北阿尔金喀孜萨依二长花岗岩成因及其构造意义  

Petrogenesis of the Kazisayi monzogranite from North Altun and its tectonic implications

作　　者：郑坤 吴才来[1] 吴迪 高栋 陈红杰[4] 徐楠 ZHENG Kun;WU Cailai;WU Di;GAO Dong;CHEN Hongjie;XU Nan(Institute of Geology,Chinese Academy of Geological Sciences,Beijing,100037;School of Earth and Space Sciences,Peking University,Beijing,100871;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing,100081;Zhengzhou University,Zhengzhou,450001)

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]北京大学地球与空间科学学院,北京100871 [3]中国地质科学院地质力学研究所,北京100081 [4]郑州大学,郑州450001

出　　处：《地质学报》2019年第10期2531-2541,共11页Acta Geologica Sinica

基　　金：国家自然科学基金项目(项目编号：41872071、40672049);中国地质调查局项目(项目编号：DD20190006、DD20160022-06)联合资助的成果

摘　　要：喀孜萨依二长花岗岩出露于北阿尔金蛇绿混杂岩带北缘,为探讨其成因、源区特征及构造环境,本文对其进行了岩石学、锆石U-Pb定年、Hf同位素及岩石地球化学等方面的研究。研究结果表明,喀孜萨依二长花岗岩主要由石英、斜长石、钾长石、角闪石、黑云母等矿物组成,岩体侵位时代为425~423Ma,铝饱和指数A/CNK为0.97~1.07,属弱过铝质钙碱性-高钾钙碱性岩石,P2O5与SiO2含量呈负相关,具I型花岗岩特征。轻稀土富集而重稀土亏损,Eu异常不明显,岩石富集Rb、Ba、Th、U、K等元素,相对亏损Nb、Ta、P、Ti等元素。锆石εHf(t)值为+2.65^+6.23,二阶段模式年龄tDM2为1015~1243Ma,其源岩主要来自新生地壳。结合区域构造背景,喀孜萨依二长花岗岩体可能形成于碰撞后伸展环境。Kazisayi monzogranite pluton crops out at the northern margin of the North Altun ophiolitic mélange belt.In this paper,we present petrological,geochemical,and zircon U-Pb and Lu-Hf isotopic data of the Kazisayi monzogranites to constrain their petrogenesis,source and tectonic setting.The Kazisayi monzogranites consist of mainly quartz,alkali feldspar,plagioclase,amphibole and biotite.Zircon U-Pb dating yielded ages of 425~423Ma.The rocks have high K2O with A/CNK varying from 0.97to 1.07.The granites are weakly peraluminous and and plotted within the medium-K to high-K calc-alkaline fields.These rocks show a negative correlation between P2O5and SiO2and show significant features of I-type granite.The REE patterns show a significant depletion in HREE,relative to LREE,and lack Eu anomalies.In the primitive mantle-normalized trace-element diagram,the samples show highly enrichments in Rb,Ba,Th,U and K and depletions in Nb,Ta,P and Ti.TheεHf(t)values range from 2.65~6.23with TDM2(two-stage model ages)from 1015Ma to 1243Ma.These characteristics indicate that Kazisayi monzogranites derived mainly from the juvenile crust.Considering the regional tectonic setting,the Kazsayi monzogranites may have formed in a post-collision extensional setting.

关 键 词：二长花岗岩 地球化学 锆石U-PB定年 岩石成因 北阿尔金 

分 类 号：P58[天文地球—岩石学]