北淮阳晓天火山岩盆地片麻状花岗岩成岩年代学及地球化学特征  

The Age and Geochemical Characteristics of Neoproterozoic Gneissic Moyite in the Xiaotian Basin

作　　者：万秋 李延河[1] 王利民[2,3] 段超[1] 施珂 谭德兴[2,3] WAN Qiu;LI Yan-he*;WANG Li-min;DUAN Chao;SHI Ke;TAN De-xing(Institute of Mineral Resources,Chinese Academy of Geological Sciences,Key Laboratory of Metallogeny and Mineral Assessment,Ministry of National Resources,Beijing 100037,China;Geological Survey of Anhui Province,Hefei 230001,China;The Coverage Area Deep Resource Exploration Engineering Technology Innovation Center,Ministry of Natural Resources,Hefei 230001,China)

机构地区：[1]中国地质科学院矿产资源研究所,自然资源部成矿作用与资源评价重点实验室,北京100037 [2]安徽省地质调查院,安徽合肥230001 [3]自然资源部覆盖区深部资源勘查工程技术创新中心,安徽合肥230001

出　　处：《岩矿测试》2020年第4期620-630,共11页Rock and Mineral Analysis

基　　金：中国地质科学院基本科研业务费项目(YYWF201710);国家自然科学基金项目(41973022);合肥市人才专项。

摘　　要：岩石的锆石U-Pb定年和主量、微量、稀土元素分析是研究侵入岩成岩时代、岩石成因的主要研究手段。本文在野外地质调查工作的基础上,采用X射线荧光光谱、电感耦合等离子体发射光谱、电感耦合等离子体质谱和LA-ICP-MS等技术对晓天火山岩盆地内杨三寨附近发现的片麻状钾长花岗岩进行相关地球化学分析。结果表明:该岩体主量元素以高硅、钾和钠,低铁镁钙磷为特征,其中SiO2含量为65.86%~78.29%,Al2O3为10.89%~16.02%,MgO为0.17%~1.17%,K2O为1.37%~6.44%,Na2O为0.53%~6.50%,属于高钾钙碱性系列。微量元素方面,样品以亏损Nb、Sr、P和Ti,富集La、Ce、Nd和Zr为特征。稀土元素方面,含有较高的稀土元素(ΣREE=152.70~650.88μg/g),轻稀土富集重稀土亏损(LREE/HREE=6.77~20.64),多数具有较弱的负铕异常(δEu=0.29~1.15),铈异常不明显;稀土元素标准化曲线以右倾为特征。30个锆石点的206Pb/238U年龄分布于720~828Ma之间,加权平均年龄为776±11Ma(MSWD=2.1)。研究认为,盆地内新元古代片麻状钾长花岗岩的发现表明晓天盆地中心存在隆起,并不是之前研究认为的"斗"形的两边浅中间厚的盆地形态,这对该盆地的构造形态认识和进一步找矿具有重要的指导意义。BACKGROUND:The zircon U-Pb dating and analysis of major,trace and rare earth elements of rocks are the main research methods used to study the genesis of intrusive rocks.OBJECTIVES:To constrain the genesis of neoproterozoic gneissic moyite of the Yangsanzhai,Xiaotian volcanic basin.METHODS:Chemical composition of rocks was analyzed by X-ray fluorescence spectrometry(XRF),inductively coupled plasma-mass spectrometry(ICP-MS),and the zircon U-Pb age was determined by laser ablation inductively coupled plasma-mass spectrometry(LA-ICP-MS).RESULTS:Results show that the rock was characterized by high silicon,kalium and sodium,and low iron,magnesium,calcium and phosphorus.The content of SiO 2,Al 2O 3,MgO,K 2O and Na 2O were 65.86%-78.29%,10.89%-16.02%,0.17%-1.17%,1.37%-6.44%and 0.53%-6.50%,respectively.The rock belonged to the high potassic calc-alkaline series.The samples were characterized by depletion of Nb,Sr,P and Ti,and enrichment of La,Ce,Nd and Zr.The samples had high content of rare earth elements(ΣREE=152.70-650.88μg/g)with light rare earth enrichment(LREE/HREE=6.77-20.64).Most of the samples had weakly negative europium anomalies(δEu=0.29-1.15)without cerium anomaly.The normalized curve of rare earth elements was characterized by right-incline.The 206 Pb/238 U ages of the 30 zircon points ranged from 720 to 828Ma,with a weighted average age of 776±11Ma(MSWD=2.1).CONCLUSIONS:The discovery of Neoproterozoic gneissic moyite in the Xiaotian Basin indicates that there is uplift in the center of this basin,not the‘bucket’shape of thick in the middle and thin at the sides,as previously recognized.This has important guiding significance for the understanding of the tectonic morphology of the basin and further prospecting.

关 键 词：片麻状钾长花岗岩 主量元素 微量元素 稀土元素 U-Pb定年 锆石年龄 

分 类 号：P597.3[天文地球—地球化学]