揚(yáng)子西南緣早新元古代沉積物源特征及其對Rodinia超大陸聚散轉(zhuǎn)換的響應(yīng)

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[分類號(hào)］P548 [文獻(xiàn)標(biāo)志碼］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

揚(yáng)子西南緣中一新元古代構(gòu)造演化過程及其與Rodinia（羅迪尼亞）超大陸聚合-裂解的關(guān)系，長期以來主要存在2種觀點(diǎn)：一種觀點(diǎn)認(rèn)為，1 150～920Ma 期間揚(yáng)子西南緣是與造山作用有關(guān)的構(gòu)造環(huán)境，而 850～750Ma 期間則轉(zhuǎn)變?yōu)殛憙?nèi)裂谷盆地，將華南置于勞倫西緣與澳大利亞—南極東緣之間的位置（Lietal.，2002，2008；Greentree et al.，2006;Zhu etal.，2016）；另一種觀點(diǎn)則認(rèn)為 1 150～960Ma 期間揚(yáng)子西南緣為被動(dòng)大陸邊緣裂谷盆地，而 860～750Ma 期間為活動(dòng)大陸邊緣島弧環(huán)境，主張華南位于Rodinia超大陸的邊緣（Zhou etal.，2002，2006;Zhao etal.，2011;Sunetal.，2021，2022；李永成等，2025）。（剩余21754字）