滇东南南温河钨矿床成因和成矿时代:来自矿床地质特征和Sm-Nd同位素年龄的证据

Genesis and geochronology of the Nanwenhe tungsten deposit,southeastern Yunnan:Evidence from geological features and Sm-Nd isotopic age

南温河钨矿是滇东南地区规模最大的白钨矿床。从加里东期开始,区内遭受了多期构造-变质作用,地质作用复杂,导致以往对矿床成因、成矿时代等关键问题一直存在不同认识。在详实的野外地质工作基础上,结合前人研究成果,认为其为岩浆-热液控制的矽卡岩型白钨矿床;成矿热液是岩浆-热液过渡态流体,具体表现形式为“穿层”和“顺层”石英脉-长石石英脉,其控制了矽卡岩化和白钨矿化;目前勘探工作揭露的层状、似层状矽卡岩矿体为“浆-液过渡成矿流体”顺层交代的产物。获得南温河钨矿Sm-Nd同位素年龄为126±6.7 Ma(n=7,MSWD=0.33),与区内构造研究成果和其他年代学成果获得良好的印证,成矿作用与燕山晚期岩浆活动有关。结合矿床地质特征和Sm-Nd同位素年龄等证据,认为南温河钨矿是由燕山晚期岩浆-热液系统控制的矽卡岩型白钨矿床。

The Nanwenhe tungsten deposit is the largest scheelite deposit in southeast Yunnan.Since the Caledonian period,the area has been subjected to multi-stage tectonic-metamorphism.This has led to different understanding of key issues such as deposit genesis and metallogenic age.On the basis of detailed field geological work,combined with the results of previous work,it is considered to be a skarn scheelite deposit controlled by magmatic-hydrothermal fluid,and the ore-forming fluid is a magmatic-hydrothermal transitional fluid,which is characterized by"cross-bedding"and"bedding"quartz veins-feldspar quartz veins,and controls the skarnization and scheelite mineralisation of the Nanwenhe tungsten deposit.The laminated and stratiform skarn ore bodies revealed by the current exploration work are the products of bedding metasomatism of"mag~hydrothermal transition ore-forming fluid".The Sm-Nd isotopic dating of the scheelite in the Nanwenhe tungsten deposit yield a metallogenic age of 126±6.7 Ma(n=7,MSWD=0.33),which corroborates well with the tectonic research results and other chronological results in the area,indicating that the mineralization is related to the late Yanshan magmatic activity.The geological characteristics and Sm-Nd isotopic age of the deposit indicate that the Nanwenhe tungsten deposit is a skarn scheelite deposit controlled by the late Yanshanian magmatic-hydrothermal system.