Petrogenesis of late Paleoproterozoic I- and A-type granitoids in the southwestern Tarim Craton, NW China: Implications for post-collisional magmatism and tectonic evolution

Granitoids are important components of collisional orogens and record the tectonic evolution of orogenic belts. To better understand the late Paleoproterozoic orogeny in the Tiekelike area, southwestern Tarim Craton, China, we conducted a petrological, geochemical, and zircon U-Pb geochronological and Lu-Hf isotopic study of granitic dyke, quartz monzonite, quartz monzonitic dyke and granitic gneiss. The results show that these granitoids were emplaced between 1.88 and 1.85 Ga and can be divided into two groups. Group 1 (the granitic dyke and gneiss) are I-type granitoids with higher SiO2 and alkali contents, and Sr/Y ratios, but lower rare earth element contents than the group 2 (the quartz monzonite and quartz monzonitic dyke), which resemble A2-type granitoids. The Itype granitoids were generated by partial melting of ancient lower-crustal rocks, whereas the A2-type quartz monzonite and quartz monzonitic dyke were derived by melting of granodiorites under high-temperature and low-pressure conditions. All these late Paleoproterozoic I- and A-type granitoids formed in a post-collisional setting. Integrating our results with previous studies, we propose a model for the late Paleoproterozoic orogenic evolution of the Tarim Craton. The southeastern Tarim Craton (North Altyn Tagh area) first collided with other cratons/blocks at 2.00-1.95 Ga. Subsequently, the unified Tarim Craton was formed by the assembly of the southern and northern Tarim terranes at 1.92-1.90 Ga. Concurrently, the southwestern (Tiekelike area) and northeastern (Kuluketage area) Tarim Craton were also amalgamated with other cratons/blocks. The eastern Tarim Craton (Dunhuang area) then collided with other cratons/blocks at 1.82-1.80 Ga. Finally, the Tarim Craton experienced a high-temperature post-collisional orogeny. The orogeny that affected the Tarim Craton was an integral part of the tectonic evolution of the Columbia supercontinent during the Paleoproterozoic.