minor Au. The deposits are underlain by black shale of the Late Jurassic to Early Cretaceous Sorachi Supergroup. Main deposits in the district are at Usotan, Peichan, and Utanobori. A large nugget of Au weighing 769 g was found at the Usotan deposit in 1900. Saito and others, 1967. Japan L 54 03 47 57 37N 47.9602777777778 142 15 57E 142.265833333333 Au Il'inka River Placer Au Small Gold is fine-grained, 0.2 to 0.3 mm. Heavy-mineral concentrate consists of chromite, epidote, and garnet. Small gold-cinnabar occurrences are presumably sources for the placer. Deposit occurs along the Il'inka River where it discharges into Tatar Strait. Alluvium of the first (lowest) floodplain terrace is gold-bearing. Sidorenko, 1977. Russia L 54 04 47 48 00N 47.8 139 26 00E 139.433333333333 Ti Sc, Rare Erth Koppi-Nelman Placer Ti Beach placer with reserves of 1,125 thousand tonnes titanomagnetite, submarine placer with reserves of 11.3 million tonnes of titanomagnetite. Occurs along sea shore of Tartar Strait. Two types of placer deposits were explored. Sea-beach gravel, sandy-gravel, and sandy material includes layers and lenses of placer titanomagnetite. The placer is 100-1400 m long, 5-150 m wide, and 1 to 5 m thick. Titanomagnetite content ranges from 8 up to 15%. Submarine placers are near shore at shallow depth (up to 10 m). They are about 1000-6900 m long, 100-600 m wide, and 2 to 20 m thick. Titanomagnetite content varies from 3 up to 10%. Onikhimovskiy and Belomestnykh, 1996. Russia M 46 01 49 30 00N 49.5 91 53 00E 91.05 Au Burgastain-gol Placer Au 100 to 2,000 mg/m3. Proven reserves of 1.2 tonnes Au. Prognostic reserves of 5 tonnes Au. Occurs in western part of the Nuuryn metallogenic belt along the major Tsagaanshiveet fault zone. Occurs in the Burgastain-gol River Basin. Main placer Au deposits are at Burgastain-gol, Shuluun-bulag, Talynsalaa, and Khorlhoitynzag. This placer deposits range from 1.0 km to 7.0 km long, 50 m to 160 m wide, and 1.6 m to 9.0 m thick. Au-rich strata is covered by up to 2.5 m barren sediment. The Shuluunbulag placer was mined out in ancient time with extensive workings for 5.5 km. Bedrock consists of Vendian to Early Cambrian marine volcanic, Silurian sedimentary rock, and Devonian volcanic and sedimentary rock that are intruded by a Devonian gabbro-granodiorite-granite intrusive complex. The placer deposits belong to alluvial type. Placer Au is derived from nearby lode occurrences of skarn and replacement Au. O. Jamyandorj and others, written commun., 1977; N.L. Shubin and others, written commun., 1985; L.V. Chistoedov and others, written commun., 1991. Mongolia M 48 01 49 25 00N 49.4166666666667 107 22 05E 107.368055555556 Au Yoroo-gol Placer Au Average grade of 0.3 g/m3 to 2.46 g/m3 Au. Production from 0.4 tonne in 1974; 0.37 tonnes in 1992, 0.47 tonnes in 1993, 0.42 tonnes in 1994, and 1.3 tonnes in 1995; 9.7 tonne from 1974 within 1995; Proven reserves of 20 tonnes Au 880 to 960 Occurs in NE part of the North Khentii gold belt along the Yoroo-gol and Khuder River basins. District strikes in NE direction, and it occurs in the Yoroo-gol major fault zone. District is approximately 100 km long, and the width of the district ranges from 5 km to 15 km. District is divided from NE to SW, in to the Khuder, Bugant-Tolgoit, Ikh Altat and Yalbag subdistricts. Bedrock of the district consists of regionally metamorphosed early Paleozoic terrigeneous formation of the Kharaa Group that is intruded by early Paleozoic calc-alkaline rocks of the Boroogol complex gabbro-granodiorite-granite complex, a middle Paleozoic alkaline granite-leucogranite complex, and an early Mesozoic gabbro-granodiorite-granite complex in small intrusives and dikes. Early Cretaceous conglomerate with sedimentary gold occur locally. Most placers of the district were discovered and mined out partly by international Mongolor Mining Company that operated from 1900-1919. In 1926-1929 and 1939-1942, mining was renewed by the Mongolian government in small scale. During 1960-1980, placer Au exploration occurred with a proven reserve approximately 20 tonnes Au. Over 20 placer deposits were discovered. Proven reserves are 30 kg to 7000 kg. Most are rediscovered deposits. In 1974, former joint USSR and Mongolian Tolgoit placer Au mining by the former SovMonTsvetmet company, nowadays the MonRosTsevetmet joint venture, occurred in the Bugant-Tolgoit subdistrict. The joint venture expanded into the Ikh-Altat subdistrist in 1980's. Besides the joint venture, nowadays, extensive exploration is being conducted by private Mongolian mining companies. All known placer Au deposits are the alluvium type, but some parts of deposits are man-made type. The Khuder subdistrict occurs in the NE part of the district in the upper part of the Khuder-gol River and tributary Tsagaanzur and Khyars Rivers, and rivers valley such as the Buduun, Tsagaanshiluust, Buduun and Galgatai that occur SW of the Khuder River valley. The Tsagaanzur deposit was mined out, and the Khuder deposit partly by the Mongolor Company. Mining activity in the Khuder deposit was renewed in last few years. The valleys of the Khyars, Buduun, Tsagaanshiluust, Shorgoolj, and Galgatai Rivers are expecting additional exploration. The average fineness of gold of the Khuder placer is 960 (highest in the Yoroo-gol district). Gold grains range from 0.25 mm to 1.0 mm (approximately 90%) in the deposit. A significant primary source of Au has not be discovered. The Bugant-Tolgoit subdistrict occurs in the middle part of the Yoroo-gol district along the sublatitudinal Bugant River basin and northern and southern tributary valleys. Most proven reserves of placer Au deposits of the Yoroo-gol district are concentrated in the subdistrict. The larger but lower grade (the average 0.3 g/m3) deposit is at Tolgoit with proven reserves of approximately 7 tonnes Au. Grade ranges from 1.0 g/m3-2.46 g/m3 Au with up to 540 kg proven Au reserves. The known deposits range from 0.5 km to 8.0 km long, from 20 m to 300 m wide, and 1.1 m to 18 m thick. Some are covered by 2.9-12 m thick barren sediment. The fineness of Au ranges from 894 to 960; Au fineness is approximately 854 in placer deposits in valleys of southern tributaries of the Bugant River, and ranges from 893 to 960 in placers in valleys of northern tributaries. Significant primary source of Au is not known; however, deposits occur in local bedrock and in small occurrences in surrounding mountains. Most small size, high-grade placers were mined out completely by 1974 by the Mongolian-Russian joint venture. Au from of the larger Tolgoit placer has been mined from 1974 to the present. The Ikh-Altat subdistrict occurs SW of the Bugant-Tolgoit subdistrict, along the longitudinal oriented middle Yoroo-gol River, and eastern and western tributaries, including the Buural, Altan, Galt, Ikh Ajir, and Baga Ajir. The large deposits, containing from 1880-2989 tonnes, but lower grade (0.25-0.31 g/m3) are at Ikh Altat and Ikh Ajir. The Ikh Altat and Ikh Ajir deposits are respectively 7.4 km and 4.0[m long, average 183 m and 175 m wide, and average 8.6 m and 8.8 m thick. Others are 0.8-3.7 km long, 30-70 m wide, approximately 1.0 m thick, and are covered by 3.1-44.0 m thick barren sediments. The deposits were mined out by the MonRosTsevetMet joint venture. Fineness of Au ranges from 841 to 884. Significant primary source of Au is not known; however gold quartz veins occur in bedrock in the upper part of the Buural Au placer. The Yalbag subdistrict occurs in SW marginal part of the Yoroo-gol district in the valleys of the Yalbag River and NW tributary, including the Yoroo-gol River valley. They vary from 0.4-4.6 km long, 30 m to 155 m wide, from 1.0 m to 1.6 m thick, and covered by 2.2-6.2 m of barren sediment. The grade of Au ranges from 1.2 g/m3 to 2.4 g/m3. Proven Au reserves ranges from 30 kg to 1417 kg. The fineness of Au grains ranges from 870 to 906. One of primary sources of Au is a weak gold-bearing weak zone in bedrock of the Yalbag deposit. Usov, 1914; V.G. Bubennikov and others, written commun., 1962; Bolotova, 1966; Tegshil, 1968; N.S. Vidyakin and others, written commun., 1969; A.M. Yurlov and others, written commun., 1970; V.P. Larev and others, 1971; Mormily and others, 1971; A.M. Yurlov and others, written commun., 1971; Renchin and others, 1973; Jambaa and others, 1975; Chesnyakov and others, 1976; Semenov and Noov, 1976; Semenov and others, 1976; Blagonravov and Shavolovskyi, 1977; D. Bat-Erdene and others, written commun., 1979, 1982; Ts. Gombosuren, written commun., 1979, 1983; L. Basarsad and others, written commun., 1981, 1982, 1984; N. Nyam and others, written commun., 1981; V. Dovjid and others, written commun., 1981; D. Gungaanyam and B. Bold-Erdene, written commun., 1984; D. Gungaanyam and others, 1981; B. Bold-Erdene, written commun., 1986; Semeikhan, 1989; Jamsrandorj and others, 1996. Mongolia M 48 02 49 19 00N 49.3166666666667 106 45 00E 106.75 Au Sharyn-gol-Bukhlei Placer Au Average grade of 0.9 g/m3 to 2.5 g/m3 Au. Production of 0.3 tonnes Au in 1994. Reserves of 10 tonnes Au. 778 to 894 Occurs in NE part of the North Khentii gold belt in the Bukhlei-gol and Sharyn-gol River basins. District strikes NE and occurs along the major Bayangol-gol fault zone. District is approximately 50 km long, and from 15 km to 20 km wide. District is divided from NE to SW, into the Bukhlein-gol, Khuiten-gol, and Sharyn-gol subdistricts. Bedrock of the district consists of early regionally metamorphosed Paleozoic terrigeneous rock of the Kharaa group that is intruded by early Paleozoic calc-alkaline Boroogol complex containing gabbro, granodiorite, and granite, a middle Paleozoic alkaline granite-leucogranite complex, and an early Mesozoic gabbro-granodiorite-granite complex with small intrusives and dikes. Early Cretaceous conglomerate with clastic sedimentary gold, occur widely. Some placer Au deposits were discovered and mined out partly by international Mongolor mining company that operated in 1900-1919. During 1970-1980, placer Au exploration again occurred with new proven reserves of approximately 10 tonnes Au. Over 10 placer deposits were discovered. Proven reserves ranges from 100 to 3200 kg. Most are rediscovered deposits. Placer Au deposits are being mined intensively by private Mongolian mining companies. All known placer deposits are the alluvium type, but some are man-made. Primary source of is vein and replacement type Au, and conglomerate and clastic sedimentary Au. One small quartz Au vein deposit occurs in bedrock of the Baga-Noyon placer deposit, and was explored and mined out by Mongolor joint venture in 1912-1914. Most known vein and replacement Au prospects are deeply eroded. Placer Au in many deposits is derived from nearby Cretaceous conglomerate with clastic sedimentary Au. The Bukhlein-gol subdistrict occurs in NE part of the Sharyn-gol-Bukhlei district, in the upper part of the Bukhlein-gol