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

发布时间：2018-01-03 06:30

本文关键词：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　出处：《中国地质》2016年06期 　论文类型：期刊论文

【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(238~230 Ma)和晚三叠世正长花岗岩类(223~215 Ma)。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。
[Abstract]:A large area of Triassic granites are distributed in Bembal Chagan, Dongwuqi, Inner Mongolia, which is a favorable area for the study of early Mesozoic tectonic evolution in the central and eastern part of the Central Asian orogenic belt, on the basis of regional geological surveys. Using isotopic chronology, two Triassic intrusive rocks were identified in this area: the Middle Triassic Permian feldspar granitoids (238230Ma) and the late Triassic syenomorphic granitic rocks (223215Ma). ... the use of mineral chemistry. Two types of intrusive rocks have been studied by petrogeochemical methods: biotite in the former is magnesia-biotite, rocks are characterized by high silicon, potassium rich, peraluminous and calc-alkaline, and rare earth elements are relatively enriched in light rare earth elements. There are obvious negative EU anomalies, trace elements are relatively rich in large ion lithophile elements, obvious Ba negative anomalies, geochemical characteristics between I-type and A-type granite; The middle biotite of the latter is transformed from magnesia biotite to iron biotite. The rocks are characterized by high silicon, alkali rich, potassium rich and weak peraluminite. The characteristics of rare earth elements and trace elements are similar to those of the former, but the total amount of rare earth is relatively low. The negative anomalies of Ba are more severe and belong to A-type granites. Both of them may be attributed to the partial melting of the lower crust formed by the young mantle-derived components. The Triassic intrusive rocks in the study area were formed in the paleo-Asian ocean closure setting, the middle Triassic may be in the post-orogenic extensional setting, and the late Triassic may be the intraplate tectonic setting.
【作者单位】：中国地质大学(北京);中国地质调查局天津地质调查中心;中油辽河油田分公司;中国地质科学院地质研究所;
【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~~
【分类号】：P588.1;P597.3
【正文快照】： 作为全球最大增生型造山带之一[1],中亚造山带以其巨大的科学意义和丰富的矿产资源而引人关注[2]。对中亚造山带的研究不仅有助于理解该区构造演化,还将提升增生造山过程的认识。中生代的构造背景是该区争论焦点之一,目前较为主要的观点有:(1)同造山构造背景,包含俯冲[3]、后

【相似文献】