中天山东段天湖花岗岩岩石学、地球化学及其成因

发布时间：2018-02-02 14:48

本文关键词： 花岗岩地球化学印支期天湖中天山　出处：《地质学报》2017年06期 　论文类型：期刊论文

【摘要】：天湖花岗岩体由六个侵入体组成,按岩石谱系划分为三个岩相单元,归并为一个超单元,其为同一次岩浆熔融事件过程中曾经发生过三次岩浆侵入活动而形成的圆形深成岩体。LA-ICP-MS锆石U-Pb定年结果表明,天湖岩体侵位于早三叠世(241~243Ma),为印支早期的产物。来自岩体的锆石原位Hf同位素测定结果表明,ε_(Hf)(t)值变化于-2.6~5.5之间,二阶段Hf模式年龄(t_(DM2))变化于941~1435Ma之间,表明其岩浆源区均为来源于亏损地慢的新生地壳岩石。该岩体总体富硅(SiO_2为69.14%~76.62%),富碱(K_2O+Na_2O为7.39%~8.83%),而Ti,Ca,Fe和Mg含量较低,A/CNK为0.95~1.04,(K_2O+Na_2O)/Al_2O_3为0.69~0.82,属于钙碱性花岗岩。总体上富集大离子亲石元素(LILE)K、Rb和高场强元素(HFSE)Ba、Th,但贫Ta、Nb、Ce、Hf、Zr、Sm、Y及Yb。稀土元素的球粒陨石标准化配分曲线呈右倾型,轻重稀土分馏明显,重稀土分异不显著,而轻稀土分异明显,铕呈现弱负异常(δEu=0.24~0.78)。岩石学及地球化学特征研究表明,天湖岩体形成与幔源岩浆的底侵和内侵使得中-新元古代新生的地壳物质发生部分熔融有关。岩浆侵入活动的动力来源于海西晚期至印支早期古特提斯洋向北俯冲和碰撞及随后的板内伸展作用。
[Abstract]:The Tianhu granite body is composed of six intrusions and is divided into three lithofacies units according to the rock lineage and merged into one superunit. LA-ICP-MS zircon U-Pb dating results show that it is formed by three magmatic intrusions during the same magmatic melting event. The Tianhu intrusion is located in the early Triassic and is the product of the early Indosinian period. The results of zircon in-situ HF isotopic determination from the intrusive body indicate that the intrusion occurred in the early Triassic. The value of the 蔚 HfT) varies from -2.6 to 5.5, and from the age of the two-stage HF model to between 941 and 1435 Ma. It is shown that the magmatic source areas are all derived from depleted new crustal rocks, and the total SiOSP _ 2 is 69.14 ~ 76.62 ~ 2). The Na_2O of alkali-rich K2O was 7.39, and the content of Ti-Ca-Fe and mg was 0.95% 1.04. The K _ 2O Na_2O)/Al_2O_3 is 0.69 ~ 0.82, which belongs to calc-alkaline granite, and is enriched in large ion lithophile element Lilei _ (K) on the whole. RB and high field strength elements (HFSE) Ba-Thh, but the normalized partitioning curves of chondrite-like chondrites are of right-dip type, but they are poor in Ta-NbSe, Hf-NbCE-Hf-ZrSM-Y and Yb.rare-earth elements in the chondrite-like chondrites. The fractionation of light and heavy rare earths is obvious, but that of light rare earth is not obvious. Europium shows weak negative anomaly (未 EU ~ (2 +) 0.24 ~ 0.78). The petrological and geochemical characteristics show that the fractionation of light and light rare earths is not obvious. The formation of Tianhu rock mass is related to the partial melting of Meso- Neoproterozoic new crustal material caused by the submersion and internal transgression of mantle magma. The motive force of magmatic intrusion came from the late Hercynian to the early Indosinian PaleoTethys ocean to the north. Impact and collision and subsequent intraplate stretching.
【作者单位】：中核集团高放废物地质处置重点实验室核工业北京地质研究院;长安大学地球科学与资源学院;
【基金】：国防科工局“核设施退役和三废治理”项目我国高放废物地质处置新疆预选区选址和场址评价研究成果
【分类号】：P588.121
【正文快照】： 注:本文为国防科工局“核设施退役和三废治理”项目我国高放废物地质处置新疆预选区选址和场址评价研究成果。东天山造山带位于中亚造山带(Seng9r et al.,1993;Xiao W J et al.,2004)南缘,该造山带从北向南依次为博格达及哈尔里克造山带、吐哈地块、觉罗塔格造山带和中天山地

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