内蒙古额尔古纳八大关牧场“佳疙瘩组”变质岩系原岩研究  

Protoliths of the Metamorphic Rock Series of‘Jiageda Formation'in the Badaguan Area of E'erguna,Inner Mongolia

作　　者：崔芳华[1] 郑常青[1] 丁雪[2] 徐学纯[1] 李娟[1] 施璐[1] 高源[1] 高峰[1] 张行行[1] 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]青岛海洋地质研究所,山东青岛266071

出　　处：《吉林大学学报（地球科学版）》2014年第1期198-212,共15页Journal of Jilin University：Earth Science Edition

基　　金：中国地质调查局项目(1212011120654);国土资源部项目(201011083)

摘　　要：大兴安岭以北地区古老基底佳疙瘩组近年来倍受关注,前人对其形成时构造环境的不同观点制约了对该区基底性质及地质演化过程的正确认识。为查明出露于内蒙古额尔古纳八大关牧场附近的"佳疙瘩组"的岩石组合、变质变形组构、岩石地球化学特征及大地构造背景,进行了系统的野外和室内研究。结果表明:该区"佳疙瘩组"并非传统意义上的前寒武纪变质岩系,而是一套经历了构造变质变形作用的燕山期侵入体;岩石组合为黑云二长变晶糜棱岩、花岗闪长质变晶糜棱岩、糜棱岩化黑云角闪斜长片麻岩;岩石高钾、低钛、富铝,属高钾钙碱性岩系,稀土元素总量偏高,轻重稀土分馏明显且轻稀土富集,具有一定程度的负铕异常,富集地幔不相容元素且亏损高场强元素,其岩浆遭受了地壳物质的混染;形成于晚三叠-晚侏罗世蒙古-鄂霍茨克造山带同碰撞-后碰撞构造演化过程中挤压-伸展构造转换机制下;早白垩世德尔布干断裂带强烈活动使其遭受了低角闪岩相变质作用并发生了构造变质变形。As the old basement in northern Great Xing ’ an Range , the Jiageda Formation has attracted more and more attention in recent years .The different views advised by previous researchers on tectonic setting of the Jiageda Formation have significantly restricted the correct understanding of natures and geological evolution processes of the basement in this area .We conducted systematic studies on rock association ,metamorphic-deformational fabric ,geochemical characteristics and tectonic setting＆amp;nbsp;of ‘Jiageda Formation’ in the Badaguan area of E’erguna ,Inner Mongolia .Research results indicate that the ‘Jiageda Formation’ in the study area is a Yanshanian intrusion that underwent tectonic metamorphism and deformation , instead of the Precambrian strata . The rock of this intrusion are actually biotite monzo-blastomylonite , granodioritic blastomylonite , biotite amphibole plagioclase mylonitic gneiss .These rocks are characterized by high K ,Al and low Ti ,and shown as high-K calc alkaline series . They are high in total REE and LREE contents ,and show obvious fractionation of LREE from HREE with negative Eu anomaly to some extents .Such geochemical features as enrichment of the LILE and depletion of the HSFE suggest that their parent magma was contaminated by the crustal material .This suite of intrusion formed under the tectonic setting from compression to extension during the formation and evolution of the Mongolia-Okhotsk orogenic belt from the Late Triassic to Late Jurassic period .T he intense activity of the Derbugan fault during the Early Cretaceous period resulted in the low amphibolite facies metamorphism and deformation of these rocks .

关 键 词：佳疙瘩组 变质变形 原岩研究 地球化学 八大关 额尔古纳 

分 类 号：P511.5[天文地球—地质学]