Syncollisional tholeiitic magmatism induced by asthenosphere upwelling owing to slab detachment at the southern margin of the Central Asian Orogenic Belt

The mafic–ultramafic complexes containing magmatic sulphides at the southern margins of the Central Asian Orogenic Belt have
been recently proposed to result from an Early Permian mantle plume. However, in this study we show that the plume model cannot
account for the observed geological characteristics of the Huangshan–Jingerquan mafic–ultramafic belt in the Northern Tianshan.
Low K2O contents and positive correlation between TiO2 and (Fe2O3)T/MgO of the mafic–ultramafic complexes of this belt demonstrate a tholeiitic affinity. Enrichment of large ion lithophile
elements and depletion of high field strength elements (in particular Nb and Ta) relative to mid-ocean ridge basalt indicate
a subduction-modified mantle source. Lead isotope values and compositions of chromite indicate a significant contribution
from the melting of asthenosphere. The absence of Late Carboniferous strata in the Huangshan–Jingerquan belt and Early Permian
exhumation of blueschist and eclogite along the Aqikkuduk suture at the southern boundary of the belt indicate that an arc–continent
collision occurred in the Late Carboniferous to Early Permian. We propose that the detachment of oceanic lithosphere from
continental lithosphere during the collision induced asthenospheric upwelling, which resulted in melting of both the asthenosphere
and the overlying metasomatized mantle wedge, and the formation of the mafic–ultramafic complexes with ages of 270–285 Ma
along the Huangshan–Jingerquan belt.

位于中亚造山带南部边缘的富含岩浆硫化物的中基性-超基性岩体群，近期被提出可能源于早二叠纪的地幔柱。然而，本研究表明，地幔柱模型无法解释黄山-靖泉中基性-超基性岩带所展现的地质特征。该带中基性-超基性岩体群低钾含量以及TiO2与(Fe2O3)T/MgO之间的正相关关系显示出岛弧岩浆岩的亲缘性。相对于中洋脊玄武岩的大离子亲石元素富集和高场强元素（尤其是Nb和Ta）的亏损，表明了俯冲改造的地幔源区。铅同位素值和铬铁矿成分表明了上地幔熔融的显著贡献。黄山-靖泉带内无晚石炭纪地层，以及沿带南部边界阿克苏沟缝合带的蓝片岩和榴辉岩在早二叠纪的抬升，表明在晚石炭纪至早二叠纪期间发生了弧-大陆碰撞。我们提出，碰撞期间洋壳与大陆壳的分离引发了软流圈上升，导致软流圈和上覆交代变质的地幔楔熔融，并在黄山-靖泉带形成了年龄约为2.7亿至2.85亿年的中基性-超基性岩体群。