Alkaline basalts in the Karamay ophiolitic mélange, southern Central Asian Orogenic Belt

摘要

Here we report geological, geochronological, geochemical, and whole-rock Sr-Nd isotopic data for alkaline basalts from the Karamay ophiolitic mélange of West Junggar, southern Central Asian Orogenic Belt (CAOB).U-Pb analyses of zircon grains from a representative basalt by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) yielded a crystallization age of ca.395 ± 3 Ma, suggesting formation during the Middle Devonian.Geochemically, all the samples bear the signature of ocean island basalt (OIB), and are characterized by alkaline affinity.The results suggest that all the alkaline basalts were derived from a mantle plume-related source in an intra-oceanic setting.These observations, in combination with previous work, indicate that the alkaline basalts from Karamay can be correlated to Middle Devonian mantle plume magmatism within the Paleo-Asian Ocean.