| Xiadapu gold deposit is located in the eastern part of the northern margin of theNorth China Craton Qingyuan granite-greenstone terrane. Magmatic activities in the areaof strong, complex geological structure, metallogenic condition is superior, the southernTaizi River depression, North Pan River depression, Hunhe river deep fault in NEEdirection across the region, it is the area of a fracture, is the Eastern Branch ofTancheng-Lujiang Fault Zone in Liaoning Province, the fracture extension in JilinProvince after the Huifahe fault, finally through Heilongjiang into the territory of russia.Mining area stratum mainly for the Archean Anshan group stone shed group, secondsaw the Mesozoic Upper Cretaceous hit stone ditch group and Cenozoic Quaternary;Magmatic rocks in the mining area is mainly in nankouqian granite, followed by acidic,basic types of dikes.In addition to altered diabase dikes is too late antiquity, the rest areMesozoic product, acidic veins in North East, intermediate-basic dikes in the North Westto the output, and the former is earlier than the latter. Mine is located in the intersectionparts under the fault and the Hunhe fault, fault development, mainly for the North West tothe ore.The main useful minerals of Xiadapu gold ore deposit in native gold, electrum,followed by natural silver, gold and silver ore. Other metallic minerals are pyrite,chalcopyrite, galena, sphalerite, magnetite, hematite, limonite, malachite, chalcocite,covellite.. The gangue minerals include feldspar, albite, quartz, feldspar, in dolomite,calcite, sericite, chlorite, epidote and apatite amount. The ore structure as granular structure, cataclastic structure, followed by metasomatic texture. Ore structures are mainlyvein structure, brecciated structure and disseminated structure etc. The wall rock alterationinclude potash feldspathization, silicification, sericitization, chloritization, carbonation,pyritization etc.Xiadapu gold deposit has experienced four stages of mineralization: Ⅰpotassiumfeldspar quartz pyrite stage; Ⅱ gold-quartz-pyrite stage; Ⅲ gold-quartz polymetallicsulfide quartz stage, which belongs to the main metallogenic stage, the fourth stage isquartz carbonate stage.In the mining area, south of rock is widely distributed, ore-bearing zone are mainlydistributed in the inner contact zone of granite body in nankouqian. Geochemical studiesindicate that the I type granite geneses of the rock mass as a set of high K Calc alkali, rockmass with enriched in light rare earth elements and large ion lithophile elements, butdepleted in high field strength elements, formed in the subduction zone of island arccalc-alkaline tectonic environment. Xiadapu gold deposits and gold mineralization innankouqian rock have a certain relationship, mainly for the mineralization of rock mass.Andesitic porphyrite dikes in the coal mining area as an important area in goldappeared in large numbers, often parallel distribution of the ore body, closely associatedwith orebodies, reflect the intrinsic link between them. Andesitic porphyrite is a set ofhigh K calc alkaline volcano rock, with enrichment of LREE and lile, depleted in heavyrare earth elements and high field strength elements, partial melting of enriched mantlesource in subduction zone and formation fluid metasomatism, formed in the subductionzone arc calc-alkaline tectonic environment. Andesitic porphyrite dikes in the coal miningarea as an important area in gold appeared in large numbers, often parallel distribution ofthe ore body, closely associated with orebodies, close relation with gold deposit formation.Xiadapu gold deposit, fluid inclusion studies indicate that the ore-forming fluid forlow salinity （0.35～19.55wt%NaCl.eqv）, low density （0.491.04g/cm3）, rich in H2Oand CO2NaCl-H2O-CO2system, the ore-forming process of ore-forming fluidimmiscibility happened obviously, temperature of the main metallogenic stage for260320℃, the metallogenic pressure75150MPa, metallogenic depth is7.048.48km. Range of δ34S pyrite xiadapu gold deposit in values for-2.0‰～+1.4‰34S‰,δ34S value range is small, tower effect is obvious, that the ore-forming materials werederived from a mantle source or deep source bed; Research on H-O isotopes and fluidinclusions suggest that the ore fluid in the mantle fluid, accompanied by minor meteoricwater. Research thinks xiadapu gold deposit ore-forming fluid phase separation took placein the metallogenic process, namely the NaCl-H2O-CO2fluid into a two fluid, H2O-NaCland CO2-H2O, happened to CO2lost for the characteristics of the immiscible phenomenonin the process of mineralization.Combined with the metallogenic background that mesothermal vein type gold depositxiadapu gold deposit belongs to the production in the Archean granite-greenstone terranein, can be classified as Groves （1998） proposed in orogenic gold deposits.Xiadapu gold deposit and its metallogenic age from the Archaean to Mesozoic, havea "genetic relationship between inherited", showed that long-term the gold mineralization,but the late Indosinian-early Yanshan structural-magmatic activities is metallogenicfactors leading, is due to the subduction of the Pacific plate and the water formed in theearth’s crust mantle fluid, in experienced the complex evolution, formed by mantle fluidfaults in mineralization of mesothermal vein gold deposit. |
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