Eclogite in the East Kunlun Orogen, northwestern China: A record of the Neoproterozoic breakup of Rodinia and early Paleozoic continental subduction

An early Paleozoic eclogite belt extends discontinuously for 500 km in the East Kunlun Orogen, northwestern China, which provides insight into the evolution of the Proto-Tethys Ocean. However, the nature and age of the eclogite protoliths and subsequent metamorphism are unclear. Here, we report mineral chemical, zircon, and titanite geochronological; whole -rock major and trace elemental; and Sr-Nd isotopic data for eclogites from the Xiarihamu area in the western East Kunlun Orogen. At a minimum, these eclogites underwent peak eclogite-facies metamorphism at 27-28 kbar and 630-650 degrees C, post -peak decompression, and retrograde amphibolite-facies overprinting. Geochemically, eclogites have characteristics typical of enriched mid -oceanic -ridge basalts and oceanic -island basalts. Inherited magmatic zircon cores yielded a protolith age of 828 Ma, and metamorphic zircons yielded peak and post -peak decompression ages of 443 Ma and 422 Ma, respectively. A titanite U-Pb age of 413 Ma constrains the timing of later amphibolite-facies overprinting. The protoliths of the Xiarihamu eclogites were the products of continental rift -related basaltic magmatism, which was generated during the initial breakup of Rodinia. The protoliths experienced eclogite-facies metamorphism in a continental subduction/collisional setting during the early Paleozoic. The formation of the Xiarihamu eclogites suggests that the Proto-Tethys Ocean had closed by 443 Ma. Given the spatio-temporal relationship between the Xiarihamu magmatic Cu-Ni sulfide deposit and the eclogites studied, the former may have formed in a post-collisional extensional setting. The eclogites and magmatic Cu-Ni sulfide deposit from the Xiarihamu area jointly reveal the evolution of East Kunlun Orogen from Neoproterozoic supercontinent breakup to early Paleozoic tectonic transitions from collisional convergence to post-collisional extension.