内蒙古东部红山子复式岩体晚侏罗世黑云母花岗岩地球化学特征及地质意义  

Geochemistry of Late Jurassic biotite granite in the Hongshanzi area,Hexigten Banner,Inner Mongolia,and its geological implications

作　　者：祝洪涛[1] 巫建华[2] 唐大伟 郭恒飞 杨东光 王良玉[1] 吴仁贵[3] ZHU Hongtao;WU Jianhua;TANG Dawei;GUO Hengfei;YANG Dongguang;WANG Liangyu;WU Rengui(No.243 Geological Party of Nuclear Industry,CNNC,Chifeng,Inner Mongolia,024000;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang,330013;School of Earth Science,East China University of Technology,Nanchang,330013)

机构地区：[1]核工业二四三大队,内蒙古赤峰024000 [2]东华理工大学核资源与环境国家重点实验室,南昌330013 [3]东华理工大学地球科学学院,南昌330013

出　　处：《地质论评》2020年第3期765-785,共21页Geological Review

基　　金：中国核工业地质局铀矿地质勘查项目(编号:201801);国家自然科学基金资助项目(编号:41372071);中国核工业集团公司项目(编号:中核地计[2008]74)的成果。

摘　　要：位于沽源-红山子铀成矿带北东段的红山子复式岩体,由晚侏罗世早期碱长花岗岩、黑云母花岗岩和早白垩世早期细粒黑云母花岗岩、花岗斑岩组成,并以晚侏罗世早期碱长花岗岩、黑云母花岗岩为主体。晚侏罗世早期黑云母花岗岩包括中细粒黑云母花岗岩和似斑状黑云母花岗岩两种,它们均具高硅、富碱、钾和铁、贫铝和低钙、镁的主量元素特征,SiO2分别为75.2%~76.6%和74.6%~75.3%,(K2O+Na2O)分别为8.19%~8.96%和8.78%~9.10%, K2O/Na2O分别为1.19~1.39和1.29~1.35,在SiO2-MALI图解中落入钙碱值与碱钙值A型花岗岩区域内;Al2O3的含量分别为11.5%~12.3%和12.5%~12.7%,CaO分别为0.30%~1.24%和0.76%~0.83%,A/CNK分别为0.90~0.97和0.93~0.96,均不含标准矿物刚玉;FeO+Fe2O3分别为2.23%~2.65%和2.33%~2.48%(均>1.00%),锆石饱和温度分别为834~869℃和819~839℃(均>800℃),具有A型花岗岩的富铁和高温特征。中细粒黑云母花岗岩和斑状黑云母花岗岩稀土含量较高、富集轻稀土、重稀土分异不明显和Eu强烈亏损,富集大离子亲石元素Rb、Th、K等和高场强元素Zr、Hf、Nd、Ta、Y等,亏损大离子亲石元素Ba、Sr等,Zr+Nb+Ce+Y的含量分别为897×10-6~1236×10-6和513×10-6~643×10-6(均>350×10-6),10000Ga/Al值分别为6.28~6.90和3.28~3.98(均大于2.6),具有A型花岗岩的微量元素特征。在Nb-Y-3Ga、Nb-Y-Ce和Y/Nb-Rb/Nb图解中显示A1和A2型过渡型花岗岩的特征,微量元素构造判别图解显示板内拉张构造环境。中细粒黑云母花岗岩和斑状黑云母花岗岩具有较低的■、较高的εNd(t)、较年轻的TDM2、较低的■、■、■和较低的δ18OV-SMOW,表明岩浆源于年轻下地壳底部的部分熔融,且经历了高温热液蚀变作用。可见,中细粒黑云母花岗岩和斑状黑云母花岗岩是在板内拉张构造环境下,由源于Ⅰ型富集地幔的基性岩浆底侵于下地壳和少量古老下地壳混染后,形成的年轻下地壳再部分熔融形成Objectives:The Hongshanzi complex intrusives located in the northeastern part of the Guyuan—Hongshanzi uranium belt,which is composed of early Late Jurassic alkali feldspar granite,biotite granite and early Cretaceous early fine-grained biotite granite and granite porphyry.The composition of the rock is dominated by the alkalifeldspar granite and biotite granite in the early Jurassic.The early Late Jurassic biotite granites include medium-fine-grained biotite granites and porphyritic biotite granites,At present,uranium mineralization has been found in the inner and outer contact zone between the Early—Late Jurassic mid—fine-grained biotite granite and the Late Jurassic volcanic rock in the compound rock body,indicating that this zone is a favorable place for further uranium exploration.However,the geochemical characteristics of the Late Jurassic alkaline feldspar granite and biotite granite that make up the Hongshanzi complex rock mass have not been systematically studied,which restricts the in-depth study of uranium mineralization.Methods:Based on detailed observations of occurrence of Hongshanzi complex rock mass in the field,we have studied the petrology,geochemistry,Sr-Nd-Pb radio isotope and O isotope of these biotite granite to discuss nature of source region and tectonic setting,than,we have discussed the relationship between biotite granite and uranium mineralization.Results:All of biotite granite are characterized by high SiO2(75.2%~76.6%and 74.6%~75.3%,respectively),(K2O+Na2O)(8.19%~8.96%and 8.78%~9.10%,respectively),and K2O/Na2O(1.19~1.39 and 1.29~1.35,respectively),low Al2O3(11.5%~12.3%and 12.5%~12.7%),CaO(0.30%~1.24%and 0.76%~0.83%,respectively).It does not contain standard mineral corundum,indicating that the magma source area is magmatic rock;FeOT is 1.79%~2.13%and 1.80%~1.91%,respectively,both greater than 1.00%,with iron-rich characteristics of A-type granite;zircon saturation temperatures are 834~869℃and 819~839℃,greater than 800℃,with the high-temperature characteristics of A-type g

关 键 词：黑云母花岗岩 A型花岗岩 晚侏罗世 地球化学 沽源-红山子铀成矿带 

分 类 号：P619.14[天文地球—矿床学]