摘要
思泰岩体位于扬子地块与华夏地块拼合带的西南段,对剖析华南区域构造演化具有重要的地质意义。思泰岩体主要由辉长岩、辉长闪长岩组成。LA-ICP-MS锆石U-Pb年代学分析表明,辉长岩的侵位结晶时限为(445±1)Ma,属于加里东期岩浆活动产物。岩石具有高钾钙碱性特征;其铝饱和指数为0.95~1.99,属准铝质-过铝质岩石;岩石具有中等偏高的Mg#值(0.43~0.51)。锆石的εHf(t)值主要集中在0.39~5.84之间,其一阶段模式年龄为1 181~855 Ma,暗示其源区主要为中-新元古代岩石圈地幔。综合地球化学、锆石Hf同位素组成特征及区域地质资料,认为思泰岩体是在陆内碰撞造山期后伴随岩石圈局部伸展-减薄,软流圈高温地幔物质上涌,从而导致中-新元古代岩石圈地幔物质的部分熔融,随后岩浆发生上升侵位固结成岩,在上升侵位的过程中受到少量的地壳物质的混染而形成。
The Sitai pluton, located in the southwestern segment of the assembly belt in the Yangtze and Cataysia blocks, could provide tight constrants on the tectonic evolution of South China. The intrusion is mainly composed of gabbro and diorite. In this paper, the LA-ICP-MS zircon U-Pb dating indicates that the gabbro was emplaced at （445±1）Ma, and was the refore formed in Caledonian. The Sitai samples be- long to high-K calc-alkaline series and are metaluminous-peraluminous （A/CNK=0. 95-1. 99）. The Mg number （Mg# ） are 0.43 to 0.51. The εHf（t） values ranging from 0.39 to 5.84, suggest that they might have been derived from Mesoproterozoic subcontinental lithospheric mantle. Combined with the regional geology, the geochemical features and zircon Hf isotopic composition indicate that development of local lithospheric extension and thinning after intracontinental collision orogenic process could trigger extensive upwelling of high temperature asthenosphere mantle materials. Such processes could lead to partial melt of Meso-Neoproterozoie subcontinental lithospheric mantle. The magma also has undergone small amount of crustal material contamination during magma ascent and/or emplacement.
出处
《地质科技情报》
CSCD
北大核心
2017年第6期113-121,共9页
Geological Science and Technology Information
基金
中国地质调查局项目"桂东-粤西地质矿产调查"(DD20160035)
