Petrogensis And Metallogeny Of Hongshan Orthophyre In Southern Taihang Mountain

Since Mesozoic,the North China Craton have entered into a strong tectonic active stage,with large-scale deformation,magmatic activities,basin formation and the generation of major metallic deposits.The study area is located in the southern part of the NCC central belt,and east to Taihang mountain fault zone.Based on the detailed geological investigation,we studied the diagenesis and mineralization of the porphyry copper deposit in Hongshan.The ore forming intrusive rock of Hongshan porphyry copper deposit is orthophyre.The copper ore body occurs in within the intrusion,and its grade is generally between0.2%?0.53%and up to 1.82%.Major and trace element data shows that the orthophyre belongs to alkaline rock,with high Si O₂,Al₂O₃ and total alkali contents.The intrusion is characterized by LREE enrichment and HREE depletion.The chondrite-normalized REE patterns show weak positive Eu anomaly.In the primitive mantle normalized trace element spider diagrams,the samples show strong enrichment in LILEs,and relatively depleted in HFSEs features.Meanwhile orthophyre‘s LA-ICP-MS zircon U-Pb dating declares that the host porphyry crystal ized at 131±1.8Ma,belonging to the early Cretaceous.The Sr-Nd-Hf data and AFC model indicate that magmas of Hongshan and Xishu-Wu'an intrusions are generated through partial melting of the EM1,belonging to different magmatic events and different magma chambers,together with minor lower crustal contamination.The metallogenic period is identified as Py+Ccp+Agt,Py+Ccp+Mag and Py+Q.S-Pb isotope results show that the ore has similar isotopic characteristics with surrounding rock,indicating that they have the same material source,rooted in the deep earth.The fluid inclusion and H-O isotopic results show low temperature and low salinity feature,suggest that the ore-forming fluids of the Hongshan C u deposit are predominantly magmatic with meteoric water influx during the late mineralization stage.The Hongshan porphyry copper deposit's diagenetic and mineralization has obvious consistency,outputting in the crust extension environment,which coincide with the major Mesozoic magmatism and mineralization and in the North C hina Craton.This may be one of the important ways of lithospheric mantle thinning.