山西南部塔儿山岩体锆石LA-ICP-MS U-Pb年龄 、地球化学特征及其地质意义
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本文为国家自然科学基金重点项目(编号:41330315)和西北大学大陆动力学国家重点实验室科技部专项经费项目(编号:201210122)资助的成果。


The Zircon LA-ICP-MS U-Pb Ages and Geochemical Characteristics of Ta’ershan Intrusions, Southern Shanxi Province, and their Geological Implications
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    摘要:

    塔儿山岩体位于华北克拉通中部山西南部临汾地区。对该岩体的锆石UPb定年分析表明,锆石发育典型的岩浆震荡环带,且具有高的Th/U比值(0.03~1.98),两个样品边部年龄分别为129.2 ± 2.9 Ma和124.7 ± 5.5 Ma,指示该岩体的形成时代为早白垩世;而2.4~2.5 Ga、2.0~2.2 Ga和1.7~1.9 Ga左右的核部年龄可能代表了早期的残留锆石。该岩体主要为石英闪长岩和石英二长岩,其SiO2含量为62.15%~65.05%;Na2O + K2O含量为8.75%~8.62%;A/CNK为0.96~1.01;岩体显著贫镁,铁相对镁较富,FeOT/( FeOT+ MgO)为0.79~0.83,属于碱性系列;大离子亲石元素和轻稀土元素富集,亏损高场强元素及重稀土元素。分析认为,该岩体为幔源岩浆通过分离结晶作用后,在侵位过程中受到下地壳物质混染形成。通过分析对比山西不同地区燕山期岩体地化指标,认为这些岩体均属于Fe质花岗岩(A型花岗岩)。结合区域地质背景,提出塔儿山岩体形成于华北克拉通中生代构造体制转折后的岩石圈伸展构造环境。

    Abstract:

    Objectives: Ta’ershan intrusions are located in Linfen area of southern Shanxi province, central North China Craton (NCC), Consisting of quartz diorite and quartz monzonites. They intruded the sandstone of the Triassic Ermaying Group. Our research mainly focuses on the formation age and the geochemistry of the Ta’ershan intrusions and their geological implications. Methods: Based on detailed observations of the Ta’ershan intrusions in the study area, we have studied the petrology, geochemistry and chronology of the intrusions, by the comparison of the geochemical characteristics and the age data of the intrusions in different regions of Shanxi province, central part of the NCC, we have discussed the geological implications of the Ta’ershan intrusions. Results: LA-ICP-MS zircon U-Pb dating on the zircon rims with well-defined oscillatory zoning yielded weighted mean 206Pb/238U age of 129.2 ± 2.9 Ma and 124.7 ± 5.5 Ma, respectively, which are interpreted as the timing of magmatic intrusion. The analysis on the cores yielded the ages of 2.4~2.5 Ga, 2.0~2.2 Ga and 1.7~1.9 Ga, regardless of their magmatic or metamorphic protolith. The quartz diorite and quartz monzonites contain SiO2 contents of 62.15%~65.05%; Na2O + K2O contents of 8.75~8.62 %; A/CNK= 0.96~1.01; The rock is riched in iron, with FeOT/( FeOT+ MgO)= 0.79~0.83, which belongs to alkaline series. They are characterized by enrichment of light rare earth elements and large ion lithophile element (LILEs), but depletion in heavy rare earth elements, high field strength element (HFSEs).  Conclusions: This study suggests that the Ta’ershan intrusions were formed by partial melting of enriched lithospheric mantle, with contamination of lower crust-derived basement rocks. According to the geochemical data of Yanshanion intrusions reported in different parts of Shanxi province, these intrusions all belong to Atype granitoids. Combined with regional geological background, the Ta’ershan intrusions were formed under a back-arc extensional regime after Mesozoic tectonic regime inversion in the North China Craton.

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杨瑶,赵俊峰,刘池洋,薛锐,闫占冬.2017.山西南部塔儿山岩体锆石LA-ICP-MS U-Pb年龄 、地球化学特征及其地质意义[J].地质论评,63(3):809-821,[DOI].
YANG Yao, ZHAO Junfeng, LIU Chiyang, XUE Rui, YAN Zhandong.2017. The Zircon LA-ICP-MS U-Pb Ages and Geochemical Characteristics of Ta’ershan Intrusions, Southern Shanxi Province, and their Geological Implications[J]. Geological Review,63(3):809-821.

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  • 收稿日期:2016-07-18
  • 最后修改日期:2017-03-24
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  • 在线发布日期: 2017-05-24
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