River basin along the Khargana, Olont, Tsamkhag the Mogoi Rivers. Known placer deposits are approximately 5 km long, 100 m wide, and 1.5 m to 4.3 m thick, and are covered by barren Quaternary sediments with a thickness of 3.2 to 12.5 m. Average grade is approximately 1.0 g/m3 Au. The Khuiten-gol subdistrict occurs in the middle part of the district, along the upper part of the Kuiten gol River and eastern tributaries the Baga-Noyon and the Ikh-Noyon Rivers. The largest is the Khuiten placer Au deposit with average grade of 1.2 g/m3 Au. The deposit is 12.4 km long, 45 m wide, 1.2 m thick, and is covered by barren Quaternary sediments that average 3.5 m thick. The Sharyn-gol subdistrict was discovered in 1984-1990. The subdistrict occurs in SW margin of the Sharyn-gol River valley, and NE tributaries of the Shaazgait, Khavchuu, and Burkhant Rivers. Known deposits have proven Au reserves from 100 kg to 3200 kg with an average grade from 0.9 to 2.5 g/m3 Au, range from 0.8-3.0 km long, and average 70 m to 150 m wide and 2.5 m to 3.0 m thick. They are covered by barren Quaternary sediment with an average thickness of 4.0 to 12.0 m. Most placer Au deposits have two Au-rich horizons; the lower horizon is mostly buried under the upper horizon. Most primary Au sources are vein and replacement types, are deeply eroded, with Au is deposited in Early Cretaceous conglomerate. Placer Au in most deposits is derived from nearby Early Cretaceous conglomerate. Usov, 1914; Bolotova, 1966; Tegshil, 1968; Jambaa and others., 1975; Mormily and others, 1971; Renchin and others, 1973; L. Basarsad and others., written commun., 1979; B. Bold-Erdene and others., written commun.,1985; Gmitron and others., 1976; Ts. Gombosuren, written commun., 1979, 1983, 1986; Gromov and others., 1971; Blagonravov and Shavolovskyi., written commun., 1977; D. Gungaanyam, written commun., 1981; D. Gungaanyam and L. Basarsad, written commun., 1981; D. Gungaanyam and B. Bold-Erdene, written commun., 1984; N. Nyam and others., written commun., 1984; Semeikhan, 1989; Jamsrandorj and others, 1996. Mongolia M 48 03 48 32 05N 48.5347222222222 106 45 00E 106.75 Au Boroo-Zuunmod Placer Au Average grade of 1.0 g/m3 Au. Production of 0.5 tonnes in 1993 to 1995. Reserves of 10 tonnes Au, 850 to 900 Occurs in the middle part of the North Khentii Au belt in upper western part of the Kharaa-gol River basin. Occurs at the intersection of NE-trending major Yoroo-gol fault zone and NW-trending Nariin-khondii fault system. District is 65 km long (NE direction), and 45 km wide (NW direction). The bedrock consists of the early Paleozoic the Kharaa Group that contains terrigeneous rock intruded by a Ordovician gabbro-granodiorite-granite complex, a Devonian granite batholith and coeval rhyolite subvolcanic bodies and dikes, and an early Mesozoic gabbro-granodiorite-granite complex with small intrusives and dikes. District is divided in to the Boroo, Zuunmod and the Borkhujiryn-gol subdistricts. The largest placer deposits are at Ikh Tashir and Gachuurt. Most placer deposits were discovered in 1985-1995. Direct exploration guides of placer Au deposit in the area around the Au the Boroo lode deposit and in other places, were known from 1955, but significant exploration on placer Au only occurred after 1985. Au in most known placer deposits is derived from nearby lode gold deposits. Placer Au deposits are the complicate eluvial-deluvial-proluvial, eluuvial-alluvial, and eluvial-deluvial-alluvial types. Placers formed during two periods, Pliocene, and Quaternary. First period placers are mostly buried under very thick (up to 50 m) Quaternary sediments, and second period placers are closely related to late Quaternary to Holocene and Holocene elluvial, deluvial, proluvial and alluvial deposits. The Boroo subdistrict occurs in NW part of the Boroo-Zuunmod district, and is related to nearby lode Au deposits. The largest is at Ikh Tashir. The primary source is the eastern Boroo vein and replacement deposit. The placer deposit has two Au rich strata. The lower and the upper strata occur together in the upper part of the placer deposit, but the middle and lower parts of these strata are separated vertically and horizontally. The lower strata occurs in red and red-yellow Pliocene proluvial-alluvial deposits with an average thickness of 1.0 m. The middle and the lower parts of the upper strata occurs in proluvial deposits of the Ikh Tashir valley. The upper part of the placer deposit occurs in thick (up to 15 m) eluvial-deluvial-proluvial deposits that consist of red and red-yellow Pliocene eluvial-deluvial deposits in the lower part, and Late Quaternary to Holocene eluvial-deluvial-proluvial deposits in upper part. The upper part of the deposit is being mined by a private Mongolian company. The proven reserve of Au is approximately 4.0 tonnes with an average grade of 1.3 g/m3 Au. The Zuunmod placer Au subdistrict occurs in SE marginal part of the Boroo-Zuunmod district and is closely a local lode deposit. The subdistrict occurs along the NE-trending major Yoroo-gol fault zone. The largest placer Au deposits is at Gachuurt that occurs along a NE-trending valley along the major Yoroo-gol fault zone that controls both the Boroo-Zuunmod hard rock and placer Au ore district. This fault zone contains the Sujist lode Au ore-field. Bedrock consists of early Paleozoic granodiorite and granite, and Devonian subvolcanic rhyolite that are strongly foliated and altered. Placer Au and prospects are alluvial type. The Borkhujiryn-gol subdistrict occurs in southern marginal part of the Boroo-Zuunmod district, and also along the major Yoroo-gol fault zone. Known placer Au prospects are proluvial-alluvial hybrid, and alluvial types. The subdistrict is related closely to the nearby lode Au ore field. V.N. Loginov, written commun., 1958; Blagonravov and Shavolovskyi, 1977; Jamsrandorj and others, 1996; Semeikhan, 1989. Mongolia M 48 04 48 32 05N 48.5347222222222 104 32 05E 104.534722222222 Au Zaamar Placer Au Average grade of 0.5 g/m3 to 2.0 g/m3 Au. Production: of 1.4 tonnes Au in 1990-1994. Proven reserves: of 82 tonnes Au and prognostic resource 18 tonnes Au. 900 Occurs in SW part of the North Khentii Au belt along NE-trending the major Bayan-gol fault zone. Both lode and placer Au deposits and prospects occur. District extends NE-SW, is approximately 100 km long and 15 km wide. District was explored in 1982-1990. Most economical placer Au deposits occur along NW slope of Zaamar Mountain range, Tuul River valley, and in tributaries. District is underlain by the early Paleozoic the Kharaa Group of terrigeneous rock, early Paleozoic and Devonian granitoids, Carboniferous and Permian sedimentary clastic rock, early Mesozoic variable composition dikes, and Early Cretaceous conglomerate. Cenozoic sediments occur mostly in the Tuul River and tributaries. District contains notable examples of placer Au deposits. River basins of the district, are filled mostly with Neogene red, clay-rich deposits, and Quaternary sand and clay beds. Placer deposits are multi-stream and multi-stratal. Deposits are lenticular, vary from 80 m to 160 m wide, up to 10 m thick. Concentration of Au started in Pliocene with most forming in Quaternary sedimentary deposits, directly overlying greenschist facies metamorphosed rock of the early Paleozoic Kharaa Group. Sediment reworking along the Tuul River and SE tributaries resulted in redistribution and local enrichment of placer deposits. The largest placer Au deposits in the district are the Tuul (average grade of 528mg/m3 to 791 g/m3; and 21197 kg Au reserve), the Bayangol (average grade of 401 to 569 mg/m3; and 5757 kg Au reserve), and the Khailaast (average grade 2460 mg/m3; and 5721 kg Au reserve). Alkin and others, 1989; Jamsrandorj, 1987; Jamsrandorj and Diatchkov, 1996; Semeikhan, written commun., 1989. Mongolia M 49 01 49 01 00N 49.0166666666667 110 15 00E 110.25 Au Baljiin-gol Placer Au Average grade of 312 mg/m3 to 1,140 mg/m3 Au.. Reserves of 50 tonnes Au. Occurs in NE part of the South Khenii metallogenic belt near Russia along Balj-Gol River and northern tributaries. Main placer Au occurrences are at Khomol-gol, Khavirgan, Baruunkhuurain-gol, Chahal-gol, and Galgatai-gol. Placer Au occurrences range from 1.5 km to 4.0 km long, 40 m to 1.0 km wide, and 2.0 m to 6.0 m thick. Bedrock consists of early Paleozoic clastic rock intruded by Mesozoic granitoids. Lode Au occurrences are granitoid-related Au vein and replacements. Blagonravov and Shavolovskyi, 1977; J. Byamba, written commun., 1990. Mongolia M 49 02 48 31 00N 48.5166666666667 108 29 00E 108.483333333333 Au Terelj Placer Au Range of 312 mg/m3 to 1140mg/m3 Au. Prognostic reserves of 50.0 tonnes Au. Occurs in the middle part of the South Khentii metallogenic belt in the upper parts of the Tuul and Kherlen Rivers. Main placer deposit is at Altansuudal in Altansuudal River valley that is one of NE tributaries of the Kherlen River. It averages 3.0 km long, 80-100 m wide, and 1.7 m thick. The placer is covered by 2.2 m thick barren sediment. Bedrock consists of Devonian and Carboniferous terrigenous rock intruded by Mesozoic granite rock. The primary source of placer Au is not known. Blagonravov and Shavolovskyi, 1977; B.V. Shekin and others, written commun., 1985. Mongolia M 49 03 49 31 00N 49.5166666666667 113 15 00E 113.25 Au Turgen Placer Au Average grade from 100 mg/m3 to 1000mg/m3 Au. Production: 0.0 tonne Proven reserves: of 0.5 tonne Au Occurs in NE part of the Khoit Kherlen metallogenic belt in northern tributaries of the latitudinal part of the Ulz River. Major placer Au deposits are at Tsagaanchuluut-khudag, Tsagaanchuluut-khooloi, Gun-Ondoriin-khooloi, Arshaant, and Ovoljoon. Proven reserves range from 0.1 to 4.0 tonnes Au. The Tsaganchuluut-khudag deposit is being mined. Bedrock consists of Paleoproterozoic metamorphic rock with younger early Paleozoic, late Paleozoic, and Mesozoic intrusives. Placer Au is derived from nearby lode Au occurrences. The placers occur mainly in two Au rich strata, vary from 1.0 km to 8.0 km long, 40 m to 160 m wide, and 0.5 m to 4.0 m thick. The Au rich upper strata are covered by approximately 1.5-3.0 m of barren sediments. The upper Au-rich strata are alluvial -proluvial, and the lower Au-rich strata is alluvial type. B. V. Shekin and others, written commun., 1985. Mongolia M 49 04 48 20 00N 48.3333333333333 112 28 00E 112.466666666667 Au Narsynkhondlon Placer Au Average grade of 200 mg/m3 to 1,000 mg/m3 Au. Production: of 0.2 tonnes Au. Proven reserves of 1.0 tonnea Au. Prognostic reserves of approximately 5.0 tonnes Au. 850 Occurs in the middle part of the Khoit Kherlen metallogenic belt. Bedrock consists of Devonian, Carboniferous, and Permian volcanic and sedimentary rock with Devonian, Permian and Mesozoic intrusive rock. Main placer Au deposits are at Salkhit and Tokhoi. Deposits are proluvial type, vary from 0.5 to 1.0 