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Title Transition equilibria from the prehnite-pumpellyite to greenschist facies in the Karmutsen metabasites, Vancouver Island, B.C.
Creator/Author Cho, M. ; Liou, J.G.
Publication Date1985 Jan 01
OSTI IdentifierOSTI ID: 6612079
Report Number(s)CONF-8510489-
Other Number(s)CODEN: GAAPB
Resource TypeConference
Specific TypeJournal Article
Resource RelationGeol. Soc. Am., Abstr. Programs ; Vol/Issue: 17; 98. annual meeting of the Geological Society of America; 28 Oct 1985; Orlando, FL, USA
Research OrgStanford Univ., CA (USA)
Subject580300 -- Mineralogy, Petrology, & Rock Mechanics-- (-1989) ;580400 -- Geochemistry-- (-1989); BASALT-- METAMORPHISM;BRITISH COLUMBIA-- BASALT;BRITISH COLUMBIA-- HORNFELSES;BRITISH COLUMBIA-- SCHISTS;HORNFELSES-- GEOCHEMISTRY;HORNFELSES-- MINERALOGY;SCHISTS-- GEOCHEMISTRY;SCHISTS-- MINERALOGY; CALCITE;CHEMICAL COMPOSITION;EPIDOTES;EQUILIBRIUM;GEOLOGIC MODELS;MINERALIZATION;PARAGENESIS;PHASE STUDIES;ZEOLITES
Related SubjectALKALINE EARTH METAL COMPOUNDS;ALUMINIUM COMPOUNDS;ALUMINIUM SILICATES;CALCIUM CARBONATES;CALCIUM COMPOUNDS;CALCIUM SILICATES;CANADA;CARBON COMPOUNDS;CARBONATE MINERALS;CARBONATES;CHEMISTRY;IGNEOUS ROCKS;INORGANIC ION EXCHANGERS;ION EXCHANGE MATERIALS;IRON COMPOUNDS;IRON SILICATES;MATERIALS;METAMORPHIC ROCKS;MINERALS;NORTH AMERICA;OXYGEN COMPOUNDS;ROCKS;SILICATE MINERALS;SILICATES;SILICON COMPOUNDS;TRANSITION ELEMENT COMPOUNDS;VOLCANIC ROCKS
Description/Abstract Thermally-metamorphosed Karmutsen metabasites in NE Vancouver Island, B.C. expose a complete set of progressive mineral assemblages ranging from the zeolite to pyroxene hornfels facies toward the intrusive contact.^This study deals with characteristic mineral assemblages ranging from (i) prehnite (pr) + pumpellyite (pp) + epidote (ep), pr + pp + calcite (cc), and pp + ep + cc for prehnite-pumpellyite (PP) facies; through (ii) pr + ep + cc for prehnite-actinolite (PRA) facies; to (iii) actinolite (act) + ep + cc for greenschist (GS) facies.^Wairakite with a significant analcime component (wk76am24) coexists with epidote or Al-rich pumpellyite in one PP facies sample.^Mg-bearing epidote (up to 1.2 wt % MgO) pseudomorphic after pumpellyite often occurs as a transitional phase in the PRA facies rocks.^Mineral compositions of amygdaloidal assemblages from 21 samples were studied in detail.^Progressive changes in the compositions and assemblages of Ca-Al silicates are chemographically and theoretically interpreted, on the basis of the predicted P-T grid for the model basaltic system, CaO-MgO-Al/sub 2/O/sub 2/-Fe/sub 2/O/sub 3/-SiO/sub 2/-H/sub 2/O-CO/sub 2/.^Although the facies boundaries are gradational due to the multi-variance of the assemblages, two transition equilibria are established for the Karmutsen metabasites: (1) pp + qtz + CO/sub 2/ = pr + ep + cc + chl + H/sub 2/O for the boundary between PP and PRA facies; (2) cc + chl + qtz = ep + act + H/sub 2/O + CO/sub 2/ for that between PRA and GS facies.^At constant X/sub H20/, the former is a discontinuous reaction but the latter is of continuous type in the model system.^Phase equilibria together with the paragenetic and compositional data of Ca-Al silicates indicate that the PP to GS facies metamorphism occurred at: 14. kb < P < 1.8 kb and 250/sup 0/C < t < 350/sup 0/C.
Country of PublicationUnited States
LanguageEnglish
FormatPages: 545
System Entry Date2001 May 13

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