Zircon U-Pb dating and geochemical features of Hangou granitic body in Xiaoshan Mountain, western Henan Province, and its geologic implications

Hangou monzonitic granite porphyry body lies in northern Xiaoshan Mountain, western Henan Province. Petrogenetic research on Hangou rock body is important for recognizing tectonic evolution in northern Xiaoshan Mountain area, and it is also significant for estimating mineralization potential. The zircon U-Pb dating method of LA-ICP-MS was used to confirm the age of biotite monzonitic granite porphyry sample named LLHG01 from Hangou rock body. The results of 20 zircon spots are consistent with ²⁰⁷Pb/235U-²⁰⁶Pb/²³⁸U trend line, with ²⁰⁶Pb/²³⁸U ages being from 142 Ma to 147 Ma, and weighted average age being (145.1±0.7) Ma. Hangou rock body is characterized by higher SiO₂ and alkali, enrichment of K₂O, and lower MgO and CaO. Compositional spots of Hangou rock body fall into high-K calc-alkaline series in the SiO₂-K₂O diagram, and it belongs to K-rich calc-alkaline granite (KCG). In chondrite-normalized REE patterns, Hangou rock body samples have shown the characteristics of LREEenrichment and HREE depletion with trivial Eu positive anomaly, whose (La/Yb)_N ratios are from 10.41 to 11.51. Samples from Hangou rock body are enriched in large ion lithophile elements and depleted in high field-strength elements, which has formed troughs of Nb, Ta and Ti in spider diagram. Samples of Hangou rock body have higher Sr and lower Y and Yb, suggesting that Hangou rock body is adakite. According to the content of Na₂O and K₂O, Hangou rock body is C-type adakite. Hangou rock body originated from partial melting of the thickened lower crust, and its residual phases of partial melting source included garnet and rutile, with no plagioclase. North Xiaoshan Mountain area underwent the process of lithosphere delamination of different scales in~145 Ma and~130 Ma, and Hangou rock body is a product of smaller scale lithosphere delamination that occurred at~145 Ma. The formation age of Hangou rock body falls into the time interval of~145 Ma stage of acid magmatism and endogenetic mineralization in western Henan Province. In the disaster process of lithosphere delamination in Hangou area, huge deep fluids were driven and discharged rapidly, suggesting that Hangou rock body and its concealed part have large mineralization potential. There are 11 Au deposits and Au mineralization spots around Hangou rock body, which constitute the best exploration evidence.