云南景东县文玉铜(银)矿成矿地质背景:来自赋矿火山岩年代学和地球化学的证据  

Wenyu Copper (Silver) Deposit Ore-Forming Geological Background,Jingdong County,Yunnan:Geochronology and Geochemistry Evidences from Ore-Bearing Volcanic Rocks

作　　者：宋俊龙[1,2] 丁俊[2] 王保弟[2] 刘严松[1,2] 赵荣春 舒跃红 Song Junlong1,2, Ding Jun2. , Wang Baodi2, Liu Yansong1,2, Zhao Rongchun3, Shu Yuehong3(1.College of Earth Science,Chengdu University of Technology,Chengdu 610059,China 2.Chengdu Center,China Geological Survey ,Chengdu 610081,China 3.Jingdong Lihuateng Mining Company Limited,Pu＇er 676200,Chin)

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]中国地质调查局成都地质调查中心,四川成都610081 [3]景东立华腾矿业有限公司,云南普洱676200

出　　处：《地球科学》2018年第3期696-715,共20页Earth Science

基　　金：中国地质调查局地调项目(No.DD20160016);国家自然科学基金项目(No.41773026)

摘　　要：文玉铜(银)矿是云县-景洪火山弧上重要的与火山作用相关矿床,了解矿区成岩成矿地质背景是探讨成矿作用的基础.本文报道了赋矿火山岩的岩石学、地球化学及锆石LA-ICP-MS年代学.小定西组火山岩由基性岩夹少量酸性岩组成,SiO_2分别介于47.94%~54.02%和76.92%~84.16%之间,具"双峰式"火山岩特征.流纹岩锆石U-Pb年龄为238.4±2.4 Ma(MSWD=1.4),表明小定西组时代为中三叠世,而并非前人认为的晚三叠世.小定西组基性火山岩具低镁高铝特征,属于钾玄岩-高钾钙碱性-钙碱性系列,具较强Sr、Ti、Nb和Ta负异常、弱Eu负异常以及较低的Mg~#、(La/Yb)_N比值和Cr、Ni含量等特征;酸性火山岩属于过铝质高钾钙碱性系列,具有强的Sr、Ti、P、Nb、Ta、Ba和Eu负异常,Nb/Ta和Th/Ce比值与大陆地壳较为一致,具高Th含量和低Mg~#特征.地球化学特征显示其可能形成于中三叠世早期弧(陆)-陆碰撞边缘下的伸展环境,是洋壳俯冲板片断离作用的结果.结合区域火山作用及成矿作用研究,中三叠世碰撞伸展作用阶段伴随多期次多阶段火山作用,具有良好的火山成矿作用前景.Wenyu copper（silver）ore,located in Yun county-Jinghong volcanic arc,is important deposit related to volcanism.It is important to understand its geological background since it is basic for discussing mineralization of Wenyu ore area.This paper reports petrology,geochemistry and zircon LA-ICP-MS chronology of volcanic rocks from Xiaodingxi Formation in the mining area.Results show that they are composed of basaltic rocks and a small amount of acidic rocks,with SiO_2 ranging from 47.94%-54.02% and 76.92%-84.16%,respectively,exhibiting the features of bimodal volcanic rocks.Zircon U-Pb age of rhyolite is 238.4±2.4 Ma（MSWD=1.4）,showing that volcanic rocks in Xiaodingxi Formation formed at Middle Triassic,rather than Late Triassic.The basaltic volcanic rocks are characterized by low Mg and high Al,belonging to shoshonite-highKcalc-alkaline-calc-alkaline series,with strong negative Sr,Ti,Nb and Ta anomalies,weak negative Eu anomalies,and lower（La/Yb）_Nratio and Mg~#,Cr and Ni contents.Acidic volcanic rocks belong to peraluminous high K calc-alkaline series,with strong negative Sr,Ti,P,Nb,Ta,Ba and Eu anomalies.Nb/Ta and Th/Ce ratios are relatively consistent with those of continental crust,displaying characteristics of high Th and low Mg~#,which suggests that it formed in an extension setting during a margin of arc（continent）-continent collision in the early Middle Triassic,which is a result of oceanic crust subduction slab break-off.In combination with regional volcanism and metallogenesis research data,it is concluded that multi-stage volcanism in the collision extension environment occurred many times during the Middle Triassic,indicating agood prospect of volcanism mineralization.

关 键 词：锆石U-PB年龄 火山岩 地球化学 文玉铜(银)矿 云南 

分 类 号：P597[天文地球—地球化学]