Geological Studies on the Dolomite Deposits of Chichibu Terrain

概要

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Dolomite deposits of western Shikoku are distributed in some definite stratigraphic and geotectonic zone. They are classified into the following group.<BR>1) Siliceous dolomite deposits of the northern zone of upper Carboniferous in age. These deposits are associated with red tuff, red chert, and other clastic sediments of volcanic materials.<BR>2) Some workable dolomite deposits of the southern zone of lower Triassic Uonashi formation, independent of volcanic activities.<BR>Chief factors of the formation of dolomite are temperature, pH, Eh and concentration of Mg-ion in the sea-water of geosynclinal basin. These factors are related to some paleogeographical environments, such as submarine volcanism (Northern zone) and development of shallow sedimentary basin of nearshore line (Southern zone).<BR>Chemical compositions of mineral dolomites, mechanism of dolomitization, deformation and recrystallization of ores, and relation of dolomite bed to other submarine sedimentary ore deposits are also discussed in this paper.
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