Mode of occurrence and significance of jadeite in the Kamuikotan metamorphic rocks, Hokkaido, Japan |
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| Authors: | MASASHI TAKAYAMA |
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| Institution: | Department of Geology and Mineralogy, Faculty of Science, Kyoto University, Kyoto 606, Japan |
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| Abstract: | Abstract In the Kamuikotan zone, jadeite occurs in pelitic rocks, in metaplagiogranites, in veins in amphibolites and mafic sedimentary rocks, and in jadeite-albite rocks. In the first and second types, jadeite is associated with quartz, and is often in direct contact with it. However, such rock-types never occur as part of the coherent metamorphic sequence, but are found only as exotic blocks enclosed in serpentinite. Thus, jadeite + quartz-bearing assemblages are not regarded as representative of the Kamuikotan metamorphism. Lawsonite and aragonite, however, commonly do occur in the Kamuikotan metamorphic rocks, and this metamorphism belongs to a subfacies of the lawsonite-albite facies, in which aragonite is stable. The serpentinite matrix which carried jadeite + quartz-bearing pelites and metaplagiogranites into the metamorphic sequence is interpreted as a tectonic rather than a sedimentary melange. |
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| Keywords: | Key-words: jadeite + quartz-bearing assemblages Kamuikotan metamorphic rocks Japan tectonic inclusion |
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