内蒙古多伦晚中生代中酸性火山岩岩石地球化学特征及构造环境分析
投稿时间:2018-01-22  修订日期:2017-09-04  点此下载全文
引用本文:王春林.内蒙古多伦晚中生代中酸性火山岩岩石地球化学特征及构造环境分析[J].地质与勘探,2018,54(5):988-1000
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王春林 成都理工大学,四川成都 四川省地质矿产勘查开发局四0三地质队,四川峨眉山 云南地矿工程勘察集团公司,云南昆明 1272892534@qq.com 
基金项目:内蒙古矿产地质调查基金项目(项目编号:NMKD2009-12
中文摘要:多伦地区晚中生代中酸性火山岩地球化学特征表明:区内中酸性火山岩属高钾-钾玄、碱性-钙碱性系列,具后碰撞火山岩特征;岩石轻重稀土分馏现象明显;Rb、K等大离子亲石元素(LILE)及Th、U、Zr、Hf等高场强元素(HFSE)相对富集,Ba、Nb、Sr、P和Ti亏损;岩石锆石定年结果显示:满克头鄂博组流纹岩锆石年龄为163.2±2.1 Ma,属晚侏罗世;义县组粗面岩锆石年龄为144.2±1.4Ma,属早白垩世;岩浆起源为中-下地壳,部分存在地幔组分的混合。早期火山旋回中的岩石组合具有不同的岩浆来源,晚期火山旋回中的岩石组合具有相同的岩浆来源,岩浆演化特征以分离结晶作用为主。通过岩石化学和岩石地球化学特征对岩石形成的大地构造环境研究认为:满克头鄂博组到玛尼吐组位于碰撞后-火山弧构造环境,玛尼吐组到白音高老组位于火山弧-弧后伸展构造环境,白音高老组到义县组位于弧后伸展-裂谷构造环境。
中文关键词:地球化学特征 U-Pb锆石年代学 岩石成因 构造演化 多伦火山岩 内蒙古
 
Geochemical characteristics of intermediate-acid volcanic rocks and the tectonic environment in the Duolun area, Inner Mongolia
Abstract:This paper deals with geochemical characteristics of Late Mesozoic intermediate-acid volcanic rocks in the Duolun area, Inner Mongolia. The data suggest that these rocks belong to high potassium-shoshonite and alkaline-calcium alkaline series, associated with a post-collision tectonic setting. Fractionation phenomenon of LREE and HREE is obvious, with enrichment of LILE (Rb and K) and HFSE (Th, U, Zr and Hf), depletion of Ba, Nb, Sr and Ti. Zircon dating results show that the Manketoue'bo rhyolite formation age is about 163.2±2.1 Ma, which is the Late Jurassic epoch. The Yixian trachyte formation age is 144.2±1.4Ma, i.e. Early Cretaceous. Their magmatic origin is middle and lower crust, partly blended by mantle component. Rock assemblage in early volcanic cycles has different sources of magma, while that in later volcanic cycles has the same source of magma. The evolution of magma was dominated by the separation of crystallization. Chemical characteristics of rocks and petrochemistry suggest that Manketoue'bo Formation to Ma'nitu Formation was located in a post-collision volcanic arc tectonic environment, and Ma'nitu Formation to Baiyin'gaolao Formation in a volcanic arc or back-arc extensional tectonic setting, and Baiyin'gaolao Formation to Yixian Formation in a back-arc extension-rift tectonic environment.
keywords:geochemical characteristics,U-Pb zircon chronology,petrogenesis,tectonic evolution,Duolun volcanic rocks,Inner Mongolia
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