Unraveling deformation mechanism of the Fukang fold-and-thrust belt: Insight into intracontinental orogenesis of the Bogda Mountain, NW China

Abstract

Characterized by the superposition of well-developed thick-skinned and thin-skinned structures, the Fukang fold-and-thrust belt is an ideal place for understanding the intracontinental orogenic process of the Bogda Mountain in the Tianshan orogenic belt, China. This study comprehensively examines the geological architecture, structural evolution, and deformation mechanism of the Fukang fold-and-thrust belt using high-resolution seismic reflection data, apatite-fission track analysis, and discrete element simulation. Seismic profile reveals that the Fukang fold-and-thrust belt exhibits superimposed tectonic styles, including a thrust duplex involving Carboniferous strata and an overlapping thrust imbricate structure. Stratigraphic unconformities and thermochronological results from apatite fission track suggest that this belt experienced five main episodes of compressional deformation in the Late Permian, Middle-Late Triassic, Middle-Late Jurassic, Late Cretaceous-Paleocene, and Late Miocene-present. The discrete element simulation results indicate that the Late Permian initial compressional deformation was triggered by reactivation of the pre-existing extensional faults. Subsequent episodic deformation was primarily controlled by thrusting along the Upper Carboniferous and Middle Permian decollement layers. This study highlights the predominant roles of the pre-existing faults and the decollement layers in the formation and evolution of the piedmont fold-and-thrust belt of the Bogda Mountain at distinct stages, serving as critical factors in determining the extent and amplitude of an intracontinental orogenic belt.