Geochemical Evidence of Plume Sources for High-MgO Lavas in the Western Kunlun Orogenic Belt.

This article focuses on the petrogenesis and mantle source characteristics of Late Permian–Late Triassic high-MgO lavas near the Chalukou area in the Western Kunlun (WK) orogenic belt, NW China. Detailed mineralogical, geochemical, and isotopic analyses indicate that these lavas are picritic in composition, derived from a peridotite-dominated mantle source with minor pyroxenite involvement, and exhibit oceanic island basalt (OIB)-like geochemical signatures. The parental magmas are volatile-rich, with estimated H₂O contents of 3.67 ± 1.0 wt %, and formed under high mantle potential temperatures (1522–1556 °C) and elevated oxygen fugacity (fayalite-magnetite-quartz buffer +0.93), consistent with a hydrous mantle plume origin. Isotopic data (Sr–Nd–Os and oxygen isotopes) show typical mantle values without evidence of crustal contamination or recycled materials, supporting the interpretation that the WK high-MgO volcanism originated from a volatile-rich mantle plume source associated with fragments of oceanic islands or plateaus in the Paleo-Tethys Ocean.