km long, 40-80 m wide, and 2.5 m to 4.0 m thick. Deposits have being mined. S. Ch. Norobsambuu and others, written commun., 1987; O. Nasantogtokh and others, written commun., 1994; Ts. Gombosuren and others, written commun., 1995. Mongolia M 49 05 49 13 00N 49.2166666666667 109 06 00E 109.1 SnO2 (Mn,Fe)WO4 Deed Kumiir Placer Sn Averade grade of 887g/m3 SnO2 . Average grade of 1,130 g/m3 WO4 Reserves of 1,277 tonnes SnO2. Reserves of 1,022 tonnes WO4. More than three placer deposits occur near the Deed Kumiir tin-tungsten lode deposit, in an area of moderate relief. Placer deposits are alluvial, valley-fill, deeply-buried, and complex types. Tin and wolframite occur in commercial concentrations. Heavy minerals are cassiterite, scheelite, and wolframite. Placer deposits occur in first- to second-order streams and formed from late Pleistocene to Holocene. Placers are characterized by relatively contstant thickness of stratum. Thickness economic gravels ranges from 1.5 to 2.5 m. Sn-W lode deposits at Deed Kumiir, Tom Zelenga, and other cassiterite-tungsten-quartz deposits are source of placer deposits. K.D. Pomazkov, written commun., 1944; N.M. Khrenov, written commun., 1946; Ts. Tseden., written commun., 1980; Khasin and Suprunov, 1977. Mongolia M 49 06 49 06 30N 49.1083333333333 109 29 30E 109.491666666667 SnO2 Zuuntarts Placer Sn Averade grade of 500 g/m3 SnO2. Reserves of 7,090 tonnes SnO2. Consists of two placer deposits in the upper Onon district that occur at the boundary between late Paleozoic and Jurassic granitoids. Placer deposits occur in first-to third-order streams as buried alluvial thalwegs. Pay zones in placer deposits extend for 1 km and at 1 to 2 m depth. Minor wolframite occurs in along with cassiterite. The Zuuntarst and Big Zilenda cassiterite-quartz vein lode deposits are the principal lode source for the placer deposits. Cassiterite concentration ranges from 156 g/m3 to 417 g/m3 and wolframite concentration ranges from 13 g/m3 to 56 g/m3. N.I. Khomizurin and others., written commun., 1952; Khasin and Suprunov, 1977; Ts. Tseden., written commun., 1989. Mongolia M 52 01 49 10 00N 49.1666666666667 130 55 00E 130.916666666667 Au Malokhingansky (Malokhingan) district Placer Au Production of 4.0 tonnes Au. Proven reserves of 1.0 tonne Au. Inferred reserves of 18.0 tonnes Au. District divided into the Nizhnebureisky and Arkharinsky subdistricts. The largest lode deposit in the area is at Prognoznoe in the Nizhnebureisky subdistrict. This deposit was discovered in 1972 during geologic mapping. Small placers (Simichi River and Gniloi Spring) were discovered in 1972 near the Prognoznoe lode deposit. Placer gold is derived from nearby lode deposits. Arkharinsky subdistrict occurs in the SE part of the Malokhingansky district. Bedrock is mainly early Paleozoic and early Mesozoic granitic rock. Neogene to Quaternary basalt locally overlies unconsolidated Cenozoic deposits in the headwaters of the Maly Bira and Uril Rivers. Estimated placer gold potential wasconsidered high at the beginning of previous century. Richest placers were mined along the Maly Bira River. Undiscovered placer deposits may occur beneath the basalt. Deposits as at Paskhalny Spring were completely mined out by underground mining in the 1950's. Mesozoic and Cenozoic sedimentary units may also contain older placer deposits. V.D. Melnikov and others, written commun., 1985. Russia M 52 02 50 50 00N 50.8333333333333 127 25 00E 127.416666666667 Au Blagoveshchensk-Svobodnensky district Placer Au Production of 1.0 tonnes Au. Proven reserves of 0.0 tonnes Au. Inferred reserves of 10.0 tonnes Au. Occurs in an area adjacent to the Amur River from the city of Blagoveshchensk to the village of Chenyaevo, and along the Zeiya River from the mouth to the Selemdzha River. Area is overlain mostly by unconsolidated deposits of the Amur-Zeiya valley. Bedrock crops out occur near the Amur River and is part of the Norsk-Sukhotinsky terrane. Placer gold deposits in the district have been known since the beginning of the previous century when prospectors started operations on bars and islands of the Amur and Zeiya Rivers. The Surazhevka bar placer in the Zeiya River, near the town of Svobodny, has been mined. The most promising area for placer deposits is the northern bank of the Amur River from the city of Blagoveshchensk to the village of Ushakovka. This area continues into China, on the opposite bank of the Amur River into the Fabelakhe subdistrict. Dzu Sung, 1991; V.D. Melnikov and others, written commun., 1989. Russia M 52 03 51 55 00N 51.9166666666667 131 55 00E 131.916666666667 Au Turansky district Placer Au Production of 0.3 tonnes Au. Proven reserves of 6.0 tonnes Au. Inferred reserves 29.0 tonnes Au. 937 Occurs in the Turansky subterrane of the Bureya terrane. District is divided into the Byssinsky, Ulmiisky, and Aleunsky subdistricts. Only the Byssinsky subdistrict is economic. The only lode source is the unexplored Buyanovsky occurrence. Bedrock consists of Precambrian metamorphic rock overlain by Early Cretaceous volcanic rock. A large placer was discovered on the Sinnikan River and tributaries. Length is 9 km, average width is 80 m, thickness of economic bed is 0.54 m, and gold grade in economic bed is 1059 mg/m3. Proven reserves of the placer are 980 kg. Tributaries of the Sinnikan River have potential for undiscovered deposits. V.D. Melnikov and others, written commun., 1989. Russia M 52 04 50 05 00N 50.0833333333333 126 40 00E 126.666666666667 Au Garnet Huma Placer Au Large Average grade of 0.1 to 9 g/m3 Au. Production of 125 tonnes Au from 1970-1995. 845 District covers 40,000 km2 along the Heilongjiang River and tributaries, including Huma, Fabiela, Lunjiang, Menluhe, and Keluo Rivers. Permafrost occurs in the area. Placer deposits in modern and small valleies have greater economic significance. Gold mainly derived from the lode gold and vein deposits that are widely developed in the Proterozoic metamorphic bedrock, Paleozoic granite, and Jurassic volcanic rock. Thee Dalahan placer deposit is representative and contains ore bodies that are single-layered and banded, and occur along a river valleyThe deposit is alluvial valley type and is redeposited from drift sediments. Au grain size is 0.2-0.5 mm, with common local Au grains of 2.00 mm. Associated minerals are ilmenite, magnetite, pyrite, tourmaline, and garnet. Garnet locally abundant. Mining started in about 1860. Lu Yingjie and others, 1988; Chen Jiming and others, 1997 China M 54 01 50 48 34N 50.8094444444444 139 36 41E 139.611388888889 Au Oemku Placer Au Small 800-850 Occurs in stream deposits of the Oemku River and other northern tributaries of the Muli River that flow into the Tumnin River. Gold-bearing beds contain fine- and medium-grained gold. Gold is derived from the Oemku lode deposit that contains gold-rich quartz veins. Local bedrock is Early Cretaceous siltstone and sandstone. A.M. Peshkov, written commun., 1972. Russia M 54 02 50 10 07N 50.1686111111111 142 57 07E 142.951944444444 Au Langeriiskoe Placer Au Medium 879-932 Occurs in several river valley placers that range from 1000 to 7200 m long and 20 to 30 m wide. A zone of alluvium, from 1.8 to 2.0 m thick adjacent to bedrock, is most enriched in gold. Gold grains range from less than 0.5 mm (30%), 0.5 to 1.0 mm (33%), 1.0 to 2.0 mm (26%), to 2.0 mm (11%). Chromite, pyrite, zircon, rarely cinnabar, scheelite, arsenopyrite, galena, and hematite also occur in heavy concentrates. Placer gold is derived from Au quartz vein deposits in quartz-micaceous schist. Sidorenko, 1977. Russia N 51 01 55 40 00N 55.6666666666667 125 00 00E 125 Au Verkhneselemdzha Placer Au Production of 5 tonnes Au. Proven reserves of 6 tonnes Au. Inferred reserves of 55 tonnes Au. District is the best known placer district in the Amur region and includes the Kharga, Malomyrsky, Verkhnestoibinsky, and Tokur-sagursky subdistricts. Total inferred reserves for the district are 226 tonnes gold, 13.7% of the total reserves of the Amur region. The majority of mined lode gold deposits also occur in this district (Zazubrinsky, Poiskovoe, Sagur, Afanas'evsky, Kharga, Unglichikan, and Yasnoe). Most lode gold deposits occur in metamorphic rock. District includes large placers that can be mined by dredge (Selemdzha River, Verkhny and Nizhny Stoiba, Kharga, Maly Naergen, Elga, Semertak, Ugokhan, and Bolshoi, and Maly Karaurak). Placer mining began in 1972 and continues. Nizhneselemdzha (Maisky) gold-bearing subdistrict covers the areas near the mouths of the Orlovka, Selemdzha, and Aldikon Rivers. Most placers occur in the Neklya River valley. Placer mining began in 1895 and continues. Bedrock consists of metamorphic rock, mainly Silurian schist cut by large early Paleozoic granitoid intrusions. The largest placer in the subdistrict is on the Neklya River and consists of shallow- and deep-seated gold-bearing beds. This placer has been mined since 1902 and has produced 9.5 tonnes gold. The placer occurs between two granitic stocks (Tatarkinsky in the north and Ust-Orlovsky in the south) early Paleozoic schist inbetween. An economic placer that is 15 km long and averages 140 m wide occurs in the headwaters and middle part of the Neklya River valley. In the upper part of this deposit, the first gold-bearing layer is 1.5 m thick and occurs at 6-8 m below the surface. Downstream, the deposit splits into two beds with a bed of gold-free alluvium 10-12 m thick between. The beds coincide in plan view. A paleoplacer plunges to the south and has been explored to a depth of 24 m. Gold-bearing deposits consist of quartz pebble and cobble gravel with a compact clay matrix. Average gold grade in being mined at present is 115 mg/m3, and fineness of native gold is 900. Gold is fine and average size is 0.64 mm. Most gold in placers is dense, but several dendritic grains occur. Unlike the lower bed, the upper one has smaller gold grains that are poorly rounded. Poorly-rounded nuggets intergrown with quartz also occur. Fragments of veined quartz found in headwaters of the Neklya River, contain up to 2.4 g/t gold. The placer is presently being mined with a dredge. Malomyrsky subdistrict is small, but gold grades are high. It also includes the medium-sized Malomyr lode deposit. The largest placer occurs on the Nizhny Stoiba River. Verkhne-Stoibinsky placer subdistrict includes two small lode gold deposits (Pokrovka and Voroshilovka) and large placers in the valley of the Verkhny Stoiba River. Gold is mainly concentrated near granitoid intrusions and lode sources. Tokur-Sagursky subdistrict includes several deposits. The Tokur lode deposit and several rich placers in the headwaters of the Bolshoi Karaurak and Tarnakh Rivers occur in the northern part of the subdistrict. Numerous small lode occurrences in greenschist facies metamorphic rock and small placer deposits occur in the middle part of the Bolshoi and Maly Karaurak Rivers. Some