Tectonic Characteristics and Geological Significance of the Yeba Volcanic Arc in the Southern Lhasa Terrane
Source abstract
Abstract
The Southern Lhasa Terrane, as the southernmost tectonic unit of the Eurasian continent, has long been a focal area in global geoscientific research due to its complex evolutionary history. The Yeba Formation exposed in this terrane comprises an Early–Middle Jurassic volcanic–sedimentary sequence that records multiphase tectonic deformation. This study applies structural analysis to identify three distinct phases of tectonic deformation in the Yeba Formation of the Southern Lhasa Terrane. The D1 deformation is characterized by brittle–ductile shearing, as evidenced by the development of E-W-trending regional shear foliation (S1). S1 planes dip northward at angles of 27–87°, accompanied by steeply plunging stretching lineations (85–105°). Both south- and north-directed shear-rotated porphyroclasts are observed in the hanging wall. 40Ar-39Ar dating results suggest that the D1 deformation occurred at ~79 Ma and may represent an extrusion-related structure formed under a back-arc compressional regime induced by the low-angle subduction of the Neo-Tethys Ocean plate. The D2 deformation is marked by the folding of the pre-existing shear foliation (S1), generating an axial planar cleavage (S2). S2 planes dip north or south with angles of 40–70° and fold hinges plunge westward or NWW. Based on regional tectonic evolution, it is inferred that the deformation may have resulted from sustained north–south compressional stress during the Late Cretaceous (79–70 Ma), which caused the overall upward extrusion of the southern Gangdese back-arc basin, leading to upper crustal shortening and thickening and subsequently initiating folding. The D3 deformation is dominated by E-W-striking ductile shear zones. The regional shear foliation (S3) exhibits a preferred orientation of 347°∠75°. Outcrop-scale ductile deformation indicators reveal a top-to-the-NW shear sense. Combined with regional tectonic evolution, the third-phase (D3) deformation is interpreted as a combined product of the transition from compression to lateral extension within the Lhasa terrane, associated with the activation of the Gangdese Central Thrust (GCT) and the uplift of the Gangdese batholith since ~25 Ma.
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Research context
OpenAlex topics: Geological and Geochemical Analysis · earthquake and tectonic studies · Geochemistry and Geologic Mapping
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
Affiliations
State Key Laboratory of Continental Shale Oil, Northeast Petroleum University, Daqing 163318, China
School of Earth Sciences, Northeast Petroleum University, Daqing 163318, China
Policy Research Office, Daqing Oilfield Limited Company, Daqing 163453, China
School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China
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