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Origin of hydrothermal fluid of mineralization

成矿热液的来源

基本信息

批准号：
08404033
负责人：
NEDACHI Munetomo
金额：
$ 21.76万
依托单位：
Kagoshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08404033/
关键词：
Mineralization Sulfur isotopic composition Halogen element Origin of hydrothermal fluid Alteration Igneous activity 酸素同位体比

项目摘要

The purpose of this research is to understand the relationship between magmatism and mineralization, and to consider the contribution rate of magmatic water, seawater, meteoric water, and others.l) We survey the hydrothermal ore deposits and geology in the Hokusatsu district, Kagoshima Prefecture. The hydrothermal fluid was produced at the top of cupola shaped felsic magma that supplied dacitic volcanics, and was rich in chlorine and oxidized sulfur species such as SOィイD22ィエD2. Chlorine has joined with gold and other metals to form chloro-complex. The fluid has emanated and was cooled in the overlying anoxic Shimanto Supergroup, where the chloro-complex of gold was destroyed, and the SOィイD22ィエD2 was converted to HS-. The gold released from chlorine reacted with HS- to form Au(HS)ィイD22ィエD2-. At the most top of the Shimanto Supergroup, hydrothermal fluid was oxidized by meteoric water and by volcanic rocks of magnetite series. In this process, magmatic water played essentially important role to mineralization, and meteoric water played as oxidant to precipitate the gold. Similar phenomena can be confirmed at the Ladolam ore deposits, Papua New Guinea.2) The origin of hydrothermal fluid was also examined on the fumarole in Kagoshima Bay. Volcanic gas added to the seawater, and bio-activity played important role to change the sea water to ore fluid. The bio-activity was also recognized in the Tizapa VMS mine in Mexico.3) The contribution of felsic magma was also confirmed by the research on the granitic rocks in Kyushu area. The asymmetrical zonation of the Tertiary granite could be recognized from the aspects of halogen geochemistry, REE distribution, and isotopic phenomena. The source area of ore fluid can be expected at the middle and/or lower crust.During the research, the isotopic compositions contribute for consideration. The methodology of measurement was developed through this research.

本研究的目的是了解岩浆作用与成矿作用之间的关系，并考虑岩浆水、海水、大气水等的贡献率。l)对鹿儿岛县北佐地区的热液矿床和地质进行了调查。热液产生于冲天炉状长英质岩浆顶部，供给英安质火山岩，富含氯和氧化硫物质，如SOiiD22ィエD2。氯与金和其他金属结合形成氯络合物。流体在上覆的缺氧四万十超群中散发出来并被冷却，其中金的氯络合物被破坏，SOiiD22ィエD2被转化为HS-。从氯中释放出的金与HS-反应生成Au(HS)ィイD22ィエD2-。在四万十超群的最顶部，热液被大气水和磁铁矿系火山岩氧化。在这个过程中，岩浆水对成矿起到了至关重要的作用，而大气水则起到了氧化剂的作用，使金沉淀出来。巴布亚新几内亚的Ladolam矿床也证实了类似的现象。2)还在鹿儿岛湾的喷气孔上考察了热液的来源。火山气体添加到海水中，生物活性对海水转变为矿液发挥了重要作用。墨西哥Tizapa VMS矿的生物活性也得到了证实。3)对九州地区花岗岩的研究也证实了长英质岩浆的贡献。第三纪花岗岩的不对称分带可以从卤素地球化学、稀土元素分布和同位素现象等方面来认识。预计成矿流体的源区位于中地壳和/或下地壳。在研究过程中，同位素组成也需要考虑。通过这项研究开发了测量方法。