placer deposits occur within the Sagur dome-like structure. The largest placer at Koboldinsky occurs in the Koboldinsky part of the Selemdzha River between the Ogodzha and Maly Karaurak Rivers. The Sagursky lode deposit occurs to the east, and bedrock near this deposit contains numerous metamorphic gold occurrences. To the west of the placer are promising lode gold deposits (Pridorozhnoe and Mostovoe). Kharga subdistrict contains six small Au and Au-W lode deposits and one Au-Sb lode deposit. Three placer gold-bearing areas are distinguished and occur in metamorphic domes and outcrops of small intrusions. The Kharga placer is the largest in the subdistrict and produced over 20 tonnes. Au was produced from valley part of the deposit. This deposit has several lode sources. The richest part of the placer occurs close to the Kharga lode deposit. Numerous metamorphic gold occurrences with high gold grades occur the placer. The upper part of the Kharga Creek valley was recently explored. The richest part of the placer occurs immediately adjacent to the Talyminsky Au-Sb lode deposit. V.D. Melnikov, written commun., 1990. Russia N 51 02 54 53 00N 54.8833333333333 124 15 00E 124.25 Au Srednenuykzhinsk Placer Au Production of 23 tonnes Au. Proven reserves of 25 tonnes Au. Inferred reserves of 76 tonnes Au. Srednenyukzhinsky district contains three gold-bearing subdistricts - Elgakan, Urkimin, and Dzheltulak. Elgakan subdistrict occurs on the western side of the Nyuksha River. Several small hydrothermal lode gold occurrences occur in this area; including Balykhtakh that occurs along a EW-trending fault bounding the southern edge of the Mesozoic Chilchinsky granitic pluton. Only low-grade gold placer deposits occur. Urkimin subdistrict occurs on the eastern side the Nyuksha River. The Dzheltula and Sredny Larba placer deposits occur in the Dzheltulak (Burpalin) fault zone that separates metamorphic rock to the north from the Anosov pluton to the south. Placers of the Urkimin subdistrict are extremely high-grade. They include large prospected placers along the Urkima, Onon, Odolgo, and Agin Rivers, presently being mined by dredges, and smaller placers on the Glubokaya, Razdolnaya, Sivagli, and other rivers, where some recent mining has occurred. The largest placer is on the Urkima River. There are over 20 lode gold deposits in the area that are related to hydrothermal alteration of metamorphic rock. The largest lode deposit is at Odolgo. High-grade lode gold deposits occur near the placer of Berikan Creek. The lode deposits were mined in the early 1900's. The Urkimin valley-type placer was discovered in 1913 on the Urkima River, the eastern tributary of the Nyuksha River. The deposit was mined by hand from discovery until 1947 when a low-capacity dredge (250 liter) began operation. The total production from 1913 through 1980 is estimated as 810 kg. The placer is 18 km long, average width is 236 m, average thickness is 7.2 m, total volume of gold-bearing gravel is 32 million m3, average gold grade is 225 mg/m3, fineness of native gold is 881, and proven reserves are 7 tonnes. At present, the placer is being mined with dredges. V.D. Melnikov and V.V. Ratkin, written commun., 1994. Russia N 51 03 53 55 00N 53.9166666666667 122 30 00E 122.5 Au Verkhne-Indigirsky Placer Au Average grade of 133 mg/m3 Au. Range of 58 to 237 mg/m3 Au. Production of 169 tonnes Au. Proven reserves of 3.5 tonnes Au. Inferred reserves of 50 tonnes Au. District contains more than 250 different and non-contemporaneous placer deposits. Most deposits are flood-plain and bench placers that occur in Holocene and interglacial deposits. Three stages of placer formation occurred in the Oligocene-Miocene, Pliocene-Early Pleistocene, and Late Pleistocene-Holocene. Highest-grade deposits are Pliocene and Early Pleistocene, as at Sana, Bazovy, Dirin-Yuryak, and Elgi. These deposits occur in intermontane depressions along major fault zones. Placers occur on terraces 6 to 200 m above river level. Most have 0.2-20 m of overburden, but some have up to 150 m overburden. Gold-bearing beds are 0.2-6.6 m thick and gold grades range up to 1 kg/m3 (as at Sana). Gold nuggets up to 5 kg weight occur. Commercial placers are mostly confined to late Pleistocene and modern fluvial deposits. These deposits have 10 m or less overburden, are 0.5 to 15 km long, and contain gold-bearing beds that range from 1-6.8 m thick, and have a gold fineness of 582-907. Major deposits occur at Promezhutochny Creek, Tuora-Tas Creek, Khangalas Creek, and Kurun-Agalyk Creek. Promezhutochny Creek deposit consists of a buried placer deposit that occurs in Neogene to early Pleistocene gravel. Thickness of overlying alluvial, colluvial, and glacial deposits varies from 50 to 140 m, and averages 63 m thick. Gold grade is 8.6 g/m3. The gold-bearing bed is 3.28 km long and averages 62.8 m thick. The majority of the gold (80%) occurs in the bedrock eluvium. Large gold particles comprise less than 10%; and fineness is 840-863% with an average of 849. Gold is associated with arsenopyrite, pyrite, anatase, and garnet. Tuora-Tas Creek flood-plain gold placer is 10 km long and occurs in a broad valley with multiple well-formed terraces. The gold-bearing bed is about 1.5 m thick, gold fineness is 798, and gold particles are about 4 mm in size. Khangalas Creek deposit consists of flood-plain and bench placers that range up to 3 km long and 150 m thick. Some individual paystreaks are 180-1,000 m long, 0.4-3 m thick, and have 0.4 to 6 m of overburden. Gold fineness is 850. Bedrock sources of are gold-quartz veins of the Khangalas deposit. Kurun-Agalyk valley placer is 5,500 m long and 20-150 m thick. The gold-bearing bed is 0.2-3.6 m thick, with 2-3 m thick overburden. Gold fineness is 856-891 and gold particles are 0.5-8 mm in size. E.I. Belousov and V.D. Melnikov, written commun., 1979; B.Y. Grezin and V.S. Borodin, written commun., 1982. Russia N 51 04 53 30 00N 53.5 125 30 00E 125.5 Au Gonzhinsky (Gonzha) Placer Au Production of 48 tonnes Au. Proven reserves of 8 tonnes Au. Inferred resources 66 tonnes Au. Occurs in the western part of the Burea superterrane. Area is underlain mainly by Precambrian metamorphic rock. The largest gold-bearing deposits of the district (Pokrovskoe, Pioneer, Borgulikan, Burinda, and Kulikan) are interpreted as being derived from Early Cretaceous volcanic overlap assemblages. Osezhinsky subdistrict is underlain by the Late Jurassic and Early Cretaceous clastic trough. The largest placer is along the Bolshoi Burgali River (the Alma-Burgali subdistrict) that has been mined intermittently since 1890 with a total of production of 1.7 tonnes gold. The placer is 9 km long, averages 250 m wide, and the alluvium is 4-5 m thick. Gold-bearing strata occur in the lower part of alluvium and are 1.6 m thick. Gold is fine (0.3-0.4 mm) and poorly rounded. The placer is being mined again after additional exploration. Tygda-Ulundy gold-bearing subdistrict occurs in a hilly area in the NW part of the Cenozoic Amur-Zeiya Basin. The area contains wide river valleys with gentle slopes that grade into drainage divides. Topographic relief is commonly 20 to 50 m, rarely 100 m, with the highest relief being 340 to 360 m. The Ulunginsky placer is largest in the subdistrict. The Ulunginsky placer deposit occurs in the valley of the middle part of Bolshoi Ulunga Creek. The first prospect (Pioneer) was discovered in 1911. Mining operations began in 1915 and are occurring. The Aprelsky prospect, containing both just-subsurface and also deep-seated placer material, was discovered in 1937. The stratigraphic section (from top to bottom) consists of: 0-3 m of yellow viscous clay and ooze; 3-7 m of dark-brown compact ooze; a first gold-bearing bed (5-7 m below the surface); 7-12 m of false bedrock consisting of angular pebbles derived from granodiorite, decomposed to varied-color clay; and a second gold-bearing bed (5 to 7 m) consisting of coarse grained gray sand with poorly-rounded quartz pebbles. Granite boulders up to 40 cm occur locally. About 75% of gold is irregular in shape and less that 0.25 mm comprises about 75%. Gold from 0.5 to 2 mm diameter is of tabular shape and very light in color. Proven reserves of the deep-seated placer are 186 kg, and inferred reserves are 500 kg. The placer is 10 km long, average thickness of the gold-bearing bed is 1.3 m, and average thickness of the pit layer is up to 20 m. Gold content varies from 641 to 1419 mg/m3. Gold is 0.25 to 2.0 mm with fineness of 800. V.D. Melnikov and V.V. Ratkin, written commun., 1994. Russia N 51 05 52 37 00N 52.6166666666667 121 40 00E 121.666666666667 Au Mohe Placer Au Large Grade rangefrom 0.1-9 g/m3 Au. Production of 125 tonnes Au from 1970-1995. 856-897 Mining began in 1860 and in the past 130 years, totally 300 tonnes Au has been produced (including district N51-02). The area covers 25,000 sq.km. and exhibits a glacial geomorphogical landscape. District occurs along second to fourth order branches of the Argun and Heilongjiang Rivers. Placers are classified as allurial-slope-proluvial valley channel, allurial-slope-proluvial valley flat, and valley terrace types that formed in Late Pleistocene and Holocene. The Holocene placers are the most economic. Placer Au is related to the ancient placer in Jurassic conglomerate, and to Au quartz veins in metamorphic rock and in Paleozoic granite and Mesozoic pyroclastic rock. The Fulaoshan Placer Au is most representative with ore bodies that dip gently along the river channel. The size of Au grains is 0.1-0.5mm, even up to 1.0-1.5cm. Lu Yingjie and others,1988; Chen Jiming and others, 1997. China N 52 01 54 55 00N 54.9166666666667 131 05 00E 131.083333333333 Au Verkhnezeisk Placer Au Production of 24 tonnes Au. Proven reserves of 6 tonnes Au. Inferred reserves 76 tonnes Au. Occurs in the eastern part of the Nora-Sukhotin terrane. The Mesozoic Mulmugin, Toksky, and Okonon plutons underlie over half of the district, and the rest of the district is underlain by nearly equal amounts of Early Archean metamorphic rock and Precambrian igneous rock. District consists of the Sugdzhar, Verkhnetok, Kupuri-Maisky, and Arginsky subdistricts. Sugdzhar subdistrict occurs near the giant Malmugin and Okonon granitoid plutons. Most lode and placer deposits of the Sugdzhar subdistrict occur within the Sivakan-Toksky block of metamorphic rock. About 20 lode occurrences occur and are related to a long, wide (up to 7 km) shear zone that cuts zones of schistose rock and retrograde metamorphic rock that contain disseminated sulfides. Gold occurs in small quartz, quartz-pyrite, quartz-epidote, and quartz-feldspar veins and veinlets, in altered gabbro-amphibolite, and in gneisses containing quartz-filled fractures. Most commonly, gold has a fineness of 720 to 830. Gold grains are angular, intergrown with quartz (up to 2.5 wt.