延边开山屯花岗闪长岩-石英闪长岩体年代学、地球化学特征及对古太平洋板块俯冲作用时限的制约

发布时间：2018-05-19 20:06

本文选题：石英闪长岩 + 岩浆混合　；参考：《岩石学报》2016年09期

【摘要】：近年来古太平洋构造域的构造演化备受学者关注。本文报道的延边开山屯地区花岗闪长岩-石英闪长岩体LAICP-MS U-Pb年龄表明其形成时间为早侏罗世早期(198±1Ma),所采样品可根据Zr/Hf值分为高Zr/Hf值组花岗闪长岩和低Zr/Hf值组石英闪长岩。高Zr/Hf值组花岗闪长岩起源深度浅,富集Rb、Th、U、K等大离子亲石元素(LILEs),贫Nb、Ta、Ti等高场强元素(HFSEs),具壳源岩浆的特点。低Zr/Hf值组为壳源岩浆与来自深部的亏损地幔岩浆混合而成,岩石亏损Nb、Ta、Zr、Hf、Ti等高场强元素,具有典型的弧型岩浆地球化学特征。岩体中存在细粒闪长质包体,镜下可见针柱状磷灰石。开山屯岩体属钙碱性系列岩石,结合前人资料,认为其与该地区同时代火成岩组成北-东向分布的早侏罗世活动大陆边缘型火成岩带,而位于该带西侧的小兴安岭-张广才岭地区存在同时代弧后拉张带,两者构成典型的大陆弧与弧后拉张带模型,共同揭示了早侏罗世早期古太平洋板块对东北地区的俯冲作用。
[Abstract]:In recent years, the tectonic evolution of the paleo-Pacific tectonic domain has attracted much attention. The LAICP-MS U-Pb age of granodiorite-quartz diorite in Kaishantun area, Yanbian, reported in this paper indicates that the age of its formation is 198 卤1MaA in the early Jurassic. The samples can be divided into granodiorite with high Zr/Hf value and quartz diorite with low Zr/Hf value according to Zr/Hf value. The granodiorite of high Zr/Hf value group is of shallow origin and is rich in large ion lithophile elements such as RbZr/Hf, Th, UK and Lil Esn, and is poor in high field strength elements such as NbSe Ta-Ti, which is characterized by crust-derived magma. The low Zr/Hf value group is composed of crust-derived magma and depleted mantle magma from deep depth. The rocks are depleted of high field strength elements such as NbTa-Tazo-Zr-Hf-Ti, and have typical geochemical characteristics of arc magma. There are fine grained diorite inclusions in the rock mass and needle-columnar apatite can be seen under the microscope. The Keshantun rock body is a calc-alkaline series of rocks. In combination with previous data, it is considered that its contemporaneous igneous rocks formed the early Jurassic active continental margin type igneous belt with the distribution of the north-east direction of the igneous rocks. In the west of the belt, there is a contemporaneous back-arc extensional belt in the Xiaoxing 'anling-Zhangguangcailing area, which constitutes a typical continental arc and back-arc extensional belt model, which reveals the subduction of the Paleo-Pacific plate in the early Jurassic to the Northeast.
【作者单位】：吉林大学地球科学学院;大庆油田有限责任公司勘探开发研究院;
【基金】：中国地质调查局工作项目(1212011085484) 国家自然科学基金项目(41072150)联合资助
【分类号】：P588.122;P597.3

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