Newly identified late Mesoproterozoic magmatic and metamorphic rocks in the southwestern Tarim Craton and their implications for the assembly of Rodinia

Abstract

The Tarim Craton is thought to have been involved in the assembly of Rodinia during the late Mesoproterozoic–early Neoproterozoic; however, late Mesoproterozoic magmatic rocks related to the Grenville Orogeny have not previously been found in the Tarim Craton. We identified Grenville-age granites and amphibolites in the southwestern Tarim Craton. The granites were emplaced at 1129 Ma and have high Sr (303–661 ppm) and low Y (5.74–10.3 ppm) and Yb (0.63–1.34 ppm) contents and high Sr/Y ratios (41–81), indicating an adakitic affinity. The geochemistry of these rocks suggests that they were generated by partial melting of subducted oceanic crust with the involvement of subducted sediment and slab-derived fluid. SHRIMP U–Pb zircon ages reveal that the amphibolite protoliths were formed at 1128–1098 Ma. The amphibolites can be divided into two groups based on their geochemistry. Group 1 samples are enriched in light rare earth elements and large-ion lithophile elements and depleted in high field strength elements, similar to typical subduction-related volcanic rocks derived from mantle wedge metasomatized by subduction-derived fluid. Group 2 samples are characterized by high Nb contents (27–55 ppm) and resemble high-Nb basalt that originates from mantle wedge metasomatized by adakitic slab melts with the involvement of subducted sediment. Combining our results with evidence from regional magmatism, we propose that the southern Tarim Craton experienced long-lived subduction during the late Mesoproterozoic–early Neoproterozoic, and the 1129–1098 Ma magmatic events may represent the beginning of the assembly of Rodinia. Thus, we propose that the Tarim Craton was located at the periphery of Rodinia.