%), and are small (normally less than 1 mm). Lode sources for gold are interpreted as forming during Late Jurassic accretion; lode deposits occur in the areas of intense shearing and retrograde metamorphism. Verkhnetok subdistrict occurs between the Toksky and Okonon granitic plutons. Late Archean metamorphic rock and mafic granitic rock predominate. Estimated placer potential of the Verkhnetok subdistrict is 6 tonnes gold. Kupuri-Maisky placer subdistrict occurs in the eastern Okonon pluton in the valley of the headwaters of the Kupuri and Maai Udsky Rivers. Archean metamorphic rock and gabbro-amphibolite predominate, and granodiorite and diorite are subordinate. Neronsky and Dobraya, 1976, V.D. Melnikov, written commun., 1979. Russia N 52 02a 54 40 00N 54.6666666666667 126 40 00E 126.666666666667 Au Dambuki-Part A Placer Au Production of 185 tonnes Au. Proven reserves of 56 tonnes Au. Inferred reserves of 88 tonnes Au. District is well defined. Internal division is difficult because gold occurs throughout. Seven tentative subdistricts are distinguished: Mogoktak-Talginsky, Ilikan-Unakhinsky, Kokhaniisky, Zolotogorsko-Uspensky, Dzhalta-Uldegitsky, Ugan-Mogotsky, and Zhurbansky. The shallow Khugdersky placer and the deep Petrovsky and Yasnopolyansky placers are described as examples. The lode sources for the Khugdersky placer deposit are the Zolotaya Gora deposit and retrograde metamorphic Au lode deposits. The deposit is 15.6 km long, averages 189 m wide and 4.0 m thick, and has an average gold grade of 285 mg/m3. Fineness of gold is 940. The bedrock consists of metamorphic rock (amphibolite, gneiss, gneissic granite, and diapthorite). Loose sediment consists of 41% pebbles (more than 5 mm), 31% gravel (1-5 mm), 21% sand (less than 1.0 mm), and 3% ooze and clay. Gold is fine- and medium-grained: 1.2% is up to 0.2mm, 50.6% is 0.21-0.63 mm, 7.2% is 0.64-2.5mm, and 1% is greater than 2.5 mm. Gold grains are tabular and bright yellow, locally with a reddish tint. More than 8 tonnes of gold is mined. Nuggets up to 18 kg were recovered. Heavy-mineral concentrates contain scheelite, zircon, rutile, sphene, anatase, ilmenite, monazite, andalusite, kyanite, molybdenite, apatite, epidote, garnet, pyrite, amphibole, and pyroxene. Anert, 1928; V.D. Melnikov and others, written commun., 1989. Russia N 52 02b 54 40 00N 54.6666666666667 126 40 00E 126.666666666667 Au Dambuki-Part B Placer Au Production of 185 tonnes Au. Proven reserves of 56 tonnes Au. Inferred reserves of 88 tonnes Au. Petrovsky placer deposit occurs in a saddle on the Tukuringra Ridge. The placer was discovered in 1897 and has been mined since 1898. It does not coincide with a modern river system. Major accumulations of unconsolidated Cenozoic sediments occur in a small, elongated NS-trending basin. The slopes of the basin are mostly gentle, with well-preserved piedmonts and wide erosional terraces, corresponding to ancient piedmonts with elevations of 700 to 750 m. The floor and slopes of the basin consist mostly of gneiss and amphibolite with Early Archean marble lenses. The basin floor is rather wide (about 500 m and indulated, with local depressions ranging from 5-10 m and 60-100 m wide). Unconsolidated sediments are 60 m thick. Bedrock exhibits a thick weathering crust consisting of a layer 1-3 m thick of angular pebble-sized fragments that occurs almost everywhere at the base of the sequence of gold-bearing gravel. Unconsolidated material is mainly sandy pebble gravel to pebble sand, with beds and lenses of gravelly mud and peat, muddy sand, and compact clay. The largest and most poorly-rounded clasts are concentrated in the deepest part of the basin, its center. There are several gold-bearing beds in the section, although the richest gold deposits occur in the lowermost gravel beds and in the bedrock weathering crust. Grains less than 1.0 mm form 82-90% of the gold of this ancient placer. Some nuggets occur, mostly 2 to 12 kg and rarely up to 100 kg. Fineness of gold is 950-962. An alluvial origin is interpreted for the sediments of the Petrovsky placer. Anert (1928) proposed initially an origin as an eluvium placer that was redeposited virtually in situ. The placer is presently being mined as a small-scale operation, producing 30 to 60 tonnes gold per year. A total of 4-5 tonnes gold have been produced. Proven reserve is 1 tonne Au; inferred reserves are 2-3 tonnes Au. Anert, 1928; V.D. Melnikov and others, written commun., 1989. Russia N 52 03 53 50 00N 53.8333333333333 130 00 00E 130 Au Dzhagdy Placer Au Production of 20 tonnes Au. Proven reserve of 2 tonnes Au. Inferred reserve 51 tonnes Au. Occurs in the Tukurigra-Dzhagdi terrane and is subdiviided into the elongate, EW-trending Un'ya-Bomsky subdistrict that contains most of the placer gold deposits, and a group of subdistricts to the south (Verkhnedepsky, Tuksinsky, and Egorsky). Placer and lode deposits clearly restricted to the EW-trending Un'insky thrust fault. Streams are rapid and steep and occur in canyons. Un'ya Creek has the widest flood plain (300-450 m) and the the valley of the Bom Creek is steep. Valleys of tributaries (rapids) of the Bom Creek are steeper. Yasnaya Polyana placer deposit occurs in the Yasnaya Polyana basin. The upper level of ancient alluvium was mined in the 1920s. The Yasnaya Polyana basin is 14 km long and 0.6-2 km wide. The basin occurs in a fault zone between Early Archean Dambuki and Late Archean Ilikansky blocks. The basin is filled with sand, pebble gravel, and clay. Clasts are well-rounded and consist of granite, gneiss, and quartzite, with less common amphibolite and volcanic rock (rhyolite, andesite, and dacite). The placer occurs at the thalweg of a northwest-trending paleovalley. Absolute heights (elevations over the sea level) range from 462.7 m at the western part of the deposit to 403.5 m at its eastern part. The gold-bearing beds are predominantly gravel and pebble with larger clasts. Coarse sand makes up 20%, and clay 15%. The thickness of the gold-bearing bed ranges from 1 to 17.6 m, gold grade varies from colors to 17,966 mg/m3. Gold grains occur 0.4-0.8 m into the bedrock. Gold grains are either small (less than 0.1 mm) of irregular dendritic shape, or are larger, tabular, poorly-rounded grains. Scarce intergrowths of gold with other minerals (quartz, pyrite commonly with galena) generally occur as small grains (less than 0.16 mm). Gold is bright yellow, about 15% of grains are light yellow (straw-like color). These grains are rounded, spindle-shaped. The fineness of native gold is 967. The bedrock consists of granite, Paleoproterozoic granodiorite and gneiss, and Archean amphibolite. Born Creek placers are largely concentrated in the first flood plain terrace that is 40-45 m high and 400-450 m wide. The deposits are about 5 m thick and gold-bearing throughout the whole length of the creek. Gold distribution is extremely irregular. Gold occurs locally on the floor of the creek and in tiny fractures in the greenschist bedrock. Gold grains are coarse and nuggets up to 400 kg g occur. Un'ya Creek deposit contains both terrace- and valley-type placers. The valley placer part is 20 to 120 m wide. Valley alluvium is 2.5 to 6.0 m thick. The gold-bearing bed consisting of gravel and pebble near the bedrock is 0.2 to 0.6 m thick. Terrace placers of Un'ya Creek are also mainly related to the first flood plain terrace, that is 15-20 m high. Terrace alluvium ranges from 6 to 25 m thick. Gold distribution is irregular. Gold is coarse and poorly rounded. Quartz fragments in some places contain visible gold and scheelite. V.D. Melnikov and others, written commun., 1985. Russia N 52 04a 52 50 00N 52.8333333333333 128 50 00E 128.833333333333 Au Zeiya-Selemdzha-Part A Placer Au Production of 111 tonnes Au. Proven reserves of 29 tonnes Au. Inferred resources 101 tonnes Au. District is underlain by Early Cretaceous volcanic rock that mostly overlie the Nora-Sukhotin terrane. District is divided into the Umlekan, Yasnensky, Oktyabrsky, Sokhatiny, Chagoyan, and Nizhneselemdzha subdistricts. The Zeiya-Selemdzha placer gold district has the largest gold reserves in the the Amur region. Umlekan subdistrict covers an area of about 3,000 km2 in the valley of the Umlekan and Nemogin Rivers, and in the valley of the Zeiya River from the mouth of the Chalbachi Creek to the mouth of the Bugo Creek. The first discovery was a rich placer on a bar in the Zeiya River near the mouth of the Bugo Creek. The subdistrict occurs in an Early Cretaceous caldera. Numerous lode occurrences are in the subdistrict and consist of quartz veins in hydrothermally altered volcanic rock and in granodiorite that intrudes Jurassic sandstone. About 20 small placers occur in the subdistrict. Some are exhausted; others were only explored (Umlekan and Algachan Rivers). Gold in placers is of variable size and shape, often in intergrowths with quartz. Fineness is 750-850. The sources for shallow-seated placers of small creeks are gold-bearing, hydrothermally-altered volcanic rock. Yasnensky subdistrict occurs in the basin of the Yasny Creek, the adjacent valley of the the Dep River, and the headwaters of the Gar 1 and Gar 2 Rivers. Most placers are occur in early Quaternary deposits. More than 25 placers occur in the subdistrict, most are exhausted. Extremely interesting data were obtained from a prospecting trench crossing the valley of the Gar 2 River at the mouth of the Karakatitsa Creek. This trench contains a displaced weathering crust of greenstone rock, and the 665 nuggets recovered from this trench differ sharply from gold of the placer by having higher fineness values. The lode source is unknown. V. Lozhnikov and others, written commun., 1984; V.D. Melnikov and others, written commun., 1985. Russia N 52 04b 52 50 00N 52.8333333333333 128 50 00E 128.833333333333 Au Zeiya-Selemdzha-Part B Placer Au Production of 111 tonnes Au. Proven reserves of 29 tonnes Au. Inferred resources 101 tonnes Au. The largest placer of the Yasnensky subdistrict is the Yasny Creek placer, discovered in 1934. It was mined from 1935 to 1937. More recently, the deposit was mined using a dredge and exhausted. The bedrock consists of crushed extrusive rock, with less common sandstone and siltstone. Gold-bearing gravel directly overlies bedrock. Gold distribution is uneven. Gold content decreases sharply to colors as distance above bedrock increases. Gold grain shapes are irregular and rounded. Intergrowths with quartz or quartz and tourmaline are common. Gold fineness is 900, gold grains are coarse (2-4 mm), and nuggets of 30-60 g are common. Nuggets locally locally reach 100 g. The gold-bearing bed is overlain by gold-bearing ooze and clay (0.5-4.0 m), and less common sandy-clay deposits 0.3-1.7 m thick. The section is covered by a bed of soil 0.3-0.5 m thick. V. Lozhnikov and others, written commun., 1984; V.D. Melnikov and others, written commun., 1985. Russia N 52 04c 52 50 00N 52.8333333333333 128 50 00E 128.833333333333 