地质学报2018，Vol.92Issue(5)：928-945,18.
北山造山带南带中元古代副变质岩的锆石U-Pb年代学和Hf同位素研究——对北山造山带南带前寒武纪物质演化的探索
Zircon U-Pb Chronology and Hf Isotopic Study on the Mesoproterozoic Metasedimentary Rocks: Insight into the Evolution of Precambrian Materials in the South Section of Beishan Orogen
摘要
Abstract
The Beishan orogen,located in the southern Central Asia Orogenic Belt (CAOB),mainly consists of a series of subduction-accretionary complexes.Some Precambrian rocks are sporadically distributed within the wide accretionary zone of Beishan.Due to the metamorphism and deformation during the strong orogensis and subsequent intracontinental orogensis since the Paleozoic,it is difficult to distinguish the Precambrian rocks and the products of orogensis in Beishan.Thus,the Precambrian affinity in the Beishan orogen is still controversial.Based on detailed field work,we carried out petrographic,zircon U-Pb geochronological and Hf isotopic analysis on Precambrian metasedimentary rocks from the Mazongshan block in the central Beishan area.The relatively high metamorphic degree,rock assemblage and detrital zircon U-Pb age spectrum show significant differences from that of Paleozoic passive continental margin products,indicating that the metasedimentary rock in Beishan is remnant part of the Precambrian basement rocks formed between ～1.1 and 1.66 Ga.Combined with previous studies,the following understanding can be summarized:the Beishan area presents similar features as the Tarim and Mongolia blocks in material sources,suggesting that the three involved into the assembly and break-up event of the Rodina supercontinent after the Neoproterozoic,but show multiple sources before the Neoproterozoic (＞1.1 Ga).The Mesoproterozoic para-metamorphic rock in the Beishan orogen in this study shows that it is different from the Tarim craton,but similar to the Mongolia block.The Hf isotopic analysis further reveals that the Precambrian para-metamorphic rocks and Dunhuang block in the Beishan orogenic belt all record the history of new-born crust event during the middle and late Paleoproterozoic and show differences from the Tarim craton.This also implies that the Dunhuang block and the beishan orogenic belt probably have a uniform Precambrian basement before the Mesoproterozoic (～1.58 Ga).关键词
中亚造山带/北山造山带/前寒武纪亲缘性/蒙古地块/敦煌地块Key words
Central Asia orogenic belt/Beishan orogen/Precambrian affinity/Mongolia block/Dunhuang block引用本文复制引用
周海,陈亮,孙勇..北山造山带南带中元古代副变质岩的锆石U-Pb年代学和Hf同位素研究——对北山造山带南带前寒武纪物质演化的探索[J].地质学报,2018,92(5):928-945,18.基金项目
本文为中国地质调查局项目(编号1212011121137),国家自然科学基金项目(编号40602023,41072147)资助成果. （编号1212011121137）
