甘肃北山扫子山辉长闪长岩成因及地质意义OA

To understand mantle-derived magmatism and tectonic evolution in the Hongshishan area of the Central Asian Orogenic Belt,this study presents LA-ICP-MS zircon U-Pb ages,whole-rock major and trace element geochemistry,and Sr-Nd isotopic data from the Saozishan gabbro-diorites in Beishan,Gansu Province.The zircon U-Pb age of 327.3±2.4 Ma represents the crystallization age.The samples exhibit low SiO2(45.72％～55.40％)and moderate MgO contents(4.18％～5.43％),with significant enrichment in large-ion lithophile elements(LILEs;e.g.,Rb and K),depletion in high field strength elements(HFSEs;e.g.,Nb and Ta),and right-dipping REE patterns featuring light REE enrichment and heavy REE depletion,with weak negative Eu anomalies(Eu/Eu*=0.77～0.99).Initial 87Sr/86Sr ratios(0.704109～0.704911)and εNd(t)values(-2.0 to+2.1)indicate that the gabbro-diorites were derived from a spinel lherzolite mantle source with negligible crustal contamination.These features suggest that the Saozishan gabbro-diorites formed in a continental arc setting induced by the southward subduction of the Hongshishan Ocean,implying that subduction of the Paleo-Asian Ocean continued into the Early Carboniferous.