Geological Survey Circular 217 Preliminary Report on the White Canyon Area, San Juan County, Utah

Ore criteria

Although the origin and local controls of the copper-uranium ores are still matters for debate, experience both in the White Canyon area and elsewhere in the Colorado Plateau shows that certain physical and chemical features are characteristic of mineralized areas, and that the presence of one or more of these features may indicate concealed ore bodies.

The following section, intended to aid future prospecting in the White Canyon district, is a brief discussion and evaluation of the features associated with ore deposits. These features are grouped in three categories: first, features observed only in mineralized areas; second, features apparently associated with some deposits but observed also in unmineralized areas; and third, features that are associated with deposits in other parts of the plateau but that show little relation to the ore deposits in White Canyon.

Features observed only in mineralized areas

1. Visible uranium minerals.

2. Sulfide minerals.

3. Secondary copper sulfates and carbonates.

4. Alunite(?).

5. Hydrocarbons.

Visible uranium minerals.--Visible secondary uranium minerals, zippeite, johannite, and torhernite, were noted in the following claims (in order of their significance): Happy Jack, Posey, Hideout, Frey no. 4, White Canyon no. 1, Yellow John, Bell, Jerry, North Point, Gonway, Scenic no. 2, Scenic no. 4, Sunrise no. 1, and Ace of Hearts (fig. 2). These secondary uranium minerals may indicate the presence of a uranium-bearing sulfide deposit beyond the oxidized zone.

Sulfide minerals.--Sulfide minerals chalcocite, bornite, covellite, pyrite, arsenopyrite, chalcopyrite, galena, and sphalerite were noted in the following claims (in order of their significance): Happy Jack, Posey, Hideout, Frey no. 4, Yellow John, Bell, Found, Jerry, W. G. J. N. W., Scenic no. 2, Woodenshoe(?), Jacobs Chair, and Bankrupt (fig. 2). These sulfide minerals may indicate the presence of a uranium deposit.

Secondary copper minerals.--Disseminated secondary copper minerals may indicate the presence of a uraniferous-sulfide body. Near the surface these minerals are principally the hydrous sulfates and carbonates, and are found disseminated and as fracture coatings.

Alunite.--A white clay mineral, identified by X-ray diffraction as alunite, occurs in some of the uranium deposits, both along fractures and along bedding planes. Alunite is common in the North Point, Gonway, and Woodenshoe(?) claims (fig. 2).

Hydrocarbons.--Hydrocarbons were noted in veinlets and as globules in some of the copper-uranium deposits in the White Canyon district. The following claims, arranged according to their significance, contain probable hydrocarbons: Happy Jack, Posey, Hideout, Woodenshoe(?), and Four Aces (fig. 2). The hydrocarbons are commonly uraniferous, and may indicate a favorable ore zone.

Features observed at many deposits but seen in unmineralized areas as well

The association of several of these features may indicate an area favorable for prospecting.

0. Bleaching and alteration of the Moenkopi formation.

1. Fracturing.

2. Iron and manganese staining.

3. Carbonized wood fragments and vegetal material.

4. Channel filling.

5. Jarosite(?).

6. Facies change within the Shinarump conglomerate.

Bleaching and alteration in the Moenkopi formation.--Bleaching and alteration in the Moenkopi formation below the Shinarump conglomerate was noted at some of the more favorable uranium prospects. The following claims showed considerable bleaching and alteration associated with fracturing in the Moenkopi: Happy Jack, Gonway, North Point, and Found (fig. 2). This bleaching, however, is not present under many deposits and its absence does not make an area favorable. Little or no bleaching was noted at the Frey no, 4 and Woodenshoe(?) claims.

Fracturing.--Close fracturing of the sandstones and conglomerates of the Shinarump is in some places a favorable criterion for prospecting. The fractured zones associated with the copper-uranium bodies generally show a considerable shattering of the rock.

Iron and manganese staining.--A red, brown, and black coating commonly occurs on fractures and outcrop surfaces over a large portion of the sandstones and conglomerates of the Shinarump and Chinle formations. However, iron and manganese staining is especially common near some areas showing considerable sulfides, and secondary copper and uranium minerals.

Carbonized wood fragments and vegetal material.--Carbonized wood fragments and vegetal material are relatively abundant in the Shinarump conglomerate. Many of these carbonized remains, especially the charcoal fragments, are highly uraniferous, and may suggest a favorable area for subsurface prospecting. Other outcrops containing carbonized wood are not radioactive.

Channel filling.--Many channels are cut into the Moenkopi formation and are filled by the Shinarump conglomerate, especially in upper White Canyon. Only a few of them, however, contain appreciable amounts of uranium or copper minerals. Included in this group are the Posey, Hideout, Bell, Yellow John, Frey no. 4, and Scenic no. 4 claims (fig. 2).

Jarosite(?).--Yellow jarosite(?) coats many crop surfaces of the Shinarump conglomerate and is commonly associated with a gray silty sandstone. This mineral is present in many of the uranium deposits, but it has also been noted where no radioactivity could be detected.

Facies change within the Shinarump conglomerate.--Conglomerates and sandstones of the Shinarump conglomerate commonly contain clay, shale, and siltstone lenses that are mildly radioactive, but generally these lenses are low-grade and too small to produce any commercial uranium ore.

Features not apparently related to ore deposits

1. Massive sandstone.

2. Conglomerate.

3. Hydrous mica.

4. Freckled limonite.

Four criteria have been used as prospecting guides in other uranium-bearing areas. In the White Canyon area they bear little relation to the ore bodies and are considered by the writers to have little importance in finding concealed uranium deposits.