西南地区煤中稀土元素富集过程的氢-氧同位素示踪

The study of rare earth elements in coal has important geological significance and application value. Coal-bearing strata in Southwest China are enriched in rare earth elements. Hydrothermal fluids and alkaline volcanic ash are the key factors for the enrichment of rare earth elements. However, the nature of the hydrothermal fluids and the process are not clear. Hydrogen and oxygen isotopes are ideal methods for tracing hydrothermal fluids. This project takes the rare earth elements-rich coal of Late Permian in southwestern China as the research object. It intends to investigate the hydrogen-oxygen isotope composition characteristics of coal. Based on the theory of stable isotope fractionation, combined with the methods and theories of geochemistry, coal geology and mineralogy, this project is to trace the source, enrichment process and preservation of trace rare earth elements in coal, reveal the influence mechanism of various geological factors during and after the coal formation on the enrichment of rare earth elements, and provides inspiration for regional geological evolution. The results will provide a theoretical basis for the extraction of rare earth elements from coal and provide a scientific basis for the search of rare earth elements deposits in coal-bearing strata.

煤中稀土元素的研究具有重要的地学意义和战略价值。中国西南地区的某些煤系地层中高度富集稀土元素，热液流体和火山灰是煤系地层中稀土元素富集的重要因素，然而对于热液流体的性质及影响方式尚不明确，对稀土元素的富集过程缺乏研究。氢-氧同位素是用于热液流体示踪的理想方法，本项目将以西南地区晚二叠世富稀土元素的煤层为研究对象，查明煤及夹矸中氢-氧同位素组成特征，基于稳定同位素分馏理论，结合地球化学、煤地质学、矿物学的方法和理论，示踪稀土元素的来源、富集过程及保存条件，揭示成煤作用过程中及成煤后的地质因素对稀土元素富集的影响机制，为区域地质演化提供证据。项目成果将为煤中稀土元素提取提供理论基础，为煤系地层中稀土元素矿床的寻找提供科学依据。

本项目以西南地区富集稀土元素的煤层为主要研究对象，通过地球化学、煤地质学、矿物学的方法和理论，研究了稀土元素在煤层中的富集和分布特征；结合煤层样品的碳同位素和汞同位素的组成特征以及矿物学特征，分析了煤层中稀土元素的来源、迁移和再分配，火山灰作为稀土元素的重要来源，通过大气水、热液等流体的搬运，可能会在与火山灰蚀变黏土岩相邻的煤或炭质泥岩样品中富集稀土元素；探讨了汞同位素组成对煤层中矿物质来源的示踪。对煤层中稀土元素来源和迁移的研究，为煤系关键金属元素的找矿提供理论依据。项目负责人在Chemical Geology、Minerals等国际期刊发表学术论文2篇。