内蒙古东乌珠穆沁旗查干敖包花岗岩体时代、成因及地质意义

发布时间：2018-10-13 17:57

【摘要】：内蒙古东乌珠穆沁旗北部的查干敖包岩体可分解为灰黄色细粒花岗岩单元和灰黄色中细粒似斑状含二云母花岗岩单元。前者锆石U-Pb加权平均年龄为(306.4±2)Ma,为晚石炭世岩浆活动产物,后者锆石U-Pb加权平均年龄为(278.3±2)Ma,为早二叠世岩浆活动产物。两期花岗岩具有相似的地球化学特征,主量元素均具有富Si,贫Ti、Mg、Ca,且有较高的碱/铝(NK/A)比值等特征;均表现出明显的负Eu异常;微量元素富集Rb、Th、U、K,弱富集P、Zr及Hf,强烈亏损Ba、Sr及Ti。通过分析讨论,认为晚石炭世晚期细粒花岗岩单元和早二叠世中细粒似斑状花岗岩单元的成因类型均为I-S过渡型钙碱性花岗岩。岩石化学、岩体产状、分布特点和源岩特征都表明,查干敖包岩体晚石炭世晚期和早二叠世花岗岩构造背景环境一致,均为晚古生代中亚造山大地构造背景下碰撞后转换期构造—岩浆事件产物。
[Abstract]:The Chagan Aobao rock body in the northern part of East Wuzhimuqin Banner of Inner Mongolia can be decomposed into gray-yellow fine-grained granite units and grain-yellow meso-porphyry migmatite granite units. The former zircon U-Pb weighted average age is (306.4 卤2) Ma, is the product of late Carboniferous magmatic activity, the latter zircon U-Pb weighted average age is (278.3 卤2) Ma, is the early Permian magmatic activity product. The granites of the two periods have similar geochemical characteristics, the principal elements are rich in Si, poor in Ti,Mg,Ca, and have high ratio of alkali to aluminum (NK/A), all of them show obvious negative Eu anomalies, and trace element Rb,Th,U,K, is enriched weakly in Rb,Th,U,K, and Hf, is strongly depleted in Ba,Sr and Ti.. Through analysis and discussion, it is considered that the genetic types of the late Carboniferous fine-grained granite unit and the early Permian fine-grained porphyry granite unit are I-S transitional calc-alkaline granites. The petrochemistry, occurrence, distribution and source rock characteristics all indicate that the late Carboniferous and early Permian granitoids of Chagan Aobao have the same tectonic setting. They are the products of tectonic-magmatic events during the post-collision transition period in the late Paleozoic Central Asian orogenic tectonic setting.
【作者单位】：北京市地质调查研究院;中国地质科学院地球物理地球化学勘查研究所;中国地震局地质研究所;
【基金】：中国地质调查局“内蒙古1∶5万巴彦敖包等四幅区域地质调查”项目(基[2010]矿评01-09-04)
【分类号】：P588.121

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