Au Zeiya-Selemdzha-Part C Placer Au Production of 111 tonnes Au. Proven reserves of 29 tonnes Au. Inferred resources 101 tonnes Au. Sokhatiny gold-bearing subdistrict occurs in the valley of the Sokhatiny River and headwaters of the Mamyn River (Orlovka, Levy and Pravy Mamyn Creeks). The placers of the Sokhatiny River were discovered in 1942, and have been mined from 1948 through the present time. Bedrock consists of early Paleozoic granitic rock cutting Proterozoic to Cambrian deposits, as well as small Early Cretaceous intrusions and numerous dikes. Only three lode occurrences occur in the subdistrict, consisting of quartz-tourmaline breccia zones with sulfides and altered quartz-sericite rock. About 30 placers have been discovered; many of them are mined out. The valley of the Adamikha River is being explored. Oktyabrsky subdistrict occurs in the valley of the Dzheltulak River and the headwaters of Inkan, Elna, and Bolshoy Kalakhta Creeks. Gold was discovered in 1937 in the Dzheltulak 1 and Dzheltulak 2 Rivers, and in a very rich placer in Sandunovsky Creek, a tributary of the Dzheltulak 1 River. Numerous placers were later discovered and prospected within the subdistrict, that are still being mined using dredges. The subdistrict is underlain mainly by early Paleozoic granite with fragments of Late Proterozoic to Early Cambrian schist and marble, Silurian conglomerate, sandstone, siltstone, and Devonian clastic carbonate rock. Numerous lode gold occurrences are in quartz-carbonate and calcedony veins. Small gold-bearing skarn bodies in limestone are less common. Most gold placers are hosted in early to middle Quaternary sediments. Almost all placers are alluvial, either valley or terrace, locally mixed. Eluvium and talus placers such as Nagornaya and Morennaya are uncommon. Modern and ancient placers occur separately: modern ones occur below the talweg of the valley (or close to it) at a depth of 3-6 m. Old placers are not related to the modern valley floor and much deeper (5 to 15 m). Locally old and modern placers occur one above the other and are separated by a layer of barren sediment. In some valleys, old placers are eroded either completely or partly, forming modern placers. The bedrock is generally heavily weathered granite that forms angular pebbles and clay. The gold-bearing bed of old placers consists of heavily eroded pebbles with clay patches of different shades and pebbly sandy-clay deposits. Gold generally occurs in the middle part of beds. Native gold fineness is commonly high, up to 950. Large nuggets up to 500 grams occur locally as at the headwaters of the Kalakhta River. Gold in placers is associated with scheelite and cinnabar, and less commonly with galena. Modern placers have lower gold grades, occur in the flood valley alluvium, and consist of clay, ooze, and sand with pebbles. Native gold fineness in modern alluvium placers (up to 885) is locally significantly lower than in older placers. The lower fineness results from being derived directly from lode sources, rather than from erosion and reconcentration Chagoyan gold-bearing subdistrict occurs in the southern area in the Zeyia River valley from the mouth of the Tygad River to the mouth of the Gramatukha River, including tributaries. Placers have been mined since 1893. Lode gold occurrences (seen in talus) in the valley of the Malyutka River contain fragments of veined quartz with visible gold. A prospecting drill hole on the Chagoyan polymetallic deposit has high gold grades at depths of 29-32 m. Gold placers within the Chagoyan subdistrict occur either in bars or river bottom. Gold is coarse and of different shapes. In the headwaters of Maly Chukan and Chagoyan Creeks, nuggets up to 140 g occur as intergrowths with quartz. Native gold fineness is 675-911. V. Lozhnikov and others, written commun., 1984; V.D. Melnikov and others, written commun., 1985. Russia N 53 01 53 00 00N 53 132 45 00E 132.75 Au Verkhne-Yansky Placer Au Production of 137 tonnes Au. Proven reserves of 29.0 tonnes Au. Inferred reserves of 60.0 tonnes Au. District contains about 60 cassiterite placer occurrences that form groups of three to ten placer deposits; each group is closely related to their bedrock sources. Main types are eluvial-slope and ravine placer deposits that range up to some km long and about 100 meters wide. Thickness of the payable bed ranges up to 15-20 m and sometimes larger. Cassiterite is generally fine- to sometimes coarse-grained. Buried placers also occur. A major deposit occurs at Kerbeng Creek. Kerbeng Creek deposit consists of three cassiterite-bearing beds from 4-15 m thick. The paystreak is 100-620 m wide and occurs under 1.7-24 m of overburden. Grades are 330-2,000 g/m3 cassiteriete and 45-81 g/m3 wolframite. Bedrock sources are Sn quartz veins and stockworks of the Kuturuk Mountain. V.D. Melnikov and others, written commun., 1985 ; V.D. Melnikov and V.D. Polevanov, written commun., 1990. Russia N 53 02 52 13 50N 52.2305555555556 133 52 59E 133.883055555556 Au Sofiiskoe Placer Au Medium Deposits are mined out. 750-800 Occurs in stream deposits in the upper reaches of the Niman River (a tributary of the Burea River). Total length of placers is approximately 30 km. Fine- and medium-grained gold occurs irregularly. Gold fineness is 750-800. Gold is derived from greenschist facies rock of the Sofiisky metamorphic dome that contain streaks, veins, and lenses of gold-bearing quartz. Gold-bearing tributaries drain small veinlet deposits. Placer deposits are exhausted. N.V. Ognyanov in Nokleberg and others, 1997. Russia N 53 03 52 24 00N 52.4 135 44 28E 135.741111111111 Au Kerbi Placer Au Small 800-850 Occurs in Kerbi River valley numerous tributaries. Total length of gold-bearing beds is approximately 35 km. Gold is fine- and medium-grained with fineness of 800-850. Bedrock is Jurassic black shale that is metamorphosed to greenschist facies with thin scattered streaks of gold-bearing quartz. N.V. Ognyanov in Nokleberg and others, 1997. Russia N 54 01 53 51 32N 53.8588888888889 139 49 27E 139.824166666667 Au Ulskoe Placer Au Small 850-900 District contains stream and bench placers of the Ul Orelsky River and tributaries. Total length of placers along the Ul Orelsky River and tributaries is approximately 15 km. Gold is associated with vein quartz and fineness is 850-900. Local bedrock consists of Early Cretaceous siltstone, sandstone, and Late Cretaceous volcanic rock. Deposit derived from the Mnogovershinnoe lode gold deposit. N.V. Ognyanov in Nokleberg and others, 1997. Russia N 54 02 53 34 49N 53.5802777777778 140 21 18E 140.355 Au Kolchanskoe Placer Au Small 500-600 District contains low-grade stream placers along the Kolchan River and tributaries with a total length of approximately 10 km. Gold is fine-grained, and fineness is 500 to 600. A few nuggets occur, ranging up to 10-20 g. Gold is associated with quartz and adularia. Local bedrock consists of volcanic rock and hydrothermally altered siliceous rock. Placer deposits are derived mainly from the Belogorsk lode deposit that consists of late Paleogene gold-bearing altered siliceous rock with quartz-adularia alteration. Deposits are mined out. N.V. Ognyanov in Nokleberg and others, 1997. Russia N 54 03 53 02 26N 53.0405555555556 138 46 04E 138.767777777778 Au Kherpuchinskoe Placer Au Medium 700-850 District contains stream deposits along the Kherpuchi River and tributaries of the Somni spring (a tributary of the Amgun River). Placer deposits occur both in main and branch valleys along a distance of over 25 km. Gold is fine- or medium-sized, and high-grade. Vein quartz occurs in the gold-bearing sand. Gold is derived from small quartz veins and veinlets that contain gold and arsenic sulfides. Local bedrock consists of Early Cretaceous sandstone and siltstone. N.V. Ognyanov in Nokleberg and others, 1997. Russia N 54 04 52 36 45N 52.6125 139 28 35E 139.476388888889 Au Oktyabrskoe Placer Au Small 800-850 District contains alluvial-colluvial placers that the valley and slopes of the Pochel River (a tributary of the Amgun' River). Gold is concentrated largely in a weathering crust developed in a gold-bearing, mid-Cretaceous tonalite that contains quartz streaks with As and Pb sulfides. Rock-forming minerals from the tonalite and veined quartz are abundant in gold-bearing sands. Gold is fine- and medium-grained. N.V. Ognyanov in Nokleberg and others, 1997. Russia N 54 05 54 05 51N 54.0975 142 55 26E 142.923888888889 Au Schmidtovskoe Placer Au Small 800-900 District contains small placers, 30 to 10 m wide and up to 1000 m long. Gold occurs throughout a 3 to 4 m thick section of modern alluvium, although a 1.2 to 1.4 m thick zone near bedrock is the richest. Alluvium consists of ultramafic and mafic rock that are altered to chlorite, zeolite, and albite. Heavy-mineral concentrates contain chromite, magnetite, pyrite, and siderite. Gold grains are normally larger than 0.5 mm. Some gold forms intergrowths with albite and magnetite. The bedrock source of the placer deposits is gold-bearing zeolite-epidote-prehnite-chlorite and albite-pyrite-chlorite rock that occurs at the contact with serpentinized ultramafic rock and propylitic altered gabbro. Source rock contain up to 2 g/t Au. V.D. Sidorenko, 1977. Russia O 51 01 56 28 00N 56.4666666666667 122 01 00E 122.016666666667 Au Nizhnenyukzinsky district Placer Au Inferred reserves of 35 tonnes Au. District is the largest in the Russian Far East and occurs north of the Mesozoic Chilchinsky granitic pluton that intrudes Early and Late Archean metamorphic rock. Pluton consists of anorthosite (Kalar pluton), syenite (Tassky pluton), and granite (Sedolchinsky and Cheremkhalaksky plutons). In the northern part of the district, zones of retrograde metamorphism occur along the Stanovoi and Yuzhnoaldan regional faults that occur between the Aldan shield (Siberian Craton) and Nora-Sukhotin terrane. Only a few placers occur. The total potential (mined + proven reserves + inferred reserves) comprises 2% of the total potential of the Amur Region. Darynmakitsky placer deposit, the best-studied deposit in the district, was discovered in 1929 and was mined during the 1930s. Gold occurs for a distance of 10 km. The placer averages 60 m wide, alluvium ranges from 4 to 6 m thick, and gold-bearing gravel occurs in the lower 2 m of the alluvium. Average grade is 450 mg/m3 Au. The richest part of the placer occurs near bedrock and consists of eluvium, with gold-bearing sand filling fractures. Lode sources for the placer are presumably quartz veins and zones of cataclastic and weakly altered sulfide-bearing rock, both closely related to the Stanovoi fault zone. V.D. Melnikov, written commun., 1979. Russia O 53 01 58 37 01N 58.6169444444444 137 11 02E 137.183888888889 Au Kurun-Uryakh Placer Au Average grade of 3.2-4.5 g/m3 Au. Production of about 12 tonnes Au. Consists of a buried placer that is 5 km long and 0.2-0.4 km