Zircon U–Pb Dating and Geochemical Characteristics of Chahannuo Gabbros in the Northern Margin of Qaidam Basin, Northern Tibetan Plateau

Late Paleozoic–early Mesozoic intrusive rocks are distributed widely along the northern margin of Qaidam Basin in Tibetan Plateau. To constrain tectonic evolution, we carried out petrological, chronological, and geochemical studies Chahannuo gabbros. LA-ICP-MS Zircon U–Pb dating yields an age 255.0 ± 0.9 Ma for gabbros, which confirms existence Indosinian tectono-magmatic activity on Basin. The gabbros have low whole-rock SiO2, Fe2O3 contents, high Al2O3 suggests a calc-alkaline affinity. In addition, MgO, Cr, Ni contents Mg#, similar to those predicted regional basaltic melts, indicating that they were affected mainly by fluid from subducted slab. characterized arc-like trace element patterns, with enrichment LREE LILE, depletion HREE HFSE. No obvious negative Eu anomalies also indicate no significant magmatic differentiation has occurred. Nb/La ratio Ti content samples partially contaminated crust during their formation. incompatible ratios (Rb/Sr, Th/Nd, Th/La), closer category enriched mantle. Combing our data previous contemporaneous magmatism region, suggest formed continental arc environment related northward subduction Paleo-Tethyan oceanic plate.