The Discussion On Genesis And Prediction To Minerlization At Depth And Surrounding Of Jincheng Gold Ore Deposit, Luoshan County, Henan Province

The Tongbai-Dabie area has the characteristic of multi-cycle evolution, which has experienced multistage plate subduction-collision to plate activities, and resulting in development a series of nearly EW-trending ductile shear zone with different levels, different scales, and different characteristics. These nearly EW-trending ductile shear zone controls the northern tongbai-dabie Au-Ag-polymetallic ore belt. The Jincheng gold deposit, in the Luoshan County of the Henan Province, lies in the middle of Tongbai-Dabie area and the west of Dabie Mountains, and occurs in the east side of Lingshan granitic mass. Ore bodies occur as veins and lens which are controlled by the ductile shear zone, and hosted by metamorphic rocks of the upper Proterozoic Huwangang formation. Ore-bearing rocks are altered amphibolite, altered mica schist and interbedded thin-layer marble.Based on geological works in field and previous research data, this paper discussed the regional geological background, and sysmatically studied the geological features including orebody characteristics, ore fabrics, hydrothermal alteration and mineralization period stage and summarized the main ore-controlling factors. Finally, the paper discussed the prospecting directions and favorable places for prospecting on the basis of geological, geophysical and geochemical data.Jincheng gold ore structures mainly are disseminated, fine-veined and brecciated. According to paragenetic association of minerals and intercalation relationships of different veins, hydrothermal ore-forming period can be divided into3stages:quartz-pyrite stage(Ⅰ); quartz-polymetallic sulfides stage(Ⅱ); quartz-fluor-carbonate minerals stage(Ⅲ). The crystalline sequence of minerals were fromed from high temperature to low temperature, following the stage from silicates-oxides-sulfides-carbonate minerals. Pyrite is the main gold_bearing mineral, the native gold in early stage (Ⅰ) occurs in the boundary of pyrite grains (I), and the native gold in later stage(Ⅱ) occurs as inclusions in pyrites(Ⅱ)which are fine-grained and shaped.The83S value of pyrite in the main orebody ranges from-6.9%o to5.5%o with a mean of 2.33‰. The lead isotope composition shows the characteristic of the lower crust’s Pb isotopic, suggests that sulfur and lead were from the lower crust, similar to those of Huwan formation. The δ8OH2O,δDh2O, and813CCO2values in the ore forming fluid range from-6.09‰o～+4.0‰,-62‰～-86‰, and-6.3‰～-2.8‰.The O-H-C isotope composition infers that the ore-forming fluids are originated from the mixing of magmatic, meteoric water. So this paper concludes that magmatic water as Jincheng gold mine initial ore-forming fluids carried some minerals this fluids flow throught the deep fault and rise to shallow place,in those process, the fluid extracted mineral elements from Huwan formation; At late stage meteoric water leached some mineral elements from the metamorphic strata, those mineral elements together with mineral elements from magma make up material source of this deposit.In hydrothermal mineralization stage, homogenization temperature of fluid inclusions in quartz concentration on120℃～340℃, and salinity concentrated on OωNaC1%-16ωNaC1%; and homogenization temperature of fluid inclusions in fluor ranges from129℃to180℃, and salinity concentrated on0ωNaC1%～10ωNaC1%.The ore-forming fluids evolution and migration along the ductile shear zone from high temperature to low temperature, from high pressure to low pressure. Finally, the metallogenic material enriched gradually in favorable structures. The main mineralization’s homogenization temperature (quartz-pyrite stage, quartz-polymetallic sulfides stage) are between180℃to340℃, which is mesothermal mineralization; the mineralization depth is about1.5km～4.0km,belongs to middle-sallow depth.According to the research works mentioned above, the paper concluded that Jincheng gold deposit had experienced pre-enrichment by the effect of the metamorphism and deformation, form ed ore-bearing hydrothermal solution by the later activate from the effect magmatic hydrothermal, then mineralization by the infilling and metasomasis when the ore-bearing hydrothermal solution move to the fault which is ranged from brittle to brittle-ductile.Based on the geological features, geophysical and geochemical information, we believe that I orebody and Ⅳ orebody have deep extension trend, this lot has good exploration potential below the elevation of-300m; at shallow place of the mine, the east part of II orebody probably also be the reproduction area; In the eastern and western part of peripheral mine, that is to say the area of of gaoan-taotang and badouwa-longwan also have good exploration potential. So this paper presents the next prospecting area, including two first-grade prospective areas and two second-grade prospective, and proposals the recommendations of the arrangement of exploration engineering.