Publication Type:
Journal ArticleSource:
Ganseki Kobutsu Kosho Gakkai-Shi = Journal of the Japanese Association of Mineralogists, Petrologists and Economic Geologists, Nippon Ganseki Kobutsu Kosho Gakkai, c/o: Tohoku Daigaku Rigakubu, Sendai, Japan, Volume 82, Number 12, p.419-432 (1987)ISBN:
0021-4825Keywords:
Asia, chemical composition, Far East, fractional crystallization, gabbros, granites, granodiorites, igneous rocks, intrusions, Japan, major elements, mineral composition, petrography, Petrology, plutonic rocks, plutons, Trace elementsAbstract:
Geological, petrographic, and geochemical studies were carried out on the Batow pluton, a small gabbroic body; chemical analyses of 17 host rocks, 7 clinopyroxenes and 7 amphiboles are given. The body has a wide compositional range from melagabbro to granodiorite (42.8-62.7 wt.% SiO (sub 2) ). The rocks have similar features to calc-alkaline magnetite-series I type plutonic rocks and are rich in lithophile elements, comparable to the shoshonite rock association. The calculated crystallization path and petrographic observations suggest that the wide compositional variation results mainly from amphibole- and plagioclase-dominated fractionation of a gabbroic magma with minor fractionation of clinopyroxene, biotite and K-feldspar. This fractionation occurred at a shallow crustal level, but deeper than 2 kbar, before upward migration. The granitic rocks rich in amphibole (<=39%) with minor amount of biotite (<4%) formed at a higher water vapour P and lower T than the early-crystallized gabbros. The mineralogy of the gabbroic rocks suggests that water vapour P increases rapidly during crystallization of the gabbroic melt. This rapid increase of vapour P may be due to the intrusion of H (sub 2) O-saturated granodiorite magma to the gabbroic melt.
Notes:
GeoRef, Copyright 2018, American Geological Institute.<br/>1988-043185<br/>Batow Pluton<br/>central Japan<br/>Yamizo Mountains
