Gold Mineralization And Metallogenic Model Of The Jiaoxibei Gold Deposit Concentrated Area

The Jiaoxibei gold deposit concentrated area is located in the southeastern margin of the North China Craton,the western side of the northern section of the Sulu ultrahigh-pressure metamorphic belt and the eastern side of the Tanlu fault zone.The deposits belong to the kind of endogenous hydrothermal gold deposits with frequent and intense magmatic activity.It is China's largest gold mining area,and it produces three world-class gold ore fields of over 1,000 tons(Sanshan Island Gold Mine Field,Jiaojia Gold Mine Field,and Linglong Gold Mine Field).There are more than 10 super large and large gold deposits and nearly 100 small and medium-sized gold deposits in the Jiaoxibei gold deposit concentrated area.Previous studies have shown that the gold metallogenic age of most gold deposits in the Jiaoxibei gold deposit concentrated area is within 120±10 Ma.How such a large-scale,short-term,high-intensity gold mineralization was formed under the mineralization has always been one of the key issues that scholars have tried to explore.Based on the study of the regional geological background,regional geophysics,and regional geochemical data,this paper takes the typical gold deposits in the Jiaoxibei gold deposit concentrated area as the research object and discusses the formation of the gold deposit area using various geological and geochemical methods.The mineral source,metallogenic process,and metallogenic process,to establish the metallogenic model of the Jiaoxibei gold deposit concentrated area.The gold metallogenesis in the Jiaoxibei gold deposit concentrated area is closely related to the Mesozoic tectonic magmatism.The interpretation results of regional geophysical data show that the main surrounding rocks of the gold deposit are Linglong series granite and Guojialing series granodiorite;regional geochemical characteristic parameters show that the gold concentration coefficients of Linglong super unit and Guojialing super unit are significantly higher than other geological units indicate that they are favorable metallogenic geological units;combined with regional geological background studies,it is believed that the Linglong sequence granite and Guojialing sequence granodiorite are closely related to gold mineralization,and the formation process of the Linglong sequence granite provides gold mineralization of the heat source.The granodiorite in the Guojialing sequence is a direct source rock series and plays a leading role in the enrichment and positioning of gold deposits.To further explore the source of ore-forming materials and the process of metallogenesis in the Jiaoxibei gold deposit concentrated area,we collected and selected samples of gold(rock)stones and cores from the Xinli,Jiaojia,and Dayingezhuang gold deposits,using geological and geochemical methods Perform experimental analysis and results in interpretation.The microanalysis of gold minerals shows that the darkening of the gold mineral particles is mainly caused by impurities or inclusions composed of Al,Si,O,Fe,and S;the tellurium(bismuth)gold complex starts during the process of gold migration and mineralization Plays an important role.Rock geochemical analysis results show that the Linglong sequence granite belongs to the high-calcium-calcium-basic I-S transitional granite.The trace element content of the three gold deposits was quite different;rare earth element research shows that the core samples of different rock types in each gold deposit have similar distribution patterns,and are characterized by the enrichment of light rare earth and the loss of heavy rare earth,so it is speculated that they are homologous,that is,the gold deposits in the Jiaoxibei gold deposit concentrated area have the same metallogenic source.Besides,we try to use the corresponding analysis method to study the relationship between various elements in different gold deposits,and obtain a good classification effect,reflecting the characteristics of various elements and the relationship between the deposits.The study of wall rock alteration shows the in and out of elements in different alteration processes and analyzes the causes of element enrichment and loss.For example,the loss of Zr and Hf may be related to the decomposition of zircon.The study on fluid inclusions shows that the fluid inclusions in the Jiaoxibei gold deposit concentrated area have the characteristics of medium-low salinity and low density.The main metallogenic temperature is 219.7-387.7? and the metallogenic pressure is 32-160 Mpa.Hydrogen and oxygen isotope research results show that the ore-forming fluid is a mixture of magmatic water and atmospheric precipitation,and the sulfur isotope and lead isotope indicate that the ore-forming fluid has the characteristics of the crust-mantle mixed source.Based on the above research,the metallogenic mechanism of gold deposits in the Jiaoxibei gold deposit concentrated area was summarized from the aspects of ore-forming material source,ore-forming structure,the age of mineralization and the geological process of mineralization.A metallogenic model was constructed: North China was under the tectonic background of lithospheric thinning in the Early Mesozoic Early Cretaceous.The mantle uplift triggered delamination to form a large-scale crust-mantle magma mixed zone,where the gold in the deep crust partially melted to produce gold-bearing granitic magma.The conversion from extrusion to extension further produces large-scale,high-strength magmatic activity events.Gold bearing hydrothermal solution was separated from gold bearing granitic magma during crystallization differentiation.These hydrothermal fluids migrated upward along the fracture structure and formed many gold deposits in the Jiaoxibei gold deposit concentrated area by filling and metasomatism under certain structural position and physical and chemical conditions.