Study Of The Geological Characteristics And Enrichment Regularities Of Mineralization Of Yingdongzi Ag-Pb Deposits,Shanxi Province

Yingdongzi Ag-Pb Polymetallic Deposits is lacated in southeast of Zhashuicounty,Shanxi Province, which silver mines belonging to the extra large deposit,multi-metal mine is a medium-sized deposit. Geotectonic location lies in the west ofShanyang-Zhashui metallogenic belt,which the north is bounded by Yangxie-Yinpandeep fault, and the south is bounded by Shanyang-Fengzhen deep fault. In theresearch area, exposure strata mainly is very thick terrigenous clastic rock formationof Devonian,which is angular unconformity with basement Yaolinghe Group byancient weatherying crust.The mineralization age of Yingdongzi Ag-Pb Polymetallic Deposits is between342Ma~378Ma，same with the host strata.The exposure strata in the mining area is thesecond lithologic member of Daxigou formation of he Middle Devonian.Thecomposition of the formation mainly are phyllites, platy phyllite, carbonate takessecond place, followed by rare metamorphic fine-grained sandstone and sulfate rocks.The mining area is located in the south of Meijiaping secondary superimposedfold,which lies in west of the southern wing of Heishanjie-Hongyansi multiplesyncline.This superimposed fold controls the structural form of Yingdongzideposits.Maerxia contemporaneous fault with nearly NNW. Striking is in the east sideof the mining area,which activity time is the late Middle Devonian.The fault directlycontrols the formation and evolution of the Yingdongzi sub-three hydrothermalsedimentary basin and plays an important role in the formation of Yingdongzi deposits.The intrusive rocks of the mineing area mainly is Zhashui rock which is in thenorthwest corner of mining area, In addition, lamprophyre veins is conmon.The deposits occur in the transitional position which is upper of Qingshiyaformation, where the argillaceous, silty deposition to argillaceous carbonate deposition.The deposts is composed of18ore bodies. The ore bodies which assumelayered and strat ified forms parallelly occur in the middle to lower position ofbearing bed. The ores’ occurrence is consistent with the surrounding rock’, andsynchronization fold with the strata, indicating syndepositional characteristics.The characteristics of ore-bearing formation of Yingdongzi deposits is composedof alternate fine-grained clastic rocks of turbidite deposition and chemicalsedimentary of hydrothermal exhalation.The carbon argillaceous slate on orebodyroof formed after of exhalative sedimentary mineralization is the sign of the end of theorebody.There develops a series of typical hydrothermal-sedimentary rocks, such asbaritic rocks, siliceous rocks and siliceous albitite rock etc. Chlorite rock andchloritized are widely developed in orebody footwall or in transition part of exhaliteand fine grained clastic.Our study suggests that the chlorite rock is a kind ofcodeposition alteration rock, which formed by reaction of fine-grained clastic thingsand exhalative things at the same time of the process of fine-grained clasticsedimentary and exhalative sedimentary, rather than the previous view that theexhalative rocks.Ore structure are striated structure and banded structure. Main metal minerals arepyrite, chalcopyrite, magnetite, galena, sphalerite, arsenopyrite, etc., mainly silverminerals are silver-bearingtetrahedrite-freibergite. Major gangue minerals are bariteand albite, followed by chlorite, calcite, and so on.Yingdongzi Ag-Pb Polymetallic deposits has two mineralization stage, namelyinchoate hydrothermal deposition epoch and terminal hydrothermal metamorphictransformation epoch.Because the later metamorphism is weak so the depost preservethe characteristics of the original hydrothermal sedimentation. Flow inclusionmeasured temperature of inchoate hydrothermal deposition epoch range of109.3~338.6°C, fluid salinity range of0.18~17.83%NaCl, and the fluid density of0.68to1.03g/cm3.The characteristics of sulfur isotopic showed that the sulfur of the majorore-forming stage mainly comes from the sea and a small part from magmatic fluids.Lead tectonic model graphic shows the lead from the upper crust, and a small amountof mixed orogenic belt of the crust and mantle lead.The ore-forming medium water ofinchoate hydrothermal deposition epoch is from sea water and terminal hydrothermalmetamorphic transformation epoch is composed of metamorphic and magmaticwater. The genetic type of Yingdongzi Ag-Pb Polymetallic deposits is Sullivan-typeexhalative sedimentary deposit according to tectonic position, ore-controllingstructure, wall rock alteration, wall rock characteristics, form of ore body and thegeochemical characteristic of deposits.