CAJ | 학술논문

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。
대흥안령이북지구고로기저가흘탑조근년래배수관주，전인대기형성시구조배경적불동관점제약료대해구기저성질급지질연화과정적정학인식。위사명출로우내몽고액이고납팔대관목장부근적“가흘탑조”적암석조합、변질변형조구、암석지구화학특정급대지구조배경，진행료계통적야외화실내연구。결과표명：해구“가흘탑조”병비전통의의상적전한무기변질암계，이시일투경력료구조변질변형작용적연산기침입체；암석조합위흑운이장변정미릉암、화강섬장질변정미릉암、미릉암화흑운각섬사장편마암；암석고갑、저태、부려，속고갑개감성암계，희토원소총량편고，경중희토분류명현차경희토부집，구유일정정도적부유이상，부집지만불상용원소차우손고장강원소，기암장조수료지각물질적혼염；형성우만삼첩만주라세몽고악곽자극조산대동팽당후팽당구조연화과정중제압신전구조전환궤제하；조백성세덕이포간단렬대강렬활동사기조수료저각섬암상변질작용병발생료구조변질변형。
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 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 .