中国不同时代典型花岗伟晶岩型锂矿特征及其对找矿预测的启示

Characteristics of granitic pegmatite type lithium deposits in different mineralization epochs and its enlightenment for prospecting prediction,China

【研究目的】花岗伟晶岩型锂矿是当今世界金属锂供给的主要矿床类型之一,为明确花岗伟晶岩型锂矿的共性,本文针对性地制定找矿预测工作方案,圈定优质找矿靶区。【研究方法】本文对中国花岗伟晶岩型锂矿的时空分布、构造背景、矿床地质、矿体特征、成矿规律和控矿因素等进行了系统对比,并对产锂花岗岩的特征进行归纳、总结。【研究结果】认为中国已发现的花岗伟晶岩型(锂辉石)锂矿主要分布于西部,东部以花岗岩型(锂云母)锂矿占优。古生代以来的后碰撞环境是中国现有伟晶岩型锂矿的主要产出背景,成矿时代可以延续到非造山构造环境,成矿元素组合绝大多数具有LCT型伟晶岩的特征,矿床数量和资源量都以印支晚期最多。产锂花岗岩一般是同期多阶段复式岩体,其演化分异程度较高。与花岗伟晶岩型锂矿关系最为密切的花岗岩颜色较浅、富含K、Na、P、F、Rb、U、Th,高氧逸度,高Rb/Sr、低Nb/Ta和Zr/Hf,其规模较大,结构构造稳定,更利于综合研究和遥感识别。【结论】在“全位成矿,缺位找矿”理念指导下,从寻找目标更大的产锂花岗岩入手,“先找矿、后优化、再填图”,有望在二级构造单元从挤压向伸展转换的“界山”花岗岩,尤其是侵入边界呈波浪状、舌状产出的外接触带,取得找矿突破。

[Objective]Granite pegmatite type lithium deposit is the main supplying type of metal lithium in the world today.The development and policy formulation are restricted seriously by the shortage of economic and available granite pegmatite type lithium mine in China.In order to clarify the commonality of granite pegmatite−type lithium deposits,we make a prospecting prediction plan,and delineate high−quality prospecting targets.[Methods]This paper systematically compares the spatial−temporal distribution,tectonic background,ore deposit geology,ore body characteristics,mineralization regularities and ore controlling factors of granite pegmatite type lithium depsoits in China,and summarizes the characteristics of lithium−producing granite.[Results]It is believed that the granite pegmatite−type(spodumene)lithium ores discovered in China are mainly distributed in the west part,and the granite−type(lepidolite)lithium ore is dominant in the east part.The post−collision environments since the Paleozoic are the main output background of the existing pegmatite−type lithium deposits in China,and the mineralization setting can be extended to the non−orogenic tectonic environment,and most of the metallogenic element combinations have the characteristics of LCT−type pegmatites,and the number of deposits and resources are the largest in the late Indosinian.Lithium−producing granite is generally a multi−stage compound rock mass in the same period,and its evolution differentiation is high.The granite is lighter in color,rich in K,Na,P,F,Rb,U,Th,high oxygen fugacity,high Rb/Sr,low Nb/Ta and Zr/Hf,which is the most closely related to granite pegmatite type lithium deposit,and it is easier to identify than granite pegmatite dikes.[Conclusions]Under the guidance of the concept of"whole mineralization,absent prospecting",starting from the search for lithium−producing granite with a larger target,"first prospecting,then optimizing,and mapping in the last",it is expected to achieve a prospecting breakthrough in the"boundary mountain"granite where the secondary structural unit is converted from extrusion to stretching,especially in the outer contact zone of wavied and tongue−like intrusive boundaries.