滇西南西盟—澜沧地区土壤稀土地球化学异常的发现及找矿意义OACSTPCD

The Ximeng-Lancang area in southwestern Yunnan resides in the southern section of the Nujiang-Lancangjiang-Jinshajiang o-rogenic belt in Southwest China.The 1∶50,000 geochemical soil survey revealed 24 rare-earth-element(REE)geochemical anoma-lies,which are primarily distributed in the Carboniferous Pingzhang Formation mafic volcanic rocks and the Carboniferous-Permian Yu-tangzhai Formation sedimentary carbonate rocks within and near the Changning-Menglian deep fault zone.Furthermore,the AP00 REE geochemical anomalies ranking high in the evaluation were analyzed in detail through a 1∶10,000 geochemical soil survey,a 1∶10,000 special geological survey,and light-duty prospecting engineering in mountainous areas.A new type of REE ores in weathering crusts has been first discovered in sedimentary carbonate strata,with preliminarily estimated REE resources reaching a medium scale,sugges-ting a prospecting breakthrough.This finding shows a new prospecting approach,which can be referenced for similar research.As re-vealed by a comprehensive analysis of the regional geological and geochemical settings and the data of AP00 REE anomalies,the AP00 REE ores in weathering crusts have undergone a gradual enrichment and mineralization process involving four different geological processes,suggesting polygenetic compound REE ores.Considering the low leaching efficiency of AP00 REE ores and significant struc-tural(magmatic)superimposed mineralization of the heavy REE yttrium,it is inferred that yttrium-dominated primary REE ores might exist in the deep part,implying high potential for heavy-REE ores.