A genetic link of Permian high-temperature magmatism with a mantle plume activity: a case study from the southern Chinese Altay Orogen

The origin of Permian magmatism in the Chinese Altay Orogen is highly controversial, which is crucial for understanding the evolution of the Central Asian Orogenic Belt. Through a study of the petrology, temperature and/or pressure conditions, geochemistry, and geochronology of the Wuqiagou diorites, this study provides a genetic interpretation for the in the Chinese Altay Orogen. Estimates of crystallization temperatures and/or pressures for each sample were obtained using amphibole thermobarometer and zircon saturation thermometry, yielding results of 900-1000 ℃/0.6-0.8 Gpa and 803-914 ℃, respectively. Geochemical analyses show that these rocks belong to the calc-alkaline series with relatively low SiO2 contents (SiO2 =44.9-47.9 wt.%), low total alkali contents (K2O+Na2O=2.0-5.4 wt.%), high values of Mg# (54-74) and elevated concentrations of V, Cr, Co, and Ni. These diorites are enriched in large ion lithophile elements, but depleted in high field-strength elements. The negative εHf(t) values from -1.23 to -10.13 reflect an enriched mantle source of the diorites. Zircon U-Pb data show the Early Permian emplacement ages of ~280 Ma. The calculated crystallization temperatures are all consistently higher than those previously reported. Therefore, based on the above evidence, it can be inferred that the Early Permian mantle plume activity may have brought anomalous high heat flow, leading to a genetic links between the Wuqiagou diorites and the nearby ultrahigh-temperature granulites.