Metallogenic Regularity And Prospecting Direction Of Hotwater Sedimntary Deposits, Guangxi, China

According to previous research and on field geological investigation, with advanced measuring technique and methodology for geological-geochemical in hot-water sedimentary deposits,this thesis focus on some typical hot-water sedimentary deposits such as Panlong lead zinc deposit,Xiale manganese deposit,Gaolong gold deposit and Gutang barite deposit,and the relationship between different mineralizing types and micro-geological characteristics as well as microscopic geochemical characteristics are studied by analyzing the content of major elements,the content of trace elements,REE elements,and oxygen isotopic composition.The relationship between the mineralization temporal-spatial distributing and between the evolution of geotectonics environment and the source of ore-forming materials has been investigated.Also this research summarized the metallogenetic regularities and prospecting indicators of hot-water sedimentary deposits. It supplies the scientific base for the geological prospecting of hot-water sedimentary deposits in Guangxi.It enriches and develops the theory of hot-water sedimentary deposits.The main essentials are as follows:â… .The regional metallogenetic geological background of Guangxi, multi-stage rift movement and regional sedimentary fault in the continental crust in Guangxi evolution process of geotectonics environment have been discussed.These factors controlled the mineralization distribution and evolution in time and space of hot-water sedimentary deposits in Guangxi;â…¡.Guangxi's Siliceous rock,barite,tourmaline and stratiform skam in hot-water sedimentary deposits have been investigated by combining observation in the field with experiment in the Lab.The siliceous rock usually locates under or in ore-body.The barite often locates upper ore-body.The tourmaline rock and stratiform skarn usually are direct surrounding rock of mineralization.These rocks occur as stratiform, stratiform—oid or lentiform.The rock structure mainly has lamellar, ribbon-banded,brecciaform.The rock texture has fine-cryptocrystalline and spherules;â…¢.The geological characteristics of hot-water sedimentary deposits in Guangxi has been studied by analysing some typical hot-water sedimentary deposits,the conclusions are as follows:Ore bodies controlled by some stratigraphic horizon;The lithology of host rocks usually either are platform and trench facies sediment of the combination of silica calcium mud rock,or the turbidite of main Sandstone and shale, or the carbonate rock main in dolomite.They are associated closely with mineralization of hot-water sedimentary deposits.These ore bodies occur as stratiform,stratiform—oid or lentiform and have the multi-stratiform characteristics.Mineral granularity is fine in ore.The ore texture mainly has colloid,framboidal,oolitic and pisiform and the ore structure mainly has lamellar,ribbon-banded,brecciform as well.The alteration (siliconizing especially)usually has the Characteristics of "bottom alteration structure".â…£.Based on the newest experimental data(including content of major elements(MgO),ratio of Al/(Al+Fe+Mn)and the diagram of Al-Fe-Mn,Fe/Ti-Al(Al+Fe+Mn),Al₂O₃-TiO₂ and Al₂O₃-(K₂O+Na₂O), and the contents of trace elements(As,Sb,Sr),ratio of Co/Ni and the diagram of Fe-Mn-(Cu+Ni+Co)×10,U-Tu,P₂O₅-Y as well as REE geochemistry),the article studied the hot-water sedimentary geochemical characteristics.Contrasting with the geochemical characteristics of the siliceous rock,barite rock,tourmaline rock and stratiform skam and the last research results of hot-water sedimentation in the oceanic ridge and seabed,the results indicate that these rocks mainly are result of hot-water sedimentary but parts of them have some land-matter or biogenic subject.The study of silicon and oxygen isotopic supports this conclusion.The geochemistry of sulfur-isotopic composition shows:The sulfur of Panglong deposit,Xialei deposit,Gaolong deposit came from mixing deep-seated sulfur(including magma sulfur)and sulphate in sea. The sulphur in Gutang barite deposit was from sea.â…¤.The metallogenetic regularities of hot-water sedimentary deposits in Guangxi has been summarized:â‘ The metallogenetic epoch of this deposit includes five epoches:Meso-Proterozoic,Neo-Proterozoic, Early Palaeozoic,Later Palaeozoic and Mesozoic.Devonian is the most important metallogenetic epoch.â‘¡In space,these deposits have six metallogenetic belts:tin-polymetallic metallogenetic belt of the Later Palaeozoic aulacogen in the north of Guangxi;manganese-barite-pyrite metallogenetic belt of the Devonian aulacogen in southwestern Guangxi; zinc-lead metallogenetic belt of the Early Palaeozoic aulacogen in southeastem Guangxi;lead-zinc,barite,pyrite belt of the Later Palaeozoic aulacogen in the north of Guangxi;manganese-barite-pyrite metallogenetic belt of the Devonian aulacogen in southwestern Guangxi; zinc-lead metallogenetic belt of the Early Palaeozoic aulacogen in southeastern Guangxi;lead-zinc,barite,pyrite metallogenetic belt of the Devonian strike-slip fault basin in the center-northern Guangxi;gold metallogenetic belt of the Early-Middle Triassic aulacogen in the north-west of Guangxi and iron-tin metallogenetic belt of the Proterozoic aulacogen in the north and east of Guangxi.â‘¢These deposits are controlled by environment of rift,trough regional synsedimentary fault and high paleogeothermal field.The advantaged depositional environment is platform and trench phase.The next is the phase with the confined or semi-confined platform phase,stratigraphic phase and trough phase.â‘£The metallogenesis of these deposits are controlled by stratrabound beds and Devonian is the most important horizon.⑤The different level growth faults respectively control the distribution of mineralizing belt,ore field,deposit and ore-body.The places which are near the synsedimentary growth faults,roundabout or crossed the growth faults,the margin of the lifts and sub-billabong near-by are favorable for mineralization.The hot water sedimentary rocks are the important indicate of ore genesis,mineralizing enrichment and prospecting evaluation.â…¥.On basis of actual work and other research,the author summarizes prospecting guide and points out prospecting direction: Besides strengthening tin-polymetallic and manganese deposits prospect, we must develop the prospecting work on lead-zinc-barite deposits in the center-northern Guangxi,gold deposits in the northwestern Guangxi, superimposition-reformation typical lead-zinc and tungsten deposits in the north and east of Guangxi.