Study On The Geological Characteristics And Enrichment Regularities Of Mineralization Of Majiayao Gold Deposit, Qixia City, Shandong Province

Majiayao gold deposit, located in the Qixia city，Shandong Province, is situated inthe Qixia-Penglai metallogenic belt of Jiaobei uplift in eastern margin of North Chinaplate. The Qixia-Penglai metallogenic belt, with favorable geological conditions and thelower degree of research than Zhaoyuan-Pingdu metallogenic belt and Muping-Rushanmetallogenic belt, has good prospects.The strata exposed in the mine area is simple, mainly Archean Jiaodong Group orCenozoic Quaternary, the former scattered in form of inclusion in the west and north of themine area, the latter distributed in the low-lying areas. The Neoarchaean metamorphicintrusive rocks are main magmatic rocks, and ore bodies are hosted in fine-grained gnessicamphibolite-bearing biotite tonalite of Neoarchaean metamorphic intrusive rocks.Structures are well developed in the Qixia region，mainly for later NE-NNE trending faultsuperimposed on nearly EW trending、NW trending ductile shear zone structures and theQixia anticlinorium. The secondary fault of NE trending Majiayao-Shangzhuangtou isimportant ore-hosting structure.The main metallic minerals in the ore are electrum, pyrite and chalcopyrite and so on,the electrum is the main carrier of gold. The main gangue minerals are quartz, siderite andankerite and so forth. The main ore textures are cataclastic texture, hypidiomorphic-euhedral granular texture and interstitial texture. Ore structures are mainly vein structures,fine stockwork structures and disseminated structures. Alteration is mainly beresitization,phyllic, silicification, and beresitization is most closely related with gold mineration, sothat it is a good indicator of industrial ore body. According to the symbiotic relationship of minerals and ore fabric in the Majiayao gold deposit, mineralization in the Majiayao golddeposit displays two episodes，endogenetic and exogenetic episodes，and the endogeneticepisode comprises four stages of mineralization.Ⅰpyrite-quartz stage; Ⅱquartz-pyrite（-siderite）stage; Ⅲgold-quartz-polymetallic sulphides；Ⅳ quartz-carbonate stage. Instage Ⅰ mineralization, gold mineralization is weak, while K-feldspar is strong. StageⅡ and stage Ⅲ are main stage of gold-rich mineralization, and gold mineralization isstronger in stage Ⅲ.The local enrichment of gold often form in the section where stageⅢ and stage Ⅱ superimposed, which can constitute industrial ore bodies.Through the study of physicochenmical conditions, materials source and fluidssource in the mineralization, and the study of metallogenic age. The results show thatore-forming materials come from a mixing source of main mantle and crust，and thatore-forming fluids were sourced from mantle and meteoric water was introduced in thehydrothermal system in the late stage of mineralization. The homogenization temperaturein primary mineralization stage show that the ore-forming fluids have features of lowsalinity and low density. Laser Raman Microspectroscopy of fluid inclusions impy thatfluids immiscibility occurred in the mineralization process. Study on the trapping T-Pconditions of fluid inclusions and the mineralization depth shows that Majiayao golddeposit is attributed to mesozonal and mesothermal. The corrected age of Camptonite inthe early mineralization period show that the Camptonite formed in the Early Cretaceous,which implies that Majiayao gold deposit also formed in this period.Compared with the Shancheng gold deposit in the same region，with considerationsof all above，hence the Majiayao gold deposit can be genetically attributed to themesothermal gold deposit.