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引用本文:曾忠诚,洪增林,刘芳晓,边小卫,李琦,高峰,何元方,菅坤坤. 阿尔金造山带青白口纪片麻状花岗岩的厘定及对Rodinia超大陆汇聚时限的制约[J]. 中国地质, 2020, 47(3): 569-589.
ZENG Zhongcheng,HONG Zenglin,LIU Fangxiao,BIAN Xiaowei,LI Qi,GAO Feng,HE Yuanfang,JIAN Kunkun. Confirmation of gneissic granite of Qingbaikou period and its constraint on the timing of the Rodinia supercontinent on the Altun orogenic belt[J]. Geology in China, 2020, 47(3): 569-589(in Chinese with English abstract).
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阿尔金造山带青白口纪片麻状花岗岩的厘定及对Rodinia超大陆汇聚时限的制约
曾忠诚1, 洪增林2,3, 刘芳晓4, 边小卫1, 李琦3, 高峰1, 何元方1, 菅坤坤1
1.陕西省矿产地质调查中心, 陕西 西安 710068;2.西北工业大学, 陕西 西安 710072;3.陕西省地质调查院, 陕西 西安 710054;4.中煤科工集团西安研究院有限公司, 陕西 西安 710077
摘要:
阿尔金造山带新元古代花岗岩的研究对探讨该地区Rodinia超大陆汇聚阶段构造演化过程具有重要意义。本文对在亚干布阳一带新厘定的青白口纪片麻状花岗岩开展了详细的岩石学、年代学和岩石地球化学研究。锆石LA-ICP-MS U-Pb年代学证据显示片麻状花岗岩结晶年龄分别为(883.0±3.3)Ma和(883.1±3.3)Ma,说明其侵位于青白口纪。地球化学结果显示,常量元素具有富硅、铝、钾和低钠、镁、钙和钛的特点,具钙碱性-高钾钙碱性、过铝质花岗岩特征。岩石轻稀土分馏较强而重稀土分馏较弱,具有明显的负Eu异常,总体呈右倾的“V”型稀土分配模式。岩石富集Rb、Th、LREE等大离子亲石元素,中等亏损Ba,强烈亏损Nb、Sr、P、Hf、Ti等高场强元素,总体特征显示了典型的壳源花岗岩的特征,其源于地壳变质砂岩部分熔融,形成于同碰撞晚期构造环境,属Rodinia超大陆汇聚阶段的产物。综合研究表明,阿尔金地区新元古代早期同碰撞型岩体的形成时代集中在871~945 Ma,限定了Rodinia超大陆汇聚时限,且在空间上构成了一条重要的岩浆岩带,是对Rodinia超大陆碰撞汇聚作用的响应。
关键词:  片麻状花岗岩  LA-ICP-MS锆石U-Pb定年  地球化学  构造环境  Rodinia超大陆  地质调查工程  阿尔金
DOI:10.12029/gc20200302
分类号:P588.12+1;P597;P595
基金项目:中国地质调查局项目(12120114081901、1212011120533)和国家科技重大专项项目(2019QZKK0806)共同资助。
Confirmation of gneissic granite of Qingbaikou period and its constraint on the timing of the Rodinia supercontinent on the Altun orogenic belt
ZENG Zhongcheng1, HONG Zenglin2,3, LIU Fangxiao4, BIAN Xiaowei1, LI Qi3, GAO Feng1, HE Yuanfang1, JIAN Kunkun1
1.Shaanxi Mineral Resources and Geological Survey, Xi'an 710068, Shaanxi, China;2.Northwestern Polytechnical University, Xi'an 710072, Shaanxi, China;3.Shaanxi Institute of Geological Survey, Xi'an 710054, Shaanxi, China;4.Xi′an Research Institute, China Coal Technology & Engineering Group Corp, Xi′an 710077, Shaanxi, China
Abstract:
The study of the Neoproterozoic granites in the Altun orogenic belt is significant for revealing the area of the Rodinia supercontinent convergent stage tectonic evolution. In this paper, a detailed study of petrology, chronology and geochemistry was carried out for a new division of Qingbaikou gneissic granite in Yaganbuyang area. The U-Pb dating of zircons from the gneissic granite using LA-ICP-MS yielded (883.0±3.3)Ma and (883.1±3.3)Ma, indicating that the gneissic granite was generated in Qingbaikou period. The geochemical analysis shows that major elements are characterized by high SiO2, Al2O3 and K2O values and low Na2O, MgO, CaO and TiO2 values, thus belonging to the calc-alkaline-high-K calc-alkaline series, and peraluminous.REE distribution patterns show negative anomaly of Eu, obvious fractionation of LREE and weak fractionation of HREE, with a clear V trough, which shows the features of crustal derived granite. The gneissic granite is rich in large ion lithophile elements of Rb, Th, LREE, slightly depleted in Ba and mightily depleted in high field strength elements of Nb, Sr, P, Hf, Ti. These characteristics are similar to features of the continental collision type granite. The source rock of the gneissic granite was formed by the partial melting metasandstone from the crust in the subduction-collisional environment about Rodinia supercontinent. Comprehensive study shows that these syn-collisional granites were generated between 871 Ma and 940 Ma, which constrained the timing of the Rodinia supercontinent in Early Neoproterozoic along the Altun orogenic belt. These rock bodies have the characteristics of zonal distribution in space and confirm the existence of syn-collisional granites belt about Rodinia supercontinent on the Altun orogenic belt.
Key words:  gneissic granite  LA-ICP-MS zircon U-Pb dating  geochemistry  construction environment  Rodinia supercontinent  geological survey engineering  Altun