冲绳海槽浮岩中斑晶矿物结晶的P-T条件

本文利用多种地质温度计估算了冲绳海槽浮岩中斑晶矿物的结晶条件。结果表明:灰白色浮岩中的橄榄石、辉石、基性斜长石、磁铁矿等是在大约890℃和大约三十几km深的条件下结晶的。这些矿物之所以存在于SiO2含量高达70％的酸性浮岩中是由于在岩浆喷出地表之前发生了岩浆的混合作用。根据斑晶矿物的结晶深度,推测灰白色浮岩的初始岩浆来自地幔的熔融。

THE CRYSTALLINE TEMPERATURE AND PRESSURE OF PHENOCRYSTS OF THE PUMICE IN THE OKINAWA TROUGH

There are two types of pumice in the Okinawa trough, one is greyish and the other is black. It has been noticed that there are phenocrysts of basic plagioclase (maximun of An is 89%) , pyroxene, titanomagnetite, hyalosidorite in the greyish pumice of which the content oi SiO₂ is about 70%, but almost all of phenocryst plagioclases in the black pumice are potassium andesine and the content of SiO₂ is about 59%. The crystalline temperature and total pressure of phenocrysts have been calculated by means of irontitanium oxide geothermometer, bi-pyroxene geothermometer and plagioclase geothermometer in this paper.