铂族元素和锇同位素在西南印度洋脊龙旂热液区硫化物烟囱体中的组成及物源示踪

项目名称： 铂族元素和锇同位素在西南印度洋脊龙旂热液区硫化物烟囱体中的组成及物源示踪

项目编号： No.41506074

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 天文学、地球科学

项目作者： 黄威

作者单位： 青岛海洋地质研究所

项目金额： 22万元

中文摘要： 海底热液硫化物是地球深处流体喷发到海底的金属物质的集中体现，是贯穿漫长地球演化历史而普遍存在的地质现象和重要的矿产资源。海底热液活动是深部来源铂族元素（PGE）运移到地表系统的重要媒介，是地球PGE循环的重要组成部分，并会对海洋的PGE收支产生极大的影响。因此，理解PGE和锇（Os）同位素在热液硫化物中的分布和来源具有重要的科学意义。本项目以西南印度洋龙旂热液区的硫化物烟囱体为研究对象，通过分析烟囱体不同部位、不同矿物中PGE和Os同位素的组成和变化特征，建立它们的三维分布模式和在主要矿物中的配分系数；分析PGE与其他成矿元素的共生或伴生特征，探讨它们在烟囱体不同部位的响应关系；利用PGE和Os同位素在各物源端元中的巨大差异进行物源限定，结合标准化配分模式、特征元素比值及图解，最终阐明它们在烟囱体中的主要物源端元和相对贡献，并为陆上类似矿体的物质演化规律和成因机制提供现代视角上的有益思路。

中文关键词： 硫化物烟囱体；；铂族元素；锇同位素；西南印度洋脊；物源示踪

英文摘要： Seafloor hydrothermal sulfides which will likely be mined as important mineral resources soon, are the dominant form of the metallic substances carried by the hydrothermal fluid from the deep earth to the seabed and the ubiquitous geological phenomena during the long earth's evolution. This is a natural metallogenic laboratory to study the formation process, mineralization mechanism and geological environment of the seafloor hydrothermal sulfide deposits. The hydrothermal fluids occur along seafloor are capable of transporting a great amount of platinum group elements (PGE) from deep interior of the earth where it is highly enriched to the ocean floor, this process plays a significant role in the global cycling of PGE and will have a great impact on the seawater PGE budget.The compositions and provenience of PGE and Osmium (Os) isotopes in the hydrothermal sulfides hold some of the keys to an understanding of the formation process and control factors of the seafloor massvie sulfide deposits. This project takes the sulfide chimneys from the Dragon Flag hydrothermal field on the Southwest Indian Ridge, which was the first active high temperature hydrothermal field found on any ultraslow mid-ocean ridge worldwide as the research object, analyzes the distribution of PGE and Os isotopes in the different circle layers, different parts, and different mineral assemblages of the chimneys, establishs the three-dimensional models and variation law of the distribution of PGE and Os isotopes in the chimneys, calculates the partitioning coefficient in the major mineral phases of the chimneys. In this study, we research the paragenetic or associated relationship in PGE, between PGE and other metallogenic elements, and the response relationship between PGE and Os isotopes. After comparing to the distribution of PGE and Os isotopes from other different ocean region and different tectonic environment，and considering the large contrasts among different sources of PGE and Os isotopes, we combine the normalized PGE patterns, and the ratios of the characteristic elements and Os isotopes, reveal the main material sources and the relative contribution of PGE and Os isotopes in the seafloor hydrothermal sulfide chimneys. This study has a general relevance to research on many volcanic-associated massive sulfide deposits found on land, and may deepen our understanding of the evolution law and the genetic mechanism of its historical analogue on Earth.

英文关键词： sulfide chimneys;platinum group elements;osmium isotopes;Southwest Indian ridge;provenance