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Study on the Tertiary Volcanic Rocks in the Izu-Mariana Arc

伊豆-马里亚纳岛弧第三纪火山岩研究

基本信息

批准号：
01540660
负责人：
SHIRAKI Keiichi
金额：
$ 1.09万
依托单位：
Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

1. Study on the Tertiary volcanic rocks in the Bonin Islands.(1) Sheeted dike complex at Ishi-ura on the east coast of Chichi-jima.The dikes and associated pillow lavas are composed mainly of clioenstatite-bearing boninites, which are the most primitive and undifferentiated among the Bonin Island boninites. This confirms the early suggestion that the parallel dike swarm on Ishi-ura, located at the lowest of the pillow lava sequences in Chichi-jima, represents a part of the sheeted dike complex common in many ophiolites.(2) Augite boninites in the Tatsumiwan area of southeastern Chichi-jima.The augite boninites contain augite phenocrysts attaining the highest Mg value 89.3, most magnesian so far reported from the Bonin Island boninites. These rocks crystallized augite prior to orthopytoxene and belong to cpx-HMA, which is the first discovery from the Bonin Island boninites.(3) Island arc tholeiites similar to those occurring in Haha-jima in chemistry were discovered on John Beach in southwestern Chichi-jima.2. Comparative study on boninites and other magnesian andesites.(1) Trace elements in the Tertiary volcanic rocks from western Setonaikai.The Setouchi magnesium andesites have remarkably high Rb, while Sr is rather low. The Setouchi volcanic rocks form by addition of water containing Rb, K, Ba and Zr, as well as boninites.(2) Sanukitoids quite identical with the Setouchi sanukitoids in chemical and mineral compositions were discovered in Choshi of eastern Honshu Nagasaki of western Kyushu.

1.小笠原群岛第三纪火山岩研究。(1)位于知知岛东海岸石浦的席状岩墙杂岩。岩墙和相关的枕状熔岩主要由含斜方辉石的玻安岩组成，它是小笠原岛玻安岩中最原始和未分化的。这证实了早期的建议，石浦平行岩墙群，位于最低的枕状熔岩序列在秩岛，代表了一部分的席状岩墙复合体常见于许多蛇绿岩。(2)产于日本秩知岛东南部达见湾地区的镁玻安岩，其镁含量最高，为89.3，是迄今为止小笠原岛玻安岩中镁含量最高的。这些岩石在辉石之前结晶，属于cpx-HMA，这是在小笠原岛玻安岩中的首次发现。(3)在秩次岛西南部的约翰海滩发现了化学成分与羽羽岛相似的岛弧拉斑玄武岩。玻安岩与其它镁安山岩的对比研究。(1)濑户内海西部第三纪火山岩的微量元素。濑户内镁安山岩的Rb值非常高，Sr值很低。濑户内火山岩是由含有Rb、K、Ba和Zr的水以及玻安岩形成的。(2)在九州西部的本州岛东部的长崎的铫子发现了与濑户内长子化石在化学成分和矿物组成上完全相同的长子化石。