Characteristics And Genesis Of Hydrothermal Sedimentary Facies In Pakabulak Celestine Deposit,Wuqia County,Xinjiang

Many rich mineral deposits,including a large number of metal minerals?copper,lead,zinc,etc.?-celestite-coal--uranium-oil and gas,are developed in the Pamirs Plateau-Tarim Basin-South Tianshan Orogenic Belt Mesozoic Intracontinental Basin-Mountain-Marginal Mosaic Tectonic.The area has the law of enrichment and mineralization in the same basin and different types of fluids are developed.The Pachabulak celestite deposit,which is located at the eastern extension of the Uracen complex syncline,is an important metallogenic system in the sedimentary basin,and has the characteristics of coexistence by different phases in the same basin with the super-large Uracen lead-zinc deposit.Besides,it has certain specificity in the metallogenic regularity.In order to study this particularity more,we know the diagenetic and metallogenic mechanism of celestite deposit.The main results obtained through the study of structural petrography are as follows.?1?The hydrothermal sedimentary rock of the Pachabrak celestite deposit can be classified into four hydrothermal sedimentary facies:hydrothermal syngenetic sediments-alternating lithofacies,gas-generating hydrothermal jet sedimentary lithofacies,gas-generating hot brine syngenetic deposits-alternating lithofacies and gas-generating hydrothermal filling-metasomatic facies.The types of ore mainly include thick massive celestite rock,celestite limestone,celestite siliceous fine conglomerate and hydrothermal breccia celestite rock.The minerals in the deposit are mainly celestite,calcite,dolomite.?2?The main trace element and rare earth element characteristics of the hydrothermal sedimentary lithofacies in the celestite deposit show that Na₂O and K₂O in the macroelement are low and have high component maturity.In the trace elements Ba,Cl,etc.are enriched,?Eu is positive anomaly,and?Ce is negative anomaly.As a whole,the light rare earth elements are enriched and the heavy rare earth elements are deficient.The thick massive celestite rock in the hydrothermal syngenetic sediments-alternating lithofacies has a strong negative Ce anomaly.As the content of celestite decreases,the negative Ce anomalies of other lithofacies become weak,which is closely related to the celestite syngenetic deposition.?3?The fluid composition of the celestite mineral is not single,which is a hydrothermal fluid containing Ba²⁺,Sr²⁺and SO₄^2-.The temperature of the diagenetic fluid represented by calcite dolomite is concentrated at low temperature?27¹85??,medium temperature?258²87??and high temperature?334³76??.?4?There are three main types of ore-forming fluids of the Pachabulak celestite deposit in Wuqia County,Xinjiang,including gas-phase high-temperature medium-salinity fluid,liquid-phase medium-temperature high-salinity fluid and liquid-phase low-temperature low-salinity fluid.The source depth of hot brine is 1.14¹.68km,1.99².75km and 3.56⁵.38km,and the formation depth is distributed in three ranges:0.38⁰.68km,1.15¹.42km and 2.20².25km.The formation of the deposit can be divided into two periods and five stages,of which two periods are the hot brine brine syngenetic sedimentary diagenesis mineralization period and the basin fluid transformation period.The five stages are the strontium-rich hot brine syngenetic deposition-metaphase stage,the strontium-rich hot brine syngenetic deposition stage,the hot brine jet deposition stage,the later carbonate-containing hydrothermal mixed deposition stage and the basin fluid transformation stage.