Acta Scientiarum Naturalium Universitatis Pekinensis

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Late Paleoproterozoic Geodynamic Setting in Wutai Mountains: Constraints from Geochemistry of Wangjiahui Granitoids

WANG Yueran, LIU Shuwen1, LI Qiugen, DANG Qingning, LIU Chaohui, YANG Bin, GU Libing, ZHAO Fengsan   

  • Received:2004-09-23 Online:2005-11-20 Published:2005-11-20



Abstract: The Paleoproterozoic Wangjiahui granitoid intrusion, west segment of Wutai mountains, consists mainly of quartz monzodiorite, granodiorite, monzogranite and adamellite. Petrochemical analysis of these rocks indicates that they are of metaluminous calc-alkaline feature (A/CNK<1.1). These rocks are characterized by the negative anomalies of Nb, Ta, Sr, P and Ti, and LILEs-enriched in primitive mantle normalized trace-element patterns. Especially, they display obviously high K2O and negative Sr and Eu anomalies, which are significantly different from the island arc granitoids. Combined with their εNd(2.1Ga) range of -3.82 to -2.80 and TDM = 2.6 ~ 2.7Ga, these granitoids are most likely to be derived from the partial melting of hybrids both ~ 2.6Ga metavolcanic materials in Archean Wutaishan magmatic arc and older continent crustal materials under lower than 1.2GPa. Petrological and geochemical characteristics of Wangjiahui granitoid intrusion suggest that is probably fored under post-collisional tectonic background. Integrated with other late Paleoproterozoic granitoids within the Central Tectonic Zone, it indicates that there was a tectonic transitional process from extension to compression during late Paleroproterozoic in the southern segment of the Central Zone of NCC.

Key words: Paleoproterozoic, Wangjiahui granitoids, partial melting, recycling of islands arc and continent crustal materials, tectonic transition, Wutai mountains

摘要: 五台山西段王家会古元古代花岗岩侵入体主要由石英二长闪长岩、花岗闪长岩和二长花岗岩组成。岩石地球化学分析表明这些岩石具有亚铝钙碱性特征(A/CNK<1.1),在原始地幔标准化的蜘蛛网图上表现Nb、Ta、Sr、P和Ti的亏损,大离子亲石元素富集。εNd(2.1Ga) 在 -3.82~-2.80 范围,表明王家会古元古代花岗岩最有可能形成于大约 2.6Ga 五台山大洋岛弧火山岩物质和更老的陆壳物质在 <1.2GPa 条件下的部分熔融。岩石学和地球化学研究表明王家会花岗岩属于后碰撞花岗岩,结合区域上古元古代地质特征,表明华北克拉通中部带南段古元古代晚期的花岗岩构成了与正常造山过程花岗岩浆演化相反的序列。这个花岗岩演化序列说明古元古代晚期可能发生了从伸展到挤压的构造环境的转换。

关键词: 古元古代, 王家会花岗岩, 部分熔融, 岛弧和陆壳物质再循环, 构造转换, 五台山

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