四川可尔因矿田李家沟伟晶岩锂辉石矿床岩浆-流体演化过程研究

The Lijiagou deposit, located in the southeast of the Ke'eryin pegmatite orefield, Songpan–Garze Fold Belt(SGFB) in West Sichuan Province,is a newly discovered super-large pegmatite spodumene deposit.The study degree of the Lijiagou deposit is very low.The applicants have conducted a preliminary study on the magma-fluid evolution of the Lijiagou pegmatite spodumene deposit.This research based on accurate division for the different granite, pegmatite zoning and guided by the thermodynamics.Fluid inclusions microscopic observation and compositions analysis are the main research means in this study. Through systematic research temperature,salinity, density,pressure and composition of the melt,melt fluid and fluid inclusions in quartz and spodumene from the different granitic pegmatite zoning in Lijiagou deposit, Zircon U-Pb dating and Hf isotopes analysis of granite and pegmatite, this project will find out the composition, nature and evolution of ore-forming fluid. The methods of this study include fluid inclusion thermometry, Hydrothermal Diamond Anvil Cell (HDAC),LRM,SEM/EDS,LA-ICP-MS dating and Hf analysis.This research will reveal the relationships between the magma-fluid evolution and ore-forming mechanism.This study has the important theoretical and practical significance on deeply understanding metallogenesis, guiding the exploration of the spodumene deposit in ke'eryin ore field.

四川李家沟锂辉石矿床位于川西地区松潘甘孜造山带可尔因矿田东南部，是川西地区新发现的超大型伟晶岩锂辉石矿床，研究程度很低。在申请者以及前人研究的基础上，以最新的包裹体热力学理论为指导，采用最新的热液金刚石压腔、激光拉曼光谱、扫描电镜-能谱等显微观测和成分测试技术，通过对李家沟矿床中不同花岗岩，伟晶岩分带中的锂辉石、石英等矿物中的熔体、流体-熔体和水溶液包裹体岩相学特征、温度、压力、盐度、单个包裹体成分成以及花岗岩和伟晶岩锆石 LA-ICP-MS 定年和Hf同位素示踪等系统研究，查明李家沟伟晶岩型锂辉石矿床成矿流体组成、性质及演化过程；结合成岩成矿年龄，花岗岩与伟晶岩的源区特征，探讨成岩成矿岩浆流体的演化过程与成矿机制。研究成果对深入研究可尔因矿田伟晶岩锂辉石矿床成矿作用，指导区内找矿勘查具有重要的科学意义和实际意义。

本项目以四川松潘甘孜造山带新发现的李家沟超大型锂辉石矿床为解剖对象，以包裹体热力学理论为指导，通过热液金刚石压腔，激光拉曼光谱等技术开展了富子晶包裹体，CO2-H2O包裹体和气液水包裹体单个包裹体显微观测和成分，结合C-H-O同位素和成岩成矿年代学，花岗岩与伟晶岩的源区特征，探讨成岩成矿岩浆流体的演化过程。取得了如下成果：①李家沟矿床发育的包裹体按照成分-相态分类标准可以分为5种包裹体类型，即富子晶包裹体、CO2-H2O包裹体、气液水包裹体，H2O包裹体、CO2包裹体。成矿流体具有中低盐度、中高密度、富CO2的性质，属于高温、中深成矿床；②查明了成矿流体C-H-O同位素组成（δ18O值为 7.2– -0.2‰，δD值为-85.5– -59.0‰，δ13CO2‰值为-19.9– -5.6‰），反映成矿流体主要来自于岩浆水，晚期有大气降水的加入的特点；③开展了伟晶岩和花岗岩的锆石、锡石、铌钽铁矿U-Pb定年、Hf同位素和全岩地球化学分析，查明了成岩成矿时代，形成于晚三叠世。研究表明，铌钽铁矿和锡石U-Pb联合定年更有可能提供准确的钠长石锂辉石伟晶岩结晶年龄；④拉曼分析结果表明，李家沟矿床伟晶岩的成矿流体中富含挥发分硅酸盐流体，且具有碳酸盐成分。包裹体组合从富子晶包裹体→CO2-H2O包裹体、气液H2O包裹体的变化，反映了本矿床经历了岩浆-热液过度阶段（650–750℃，490–600MPa）→热液阶段（300–400℃，180–350 MPa）的演化过程。流体不混溶是锂沉淀的重要机制。李家沟矿床的伟晶岩的形成不存在连续的从可尔因母岩到锂辉石伟晶岩的演化现象。本项目的研究，丰富了伟晶岩锂辉石矿床成矿作用的研究案例，补充和完善松潘甘孜造山带稀有金属矿床成矿理论。