广西佛子冲广平岩体成因及地质意义  

THE GENESIS AND GEOLOGICAL IMPLICATION OF THE GUANGPING SYENOGRANITE IN FOZICHONG,GUANGXI

作　　者：王泰山[1,2] 杨启军[3] 鲁海峰[1,2] 林艳海[1,2] 周辉 张鑫利[1,2] 余福承[1,2] 陈秉芳[1,2] 徐贝贝[1,2] WANG Tai-shan YANG Qi-jun LU Hai-feng LIN Yan-hai ZHOU Hui ZHANG Xin-li YU Fu-cheng CHEN Bin-fang XU Bei-bei(Northern Qinghai-Tibet Plateau Geological Processes and Mineral Resources Laboratory ,Xining 810012,China Qinghai Geological Survey Institute ,Xining 810012,China College of Earth Sciences ,Guilin University of Technology ,Guilin 541004,China Guangxi Geological Survey Institute ,Nanning 530021,China)

机构地区：[1]青海省青藏高原北部地质过程与矿产资源重点实验室,青海西宁810012 [2]青海省地质调查院,青海西宁810012 [3]桂林理工大学地球科学学院,广西桂林541004 [4]广西地质调查院,广西南宁530021

出　　处：《矿物岩石》2016年第4期86-94,共9页Mineralogy and Petrology

基　　金：中国地质调查局"全国危机矿山接替资源勘查专项典型矿床研究课题"项目的子项目之一--"广西佛子冲铅锌矿田成矿规律与模式研究"(项目编号:20089946-2)

摘　　要：针对佛子冲地区产出的正长花岗岩进行锆石LA-ICP-MS锆石U-Pb同位素年代学研究,结果表明,该岩体的形成年龄为170.8 Ma±6.3 Ma,时代为中侏罗世。岩石地球化学研究表明该岩石具有高钾钙碱性特征(K_2O+Na_2O=8.64%~9.62%,σ=2.44~2.69),准铝—弱过铝质(A/CNK=1.01~1.04),稀土含量高(ΣREE=273×10^(-6)~439×10^(-6),平均323×10^(-6)),LREE强烈富集,HREE轻度富集(La/Yb)N=10.87~16.21,平均13.68),较强的Eu负异常(δEu=0.18~0.26),总体呈向右缓倾斜的海鸥式,微量元素蛛网图上出现强烈富集Rb,Th,U,Pb,而亏损Ba,Sr,P,Ti,Eu,结合花岗岩成因类型判别图解确定其为A型花岗岩。综合区域上的研究成果,佛子冲中侏罗世正长花岗岩进一步佐证了华南地区在侏罗纪时,岩石圈发生了伸展作用,区域上是太平洋板块向西俯冲的一个地质响应。Zircon LA-ICP-MS U-Pb dating reveals that the Guangping syenogranite was intruded in 170 Ma±6.3 Ma of middle Jurassic period. The principal geochemical signatures of these syenogranite include a high-K calc-alkaline affinity （K2O ＋ Na2O = 8. 64% - 9.62%, σ=2.44 - 2.69） ,metaluminous-weakly peraluminous rocks（A/CNK= 1.01-1.04）, and slightly fractionated REE patterns in the chondrite-normalized rare earth element diagrams（∑REE-273×10^-6~ 439×10^-6 ,average 323）〈 10-6）. It shows that the rock is enriched in Rb,Th,U,Pb and depleted in Ba,Sr,P,Ti,Eu（（La/Yb）N=10.87~16.21 ,average 13.68,Eu obvious negative anomalies,δEu =0. 18~0. 26）. Plot of data points are located in the A-type granite area of the diagram of granite petrology. On the basis of previous regional research,it concludes that the middle Jurassic syenogranite of Fozichong was resulted from the lithospheric extension in South China,which was a response to the westward subduction of the Paleo-Pacific plate.

关 键 词：佛子冲 锆石U-PB年龄 岩石地球化学 A型花岗岩 伸展作用 

分 类 号：P588.121[天文地球—岩石学] P597.2[天文地球—地质学]