U–Pb zircon age, geochemical and Lu–Hf isotopic constraints of the Southern Gangma Co basalts in the Central Qiangtang, northern Tibet

Abstract

A recent study suggests that the central Qiangtang is a key locality to investigate the evolution of the opening and closure of the Paleo-Tethys Ocean. Basalts are commonly associated with supercontinent fragmentation, and they have the potential to indicate the tectonic environment into which they were erupted. In this study, laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) U–Pb zircon dating, whole-rock geochemistry, and zircon Hf isotope analysis were used to study newly discovered basalts in the southern Gangma Co area of central Qiangtang. Dating of magmatic zircons from three basalt samples indicates that the basalts erupted in the Late Devonian to early Carboniferous (early Tournaisian) at 360–350Ma. The basalts are geochemically similar to within-plate basalts and formed from a depleted mantle source. We suggest that the basalts may have been a product of the breakup of the northern margin of Gondwana in the Late Devonian to early Carboniferous (360–350Ma), which may be linked to the initial rifting and opening of the Paleo-Tethys Ocean in the Qiangtang area.