Genetic Environments of High-magnesian andesite and Related Rocks.

对四国岛东北部、野户半岛和九州西北部的高镁安山岩和小川群岛的玻安岩进行了地质、岩石学和化学研究。四国东北部的高镁安山岩(蛇绿岩类)可能是来自水化地幔橄榄岩的原生安山岩，但源区可能受到俯冲沉积物的强烈影响。诺托半岛和九州西北部的铜辉安山岩可能是由原始玄武岩和英安岩或流纹岩岩浆混合而成。小川岛玻安岩的微量元素组成具有低HFSE和较高的碱含量，具有中等碱土的特征。这种富集性(例如，高Rb/Ba和高Rb/La比值)在目前研究的高镁安山岩中很常见，这是岛弧理论的诊断。1.一些火山岩的大气熔融研究提供了新的氧逸度计。利用斜长石与岩浆之间的镁-铁分配关系。氧逸度计在对数fO_2=-6--11时灵敏，可广泛应用于斜长岩-斑岩型火山岩。

Gelogical, petrographical and chemical studies were carried out on high-magnesian andesites of northeast Shikoku, Noto Peninsula, and northwest Kyushu, and boninite of Ogasawara Islands. High-magnesian andesite (sanukitoid) of northeast Shikoku may repesent primary andesite derived from hydrated mantle peridotite, though the source area may be aeverely affected by subducted sediments. Bronzite andesites of Noto Peninsula and NW Kyushu were probably formed by mixing of primitive basalt and dacite or rhyolite magmas. Trace element composition of boninite of Ogasawara Islands is characterized by low HFSE and rather high alkali contents with intermediate alkali earths. Such enrichement (e.g. high Rb/Ba and Ba/La ratios) is common among the high-magnesian andesites presently investigated, and is diagnostic from island arc tholeiites.1-atmosphere melting studies of some volcanic rocks afforded a new oxygen fugacity meter. It uses Mg-Fe partition relationship between plagioclase and magma. The oxygen fugacity meter is sensitive at ca. log fo_2=-6 - -11, and may have wide applicability to plagioclase-phyric volcanics.