| The No.258Hill gold deposit is located at western margin of Wandashan-Xihuote-Alin orogenic belt and eastern part of Wandashan massif, where the tectonicmovement and magmatic activity are intense, and shows good ore potential for noble andmulti-metals. According to the study on regional geological background andmetallogenetic geological environment, we summarized the metallogenic geologicalconditions and metallogenic model. We set up the prospecting model by extractingcomprehensive criteria for ore prospecting in combination with the explorationgeophysical and geochemical characteristics of the region and mining area, forascertaining the prospecting orientation in deep and periphery of the deposit.There are wide-spread Yanshanian Hamahe granite (mainly consist of granodioriteand monzonitic granite) and diorite porphyrite. The diorite porphyrite have close geneticrelationship with mineralized bodies, and they are paragenesis in space. It is the magmaticactivity that provides the important ore-forming materials, hot and fluid resources, andlays the foundation for gold deposit. The major trend of fault structure are NE, NW andNNE. NE trend faults are major rock-controlling structure which control the distributionof Hamahe rock mass. Sub-faults of NW, NNE derived from main faults as the importantore-hosting structure controlled the location of the mineralized alteration zone and thegold vein. At the intersection position of the two sets of faults are the most favorablestructural position. The wall rock alteration accompanying in the mineralize process includes silicification, pyritization, serictization, chloritization and carbonatation.The ore bodies are mainly hosted in cataclastic-altered granite and altered dioriteporphyrite, forming altered rock type and quartz vein ore. The ore minerals are pyrite,chalcopyrite and sphalerite. The texture of ores is allotriomorphic granular texture,replacement of mesh texture, metasomatic relict texture, cataclastic texture, etc, and thestructure of ores is fine vein structure, sparsely disseminated structure honeycomb-cysticstructure. The hydrothermal period of gold deposit is divided into three mineralizationstages: pyrite-quartz stage, quartz-sulfide stage and quartz-carbonate stage, and the firsttwo are the main mineralization stage.The intrusive rocks in258Hill gold deposit are chemically high-K calc-alkaline rockand peraluminous, the granodiorite and monzonitic granite are characterized by partialmelting of crust. The diorite porphyrites are the the typical mantle source arc magmaticrocks. LA-ICP-MS zircon U-Pb dating results show the emplacement ages of intrusiverocks in mining area are130Ma,118-122Ma,109Ma, which display there are withmultiple source and varied stages magmatic activity. Meanwhile, there are threedistinguishing magama intrusive activities in the ore district, the ages (118~122Ma) ofgranodiorite, monzonitic granite and diorite porphyrite are consistent in the error limits,those are comagmatic in the early Cretaceous, and closely associated with goldmineralization, we infer that they may represent the metallogenic epoch.Late Early Cretaceous, due to the subduction of the Pacific plate, a series of NWtrend dyke with the characteristics of mantle source of diorite porphyrite which carriedpart of the ore-forming elements. With the changes in the environment of temperature andpressure condition and the interfusion of near-surface atmospheric precipitation, themineral unloaded in the structural fissure, gradually formed altered rock type orebodiesand gold quartz vein type orebodies, accompanying with vein rocks, in the north west toechelon arrangement.The gold bearing quartz vein fluid inclusion show that the main fluidingredients are CO2, H2O, CH4, fluid temperature varies between230℃~297℃, fluidsalinity variation range between6％~9％Nacl eqv, density varies between0.7~0.9g/cm3,pressure variation mainly range between21~31MPa, metallogenic depth varies 2.10~3.10km, We preliminary confirm that the mineralization type in the No.258Hill goldmineralization area is the typical magmatic hydrothermal gold ore deposit of themiddle-low temperature, which resulted from the continental margin environment due tothe subduction of the Pacific plate.Based on the analysis of mineralization geological condition, and combined thecharacteristics geophysical and geochemical prospecting anomalies, we summarisecollective geological prospecting indications for the deposit. Firstly, Yanshannian dioriticporphyrite and altered granite have a high content of gold, and its intergrowth withore-body intimately as important magmatic indication; the NW trend fault structure andthe intersection area with NNE trend fault structure are the important tectonic indication;Silication, sericitization, chloritization and pyritization formed accompany withmineralizing are the important wall alteration indication. Secondly, soil geochemistry ofAu anomalies which have large area， high gold content, and concentration centers areadvantageous district for gold mineralization, as the important soil geochemistryexploration indications. Thirdly, IP intermediate gradient survey shows that goldmineralization bodies have high apparent resistivity and high polarizability, influenced bylater fracture, mineralization bodies also show low resistivity and high polarizability. Thelow-gentle positive magnetic anomaly zone and contact zone of lower positive andnegative anomalies of the ground high-precision magnetic measurement are pointed outwhere blind ore bodies may exist, which are the important exploration geophysicalindicationsOn the basis of favorable degree of mineralization geological condition andmetallogenic model, we combine with comprehensive ore-searching information model,we defined twoⅠ-level minerogenetic prediction, two Ⅱ-level minerogenetic prediction,and select2prospecting target area further and certain the No.258Hill gold deposit hasthe potential for deep gold and polymetallic. |
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