Origin and tectonic setting of middle-late Triassic Lalingzaohuo granitoids in the western East Kunlun Orogen, northern Tibetan Plateau

Triassic granitoids are widespread in the East Kunlun Orogen (EKO), with Middle Triassic granitoids being dominant and Late Triassic granitoids being subordinate. This paper presents new whole-rock geochemical and Sr - Nd isotope, and zircon U - Pb age and Lu - Hf isotope data for eight granitoids in the Lalingzaohuo area, western EKO, northern Tibetan Plateau. These granitoids yield Middle and Late Triassic ages of 245-239 and 223-220 Ma, respectively. The granitoids from the Lalingzaohuo area have features typical of I-type granites and belong to the high-K calc-alkaline series. They exhibit variable rare earth and trace element patterns, and Sr - Nd - Hf isotopic compositions, indicative of different petrogenetic processes. The Middle Triassic samples have higher ISr values of 0.71440-0.71572 and lower epsilon Nd(t) values of -6.18 to -4.26 than the Late Triassic samples (ISr = 0.71139-0.71348; epsilon Nd(t) = -3.23 to -1.51), which are consistent with I-type granitoids derived from the lower crust. Geochemical and isotopic data indicate that the two stages of I-type granitoids had a significant mantle contribution. The Middle Triassic granitoids in the EKO, particularly the western EKO, have adakitic characteristics and formed by partial melting of lower continental crust. The T2-T3 granites formed by oceanic slab breakoff related to subduction and mantle convection, and the Late Triassic granites formed by lithospheric thinning and asthenospheric upwelling after slab breakoff.

Automated summary

This paper presents new data on the geochemistry, isotope ages, and petrogenetic processes of eight granitoids in the Lalingzaohuo area of the East Kunlun Orogen. The results show that these granitoids belong to the I-type granites, with Middle Triassic granitoids having higher ISr values and lower epsilon Nd(t) values compared to Late Triassic granitoids, indicating different sources in the lower crust. The geochemical and isotopic data also suggest a significant mantle contribution in the formation of these granitoids.