Late Paleoproterozoic orogenic evolution of the northern Tarim Craton, NW China: Insights from phase equilibrium modeling and zircon U-Pb geochronology of metapelitic granulite in the Kuluketage area

Abstract

Global Paleoproterozoic orogenic evolution can provide important constraints on the Columbia (Nuna) supercontinent assembly. Zircon U-Pb chronology studies on the northern Tarim reveal that a paleoproterozoic tectono-thermal event was developed, which is related to the assembly of the Columbia supercontinent. However, limited metamorphic investigations have hindered the recognition of Paleoproterozoic orogenic evolution in the northern Tarim, further affecting the understanding of the relationship between Tarim Craton and the Columbia supercontinent. The Xingditage Group in northern Tarim is the result of Paleoproterozoic orogeny which can shed light on the Paleoproterozoic orogenic evolution of the northern Tarim Craton. Our study conducted petrography, zircon U-Pb geochronology, and phase equilibria modeling of metapelitic granulite collected from the Xingditage Group. Petrographic and phase equilibria modeling indicate a clockwise P-T path involving the peak metamorphic stage (M1) at ∼840 °C/7 kbar, the near-isothermal decompression stage (M2) at ∼840 °C/3 kbar and followed near-isobaric cooling stage (M3) at ∼785 °C/2.5 Kbar. The ages of metamorphic zircons in metapelitic granulite range continuously from 1831 ± 13 Ma to 1782 ± 16 Ma. Petrographic observation shows almost all zircons grow in quartz and biotite (Bi-2), indicating they were recrystallized during the isobaric cooling stage (M3) after decompression. Thus, the ca. 1.85–1.80 Ga metamorphic age in northern Tarim records a regional post-Tmax cooling event after exhumation rather than a collisional event of crustal thickening. We further propose a tectonic evolution scenario of the northern Tarim Paleoproterozoic orogenic belt and suggests the northern Tarim has collided with an unknown block (perhaps Sharyzhalgai uplift in southwestern Siberia Craton) and became a peripheral part of the Columbia supercontinent prior to ∼1.85 Ga.