藏北扎美仁地区新生代钾质火山岩的地球化学特征及构造环境
发布时间：2018-11-13 13:56
【摘要】：当前公认青藏高原是印度板块和欧亚板块持续汇聚的产物,为全球造山过程的研究提供了一个天然实验室。藏北羌塘地区广泛发育不同系列的新生代火山岩,但对其时空分布与地球化学特征的认识还比较匮乏,也不清楚不同岩石系列之间的联系以及与岩石圈构造演化过程之间的关系,因此本文选取研究程度较低的扎美仁地区新生代钾质火山岩作为研究对象,开展岩石学、矿物学、年代学和地球化学的研究工作,结合羌塘地区新生代火山岩的研究成果,试图探讨羌塘地区岩石圈新生代构造演化过程,为青藏高原的形成演化过程的研究提供新的科学依据。扎美仁地区新生代火山岩以粗面安山岩和碱玄质响岩为主,形成于渐新世(26-33Ma)。火山岩贫硅、富钾和低镁,稀土总量(∑REE)较高,轻、重稀土分异明显,稀土配分曲线总体呈右倾型,无明显负铕异常(0.79-0.88)。岩石总体呈现富集Rb、Th、Ba、Sr等大离子亲石元素,相对亏损Nb、Ta、P、Ti等高场强元素。火山岩具有较高的87Sr/86Sr比值、206Pb/204Pb、207Pb/204Pb、208Pb/204Pb比值以及较低143Nd/144Nd比值,以上特征指示火山岩的岩浆源区与EM II型富集地幔有关,其成因机制受幔源岩浆分离结晶作用所控制,具有板内碱性火山岩和活动陆缘、岛弧火山岩的双重地球化学与构造环境属性。利用火山岩中的单斜辉石斑晶估算出扎美仁火山岩的形成的深度大约在48公里左右,结晶温度为1146-1297℃。综合对比藏北羌塘地区新生代火山岩的岩石系列、时代变化、空间分布以及地球化学等特征,指出羌塘地区出现的一系列新生代火山岩,是受印度板块向欧亚大陆的俯冲和碰撞所引起的俯冲板片断离作用以及软流圈上涌和扰动的影响而形成的。
[Abstract]:At present, Qinghai-Xizang Plateau is recognized as the product of continuous convergence of Indian plate and Eurasian plate, which provides a natural laboratory for the study of global orogenic process. Different series of Cenozoic volcanic rocks have been widely developed in Qiangtang area, northern Tibet, but their spatio-temporal distribution and geochemical characteristics are still poorly understood. It is also not clear that the relationship between different lithological series and lithospheric tectonic evolution process, so this paper selects the Cenozoic potash volcanic rocks in Zameiren area as the research object, and develops petrology and mineralogy. Combined with the research results of Cenozoic volcanic rocks in Qiangtang area, this paper attempts to explore the Cenozoic tectonic evolution process of the lithosphere in Qiangtang area, which provides a new scientific basis for the study of the formation and evolution process of the Qinghai-Tibet Plateau. The Cenozoic volcanic rocks in the Zameiren area were mainly composed of coarse andesite and alkaline-syenite, and formed in the Oligocene (26-33Ma). The volcanic rocks are poor in silicon, rich in potassium and low in magnesium. The total amount of rare earth (鈭，
本文编号：2329338
[Abstract]:At present, Qinghai-Xizang Plateau is recognized as the product of continuous convergence of Indian plate and Eurasian plate, which provides a natural laboratory for the study of global orogenic process. Different series of Cenozoic volcanic rocks have been widely developed in Qiangtang area, northern Tibet, but their spatio-temporal distribution and geochemical characteristics are still poorly understood. It is also not clear that the relationship between different lithological series and lithospheric tectonic evolution process, so this paper selects the Cenozoic potash volcanic rocks in Zameiren area as the research object, and develops petrology and mineralogy. Combined with the research results of Cenozoic volcanic rocks in Qiangtang area, this paper attempts to explore the Cenozoic tectonic evolution process of the lithosphere in Qiangtang area, which provides a new scientific basis for the study of the formation and evolution process of the Qinghai-Tibet Plateau. The Cenozoic volcanic rocks in the Zameiren area were mainly composed of coarse andesite and alkaline-syenite, and formed in the Oligocene (26-33Ma). The volcanic rocks are poor in silicon, rich in potassium and low in magnesium. The total amount of rare earth (鈭，
本文编号：2329338
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