Based on the major, trace element, and isotope data of the Cenozoic basalts in the study area, it is indicated that the basalts in this region can be classified into three distinct magma systems: alka-li basalts, tholeiite basalts, and Nushan alkali basalts. The geochemical characteristics observed in the studied basalts indicate that the mantle source in this region might have experienced met-asomatic processes prior to partial melting, which could be linked to an ancient subduction pro-cess. Combining the geochemical characteristics in the studied basalts with previous research, we propose that the underlying mantle source in Anhui province may have undergone metaso-matism due to the carbonatitic melts. These melts are believed to have originated from car-bonated eclogite, derived from subducted Pacific slab materials present in the deeper mantle. According to the Sr-Nd isotope data, it is suggested that the mantle source in the Nushan region could be derived from a depleted asthenospheric mantle, while the basaltic composition in the Niugang area may be representative of the mantle's end components associated with the EM-I enriched mantle source present in this study area. Therefore, we propose that the Anhui basalts may have originated from the partial melting of a mantle source representing a mixing of two end-members: DMM (Depleted MORB Mantle) and EM-Ⅰ (Enriched Mantle 1). The Anhui basal-tic magmas may have originated from the partial melting of EM-Ⅰ, potentially influenced by upwelling asthenospheric mantle or asthenospheric diapirism processes. The mantle source in the study area experiences partial melting at 1-5%, 15%, and 1-10%, resulting in the formation of parent magmas for alkali basalt, tholeiitic basalt, and Nushan alkali basalt. Subsequently, the parent magmas experienced fractional crystallization processes, which included minerals like olivine, pyroxene, and plagioclase. This led to the formation of various types of basalt in the study area.

Precise determination of the tectonothermal events at the Qinling-Qilian junction is extremely significant for understanding the tectonic evolution of the eastern branch of the Paleo-Tethys. The Banpo porphyry outcrops in the northern margin of the North Qinling were chosen as the research subject, and its formation and tectonic environment were analyzed using Zircon U-Pb age estimation and geochemical studies. The results indicated the final stage of the Triassic orogeny and the closure phase of the Paleo-Tethys. The weighted average values of 206Pb/238U ages of samples from 3 sites of the Banpo porphyry corresponded to 213.4 ±2.1 Ma (MSWD = 0.56), 213.0 ±1.6 Ma (MSWD = 0.92), and 213.2 ±4.4 Ma (MSWD = 1.6). This study revealed that the Banpo porphyry was formed during the Late Triassic (Norian). The porphyry with high SiO2 and high alkali is typical A-type granite, which belongs to the weak peraluminous shoshonite series. All the samples are rich in low rare earth elements. However, the heavy rare earth elements are low, especially Eu, which exhibits a seagull-type right-leaning partitioning curve. In addition, based on the regional geological data, it can be concluded that the Banpo porphyry was formed during the transition period from a post-orogenic environment to a non-orogenic environment. This study indicated the closure of the Paleo-Tethys-Mianxian-Lveyang Ocean by the Late Triassic as well as the completion of the collision between the North China and Yangtze Blocks along the Qinling orogenic belt.

In order to study the petrogenesis and tectonic setting of Permian A-type granites and their relationships with hydrothermal mineralization along the Hegenshan-Heihe suture zone (HHSZ) in northeastern China, we select the newly discovered Hongyan Cu-polymetallic deposit in the northeastern part of the HHSZ that develops three stages of mineralization associated with the Shanshenfu alkali-feldspar granite (SAFG). The zircon U-Pb dating and whole rock geochemistry suggest that the SAFG is a typical A-type granite formed in the Early Permian. The zircon Hf isotopes and trace elements suggest that the SAFG has high Ti-in-zircon temperature (721–990℃), high magmatic oxygen fugacity and largely positive εHf(t) (+6.0 to +9.9). Therefore, we propose that the SAFG was derived from the crustal assimilation and fractional crystallization of the charnockitized juvenile crust. The high oxygen fugacity favors the chalcophile elements (e.g., Cu, Au, Ag) of the source region enriched in the fluid phases after magmatic fractional crystallization, consequently facilitating subsequent hydrothermal mineralization, which is also consistent with the characteristics of ore-forming fluids that changed from the initial high temperature, high salinity, high fO2 and CO2-rich magmatic-hydrothermal fluids of stage I to CO2-poor, dilute, and cooling meteoric fluids of stage III. Combined with regional geological background, the Permian A2-type granites along the HHSZ can be formed in post-collisional slab break-off process. In subsequent exploration for hydrothermal deposits along the HHSZ, the Permian A-type granites with arc-related juvenile crustal source and high fO2 have great potential and need more attention.