Middle Permian Siliceous Rock Formation And Mineralization Effect In Eastern Qinzhou-Hangzhou Metallogenic Belt

Siliceous rocks are widely distributed,retain a wealth of reliable information about ancient geography,environment,structures and climate,source,have very close relationship with biological evolution and the formation of mineral,it is one of research hot topic in sedimentary academics and deposit field.Qinzhou-Hangzhou metallogenic belt is controlled by Qinzhou-Hangzhou suture belt,developments multi-layer siliceous build,has a close relationship with the polymetallic mineralization,such as copper,gold,iron,silver,lead,zinc,uranium.In this paper,formation,sedimentary environment,substance sources and diagenetic age and mineralization efficiency of the Permian silicalite in the eastern Qinzhou-Hangzhou metallogenic belt,have been studied in detail through rock geochemistry,silicon and oxygen isotopes,zircon U-Pb dating methods.Studies have shown that the Permian siliceous rocks are formation of the Gufeng formation and the Chetou formation,mainly distributed in Pingle downwarping region and Raonan downwarping region,marginally distributed in Huaiyu downwarping region.The main lithology are thin layer-thick massive siliceous rocks,with larger area in siliceous rocks development breccia siliceous rocks.Thin bedded siliceous rocks often have（including breccia）sedimentary tuff interlayer,thin bedded siliceous rocks also contains more fossils,radiolarians and sponge spicules in Leping.Siliceous rocks have high SiO₂（92.37-98.72%）,high Fe,poor Al,Al/（Al+Fe+Mn）value varied from 0.20-0.48,Al-Fe-Mn,in Al-Fe-Mn triangle figure most samples on hot water causes the siliceous rock area,11 samples of Fe/Ti=23.80 142.96,（Fe+Mn）/Ti=24.00-143.82,and agrees well with hot-water sedimentary silicalite.A small amount of sample may be affected by the volcanic sedimentation and biological,rather than typical hot water sedimentary characteristics.Siliceous rocks enrichment of As,Sb,Cr,U and other trace elements,some samples have obvious enrichment of Au or achieve industrial grade,and relatively poor Th generally,an average of only 0.15 Co/Ni.In Fe-Mn-（Cu,Co and Ni）x 10 triangular diagram in the vast majority of siliceous rock samples is located in the hot water deposition rich Fe area.all are generally lower content of Zr and Zr and Cr,Y and P correlation is poor,poorΣREE,Ce negative anomaly,the Eu is a weak negative anomaly or abnormal,indicating its as siliceous rocks of hydrothermal fluid sedimentary origin are well developed.And siliceous rocks of rare earth element model curve slightly leaning or nearly horizontal,mostly 2 samples for bank right,also show that they are not pure hot water deposition and may be mixed with different proportion and volcanic material.Silicon isotope characteristics also show that the siliceous rocks in this area for the hot water sedimentary origin.In siliceous rocksδ³⁰Si value is 0.2⁰.5‰,landed in hot water source quartzδ³⁰Si value range,and the hot spring water dissolved silicon and water dissolved silicon delta si value is relatively close toδ³⁰Si.δ¹⁸O range between 11.2²5.9‰,average 18.71‰,and hot springs quartzδ¹⁸O values are consistent.Gufeng formation conformable contact with underlying carbonate platform facies sedimentary strata and overlying in coal measures strata between the land and sea,its sedimentary environment should belong to shallow sea environment,rather than the deep sea-bathyal basin hunger.Siliceous rocks of Al₂O₃/Al₂O₃+Fe₂O₃)ratio of 0.48 to 0.99（average 0.80）,most of the samples locate Al₂O₃/（Al₂O₃+Fe₂O₃）-Fe₂O₃/TiO₂ diagram to continental margin siliceous zone or peripheral,Ce/Ce*value of 0.48⁰.90（average 0.67）,（La/Ce）_N value is 1.1¹.1（average1.64）,（La/Yb）_N value is 0.52 to 5.92（average 2.02）,also indicates the siliceous rocks formed in a continental margin shallow sea environment.According to the formula of oxygen isotope equilibrium temperature is,the siliceous rocks of SiO₂ precipitation when ancient seawater temperature from 52.21℃to 188.64℃.Overall look is located in the vent of thick layer,brecciated siliceous rocks sedimentary water temperature significantly higher than the thin layer of siliceous rock away from the nozzle.,including RaoNa depression shigang containing Jin Zhonghou bedded siliceous rock formation temperature is higher than other areas in thick bedded siliceous rock,this may be more conducive to the extraction,transfer and enrichment of gold precipitation.The ping le depression yaumcha song mountain thin bedded siliceous rocks of minimum temperature,may be more suitable for biological survival of the silica shell.Siliceous rocks in this area more contain a thin layer（including breccia）sedimentary tuff,shows that its formation is closely related to volcanic activity.Siliceous rocks Si0₂ mainly comes from undersea volcanoes,there may be some siliceous derived from hot water infiltration dissolution of surrounding rock.In the far away from the nozzle,the area of a comfortable temperature,plenty of hot water siliceous prompted silica shell biological reproduction,biofilm formation siliceous rocks.The containing breccia sedimentary tuff in the siliceous rocks at the bottom of Gufeng formation in Yichun and Gufeng formation in Leping,zircon U-Pb age are 262.6±1.9Ma and261.3±1.8Ma,this and the west margin of the Yangtze block I putuoshan Alexander igneous province volcanic eruption phase（²60 Ma）extremely is qin hang belt of magmatic activity response of the dongwu movement.Butte group at the bottom of the siliceous rocks containing breccia low limestone zircon U-Pb ageDongwu movement led to Qinzhou-Hangzhou suture belt reanimation,gaps occur along deep fracture in submarine volcanic eruption and eruption,hot water temperature significantly higher near the nozzle,and bring a large amount of SiO₂ and As,Sb,Mo,Cr,the microelement such As U,Au,ended up in a certain period of time,a certain range suppression carbonate deposits,make the hot water for the construction and carbonate siliceous built a phase change in vertical and horizontal relationships.Wushigang in Yanshan,Wangjiafang and Xiaolong gold ore body in Fenyi and so on,belt along the Qinzhou-Hangzhou deep fracture,controlled by hot-water sedimentary siliceous build and shows obvious hot-water sedimentary mineralization characteristics.Wangjiafang,Xiaolong gold mine for thin layer auriferous siliceous rock and mudstone,low limestone by the secondary enrichment.The Permian in the siliceous rocks to build necessary for regional hot water deposition of gold metallogenic elements,in the regional prospecting should be enough.Changkeng-Fuwan large gold and silver mine in Western Qinzhou-Hangzhou metallogenic belt,are submarine volcano-hot water depositions at the late Paleozoic.the same old plates collage with qin east section of hangzhou metallogenic belt,and is looking for this type of large and medium-sized deposits geological conditions and resource potential.