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现代地质 ›› 2017, Vol. 31 ›› Issue (06): 1147-1156.

• 岩石学 • 上一篇    下一篇

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

麦地娜·努尔太1(), 尼加提·阿布都逊1,2, 木合塔尔·扎日1,2(), 吴兆宁1, 张龙1   

  1. 1.新疆大学 地质与矿业工程学院,新疆 乌鲁木齐 830046
    2.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,新疆 乌鲁木齐 830046
  • 收稿日期:2016-11-29 修回日期:2017-05-18 出版日期:2017-12-10 发布日期:2017-12-25
  • 通讯作者: 木合塔尔·扎日,男,教授,1960年出生,构造地质学专业,主要从事区域大地构造方面的研究。Email: 1205215168@qq.com
  • 作者简介:麦地娜·努尔太,女,硕士研究生,1990年出生,矿物学、岩石学、矿床学专业,主要从事火成岩地球化学研究。Email: madina711@163.com
  • 基金资助:
    国家自然科学基金项目(41562010);国家自然科学基金项目(41502213);国家自然科学基金项目(41162006)

Petrogenesis and Tectonic Implications of Intermediate Basic Rocks from Kawabulak Complex in Central Tianshan: Constraints from Elemental Geochemistry and Sr-Nd-Pb Isotopes

MADINA Nurtay1(), NIJAT Abdurusul1,2, MUHTAR Zari1,2(), WU Zhaoning1, ZHANG Long1   

  1. 1. College of Geology and Mining Engineering, Xinjiang University, Urumqi, Xinjiang 830046, China
    2. Xinjiang Key Laboratory for Geodynamic Processes and Metallogenic Prognosis of the Central Asian Orogenic Belt, Xinjiang University, Urumqi, Xinjiang 830046, China
  • Received:2016-11-29 Revised:2017-05-18 Online:2017-12-10 Published:2017-12-25

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(206Pb/204Pb)i=18.015~18.239、(207Pb/204Pb)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。

关键词: 中天山, 卡瓦布拉克, 中-基性岩类, Sr-Nd-Pb同位素, 岩石成因

Abstract:

The study of the petrogenesis of Kawabulak Complex has great significance to reconstruct Paleozoic oceanic-continental framework and tectonic evolution processes of southern central Tianshan. On the basis of mineralogical and petrological examinations,major and trace elements and Sr-Nd-Pb isotopes of the intermediate basic components from Kawabulack Complex are studied. The rock samples are mainly of low-K-tholeiite series with relatively high contents of Na. These rocks are relatively enriched in LREEs (Rb, U, Sr) and LILEs, and are depleted in HREE and HFSE (Nb, Ta, Zr). Sr-Nd-Pb isotopic geochemistry shows that the values of ISr range from 0.706 to 0.709, while εNd(t)values change from 6.84 to 9.76. They have relatively low Pb isotopic compositions characterized by (206Pb/204Pb)i=18.015-18.239, (207Pb/204Pb)i=15.573-15.593 and (208Pb/204Pb)i=37.871-38.207. Combining with previous studies and regional geology, the authors have come to the conclusion that the parent magma of intermediate-basic rocks from Kawabulak Complex, as a product of island arc magmatism, is originated from a juvenile lithospheric mantle that was previously metasomatized by subduction zone fluids/melts in the Paleozoic, representing a section of Late Paleozoic magmatic arc of this region.

Key words: central Tianshan, Kawabulak, medium-basis rock, Sr-Nd-Pb isotopes, lithology

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