川西马尔康李家沟锂辉石伟晶岩脉中锂辉石-石英共生结构成因研究OA

In spodumene pegmatite veins,spodumene exhibits a distinctive spodumene-quartz intergrowth(SQI)texture.Studying its microstructure,textural characteristics,and genetic mechanism is of great significance for fur-ther revealing the metallogenic mechanisms of granitic pegmatite-type lithium deposits.This paper takes the Late Triassic to Early Jurassic spodumene pegmatite veins in the Lijiagou area,Markam,western Sichuan,as an exam-ple.By integrating optical microscopy,scanning electron microscopy,electron probe microanalysis,and electron backscatter diffraction,we investigated the mineral composition,major element geochemistry,and crystal-lographic orientation of the rocks.Combined with the regional geological background and previous research findings,this study provides the following preliminary insights into the formation mechanism of the SQI texture in the Lijiagou spodumene pegmatites in western Sichuan:① The fine-grained spodumene within the SQI shows high consistency with the host spodumene in terms of major element composition and crystallographic orientation.Moreover,cleavage planes of the host crystal extend continuously into the SQI domains,indicating that both originally belonged to the same crystal and share identical compositional and structural features;② The SQI did not form through magmatic-hydrothermal metasomatism or undercooling crystallization.Instead,early spodumene phenocrysts underwent brittle ductile deformation under regional tectonic stress,leading to shearing and fragmentation into fine-grained spodu-mene aggregates.Subsequently,siliceous melt infiltrated along the fracture systems and crystallized as quartz,ulti-mately forming the intergrowth texture;③ The morphology of quartz is controlled by the interstitial spaces between spodumene grains and shows no obvious signs of deformation.It is interconnected with surrounding quartz,sugges-ting that its formation occurred after the syn deformational period,representing crystallization of siliceous melt with-in the interstitial gaps along spodumene grain boundaries.In summary,the spodumene-quartz intergrowth texture in the Lijiagou spodumene pegmatite veins formed under an orogenic compressional setting and is a deformation-induced product.