中天山卡瓦布拉克杂岩带中-基性岩的成因及其构造意义:元素地球化学和Sr-Nd-Pb同位素约束

发布时间：2018-03-27 18:53

本文选题：中天山　切入点：卡瓦布拉克　出处：《现代地质》2017年06期

【摘要】：研究中天山地块卡瓦布拉克杂岩带的成因,对重建中天山南缘古生代洋陆构造格局及其演变过程具有重要意义。在查明杂岩带中-基性岩主体岩类矿物学及岩石学特征的基础上,分析了该岩类的主、微量元素和Sr-Nd-Pb同位素组成。结果显示:其属于偏基性的富钠、低钾岩石系列,富集大离子亲石元素(Rb、U、Sr)和轻稀土元素(LREE),亏损高场强元素(Nb、Ta、Zr)和重稀土元素(HREE)。全岩Sr-Nd同位素组成具有较低的锶初始比值(ISr=0.706~0.709)和较高的εNd(t)值(6.84~9.76),并具有较低的放射性成因铅同位素组成,初始铅同位素比值(~(206)Pb/~(204)Pb)i=18.015~18.239、(~(207)Pb/~(204)Pb)i=15.573~15.593、(208Pb/204Pb)i=37.871~38.207。结合前人研究成果和区域地质资料,认为其母岩浆应该来自被交代的年轻富集岩石圈地幔,代表岛弧岩浆,说明卡瓦布拉克杂岩带中-基性岩可能代表该区晚古生代岩浆弧的一部分。
[Abstract]:Study on the genesis of the Kawabulak complex in the Middle Tianshan massif, It is of great significance to reconstruct the Paleozoic oceanic tectonic framework and its evolution process in the southern margin of the Middle Tianshan Mountains. On the basis of finding out the mineralogical and petrological characteristics of the main rock types of the intermediate-basic rocks in the complex belt, the main rock types are analyzed. Trace elements and Sr-Nd-Pb isotopic compositions. The results show that they belong to a series of low-potassium, low-potassium rocks, which are moderately basic in natrium. The Sr-Nd isotopic composition of the whole rock has a low radiogenic lead isotopic composition with a low Sr ratio of 0.706 ~ 0.706 ~ 0.709) and a high 蔚 ~ (Ndtl) value of 6.84 ~ 9.76%, respectively, and a low radiogenic lead isotopic composition, which is characterized by the enrichment of the large ion lithophile element (RB ~ (+)) and the light rare earth element (LREEN), and the depletion of the high field strength element (~ (?) ~ (?)??? The initial lead isotope ratio is 206g / 204Pb / L ~ (18.01515) 18.239m ~ (207m) Pb / P ~ (15.573N) 15.593N / 208Pb / 204Pb / 204Pb ~ (2 +) ~ (37) 87138.2077.According to previous research results and regional geological data, it is considered that the mother magma should come from the young enriched lithospheric mantle, which represents the island arc magma, which is derived from the metasomorphic lithospheric mantle, and represents the island arc magma. It is suggested that the intermediate-basic rocks in the Kawabulak complex may represent a part of the late Paleozoic magmatic arc in this area.
【作者单位】：新疆大学地质与矿业工程学院;新疆大学中亚造山带大陆动力学与成矿预测自治区重点实验室;
【基金】：国家自然科学基金项目(41562010,41502213,41162006)
【分类号】：P581;P59

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