五台山古元古代晚期的动力学背景:王家会花岗岩地球化学的制约  

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

作　　者：王月然[1] 刘树文[1] 李秋根[1] 党青宁[1] 刘超辉[1] 杨斌[1] 古丽冰[1] 赵风三 

机构地区：[1]北京大学造山带与地壳演化教育部重点实验室北京大学地球与空间科学学院,北京100871

出　　处：《北京大学学报（自然科学版）》2005年第6期840-850,共11页Acta Scientiarum Naturalium Universitatis Pekinensis

基　　金：国家自然科学基金重大国际合作项目(40420120135)

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。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 traceelement patterns. Especially, they display obviously high K20 and negative Sr and Eu anomalies, which are significantly different from the island arc granitoids. Combined with their end （2-1 Ga） range of - 3.82 to - 2.80 and TDM =2.6-2.7 Ga, these granitoids are most likely to be derived from the partial melting of hybrids both - 2.6 Ga metavolcanic materials in Archean Wutaishan magmatic arc and older continent crustal materials under lower than 1.2 GPa. Petrological and geochemical characteristics of Wangjiahui granitoid intrusion suggest that is probably formed 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.

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 

分 类 号：P588.121[天文地球—岩石学]