金属稳定同位素示踪关键金属的运移和超常富集  

Tracing the migration and extreme enrichment of critical metals using metal-stable isotopes

作　　者：胡霞 邓庚辛 陈栩琦 盛佳儒 黄方[1,2] HU Xia;DENG Gengxin;CHEN Xuqi;SHENG Jiaru;HUANG Fang(CAS Key Laboratory of Crust-Mantle Materials and Environments,School of Earth and Space Sciences,University of Science and Technology of China,Hefei,Anhui 230026,China;CAS Center for Excellence in Comparative Planetology,Hefei,Anhui 230026,China)

机构地区：[1]中国科学技术大学地球和空间科学学院,中国科学院壳幔物质与环境重点实验室,安徽合肥230026 [2]中国科学院比较行星学卓越创新中心,安徽合肥230026

出　　处：《地质学报》2024年第5期1550-1572,共23页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号42373009)资助的成果。

摘　　要：关键金属矿产对于国家经济和安全意义重大,然而其富集机制仍然存在争议,即受控于岩浆的结晶分异作用还是热液流体作用。传统的地球化学手段只能间接制约成矿物质的来源,难以区分分离结晶和岩浆热液作用对成矿的影响,而Rb、Ba、Sr、U等流体活动金属的同位素体系则对这两种机制具有不同的响应。笔者分别对喜马拉雅和华南地区的富关键金属花岗岩进行了Rb和Ba同位素研究,结果表明,当矿物结晶时,残留熔体中Ba同位素变重,Rb同位素不变;而当岩浆热液作用时,花岗岩中Ba同位素变轻,Rb同位素变重。此外,深部岩浆出溶的热液流体对亲流体易迁移的关键金属元素的富集具有重要贡献。上述研究表明,金属稳定同位素(尤其是流体活动金属的同位素)对于示踪岩浆-热液作用和成矿流体来源具有非常好的效果。Critical metal minerals are significant to the national economy and security,but whether their enrichment is controlled by the fractional crystallization process or by the magmatic-hydrothermal interaction remains controversial.Traditional geochemical methods can only indirectly restrict the source of ore-forming materials,and it isn't easy to distinguish the effects of fractional crystallization and magmatic-hydrothermal processes on mineralization.The isotope systems of fluid-active metals such as Rb,Ba,Sr,and U have different responses to these two mechanisms.We have studied the Rb and Ba isotopes of granites collected from the Himalayas and South China.Our research shows that the Ba isotope in the residual melt becomes heavier and the Rb isotope remains unchanged during mineral crystallization,while the Ba isotope in the granite becomes lighter and the Rb isotope becomes heavier during the magmatic-hydrothermal interaction.The hydrothermal fluid exsolved from deep magma brings abundant critical metals that are easy to migrate with fluid.Our study shows that stable metal isotopes,especially fluid-active metal isotopes,are very effective in tracing magmatichydrothermal processes and ore-forming fluid sources.

关 键 词：金属稳定同位素 关键金属 超常富集 岩浆-热液作用 同位素示踪 

分 类 号：P618.2[天文地球—矿床学] P597[天文地球—地质学]