湖南天明金矿区云斜煌斑岩年代学、同位素地球化学及成矿意义  

Geochronology,Isotopic Geochemistry of Diorite Porphyrite in Tianming Gold Deposit,Hunan

作　　者：陈澍民 徐宏根[1] 吴金虹 缪宇 曾昊 彭勃 潘思远 CHEN Shumin;XU Honggen;WU Jinhong;MIAO Yu;ZENG Hao;PENG Bo;PAN Siyuan(Changsha General Survey of Natural Resources Centre,China Geological Survey,Changsha 410600,Hunan,China;School of earth sciences and resources,China University of Geosciences(Beijing),Beijing 100083,China;Kunming General Survey of Natural Resources Centre,China Geological Survey,Kunming 650100,Yunnan,China;Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]中国地质调查局长沙自然资源综合调查中心,湖南长沙410600 [2]中国地质大学地球科学与资源学院,北京100083 [3]中国地质调查局昆明自然资源综合调查中心,云南昆明650100 [4]中国地质科学院矿产资源研究所,北京100037

出　　处：《西北地质》2023年第6期285-300,共16页Northwestern Geology

基　　金：中国地质调查局项目“雪峰弧金锑矿资源勘查”(DD20208007);“湖南云台山地区1∶5万矿产地质调查”(DD20220968);中国地质调查局花岗岩成岩成矿地质研究中心开放基金课题(PMGR202106)联合资助。

摘　　要：湖南安化天明金矿区的勘查工作中,岩芯揭露隐伏云斜煌斑岩。为探讨脉岩与成矿关系,对云斜煌斑岩开展岩石学、LA−ICP−MS锆石U−Pb年代学、全岩主微量元素和Sr−Nd同位素组成研究。结果显示,云斜煌斑岩遭受强烈的碳酸盐化蚀变;成岩时代不早于104 Ma,可能是晚燕山期华南构造-岩浆事件的响应;(418.79±1.57)Ma与(2506±14)Ma两组谐和年龄分别记录了志留纪扬子地块华夏诸岛弧陆弧碰撞以及太古宙地壳初始大规模增生,表明基底物质来源于上述2次地质事件。云斜煌斑岩属高钾钙碱性系列,轻稀土元素(LREE)富集、重稀土元素(HREE)亏损,具有明显的Eu负异常和Ce正异常;大离子亲石元素和高场强元素亏损,相容元素含量高;全岩εNd(t)=−8.28~−7.61表明壳幔混源;认为云斜煌斑岩由地幔岩浆在源区残留角闪石、钛铁矿和/或金红石,经历以斜长石为主的分离结晶,并受地壳混染,最终在近EW向断裂中侵位形成。对比湘中地区脉岩,赋矿地层,地壳Au、Sb含量,暗示脉岩与锑可能具有深部同源性,天明矿床具有锑成矿潜力。The exploration in the Tianming Mining Area,Anhua,Hunan,has uncovered the concealed mica−plagioclase lamprophyre.In order to study the relationship between the dike and mineralization,we conducted various studies including petrographic,LA−ICP−MS zircon U−Pb chronology,whole−rock major and trace elements and Sr−Nd isotope composition analyses on the mica-plagioclase lamprophyre.The results indicate that the mica−plagioclase lamprophyre underwent significant carbonate alteration.The diagenesis age is es-timated to be no earlier than 104 Ma and may be a response to the Late Yanshanian tectonic−magmatic events in South China Block.The concordant ages of(418.79±1.57)Ma and(2506±14)Ma document the events of Silurian arc−crust collision of the Yangtze plate and the Cathaysia island arc,and Archaean crustal accretion,respectively,indicating the crystal basement material source.The mica−plagioclase lamprophyre belongs to a high−K calcium−alkaline series with an enriched light rare−earth element(LREE)and depleted heavy rare−earth element(HREE),with Eu negative anomalies and Ce positive anomalies.The rock also has large ionic lithophile and high−field strength elements depleted and high compatible element content.Whole−rockεNd(t)values ranging from−8.28 to−7.61 suggest crust−mantle mixing.Our findings suggest that the mica−plagioclase lamprophyre was formed by mantle magma in the source area with residual hornblende,ilmenite,and/or rutile.It underwent fractional crystallization dominant of plagioclase,was mixed by crust,and finally intruded in near−EW faulting tectonics.Comparison of the Au and Sb contents of dikes in central Hunan,ore−bearing formation,and crust,implies that the dikes and antimony may have deep homology.These findings suggest that the Tianming deposit has antimony mineralization potential.Overall,the study highlights the complex geological processes that lead to the formation of mineral deposits.By using a multidisciplinary approach,it is able to unravel the c

关 键 词：雪峰构造带 云斜煌斑岩 燕山期 主微量元素 ND同位素 

分 类 号：P597[天文地球—地球化学] P591.2[天文地球—地质学]