Metamorphism and geochronology of garnet mica schists from the Kuluketage area: Implications for reconstructions of the Tarim Craton in supercontinent Columbia

Abstract

The Tarim Craton has been considered a part of the Columbia supercontinent. However, the paleogeographic location of the Tarim Craton remains ambiguous or has not been considered in the reconstruction model. This problem is partly due to the dispute over the collisional time between northern Tarim and major Columbia blocks. The Xingditage Group in the Kuluketage area records important information on the Paleoproterozoic evolution of northern Tarim during the Columbia supercontinent convergence, in which the garnet mica schist unit is key to constraining the collision time. We carried out petrographic, phase equilibrium modeling, and zircon U-Pb chronological studies for two garnet mica schist samples (LJS-1 and LJS-2) from the Lower Xingditage Group. This study attempted to constrain the collision time of the northern Tarim in the late Paleoproterozoic from the metamorphic evolution perspective. Petrography shows that both samples are rutile-kyanite-garnet micaschist. The phase equilibrium modeling reveals two clockwise P-T paths. For the sample LJS-1, the peak stage was constrained at ∼ 780 °C/12 kbar and subsequently decompressed to ∼ 760 °C/4 kbar. For sample LJS-2, the peak pressure is relatively higher, reaching ∼ 790 °C/16 kbar, followed by decompression to ∼ 796 °C/3 kbar. Both P-T paths have a near isothermal decompression path, indicating a rapid exhumation process. Zircons in this study record a metamorphic age of 1907 ± 8 Ma, which can represent the collision age of northern Tarim in the late Paleoproterozoic. We propose that the northern Tarim experienced a long-lived orogenic event in the late Paleoproterozoic, and the northern Tarim became a part of the Columbia supercontinent at ∼ 1.91 Ga. In comparison with orogenic belt evolution, an affinity with southwest Siberia was established for northern Tarim during the assembly of the Columbia supercontinent.