内蒙古东乌旗宾巴勒查干三叠纪两次岩浆活动:年代学记录、岩石成因及构造背景  

Two Triassic magmatic activities in Binbalechagan area of Dong Ujimqin Banner, Inner Mongolia: Geochronologic record, petrogenesis and tectonic settings

作　　者：杨俊泉[1,2] 刘永顺[2] 张素荣 杨永恒[3] 张锋 戎合[4] YANG Jun-quan;LIU Yong-shun;ZHANG Su-rong;YANG Yong-heng;ZHANG Feng;RONG He(China University of Geosciences (Beijing), Beijing 100083, China;Tianjin Institute of Geology and Mineral Resources,Tianjin 300170, China;Liaohe Oilfield of CNPC, Panjin 124010, Liaoning, China;Institute of Geology, CAGS, Beijing 100037, China)

机构地区：[1]中国地质大学(北京),北京100083 [2]中国地质调查局天津地质调查中心,天津300170 [3]中油辽河油田分公司,辽宁盘锦124010 [4]中国地质科学院地质研究所,北京100037

出　　处：《中国地质》2016年第6期1913-1931,共19页Geology in China

基　　金：中国地质调查项目"内蒙古1:5万敖包查干幅;多钦乌拉幅;宾巴勒查干幅;满都胡宝力格幅;1252高地幅区调"(1212010881218)和"华北地区地质矿产调查评价进展跟踪与工作部署研究"(1212011220844)联合资助~~

摘　　要：内蒙古东乌旗宾巴勒查干分布有大面积三叠纪花岗岩，是研究中亚造山带中东部早中生代构造演化的有利地区。在区域地质调查的基础上，利用同位素年代学在该区识别出三叠纪两期侵入岩：中三叠世二长花岗岩类（238~230Ma）和晚三叠世正长花岗岩类（223~215Ma）。采用矿物化学、岩石地球化学等方法对两类侵入岩进行了研究：前者中黑云母为镁质黑云母，岩石以高硅、富钾、过铝、钙碱性为特征，稀土元素中轻稀土相对富集、具明显的负Eu异常，微量元素以相对富集大离子亲石元素、具明显的Ba负异常为特征，地球化学特征介于I型和A型花岗岩之间；后者中黑云母由镁质黑云母向铁质黑云母转变，岩石以高硅、富碱、富钾、弱过铝为特征，稀土、微量元素特征与前者相似，但稀土总量相对较低，Eu、Ba的负异常程度更大，属A型花岗岩。二者可能源于年轻幔源组分形成下地壳的部分熔融。结合区域资料分析，研究区三叠纪侵入岩形成于古亚洲洋闭合背景下，中三叠世时可能处于后造山伸展背景，晚三叠世可能为板内构造背景。Triassic intrusive rocks (TIRs) are widespread in Binbalechagan area of Dong Ujimqin Banner in Inner Mongolia, andhence this area has advantage of studying Early Paleozoic evolution of central- east segment of Central Asia Orogenic Belt(CAOB). Based on regional geological survey, the authors recognized two Triassic magmatic activities by evidence fromgeochronology: mid-Triassic adamellites(with isotope ages of 238-230 Ma)and late-Triassic syenogranites (with isotope agesfrom 223 to 215 Ma). The former rocks whose geochemical features are between I-type and A-type granites are characterized bymagnesia biotite, high silicon, rich K, peraluminum and calc- alkaline nature, abundant light rare earth elements and large ionlithophile elements, and significant negative Eu and Ba anomalies. However, the latter rocks belong to A- type granites and arecharacterized by high silicon, enriched alkali, abundant K and, weak peraluminum nature. Otherwise, total REE in the latter is lower,and negative anomaly degrees of Eu and Ba in the latter are more obvious than those of the former. These TIRs probably originatedfrom partial melting of the lower crust which consisted of newly derived mantle. In combination with regional information, it can beconcluded that the TIRS was formed after the closure of the Paleo-Asian Ocean. In mid-Triassic, the study area probably was inpost-orogenic background, and hence this area was mainly in an intraplate tectonic setting in late Triassic.

关 键 词：SHRIMP锆石U-PB年龄 地球化学特征 三叠纪花岗岩 构造背景 东乌旗 中亚造山带 

分 类 号：P588.1[天文地球—岩石学] P597.3[天文地球—地质学]