| The Suli copper polymetallic deposit,located in Suli Township,Tianjun County,Qinghai Province,is a newly discovered small-scale deposit.It is mainly copper,containing antimony,lead,zinc,silver and other metals.Its geotectonic location is located in the middle part of the Tuolainan Mountains on the western margin of the Middle Qilian magmatic arc.It belongs to the Middle Qilian Muli-Haiyan Caledonian-Hercynian copper,iron(titanium,gold,antimony,lead)metallogenic subzone.The deposit occurs in the clastic-carbonate formation of shallow marine facies.The weakness of theoretical research on geological characteristics and metallogenic conditions of ore deposits restricts the further development of prospecting and exploration in the mining area.On the basis of previous regional geological work,through field geological survey,data collation and research,indoor optical thin section identification and other work,using scanning electron microscopy,chemical analysis,fluid inclusion temperature measurement and other methods,the geological characteristics of the deposit have been identified,and the ore-forming conditions have been analyzed in depth.Through field geological survey,it is found that the main strata exposed in the mining area are the South Baishuihe Formation and Huaerdi Formation of the Great Wall System,the Carboniferous Chouniugou Formation and the Yanghugou Formation.Soil chemical samples and rock samples were collected in the mining area,and grooves and boreholes were laid.The ore-bearing stratum is the Nanbaishuihe Formation.Its lithology consists of metamorphic quartz sandstone,metamorphic siltstone,sandy slate,silty slate,intercalated with crystalline limestone,limestone dolomite and dolomite.Ore bodies occur mainly in carbonate rocks of the Nanbaishuihe Formation,which are lenticular and vein-like and nearly parallel.Through field geological survey and indoor thin section observation,wall rock alteration is mainly silicification,kaolinization,carbonation,sericitization and chloritization.Identification of Ore Specimens and Light Section Microscope,the main ore structures are disseminated structure,dense massive structure,fine(net)vein structure and thin film structure.The main ore structures are crystalline structure,inclusion structure,skeletal structure,metasomatic residual structure,filling structure,fracturing structure and crushing structure.According to the vein interpenetration and mineral assemblage characteristics,the mineralization process of the deposit can be divided into two metallogenic stages: hydrothermal stage and epigenetic stage.By means of microscopic identification and scanning electron microscopy,the primary ore minerals in the ore are mainly chalcopyrite,massive sulfur-antimony-copper ore,sphalerite,galena and so on.The gangue minerals are mainly pyrite,quartz and calcite,which have typical mineral assemblage characteristics of medium-low temperature hydrothermal deposits.Secondary minerals are mainly bluecopper,malachite,limonite and so on.Based on the analysis of enrichment coefficients of major elements,trace elements,rare earth elements and metallogenic elements of magmatic rocks in the mining area,the magmatic rocks in the mining area can be divided into two stages: Neoproterozoic diabase intruded into Nanbaishuihe Formation of Great Wall System and enriched copper,zinc and other metallogenic elements in the strata;Late Caledonian continental crust collision orogeny enhanced the activity and hydrothermal activity of Qilian Mountains and Caledonian orogeny.Late monzonitic granite provides ore-forming element lead and heat source.It shows that magmatic activity is one of the necessary conditions for the formation of the deposit.Based on the regional geological survey data of predecessors and combined with the field geological survey,the ore-forming tectonic conditions are deeply analyzed.The Suli copper polymetallic deposit is obviously controlled by tectonics,mainly controlled by Shule Nanshan-Lajishan fault,regional NW secondary fault and fracture zone of mining area,which respectively constitute the ore-forming fluid conducting,ore-blending and ore-hosting structures,it reflects that the metallogenic structural conditions of the mining area are good.The physical properties,chemical properties and ore-bearing properties of surrounding rocks in the region and mining area are studied in detail.The enrichment coefficients of copper,antimony,lead,zinc,gold and silver in different rocks of the Nanbaishuihe Formation in the region and mining area are studied.The results show that the Nanbaishuihe Formation has a good metallogenic background.Microscopic observations of inclusions in quartz closely related to mineralization show that the inclusions are mainly gas-liquid two-phase,generally less than 15 micron,mostly concentrated in the range of 6-10 micron,and the gas-liquid ratio ranges from 5% to 15%.The metallogenic temperature obtained by homogeneous temperature measurement is 144.6-285.5?,with an average of 197.54?;the salinity of ore-forming fluid is 2.07-9.47 wt% NaCl,with an average of 6.16 wt% NaCl;the metallogenic depth ranges from 1.29 km to 2.58 km,concentrating over 1.5 km,and mainly formed in a meso-metallogenic environment.Based on the analysis of geochemical anomalies,prospecting criteria and comparison with typical deposits,this paper briefly analyses the potential of polymetallic prospecting in the mining area and its periphery. |
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