Accretion of micro-continents and arcs in the southern Central Asian Orogenic Belt: Insights from provenance analyses of early Paleozoic sedimentary records in Beishan

Abstract

The Central Asian Orogenic Belt involves amalgamation of numerous magmatic arcs, accretionary complexes, and continental fragments during long-lived subduction and accretion. However, the nature of key microcontinental terranes, as well as their continuity, remains unclear. This study conducted outcrop observation, heavy mineral assemblage, whole-rock geochemistry, detrital zircon U-Pb dating and Lu-Hf isotope analysis on sandstones in the Beishan orogenic belt. The findings from field observations, petrographic analysis and weathering indices that the tectonic setting of the sandstone is a fore-arc sedimentary basin. The MDAs of sandstones are 503.8 ± 6.9 Ma and 431.9 ± 6.0 Ma. The provenance of the sandstone is complex, which probably originating from the Shuangyingshan and the Hanshan blocks. By comparing the detrital zircons U-Pb ages with adjacent terranes such as Central Tianshan, Duhuang and Tarim, it was observed that the Shuangyingshan block shares similary provenance with the Dunhaung terrane, while the Mazongshan-Hanshan shows affinity to the Central Tianshan Terrane. This study highlights the complex nature of sediment provenance in the Beishan orogenic belt, influenced by tectonic processes involving thrusting, accretionary complexes, and the presence of multiple terranes.