Geological Characteristics And Metallogenetic Mechanism Of Au-Ag Deposits In Linjiasandaogou-Xiaotongjiapuzi Region, Eastern Liaoning Province

Eastern Liaoning Paleo-Proterozoic rift zone distributes many Au-Ag deposits,most of which are large scale concealed ones. Linjiasandaogou-Xiaotongjiapuziregion in Easten Liaoning Province is a famous one in the rift zone. Distributed in the6thsegment clastic-carbonatite formation of Yangshugou formation Dashiqiaosub-group（Pt1Dy6）and Tangjiagou clastic formation in Gaixian sub-group（Pt1Gxt）,the deposit have hosting rocks of silicated marble, leptynite and schist. Country rockalteration, which is an low-intermediate alteration association, include silication,sericitization, pyritization, arsenopyritization and carbonatization. Natural gold havefine grain size and usually invisible gold. Gold can only be discriminated undermicroscope. Both homogenization temperature(100~200℃) and salinity（ω（NaCl）（1.91%-9.73%） of Fluid inclusions in the deposit are low. The δD value ofore-forming fluid in quartz from ores ranges from-48.0‰to-93.0‰，and calculatedδ18OH2Ovalue ranges from-8.63‰to+1.31‰. The result shows ore-forming fluidwas derived mainly from geothermal water and primary connate water, with minoritymeteoric water. Mean value of ore sulfur isotope is+8.61‰, while country rock andintrusions value is+0.50‰～+7.6‰. Sulfur isotope tests result suggests sulfur in oresderived from Paleoproterozoic strata and late Indosinian intrusions and mineralizationenvironment was a closed reductive environment. Values of206Pb/204Pb,207Pb/204Pband208Pb/204Pb in gold and silver ores are17.664～19.1867,15.044～15.883and37.693～38.784respectively. Pb has a mixing source of orogenic blet and upper crust.The crust and mantle mixture characteristics indicate the deposits are sedimentarymetamorphic-magmatic hydrothermal superimposed types.This paper studied geological characteristics, mineralization conditions,ore-forming fluid and geochemical isotope features in Linjiasandaogou andXiaotongjiapuzi Au, Ag deposits. Based on the results, the author defined themetallogenisis and metallogenetic mechanism, then enriched regional metallogenisistheory and provided gold (silver) deposit exploration clues in Liaoji Paleo-Proterozoicrift.