Geochronology, geochemistry and tectonic implications of early Carboniferous plutons in the southwestern Alxa Block

Abstract The southeastern Central Asian Orogenic Belt (CAOB) records the assembly process between several micro-continental blocks and North China Craton (NCC), with consumption of Paleo-Asian Ocean (PAO), but whether S-wards subduction PAO beneath northern NCC was ongoing during Carboniferous–Permian time is still being debated. A key issue to resolve this controversy Carboniferous magmatism in continental arc magmatism. Alxa Block western segment contiguous CAOB, their could have occurred similar tectonic settings. In contribution, new zircon U–Pb ages, elemental geochemistry Sr–Nd isotopic analyses are presented for three early granitic plutons southwestern Block. Two newly identified aluminous A-type granites, an alkali-feldspar granite (331.6 ± 1.6 Ma) a monzogranite (331.8 1.7 Ma), exhibit juvenile radiogenic features, respectively. Although granodiorite (326.2 6.6 characterized by high Sr/Y ratios (97.4–139.9), which generally treated as adikitic feature, sample has highly isotopes displays significantly higher K 2 O/Na O than typical adakites. These granites were probably derived from partial melting Precambrian crustal sources heated upwelling asthenosphere lithospheric extensional setting. Regionally, both CAOB formation extension-related magmatic rocks lack coeval sedimentary deposits, suggesting uniform setting rather simple arc.