萤石微区激光切割取样Sm-Nd同位素定年及在豫西萤石矿中的应用研究

萤石是一种具有战略意义的重要矿物，成矿年代学是萤石矿床成因研究最基本的内容之一。Sm-Nd同位素体系是唯一一种有效且可直接用于萤石定年的分析方法，然而在实际应用过程中该方法成功率较低。热液成因的萤石样品Sm/Nd比值变化较小是常规Sm-Nd同位素分析失败的主要原因。通过降低萤石用量，开展微量萤石Sm-Nd同位素定年技术是提高萤石定年成功率的有效途径。本项目拟利用激光切割技术进行微区精准取样，对微量样品进行TODGA单柱Nd化学分离纯化以及利用NdO+分析方式开展同位素稀释-热电离质谱（ID-TIMS）测试，从而实现微量萤石样品Sm-Nd同位素高精度分析。利用新建立的萤石微区精准取样和Sm-Nd同位素高精度分析方法，对豫西地区萤石样品进行微区Sm-Nd年代学研究，获得一批较精确的萤石样品Sm-Nd等时线年龄，为该地区萤石矿床的矿床成因以及成矿流体来源等研究工作提供年代学依据。

Fluorite is a mineral of great strategic importance and the metallogenic chronology is one of the most fundamental components in the genesis of fluorite deposits. Sm-Nd isotopic system is the only effective and direct analytical method for isotopic dating of fluorite samples, but this method with little success in the actual application process. The fluorite of hydrothermal origin has small change of Sm/Nd ratios, which is the primary reason for the failure of conventional Sm-Nd isotope analysis. It is an effective way to improve the success rate by reducing the amount of fluorite and developing a micro-fluorite Sm-Nd isotopic dating technology. This project intends to establish a analysis process of micro-fluorite Sm-Nd isotopic dating, specifically comprises the following parts: the precise pre-scanning and micro-sampling for thin section of fluorite using LA-ICP-MS; a single TODGA column for separation of Nd; high precision Sm-Nd isotope analysis as NdO+ by ID-TIMS. The high-precision method for Sm-Nd isotope analysis of micro-fluorite would be applied for the chronological study of fluorite samples collected in Western Henan Province. And the results would provide a chronological basis for the study of the genesis of fluorite deposits and the source of ore-forming fluids in this area.