华夏陆块晚新元古代-早古生代沉积物源的组成与演化及其对冈瓦纳大陆重建的意义

Provenance and Its Evolution of the Cathaysia Block in the Late Neoproterozoic-Early Paleozoic and Implication on the Reconstruction of the Gondwana Supercontinent

华南板块是冈瓦纳大陆的重要组成部分,其在冈瓦纳大陆中的古地理位置是恢复古大陆格局的关键要素,也是地质学界争论的焦点。本文汇总并对比了华南东南部华夏陆块多个盆地的成冰纪-奥陶纪碎屑沉积岩的岩石地层学、全岩地球化学和碎屑锆石数据,厘清了华夏陆块晚新元古代-早古生代三次重要的沉积-构造事件:晚成冰世砾岩指示的近源沉积事件,晚埃迪卡拉世硅质岩指示的海进事件,以及中寒武统底部平行不整合界面、砂岩中砾石的广泛出现指示的构造抬升事件。成冰纪-奥陶纪沉积岩中含有大量格林威尔早期(1300~1000 Ma)和晚期(1000~900 Ma)的碎屑锆石,分别主要来自澳大利亚和印度板块。印度东部为华夏盆地长期提供物质补给,而澳大利亚西部在晚埃迪卡拉世从主要源区变为次要源区。中寒武世华夏陆块抬升使内部850~700 Ma岩浆岩出露成为主要物源之一,是对外部构造应力的远程响应。因此,华夏陆块在晚新元古代-早古生代位于东冈瓦纳北缘,与印度、澳大利亚具有长期稳定的联系,毗邻东南极洲。在冈瓦纳大陆聚合过程中,印度和澳大利亚泛非期造山带的形成、抬升和剥蚀影响了华夏陆块沉积盆地的物源变化。

As a significant component of Gondwanaland,the South China Block holds a crucial role in reconstructing the paleogeographic framework of the supercontinent.In this study,we have compiled and compared lithostratigraphic,geochronological,and geochemical data from Cryogenian-Ordovician clastic sedimentary rocks across multiple sub-basins within the Cathaysia Block,situated in the southeastern portion of the South China Block.The abundance of siliceous and conglomeratic rocks,along with local unconformities in certain layers,suggests a proximal deposition during the late Cryogenian,followed by a late Ediacaran transgression and middle Cambrian uplift.Australia and India were the primary sources of zircons in the early(1300 ~ 1000 Ma) and late Grenvillian(1000 ~ 900 Ma) age,respectively,while detritus from East Antarctica contributed to a lesser extent.Notably,India served as a prolonged source terrane for the Cryogenian-Ordovician basin in the Cathaysia Block,whereas western Australia shifted from being a major to a secondary sediment supplier during the late Ediacaran.Intrinsic 850 ~ 700 Ma magmatic rocks that were exposed during the middle Cambrian uplift of the Cathaysia Block,in response to the far-field stress effects of the external tectonic movement,contributed as one of the provenances.Thus,the Cathaysia Block was inferred to be located in the northern margin of Eastern Gondwana during the late Neoproterozoic-early Paleozoic and had persistent connections with India and Australia,adjacent to East Antarctica.During the Gondwana assembly,the formation,uplift,and exhumation of the Pan-African orogenic belts in India and Australia influenced the provenance variations of sedimentary basins in the Cathaysia Block.