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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。
The Chaganobo body in the north of Dongwuzhumuqin Banner in Inner Mongolia can be decomposed into fine yellow-grained granite units and fine-grained speckle-like micaceous granite units in gray-yellow. The former zircon U-Pb weighted average age is (306.4 ± 2) Ma, which is the Late Carboniferous magmatism, and the latter zircon U-Pb weighted average age is (278.3 ± 2) Ma, which is the result of the Early Permian magmatism product. Both granites have similar geochemical characteristics. The major elements are rich in Si, lean Ti, Mg and Ca, and have a high ratio of alkali / aluminum (NK / A). Both show significant negative Eu anomalies Trace elements are enriched in Rb, Th, U and K, weakly enriched in P, Zr and Hf, and strongly depleted in Ba, Sr and Ti. Through the analysis and discussion, it is concluded that the genetic types of late-Late Carboniferous fine-grained granite units and Early Permian fine-grained granulitic units are all I-S transitional calc-alkaline granites. Petrochemistry, occurrence and distribution of rock mass and source rock characteristics all indicate that the environment of the Late Carboniferous Late Cretaceous and Early Permian granitoids in the Chaganheobao volcano is consistent with that of the Late Paleozoic mid-orogenic tectonic setting Conversion period tectono-magmatic event product.