川西花岗细晶岩-伟晶岩型锂矿含矿性评价与示矿标志

Granitic aplite-pegmatite lithium deposits in western Sichuan: Ore- bearing property evaluation and geological indicators

锂金属被誉为21世纪的绿色能源金属,是我国重要的关键金属矿产之一。寻找超大型锂矿是地学界一大难题。川西花岗细晶岩-伟晶岩型锂矿资源丰富,成矿背景优越,但地表广为第四系覆盖。针对隐伏锂矿脉含矿性评价与示矿标志,笔者以近十年来在甲基卡取得X03超大型锂矿找矿突破的实践,以成矿理论为指导,分析了“成矿地质背景-地球物理-地球化学异常”之间的内在关联,从区域远景区分析、预测和圈定找矿靶区、矿床定位等层次与流程梳理,提出了花岗细晶岩-伟晶岩型锂矿“模型指导—遥感解译—地质填图—物探定位—化探定性—钻探验证”的综合评价模式,即:针对靶区选区难的问题,采用成矿模型指导、地质填图、总结找矿标志;针对隐伏岩体采用高精度重力探测+音频电磁大地测深(ATM);针对脉体定位采用音频电磁大地测深(ATM)+激电扫面+激电测深+高密度电法等不同推测深度的方法组合;针对脉体含矿性定性,采用大比例尺土壤地球化学测量,根据地球物理与地球化学异常之间的空间关系,推断带状物探高电阻异常体是否为含锂的脉体,为钻探工程布置提供依据。将该模式拓展指导并应用于雅江县木绒超大型锂矿的深部找矿勘探和石渠县扎乌龙、雅江县仁依措等大中型锂矿找矿评价中,取得了很好的成效,为下一步战略找矿行动提供了示范。

Lithium,known as a clean energy metal and“white oil”of the 21st century,is one of the most important critical metals in China,yet finding large lithium deposits is one of the most challenging problems in geosciences.The high-grade aplite-pegmatite lithium deposits in western Sichuan have superior ore-forming conditions,but they are widely buried under Quaternary sediments.To evaluate the ore-bearing properties and identify the geological indicators of hidden lithium veins,we analyzed the internal relationship between the regional metallogenic setting and geophysical and geochemical anomalies.Combined with the regional ore prospecting,target area prediction/delineation,and ore-deposit positioning results,we developed a comprehensive evaluation method for granitic pegmatite lithium deposits,that is“model guiding-remote sensing image interpretation-geological mapping-geophysical prospecting-geochemical characterization-drilling verification”workflow.Briefly,metallogenic model analysis and geological mapping were carried out to identify geological indicators of target areas,and high-precision gravity detection and audio-frequency electromagnetic geodetic sounding(ATM)were used for hidden vein detection.To pinpoint the vein body,a combination of different depth estimation methods,such as ATM,IP scanning,IP sounding,and high-density resistivity imaging,were used.Large-scale soil geochemical measurements were used to characterize the ore-bearing property of vein bodies.Finally,the belt-shaped,geophysical high-resistance anomalous veins were evaluated according to the spatial relationship between geophysical and geochemical anomalies to identify lithium-bearing veins,that provided a basis for drilling engineering designs.This workflow has been applied to guide the deep prospecting and exploration of giant lithium deposit in Murong,Yajiang County,and in the evaluation of large to medium-size lithium deposits in Zhawulong,Shiqu County and Renyicuo,Yajiang County,and good results have been achieved.This study provided an example of strategic prospecting and exploration of lithium resource in the region.