wide. Depth of overburden ranges from 5-30 m. Gold-bearing bed is 0.2 m thick, and grade is 3.2-4.5 g/m3. Interpreted as derived from the Malyutka gold-quartz deposit. District includes several small deposits. P.P. Smirnov, written commun., 1961; N.L. Kobtseva, written commun., 1988. Russia O 53 02 57 36 14N 57.6038888888889 134 38 15E 134.6375 PGE Au Kondyor Placer PGE Major Production of 3 tonnes PGE in 1993. Second largest placer PGE producer in Russia Mining since about 1988 Consists of an alluvial placer that occurs in the north-flowing Kondeur River valley. Richest placer occurs in a 10 km-long paystreak that averages 100 m wide. Placer platinum occurs in 6-8 m thick fluvial gravels on or just above bedrock. Typical platinum grains range from 0.5 mm to 1 cm in diameter. A 4.3 kg iso-ferro-platinum nugget was recovered recently. Iso-ferro-platinum is commonly combined with chromite. Small inclusions of Ir-Os minerals occur in larger platinum nuggets. Gold comprises 10% of total production, and occurs in cubic crystalline form with individual cubes up to 1 cm across. Gold contains up to 40% Cu and up to 10% Pd. Deposit was discovered in the 1970's. Minor production occurred in early years from small, high-grade placer pockets. Present production is from placers near the head of the drainage. Kondyor placer deposits are derived from lode deposits in the Kondyor zoned mafic-ultramafic complex. V. Molchanov and V. Sapin, written commun., 1993. Russia O 53 03 56 27 00N 56.45 132 54 00E 132.9 Ti REE Sash-Yular Placer Ti Average grade of 8.2 kg/m3 monazite, 15.6 kg/m3 ilmenite, 5 kg/m3 rutile. Reserves of 82,000 tonnes monazite with 820 tonnes Th, 19,200 tonhnes REE, and 88,000 tonnes Zr. Reserves of 849,000 tonnes ilmenite. No summary provided. Onikhimovskiy and Belomestnykh, 1996. Russia O 54 01 59 44 21N 59.7391666666667 143 26 34E 143.442777777778 Au Okhotsk Placer Au Average grade of 3 to 47 g/m Au. Production of about 15 tonnes Au through 1930. Most deposits mined out. 720-850 District discovered in 1829 and covers an area of about 140 sq. km. About ten placer deposits occur in the district. Nearly all are exhausted, and a few are mined at the present. Placer deposits occur in valleys; some are buried. Gold-bearing beds range from 0.12 to 14 m thick and up to 2,000 m long. Gold nuggets to 1 kg occur. Bedrock sources for placer deposits are unknown. Examples of placer deposits are at Zolotoi Creek and Raasvet Creek/Gusinka Creek. Zolotoi Creek placer deposit is a buried placer that is 2.9 km long and averages 54 m wide. Depth of overburden is 17 m. Two placer beds occur. The lower bed is 1.8 m thick and directly overlies a weathered crust developed on Cretaceous rhyolite. The upper placer bed is 2.4-5.4 m thick and overlies a false clay bedrock. Gold grade ranges from 2.9-9 g/m3. Gold is mostly fine-grained, with an average size of 0.4 mm. Gold fineness is 717-770. Gold nuggets are scarce but nuggets up to 129 g are recovered. Bedrock sources are unknown. Gold production is about 2 tons. Raasvet Creek and Gusinka Creek placer deposits are 600 m long and range from 30-100 m wide. The gold-bearing bed is 0.2-1.8 m thick, with about 4 to 10 m of overburden. Gold grade is 1.5-42.7 g/m3. Gold is coarse-grained. One gold nugget with minor quartz, weighing nearly 1 kg, was found. Gold fineness is 820-850. Bedrock sources are unknown. Production of 233 kg gold. P.P. Smirnov, written commun., 1962; N.L. Kobtseva, written commun., 1988. Russia P 54 01 61 00 30N 61.0083333333333 138 08 55E 138.148611111111 Au Allakh-Yun Placer Au Average grade of 1 to 10 g/m3 Au. Production of about 23 tonnes Au between 1940 to 1964. 813-844 District contains about 150 placer deposits, mostly in the Allak-Yun and Yudoma River basins. Small channel-fill placers occur in the northern part of area. Medium-size and some large valley placers and sparse bench placers occur in the middle part of district. Flood-plain placer deposits and some channel-fill deposits occur in southern part of district. Gold placers occur in interglacial deposits. Gold-bearing beds range from 0.5 to 3 m thick. Depth of overburden ranges up to 100 m. The highest-grade gold placers occur in the southern part of the district. Placers range from 1 to 10 km long and up to 200 m wide. Gold nuggets to 1 kg weight occur. Bedrock sources are Au quartz vein deposits. Individual placer deposits are at Zhar Creek, Yur-Duet, and Brindakit. Zhar Creek placer deposit is 7 km long. Average thickness of gold-bearing bed is 1.4 m and the overburden is 3.5 m thick. Fine gold (particles less than 1 mm in size) comprise 87% of all gold. Five percent of gold occurs as nuggets weighing 10 to 200 g. Bedrock source of this placer is Au quartz veins. 2.7 tonnes gold produced between 1940 to 1964. Yur-Duet and Brindakit placer consist of several auriferous placer zones. Largest is 10 km long and from 10-300 m wide. Gold grade is 1-7.3 g/m3. The gold-bearing bed is 0.2-3.2 m thick, with 20-30 m overburden. The average size gold particles is 1-2 mm, fineness 813-844. Gold nuggets to 1,050 gm were common at the Yur placer deposit. About 20 tonnes of gold produced between 1940-1964. P.P. Smirnov, written commun., 1961; V.I. Korostelev, written commun., 1963; Trushkov, 1971; N.L. Kobtseva, written commun., 1988. Russia Q 52 01 65 53 47N 65.8963888888889 129 45 11E 129.753055555556 Au Verkhoyan Placer Au Average grade of up to 15 g/m3 Au. 703-766 District contains several small valley and ravine placers. Deposits range up to 4 km long and 50 m wide. Bench placers also occur. Placer deposits are buried by 1-3 m of alluvium. Gold-bearing beds are less than 2 m thick. Gold occurs irregularly in radial and ore pocket forms. Erosion-caused truncation is minor and does not indicate a wider occurrence of placer deposits. The Chochimbal Creek placer deposit is typical of deposits in this district. Chochimbal deposit occurs as a valley placer that occurs in the upper reaches of Chochimbal Creek. The deposit is about 4 km long and 10-50 m wide. Average depth of overburden is about 2 m. The gold-bearing bed is 0.6-3.6 m thick, averagely 1.71 m. Gold grade ranges up to 15 g/m3. Near bedrock, gold particles are very large (up to 10.1 mm) and gold nuggets range up to 150 g and constitute 39% of the gold. Bedrock sources are small Au quartz veins and, probable Au polymetallic veins. The deposit is exhausted. Trushkov, 1971; Ivensen and others, 1975; Yu.A. Vladimirtseva, written commun., 1985. Russia Q 53 01 67 23 09N 67.3858333333333 134 11 17E 134.188055555556 Sn Verkhnegilyui Placer Sn Ranges up to 1,169 g/m3 cassiterite. District is divided into the Apsakan, Laprin, Malogilyui, and Bryantin subdistricts. Occurs in the axial part of the Stanovoi anticline. Gold-bearing areas within the district occur close to the Mesozoic Tynda, Dyupkoisky, Unakhinsky, and Mulmugin plutons. Apsakan subdistrict occurs in basins at the headwaters of the Verkhny Larba, Nizhny Larba, and Sredny Larba Rivers, along the NW margin of the Tynda pluton that intrudes Proterozoic granite and Archean metamorphic rock. The ratio between the number of lode deposits and placer deposits in the Apsakan subdistrict is 3:2. This is the only subdistrict in the Verkhnegilyui district, where the number of lode deposits is greater than the number of placers. More than 25 lode deposits occur, and all are associated with zones of hydrothermally altered metamorphic rock. Every placer or low-grade placer deposit overlies a lode deposit. The Larba River placer is the largest in the subdistrict. It was discovered in 1929, and was prospected in the 1930's and 1940's. It includes several small creek placers with a total length of 21 km. Deposit starts in the middle of Yanvarsky Creek, continues along the valleys of the Khorogochikan Creek (from the mouth of the Yanvarsky Creek to the confluence with the Sredny Larba Creek), and terminates 4 km downstream from the mouth of Gromkachi Spring. Au content is extremely uneven. Native gold occurs in the lowest bed of pebble deposits and in the upper part of underlying eluvium. Terraces are not studied. Estimated reserves are 2003 kg. Laprin subdistrict occurs in predominantly Late Archean metamorphic rock between the Mesozoic Tynda and Dyupkoisky plutons. Cretaceous rock of the Tiptursky volcanic field occur sin the NE part of the subdistrict. Only a small portion of the subdistrict is mined. At the beginning of the previous century, only placers of the Khitrusha, Maksimovka (Lapri River basin), and Bugorikty (Mogota River basin) Rivers were mined. Placer mines are being planned for the Malinovy, Lysovsky, Tsyganka, and Medvezhi Creeks. The largest placer in this subdistrict, the Khitrusha valley-type deposit, occurs in the Khitrushka Creek that is a tributary of the Lapri River. The deposit has been mined from 1928 to 1950, and there is evidence of earlier operations (presumably 1880-1900). About 4 km of the placer deposit are mined. The placer averages 60 m wide and 3.4 m thick. Gold grade is 297 mg/m3 and fineness of native gold is 900. Inferred reserves are 1200 kg (V.D.Melnikov, written comm., 1990). Malogilyui subdistrict is related to Cambrian metamorphic rock between the Dyupkoisky granodiorite pluton and the Mesozoic Unakhinsaky granite-granodiorite pluton. Placers of the Malogilyui subdistrict were previously mined in valleys of the Des (Kamenisty), Olongo (Somnitelny, Marmontovsky), and Maly Gilui (Karlovsky, Kruglovsky, and Kurnosovsky) Rivers. The potential of the area is about 19 tonnes gold. Bryantin subdistrict occurs between the Unakhinsky and Mulmugin plutons. Au-Cu-Mo porphyry deposits occur in the area along with numerous other lode gold deposits. Additional lode gold deposits are associated with hydrothermally altered metamorphic rock. All known lode deposits have related placers deposits. Total placer potential of the subdistrict is 12 tonnes gold. P.O. Genkin and E.A. Sinuygina, written commun., 1973; M.E. Gorodinsky, written commun., 1991. Russia Q 53 02 66 42 02N 66.7005555555556 137 28 59E 137.483055555556 Au Adychan Placer Au Average grade of 0.2 to 34.4 g/m3 Au. 475 to 960 District contains more than 60 placer deposits that are mostly small and non-commercial. Deposits include buried placers in neotectonic depressions (as at Nadezhnoe), and high terrace and valley placers. Deposits in depressions are Miocene to Pliocene. Modern deposits occur on spits. Placer deposits range from 700 to 12,700 m long and 5 to 1,000 m wide. Overburden of glacial drift ranges from 0.4 to 70 m thick and gold-bearing layers are 0.2 to 7 m thick. Gold-bearing gravels in each district occurs as descrete paystreaks of two morphologies, highly elongate and sub-equant. Gold sometimes occurs in rich pockets. Gold particles range in size, and nuggets up to 580 g occur. Associated minerals are cassiterite, wolframite, scheelite, and cerolite. Twenty percent of placers