康滇地区元古宙构造运动Ⅰ:昆阳陆内裂谷、地幔柱及其成矿作用  

The Proterozoic Tectonic Movement In Kangdian AreaⅠ:Kunyang Intracontinental Rift,Mantle Plume and Its Metallogenesis

作　　者：王生伟[1] 蒋小芳[1] 杨波[1] 孙晓明[2,3] 廖震文[1] 周清[1] 郭阳[1] 王子正[1] 杨斌[1] 

机构地区：[1]中国地质调查局成都地质调查中心,成都610081 [2]中山大学海洋学院,广州510275 [3]中山大学地球科学与地质工程学院,广州510275

出　　处：《地质论评》2016年第6期1353-1377,共25页Geological Review

基　　金：国家自然科学基金青年基金资助项目(编号:41202067);国土资源大调查项目(编号:1212010911064;1212010813066;12120113053000)的成果~~

摘　　要：康滇地区是我国南方元古宙基底出露最为广泛的地区,元古宙岩浆活动频繁、成矿作用明显,是研究扬子陆块早期演化的重要窗口,也是近年研究的热点,元古宙地质演化过程争议较大。本文系统总结了发生在古元古代晚期—中元古代早期的重要构造—岩浆—成矿事件,即昆阳裂谷。昆阳裂谷前的基底为分布在东川和滇中地区少量的古元古代早期的汤丹群,其构造变形较东川群更强烈,可能与>1800 Ma的东川运动有关。昆阳裂谷期的岩浆岩系统主体为出露在东川—会理—滇中地区基性侵入岩,其次为少量的超基性岩、变质基性火山岩和中酸性侵入岩体,具有双峰式岩浆岩组合的特征。岩浆岩的年龄为1800 Ma^1450 Ma,集中分布在1750Ma^1650 Ma,反映了昆阳裂谷持续了约400 Ma,高峰期持续将近100 Ma。昆阳裂谷期基性岩浆岩的地球化学显示为典型陆内裂谷玄武岩的地球化学性质,其中滇中武定地区辉绿岩和会理拉拉地区的变质基性火山岩还具有典型洋岛玄武岩的特征,如富碱、高TiO_2、P_2O_5、低CaO/TiO_2、Al_2O_3/TiO_2比值,Nb、Ta、Zr、Hf等高场强元素不亏损,以及有较高的[n(^(87)Sr)/n(^(86)Sr)]_i初始比值以及较高的ε_(Nd)(t)值。根据区内岩浆岩组合及地球化学特征,我们提出在古元古代晚期至中元古代早期,康滇地区发生了一次由地幔柱活动引起的陆内裂谷拉张事件,即昆阳地幔柱。昆阳陆内裂谷在1450 Ma前后在会理—东川一线发展成为了局限小洋盆,并在中元古代晚期关闭。昆阳裂谷的沉积岩系统主体为东川群、河口群和大红山群,并可能延伸到了康滇北部的里伍岩群,上述地层中火山岩、凝灰岩锆石的U-Pb年龄集中在1800Ma^1500 Ma,不同岩群岩性组合差异可能与所处构造部位有关,并导致沉积相的差异。昆阳裂谷也是一次重要的成矿事件,其形成的矿床可分为两个系列,以因民组、落雪组Objectives：Kangdian area is famous for Cu—Fe deposits hosted in Proterozoic basements,Magmatic rocks and complicated geological evolution.Much research has been carried out from last century,however,confused isotopic dating data arouse bitter controversy on tectonic setting,magmatism,and metallogenesis etc.The most important tectonic—magmatic—mineralization events,i.e.Kunyan rift in Paleo-Mesoprotorozoic is summarized systematically in this paper. Results：he basement Pre-Kunyang rift is the few Tangdan group strata in Dongchuan and central Yunnan province,which have more obvious deformation than Dongchuan group,being coursed by the Dongchuan movement before 1 .8 Ga.The magmatic system of Kunyang period include mainly plenty of basic intrusive rocks distributing along Dongchuan—Huili —central Yunnan,and secondly few ultrabasic rocks,meta-basic vocanic rocks and intermediate —acid rocks,which has the typical characteristics of bimodal magmatic rock combination.The U-Pb ages for zircons of these magmatic rocks are from 1800 Ma to 1450 Ma,clustering together in 1650 ～1750 Ma, which reflect that Kunyang rift lasted for 0.4 billion,and peaked for 0.1 billion.The basic magmatic rocks geochemistry of Kunyang period have the geochemical characteristics of intracontinental basalts,and the diabases in Wuding area in central Yunnan and meta-basic vocanic rocks possess the characteristic of ocean island basalt （OIB）,such as high alkaline,TiO2 ,P2 O5 contents,low CaO/TiO2 ,Al2 O3/TiO2 ratios,no high-field-strength-elements（HFSEs）depletion,relatively high [n（87 Sr）/n（86 Sr）]I initial ratio and εNd （t）value.According the lithological association and geochemistry of the magmatic rocks,we propose that it was an intracontinental rift extensional event which was course by mantle plume activities,i.e.Kunyang mantle plume.The Kunyang intracontinental rift grew into limited small ocean basin at about 1450 Ma in Huili—Dongchuan area,and closed in late Mesoproterozoic.The sedimentary system of Kun

关 键 词：昆阳裂谷 昆阳地幔柱 东川群 河口群 大红山群 东川式铜矿 IOCG矿床 康滇地轴 

分 类 号：P542[天文地球—构造地质学] P611[天文地球—地质学]