摘要
康滇地区是我国南方元古宇地层集中出露的地区,元古宙岩浆活动频繁,是研究扬子陆块早期地质构造演化的窗口,也是最近研究的热点。近年本项目组在南北走向的元谋-绿汁江深大断裂北部、云南元谋县黄瓜园地区识别出了中元古代晚期的片麻状花岗岩。花岗岩锆石的LA-ICP-MS U-Pb年龄为1069.4±6.9Ma(MSWD=0.47,n=18)。岩石化学表现为较高的SiO_2(平均值高达72.79%)和中等Na_2O+K_2O(平均为6.62%),低TiO_2(平均0.26%)、低CaO(平均0.79%)、低MgO(平均0.52%,Mg#平均值22.13)和高Al_2O_3(平均12.84%,A/CNK平均值为1.33)含量,总体表现为亚碱性花岗岩的特征。微量元素分析显示稀土元素总量(∑REE)为132.96×10^(-6)~278.72×10^(-6),平均237.00×10^(-6),稀土配分曲线明显呈轻稀土富集、重稀土亏损的特点;δEu在0.38~0.49之间;微量元素配模式明显亏损Ba、Ta、Nb、Sr、P和Ti,相对富集Rb、Th、U、K等大离子亲石元素和La、Zr、Hf、Y等元素。岩石地球化学特征显示本区花岗岩属于A2亚类,可能源于下地壳基性岩部分熔融,为板块碰撞后伸展构造背景下的产物。花岗岩锆石U-Pb定年和地球化学特征表明在中元古代末期,康滇地区除了发生过南北向的块体汇聚外,可能还可能发生过较大规模东西向的汇聚过程,为全球性格林威尔造山运动的组成部分。此外,该区花岗岩的时代与邻近拉拉IOCG矿床中辉钼矿的Re-0s年龄高度一致,表明拉拉铜铁矿床成矿物质的最终定位富集与中元古代晚期康滇地区微陆块东西方向汇聚后的伸展运动密切相关。
Abstract： Proterozoic Eonothem stratum of South China are centralized outcropping in Kangdian area. The frequent magmatic activity in Proterozoic is the window of geological tectonic evolution study on Yangtze craton, which is a burning field of research in recent years. Our group have identified the late Mesoproterozoic gneissic granite lately in area of Huangguayuan, Yuanmou, Yunnan Province, located on the north of S--N-trending Yuanmou--Luzhijiang fault. The U-Pb age of zircons in granite is 1069.4±6.9Ma（MSWD =0.47, n = 18）. The Huangguayuan granites are characterized by high SiO2 （ave. 72.79% ） , medium alkali contents （ave. Na20 ＋ K20content of 6.62% ） , low TiO2 （ ave. 0.26% ） , low CaO （ ave. O. 79% ） , low MgO （ ave. 0.52% , ave. Mg# 22. 13 ） , and high A1203 （ ave. 12.84% , ave. A/CNK 1.33 ）, exhibiting the features of sub-alkaline granite in the mass. The content of EREE is 132.96×10^-6 - 278.72×10^-6 with an averageEREE of 237.00×10^-6. They possess the obvious characteristic of high LREE and low HREE, with a δEu value of 0.38 - 0.49. The chondrite- normalized REE pattern displays right dipping curves. The trace element patterns show that Ba, Ta, Nb, St, P and Ti are obviously depleted, whereas La, Zr, Hf, Y and the large ion lithophile elements such as Rb, Th, U and K are relatively enriched. Petrochemistry shows that, the Huangguayuan granits are A-type granite originating from the partial melting of lower crust basic rock. The formation temperature of Huangguayuan granite is about 750℃, and it is the product of extensional tectonics after plate collision. The U-Pb age and geochemistry of granites indicate that, besides S--N-trending plate convergence, Kangdian area also probably underwent the large-scale E--W-trending convergence process in late Mesoproterozoic, which is a constituent part of global Grenvillian orogenic movement. The age of granite in this area is highly coincident with the Re-Os age of molybdenite in Lala IOCG deposit nearby. It means that extension movement of small landmass in Kangdian area after E--W-trending convergence in late Mesoproterozoic is closely related to the final concentration and positioning of metallogenic substance in Lala copper and iron deposit.
出处
《地质论评》
CAS
CSCD
北大核心
2015年第2期376-392,共17页
Geological Review
基金
国土资源大调查项目(编号1212010911064
1212010813066)
国家自然科学基金资助项目(编号U1302233
40830425
40173025)
国家重点基础研究发展规划(973)项目(编号2009CB421006)的成果
作者简介
付宇，女，1986年生。博士研究生。主要从事矿床地球化学研究。Email：fuyuemailfuyu@163．com。
通讯作者：孙晓明1963年生，教授，博士生导师。主要从事矿床学研究。Email：eessxm@mail．sysu．edu．cn。
