Composition and Tectonic Environment of Nisha-Aomxia Ophiolitic Mélange in the Eastern Section of West Kunlun

Ophiolite, as the remnant of the disappeared paleo-oceanic lithosphere, is an important indicator to reconstruct the history of oceanic-continental transition and tectonic evolution in orogenic belt. The spatial-temporal distribution and outcrop scale of the Kudi-Qimanyute ophiolitic tectonic mélange have been the key to understand the tectonic evolution of the western Kunlun during Early Paleozoic. The ophiolite association is well occurred in the Nisha-Aomuxia area of Hetian City and the eastern part of West Kunlun, which is mainly composed of mantle peridotite, cumulate gabbro, volcanic lava and abyssal flysch. LA-ICP-MS zircon U-Pb analyses yield the magma crystallization ages of (450±59) Ma and (432.0±5.7) Ma for the gabbro, (480.3±6.4) Ma for the basalt and (506.4±5.5) Ma for the dacite. These geochronological data indicate that the Nisha-Aomuxia ophiolite was formed in Early Paleozoic. Based on detailed geological and geochemical studies on different rock units of the ophiolite, and combined with the characteristics of spatially related island arc calc-alkaline volcanic rock association, it's suggested that the Nisha-Aomuxia ophiolite belongs to SSZ-type and was formed in a subduction-related setting. Comprehensive analysis shows that the Nisha-Aomuxia ophiolite is an eastward extension of the Kudi-Qimanyute ophiolitic tectonic mélange, which can provide important insights into the tectonic evolution of the eastern part of West Kunlun.