Abstract:
Objective The orogenic processes associated with the Late Cretaceous Lhasa−Qiangtang collision in the central Qinghai−Xizang Plateau remain controversial. This study focuses on the Diga North granodiorite porphyry in northern Xizang. Through systematic petrological, geochemical, and geochronological investigations, combined with regional magmatic comparisons, we aim to elucidate the Late Cretaceous orogenic evolution and lithospheric history of the central Qinghai−Xizang Plateau following the closure of the Meso−Tethys Ocean.
Methods Petrological observations, zircon U−Pb geochronology, whole−rock geochemistry, and Sr−Nd isotopic analyses were conducted on the Diga North granodiorite porphyry, which intrudes the Dongco ophiolitic mélange in northern Xizang. These data were further integrated with a comprehensive synthesis of Late Cretaceous intermediate–felsic magmatic rocks across the central Qinghai−Xizang Plateau.
Results The Diga North granodiorite porphyry was emplaced at ~72 Ma and belongs to the high−K calc−alkaline series. It originated from partial melting of juvenile lower crust, with the involvement of mantle−derived materials during its formation.
Conclusions Following the closure of the Meso−Tethys Ocean, the Lhasa−Qiangtang collision resulted in pronounced crustal thickening in the central Qinghai−Xizang Plateau during the 90~80 Ma interval, subsequently followed by lithospheric delamination and thinning. The ~70 Ma Diga North granodiorite porphyry represents a magmatic response to this lithospheric delamination and thinning event.
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