Studies On The Ore-forming Material Sources Of The Dongzigou Lead-zinc Despoit In Xishui,Guizhou

Taking Dongzigou lead-zinc deposit Xishui Guizhou as the research object,Using the method of mineralogy,petrology,and mineral deposit geochemistry to analyze the ore-forming material of the Dongzigou lead-zinc deposit from the aspects of geological characteristics,mineralogical characteristics,and geochemical characteristics of the deposit.Discussing the mineralization process of the deposit,and provide the theoretical basis for finding the same type of lead-zinc deposits.The geotectonic position of Dongzigou lead-zinc deposit is located in the southeast edge of sichuan basin and the core of Sangmuchang anticline.The ore body is deposited in the breccia dolomite,and the output form is obviously controlled by the structure.Mineral composition is simple,ore mineral is given priority to with sphalerite,galena containing a small number of pyrite,galena,meneghinite,etc.Gangue minerals are mainly dolomite,barite,quartz,fluorite.The mainly wallrock alterations are silicification,dolomitization,baratization and fluoritization etc.Sphalerite trace element analysis show that the elements,such as Ba,Ge,Ag,Cu,Cd,Ga more enrichment and lower of Bi,Co,In,Ni,Mo,Se,Tl,Sn,Sb.Ga/In ratio range of 118.873?969.381,Ge/In ratio between 472.032?13803.857,Zn/Cd ratio average 216.238(n=6),indicating the ore-forming fluid medium to low temperature.The mineral quartz H-O isotope of gangue mineral indicates that the ore-forming fluid comes from the formation of water in the stratum and the late mineralization has the participation of atmospheric precipitation;dolomite C-O isotopes shows that the ore-forming fluid is derived from the dissolution of the carbonate rocks in the ore bearing strata,the dolomite is a normal marine deposit.Comprehensive the metallogenic flow of the Dongzitgou lead-zinc deposit mainly formation water,.in the late stage there is meteoric precipitation.Sulphide have similar patterns of rare earth assignments and the Dengying Formation rock,which is different from the Niutitang Formation shale,suggesting that the source of the ore-forming material maybe genetically related to ore-bearing surrounding rock in Dengying Formation.Sphalerite and baryte mineral paragenesis is?³⁴S_?S=17.883,showing that the sulfur was derived from the reduction of marine sulphate in the same period;the lead isotopic composition of sphalerite and meneghinite showed that the lead in the ore originated from the upper crust;The average value of strontium ratio in sphalerite(⁸⁷Sr/⁸⁶Sr)_j is 0.71392,the average value of strontium ratio in baryte(⁸⁷Sr/⁸⁶Sr)_j is 0.71427,and strontium ratio in dolomite(⁸⁷Sr/⁸⁶Sr)_j in is low(average is 0.713669).Meaning the strontium is the source of the earth's crust and ore-forming fluids flow through multiple strata and the content of strontium in the minerals is increased.It is considered that the Dongzigou lead-zinc deposit ore-forming minerals come from the ore-bearing strata itself.In the late Sinian,influenced by the Tongwan movement,the sedimentary environment changed,and as the stratum entered the settlement period,under the effect of sedimentary compaction,the construction water sealed up in the stratum was formed.Yanshan tectonic movement resulted in the formation of regional faults and secondary faults,which resulted in the rupture of rigid dolomite;the ore-bearing brines in the strata have undergone lateral migration under the action of structures,and the ore-forming elements in the surrounding rocks have been extracted to form ore-bearing hydrothermal fluids.Due to the capping effect of the upper Cambrian Niutitang Formation,reaction occurs with the surrounding rock,and further extraction of metal elements in the strata leads to the migration of ore-forming fluids to the Dengying Formation rupture zone.Late mineralization occurs.The increase of atmospheric precipitation(seawater)changes the temperature and p H of ore-forming fluids,leading to the precipitation of ore-forming materials in the breccia dolomite with larger fracture space.