Genetic Environments of High-magnesian andesite and Related Rocks.

对四国东北部、诺托半岛和九州西北部的高镁安山岩和小笠原群岛的玻安岩进行了地质、岩石和化学研究。四国东北部的高镁安山岩（佐怒岩类）可能是由水化地幔橄榄岩形成的原生安山岩，但源区可能受到俯冲沉积的强烈影响。诺托半岛和九州西北部的青铜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的。小笠原群岛玻安岩的微量元素组成以低高场强、高碱含量和中碱土金属为特征。这种富集（如高Rb/Ba和Ba/La比值）是常见的高镁安山岩目前调查，是诊断岛弧拉斑玄武岩。1-大气熔融研究的一些火山岩提供了一个新的氧逸度计。利用斜长石与岩浆的Mg-Fe配分关系。氧逸度计在约100 ℃时灵敏。logfo_2 =-6 --11，对斜长斑状火山岩具有广泛的适用性。

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.