Geological-Geochemical,Geochronology And Resourcet Prospect Analysis For The Lithium And Beryllium Deposit In Daqianggou,Jiulong,Western Sichuan,China

Lithium,beryllium and other rare metals are one of the important raw materials in the aerospace,defense and new energy fields.Therefore,their exploration,development,and reserves have important strategic significance.The Daqianggou Lithium Beryllium deposit is located in the Yajiang residual basin on the southern margin of the Songpan-Garze fold belt and is an important part of the Songpan-Garze lithium metallogenic belt.In recent years,the exploration of this deposit has made great breakthroughs,but the research on metallogenic theory has remained in the1960s,particularly,there are controversies in terms of mineral assemblage,occurrence state,and mineralization age.In this paper,based on the summarization of the research of pegmatite-type rare metal deposits,combined with field geological survey work,typical veins in the Daqianggou orefield are selected to conduct petrography,mineral chemistry,geochemical and geochronological studies.The main components,fabric characteristics,occurrence state of the ore have been identified,the ore-forming stages have been divided,the genesis of deposit have been explored,the characteristics of rare metal element enrichment have been summarized,and the resource potential and ore prospecting direction of orefield have been predicted.The main types of ore-bearing pegmatites in the Daqiangou orefield can be divided into albite type and albite-spodumene type,and the main ore minerals are spodumene and beryl.Lithium ore bodies are mainly distributed in the southern part of the orefield,and are found in albite-spodumene pegmatite,and is often accompanied by beryllium.The beryllium ore bodies are mainly distributed in the middle of the orefield,and are found in the albite pegmatite.Enrichment of rare metal elements in orefield have obvious regular changes with pegmatite type,zoning characters,spatial distribution,ore-bearing wall rock,metasomatism,etc.Mineralogy and mineral chemistry show that the mineral combination changes a lot.The feldspar mineral is composed of micro-plagioclase+albite?primary albite?metasodium albite.Mica changes from muscovite to lithium-rich lepidomorphite.Tourmaline belongs to the series of iron tourmaline-lithium tourmaline,with transition from iron tourmaline to lithium tourmaline.Quartz changes from primary quartz?recrystallized quartz?late hydrothermal quartz.Rare minerals change from beryl?beryl+spodumene?spodumene?spodumene+lepidolite.Therefore,the metallogenic process is divided into crystal fractionation period,metasomatism period,hydrothermal period,and supergene period.The pegmatites samples of Daqianggou deposit are geochemically characterized by relatively alkali-rich?K₂O+Na₂O=3.74%?14.56%,average 8.02%?,peraluminous?A/CNK=0.99?2.87,average 1.50?and high differentiation?DI=90.09?98.40,average94.39?.The content of trace and rare earth elements is low.The pegmatite is distinctively enriched in high field strength elements?HFSE?such as Nb,Ta,Hf and U,relatively depleted in large ion lithophile elements?LILE?such as Ba,K and Sr.The U-Pb age of zircon in NO.01 pegmatite vein is 147.5±2.3Ma,which represents the metallogenic age of the Daqianggou lithium beryllium deposit,which belongs to the Yanshanian metallogenesis.This age is basically consistent with the age of the Qiaopengzi rock mass and surrounding rocks within the error range.Therefore,it is believed that the Qiaopengzi mica granite and the surrounding rocks are genetically related to the pegmatite in the Daqiangou orefield,and it provides conditions for material source and hydrothermal explanation for Daqianggou pegmatite.The formation of pegmatite in the Daqianggou orefield is related to the magmatic events resulting from the 140?164Ma extensional decompression melting at the southern edge of the Songpan-Garz block.Based on the above research,this paper believes that there may still be a large number of hidden veins in the deep part of the Daqianggou orefield,which has the prospecting potential of Li,Be,Nb and Ta.And a large number of pegmatite veins are seen in the Shitizi,Luomo,and Yangfanggou rock masses in the periphery of the Daqianggou orefield,which has good prospecting potential for Li and Be.