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Significance of hydrocarbons in anorthite megacrysts from island arc.

岛弧钙长石巨晶中碳氢化合物的意义。

基本信息

批准号：
05453004
负责人：
KIMATA Mitsuyoshi
金额：
$ 4.8万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05453004/
关键词：
anorthite megacryst olivine garnet inclusion native copper island arc magma 島孤炭化水素 Sr-同位体比

项目摘要

Hydrocarbons, verified by high-temperature Micro-FTIR,are found to be included by the same anorthite and labradorite megacrysts containing native coppers, as described in Part 1, in basaltic rocks, from Japanese island arc and in the westem continental margin of North America, respectively. A finding of Muntz metal (Cu_<60> Zn_<40> ) within the anorthite megacryst offerred the establishment of Hume-Rothery's rule in nature. Concerning the genesis of native coppers coexistent with the hydrocarbon, the exsolution model fortified by their purity and oriented distribution has been suggested and can account for crystal growth of native coppers based on the theory of Ostwald ripening. While continental margins and lsland arcs have geological and tectonical backgrounds common to each other, remarkable difference in morphology between fractured labradorites and euhedral anorthites seems to flare up in the power of the volcanic eruption. Moreover it proved that the corroded olivines within anorthite megacrysts hereupon have also a trace amount of hydrocarbons, detection of which discloses that the magmas crystallizing these anorthite and olivines contained the same hydrocarbons. Fe/Mg ratio of the corroded olivines, Sr-content and Sr-isotope ratio of anorthite megacrysts typical of arc-volcanism in Japan afford the lateral variations from the Japan trench to the Back arc side, and their geochemical behavior witnesses the rapid crystallization of anorthite megacrysts and their corroded olivines in close association with the crust components and the slabsediments subducted beneath the island arc.

经高温显微傅里叶变换红外光谱分析证实，在玄武岩、日本岛弧和北美西部大陆边缘的玄武岩、日本岛弧和北美西部大陆边缘中，发现了相同的含天然铜的斜长岩和拉斑玄武岩巨晶。在斜长岩巨晶中发现的Muntz金属(Cu60&gt；40&gt；)为休谟-罗瑟利法则在自然界中的建立提供了依据。对于原生铜与烃类共存的成因，提出了纯度和定向分布强化的出溶模型，并以Ostwald成熟理论为基础解释了原生铜的晶体生长。虽然大陆边缘和岛弧具有共同的地质和构造背景，但断裂的拉布拉多岩和正面体斜长岩在形态上的显著差异似乎在火山喷发的力量中爆发了。此外，还证明了钙长岩巨晶中受侵蚀的橄榄石也含有微量的烃类，其检测揭示了结晶这些钙长岩和橄榄石的岩浆含有相同的烃类。日本典型的弧火山活动中受侵蚀橄榄石的Fe/Mg比值、钙长石巨晶的锶含量和锶同位素比值具有从日本海沟到弧后侧的横向变化，其地球化学行为见证了钙长岩巨晶及其受侵蚀橄榄石的快速结晶，并与地壳成分和岛弧下俯冲的板片沉积物密切相关。