were mined, and some are currently being worked. Lode sources are Au quartz veins and mineralized shear zones and, less commonly, gold-REE deposits related to granitoids. Major deposits are at Adychanskoe, Adycha, Nadezhnoe, and Lazo. Adychanskoe deposit occurs on the Adycha River terrace 75 to 100 m above river level. Deposit is 12.4 km long and up to 1 km wide. The gold-bearing bed is 0.3-1.9 m thick. Au grade is 0.72 to 11.82 g/m3. Gold particles differ in size and roundness. Gold forms intergrowths with quartz, chlorite, and galena. Gold fineness is 832-844. Adycha deposit occurs on a large spit in the Adycha River. Deposit is about 2 km long, and the gold-bearing bed is 0.4 to 2 m thick. Au grade is 0.01 to 30 g/m3. Gold particles are well-rounded, 2-5 mm in size; gold fineness is 740-810. Gold distribution is irregular, radial, locally in ore pockets. Nadezhnoe deposit is about 3 km long and occurs within a graben. The gold-bearing bed is 0.6-3.6 m thick and occurs below 70 m of overburden. Gold grade is 2.62-34.4 g/m3. Gold particles average 1-6 mm, and gold fineness is 640-880. Associated minerals are cassiterite, scheelite, wolframite, magnetite, ilmenite, and arsenopyrite. Bedrock sources are Au quartz and gold-REE veins and zones, including the Delyuvialnoe deposit. Lazo deposit is a typical valley placer deposit, is 6 km long, and displays a narrow radial distribution. Gold-bearing bed is 1.33 m thick and buried 0.2 to 1.3 m deep. The commercial part of the deposit is 2-6 m wide. Gold particles are 2 to 12 mm, and gold nuggets up to 5.3 g occur. Bedrock source is the Lazo Au quartz vein deposit. Rozhkov and others, 1964; Trushkov, 1971; Yu.A. Vladimirtseva, written commun., 1985. Russia Q 54 01 64 33 24N 64.5566666666667 142 49 34E 142.826111111111 Au Verkhneamursk Placer Au Average grade of 2.6-650 g/m3 Au. 730-969 District consists of the Solov'ev and Urusha-Oldoi subdistricts. The largest placer in the Urusha-Oldoi subdistrict is the Khaiktinsky placer, and the largest placer in the Solov'ev subdistrict is the Dzhalinda placer. Dzheltulak subdistrict includes the valleys at the headwaters of the Bolshoi Dzheltulak River and the middle part of the Tynda River that are both western tributaries of the Gilyui River. This lode and placer district has been known for a long time but only placers have been mined. A major fault in the subdistrict, the Dzheltulak shear zone, separates the Getkansky and Kurbatovsky Proterozoic plutons to the north from the Anosov pluton in the south. Intermittant mining has occurred on placers of the Ilichi, Baldyglia, headwaters of Bolshoi Dzheltulak, and Burpaly Rivers; and on numerous placers of the Tynda River, tributaries of the Burpaly River, and headwaters of the Bolshoi Dzheltulak River. All placers are spatially associated with the Dzheltulak shear zone, a major fault that separates the Getkansky and Kurbatovsky Proterozoic plutons to the north from the Anosov pluton in the south. The largest placer in the Dzheltulak subdistrict is on the Bolshoi Dzheltulak River that is a southern tributary of the Gilyui River, and contains an alluvial valley-type placer that was discovered in the period 1893-96. Approximately 1.3 tonnes gold were mined by 1959. In 1954-58, the placer reserves were recalculated based on use of a 250-liter capacity dredge that started operating in 1980. At the beginning of dredge operations, the placer was 22 km long, 114 m wide, and the gravel deposit 4 m thick. Average content of native gold is 228 mg/m3, proven reserves are 2474 kg, and the fineness of gold is 887. The deposit is now 70% mined out. The Khaiktin placer deposit occurs in the Bolshoi Oldoi River valley, a large tributary on the north side of the Amur River. Placers in the Khaikty River valley have been known since the early 1900's. The Konstantinovka and Orogzhan placers were intensely mined. Based on questionable data, over 2000 kg Au was produced from the Khaikta River valley through 1925. The Khaiktin deposit is a valley type, is 28.8 km long, and occurs along the flood plain of the Bolshoi Oldoi and Khaikta Rivers. The width of the flood plain ranges from 500 to 1000 m and alluvium thickness is less than 6.4 m. Gold-bearing sediments contain pebbles with sand, gravel, ooze, clay, and boulders. Bedrock consists of gneiss, granite, amphibolite, and diorite with a well-developed weathering crust. Bedrock has a smooth upper surface, with a relief of 0.5 to 1.2 m. Gold fineness is very fine (0.25 mm) 6.47%, fine (0.25-1.0 mm)-41.6%, medium (1.0-3.0 mm)-38.81%, and large (more than 3 mm)-13.12%. Average fineness is 876. The gold-bearing bed is 0.6 to 3.6 m thick. Nuggets are not found. Thirty-four percent of the area of the deposit has permafrost. The deposit was explored by prospect pits and drill holes across an area of 400 x 20 m. Only a small portion (3.5%) of the placer deposit is mined. The Dzhalinda placer deposit is the largest in the Amur Region. Total production exceeds 120 tonnes gold. The deposit has numerous lode sources, including the Kirovka gold-quartz deposit associated with granodiorite intrusions and metamorphic gold occurrences hosted in greenschist. The deposit is over 45 km long, averages 250-300 m wide, and alluvial deposits are 5 m thick. The placer was discovered in 1867 by N.P. Anosov, and was the first economic placer to be mined in the Verkhnee Priamur'e. Deposit was mined by hand until 1929 (production of 39 tonnes Au). Dredges have been used since from then through the present. Gold occurs throughout the section and maximum grades occur near the bedrock. The fineness is high and averages 940. Placer deposits of the Yankan River are derived from the Kirovka lode deposits. Placer deposits have been known since 1867 and have been mined since 1871. The placers are over 15 km long, average 350 m wide, and have alluvium about 6 m thick. Gold fineness is 930. The Nagim placer deposit occurs in the western part of the Solov'evsky subdistrict, and is a very thick gold-bearing deposit (up to 50 m thick). B.V. Pepelyaev, written commun., 1964; Trushkov, 1971; Yu.A. Vladimirtseva, written commun. 1987; Oleinikov, 1992. Russia R 53 01 70 20 02N 70.3338888888889 134 16 35E 134.276388888889 Au Kular Placer Au Average grade of 0.5-26 g/m3 Au. 391-962 District contains several placer deposit types, including buried Paleogene-Neogene placers that occur at the base of superimposed depressions, and small late Quaternary ravine placers. District contains about 10 known placer deposits of variable length and width. Gold-bearing beds are covered by up to 150 m of overburden. Gold particles are small in size (0.1-3.5 mm) and average 0.8-1 mm. Flattened gold particles predominate. Gold-bearing gravels form elongate zones. Valleys are up to 1,200 m wide and contain paystreaks up to 100 m wide. Equant and elongate weathering crusts up to 30-50 m thick are widespread. Most of the placers formed by water reworking of weathered rock during the early Oligocene. The bedrock sources of the placer deposits are Au quartz veins and zones, and Au-REE and Au-Hg deposits. Major deposits are at Kara-Onkuchak and Burguat. Kara-Onkuchak placer occurs in an ancient buried valley, consists of a gold-bearing bed up to 10-20 m thick, and is formed in an early Oligocene alluvial gravel with quartz pebbles (50%) cemented with light-gray sandy clay. Overburden is about 100 m thick. Average size of gold particles is 0.5-1 mm and fineness 795-815. Burguat bench placer deposit of early Pleistocene age occurs on an aggradation-denudation terrace that is 15-20 m above river level. Pay gravels consist of quartz pebbles (20%) and clastic rock of the Vekhoyan Formation. Gravels are cemented with argillaceous sand. Pay gravels are underlain by a weathering crust in the middle section of the river and by Miocene gravel in the lower reaches of the river. Some gold-bearing layers occur in the thalwegs of buried ancient valleys. Gold-bearing gravel beds range up to 10-15 m thick. Average size of gold particles ranges from 0.88 to 1.44 mm. Gold fineness is 680-886, with the maximum in the middle portion of the deposit. Ivensen and others, 1975; Samusikov and Sergeenko, 1974; Yu.M., written commun., 1963; Amuzinsky and others, 1988. Russia R 54 01 69 41 50N 69.6972222222222 140 21 57E 140.365833333333 Sn Polousnensky Placer Sn Grade ranges up to hundreds g/m3 cassiterite . District contains several tens of cassiterite-bearing zones. The Deputatskaya and Omchikandinskaya placer deposits are the most important. Placers in this district occur near granite intrusions and are closely related to bedrock sources. Placers occur close to bedrock. Sn placers are mostly alluvial, and more rarely are eluvial-diluvial. The most important Sn placers are associated with lode stockworks. Amount of cassiterite is variable, and may be associated with wolframite and sometimes with bismuth nuggets. Cassiterite is coarse and 40-50% is larger than 7 mm. Boulders of cassiterite occur. Example of deposits are at Deputatsky Creek and Omchikandya Creek. Deputatsky Creek deposit occurs in a broad valley with multiple, well-formed terraces. Overburden ranges from 3-4 m to 8 m thick. Distribution of cassiterite is rather regular. Within the mineralized layer, finer-grained cassiterite occurs in the upper portion, and coaster-grained cassiterite in the lower parts. Bedrock source is the Polousnensky lode deposit. Omchikandya Creek placer deposit occurs in a broad valley with multiple. well-formed terraces. Deposit forms a continuous wide band that completely fills the valley. The deposit is more than 3 km long and is either not overlain or overlain only by a few meters of overburden. The pay zone is 20-30 m thick. Minerals are cassiterite (larger than 7 mm fraction of 40-50%) and wolframite. Cassiterite to wolframite ratio of 2:1 to 3:1. Bismuth nuggets to 1 kg are common. Lode source is the Polyarny deposit. O.G. Epov and G.S. Sonin, written commun., 1964; Trushkov, 1964, 1971. Russia R 54 02 68 16 42N 68.2783333333333 141 38 40E 141.644444444444 Au Khatynnak-Sala Placer Au Grade ranges up to 10-15 g/m3 Au. District contains several gold placer deposits at several horizons. The placers are short. Gold is fine and platy. Placer gold occurs in gravel overlying Paleozoic limestone. One example is at Khatynnak-Sala Creek that occurs in a broad creek valley with multiple, well-developed alluvial terraces. The alluvial placer is 7.5 km long and about 90 m wide. The gold-bearing placer is 0.2-1.8 m thick. Gold has also accumulated in fissures and cavities in the Paleozoic limestone bedrock to depth of 1 m. The placer deposit is overlain by 5 to 8 m of overburden. Gold is fine and platy and often occurs in intergrowths with quartz and calcite. Gold is associated with zircon, ilmenite, magnetite, pyrite, galena, and chalcopyrite. O.G. Epov and G.S. Sonin, written commun., 1964; Trushkov, 1971. Russia