扬子西南缘早新元古代沉积物源特征及其对Rodinia超大陆聚散转换的响应

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[分类号］P548 [文献标志码］A

Abstract： The Liubatang Formation， unconformably overlying the Kunyang Group and underlying the Chengjiang Formation in the southwesterm Yangtze Block，preserves critical records of tectonic regime transition in the early Neoproterozoic.Systematic stratigraphic，sedimentological，and geochronological investigations areconductedon the Liubatang Formation in central Yunnan to constrain its depositional age，provenancecharacteristics，and tectonic implications. Zircon U-Pb dating of tuff layers from the base and top of the formation yield ages of 895±2 Ma and 856±3 Ma， respectively， refining its depositional time frame to 900～850Ma . The lower conglomerates and sandy conglomerates of the Liubatang Formation were deposited inaluvial to fluvial fan environments，with gravels predominantly composed of slate and meta-sandstone.Detrital zircons from the upper clastic rocks exhibit significant abrasion features and age distributions，comparable to those of theunderlying Kunyang Group （particularly the Meidang Formation）， indicating sedimentary recycling of preexisting strata. Based on an integrated regional stratigraphicand tectonic dataset，it issuggested that the unconformity between theLiubatang Formationand the Kunyang Group represents a tectonic uplift and erosion surface （950～900Ma ）， while the boundary with the overlying Chengjiang Formation corresponds to an extensional unconformity 850～810Ma .These two unconformities respectively record the final amalgamation and incipient breakup of the Rodinia supercontinent， providing key constraints on the tectonic transition during the assembly and breakup cycle of this supercontinent.

Key words： South China; Liubatang Formation；detrital zircon; provenance analysis；Rodinia supercontinent

扬子西南缘中一新元古代构造演化过程及其与Rodinia（罗迪尼亚）超大陆聚合-裂解的关系，长期以来主要存在2种观点：一种观点认为，1 150～920Ma 期间扬子西南缘是与造山作用有关的构造环境，而 850～750Ma 期间则转变为陆内裂谷盆地，将华南置于劳伦西缘与澳大利亚—南极东缘之间的位置（Lietal.，2002，2008；Greentree et al.，2006;Zhu etal.，2016）；另一种观点则认为 1 150～960Ma 期间扬子西南缘为被动大陆边缘裂谷盆地，而 860～750Ma 期间为活动大陆边缘岛弧环境，主张华南位于Rodinia超大陆的边缘（Zhou etal.，2002，2006;Zhao etal.，2011;Sunetal.，2021，2022；李永成等，2025）。（剩余21754字）