中国花岗伟晶岩型锂矿特征和研究进展

Characteristics and Research Progress of Granitic Pegmatite Type Lithium Deposits in China

花岗伟晶岩型锂矿是中国锂资源的重要类型之一。本文基于全国87处花岗伟晶岩型锂矿研究资料,通过与全球典型伟晶岩型锂矿的对比分析,梳理总结中国花岗伟晶岩型锂矿的时空分布规律、矿石矿物组合特征、成矿成岩温压条件、演化历史和锂同位素分馏特征,以期为今后找矿工作提供理论依据。研究表明中国花岗伟晶岩锂矿空间分布相对集中,主要分布在8个锂成矿带,主成矿期为三叠纪;含锂矿物相与花岗岩-伟晶岩体系中的H 2O、P、F和Li等挥发性元素密切相关;与国外典型花岗伟晶岩锂矿相比,中国大型-超大型伟晶岩锂矿具有成矿温度相似和成矿压力较大的特征;不同于以Harding伟晶岩为代表的侵位后P-T两阶段演化轨迹,中国花岗伟晶岩锂矿存在以川西扎乌龙为代表的单阶段快速降温降压型演化轨迹;结晶分异是花岗伟晶岩最可能的岩石成因,该地质过程中锂元素和重锂同位素富集于花岗伟晶岩;未矿化伟晶岩全岩比锂辉石矿化伟晶岩全岩更富轻锂同位素的特征表明锂成矿过程发生在流体出溶之后。

The granitic pegmatite type lithium deposit is one of the important types of lithium resources in China.In order to provide theoretical guidance for future prospecting of this mineral,we made a comparative analysis to the data of 87 granitic pegmatite type lithium deposits in China and other typical deposits in the world.We summarized spatial-temporal distribution characteristics,lithium-bearing mineral assemblage features,temperature-pressure conditions of the metallogenic process,evolution histories and the characteristics of lithium isotope fractionation of these deposits.Results show that the spatial distribution of the granite-pegmatite lithium deposits in China is relatively concentrated,mainly present in eight lithium metallogenic belts,of which the peak period of diagenesis of pegmatite and lithium mineralization is Triassic.Lithium-bearing minerals are closely related to flux elements content in granite-pegmatite systems,such as H 2O,P,F and Li.Compared with other deposits in the world,large lithium deposits in China have similar temperature and larger pressure of mineralization.Different from the Harding pegmatite with two P-T stages of evolution after emplacement,some of Chinese pegmatite has one-stage P-T evolution history with rapid cooling and depressurization represented by the Zhawulong deposit.Crystal differentiation is the most likely petrogenesis of granite pegmatite,during which the lithium element and heavy lithium isotope were enriched in granite pegmatite.The whole rock of the un-mineralized zone is richer in light lithium isotope than the spodumene mineralized zone,indicating the lithium-mineralization process occurred after fluid exsolution.