Metallogenic Regularity And Metallogenic Prediction Of The Aerhada Pb-Zn Polymetallic Deposit,Inner Mongolia

Aerhada Pb-Zn polymetallic deposit,located in Dong Ujimqin Qi,XilinGol League,is a representative hydrothermal vein type deposit in Erlianhot-Dongwuqi metallogenic belt.The orebodies mainly occur as veins and lenticular shapes in sedimentary-metamorphic strata of Angeryin Wula Formation,and controlled by the NW striking faults.Ore controlling faults underwent multiple tectonic activities,form different mineral assemblage,and correspond to?I?quartz-arsenopyrite-pyrite stage,?II?poor sulfide-quartz stage,?III?polymetallic sulfide stage and?IV?poor galena-fluorite-calcite stage.Fluid inclusion research indicated that the ore-forming fluids of early stage were the medium temperature and high salinity CH₄-NaCl-H₂O system.In the process of mineralization,as the temperature and pressure gradually decreased,and the mixing of meteoric water,CH₄ in the fluid escaped,the salinity of fluid decreased,the stability of metal complex decreased,and the metal elements such as lead and zinc precipitated.In the late mineralization stage,ore-forming fluid is gradually transformed into a low temperature and low salt NaCl-H₂O system hydrothermal fluid.Carton,oxygen and hydrogen isotope data(?¹⁸O_V-SMOW=7.1‰¹7.6‰;?D_V-SMOW=-130.7‰^-113.4‰,?C_V-PDB=-8.2^-7.1)suggested that the ore-forming fluids were derived from magmatic fluids that has undergone intense water-rock reaction during the early stage of mineralization and subsequently incorporated meteoric water during the late stage.Sulfur and lead isotope analysis(?³⁴S=1.2⁸.6‰;²⁰⁶Pb/²⁰⁴Pb=18.153¹8.685,²⁰⁷Pb/²⁰⁴Pb=15.370¹5.750,²⁰⁸Pb/²⁰⁴Pb=37.161.109³9.301)show that the ore-forming materals has a magma-crust mixing origin.After systematic collecting the pre-existing zircon U-Pb ages of the main rock masses in the Dong Ujimqin Qi,the tectonic evolution of the area is summarized as three stages:?1?The environment of the Paleo-Asia Ocean subducting northward in the Middle Carboniferous-Early Permian?330²80 Ma?;?2?The extended environment after the closure of the Paleo-Asia Ocean in the Middle-Late Triassic?250²40 Ma?;?3?The environment of the Pacific Plate subducting to the Eurasian Plate in the Late Jurassic-Early Cretaceous?160¹30 Ma?.Biotite granite in the Anerji Wula granite stock yielded a U–Pb age of 156 Ma in the Aerhada area.Combining with the dating results of the quartz diorite porphyry?162 Ma?and fine-grained granite?152 Ma?in the Anerji Wula stock,it is believed that Anerji Wula granite stock is formed at 162¹52 Ma.Whole rock geochemistry analysises show that the Anerji Wula granite stock characterized by high SiO₂ and K₂O contents,low Al₂O₃ contents.These samples are enriched in large ion lithophile element?LILE?,depleted in high field-strength element?HFSE?,belong to the peraluminous,high K,calc-alkaline series,and are similar to A-type granitoids.Muscovite from altered rocks yield a⁴⁰Ar-³⁹Ar plateau age of 156 Ma which represent the mineralization age.From the perspective of time,space,and characteristics of mineralization and alteration,the Anerji Wula granite stock is the most likely ore-causative rock.In summary,we suggested that the Aerhdada deposit is formed in the compression-extension transition environment under the subduction from the Pacific Plate to the Eurasian Plate.The study of metallogenic regularity indicated that the Aerhada lead-zinc polymetallic deposit is controlled by strata,fault and magmatite,but the most prominent is fault-controlling.The ore controlling faults are characterized essentially by left slip and normal fault.Steep areas along the trend direction and westward areas along the tendency are the favorable place where lead and zinc ore body occurrence.The thickness of the alteration zone,thickness of orebody times grade and the thickness of orebody all are consistent with the transition regions of peaks and valleys of fracture surface.The transition regions of peaks and valleys of fracture surface are the favorable place where lead and zinc ore body occurrence and mineralizing enrichment.The mineralization enrichment rules suggest that orebodies and altered belt flanking toward SW and it is potential for further exploration in deep level of the ore mine.In the mining area,combining with mineralization,wall rock alteration,geophysical and geochemical anomalies,and other factors,four ore-prospecting areas are selected using the MRAS comprehensive prospecting information system.Based on the detailed geologicalinvestigation,combiningwiththemetallogenicregularity,performed a comprehensive analysis on mineralization intensity index,like the morphology of fault surface,thickness of orebody,ore grade and the thickness of the alteration zone.We used numerical simulation technique to evaluate and predict the location on both sides and deep of I ore belt in Aerhada deposit.Eight,nine and four prospecting targets are selected for reference in middle?9-41prospecting line?,east?43-77prospecting line?and west?9-41 prospecting line?part of I ore belt,respectively.These works have achieved satisfactory prospecting results.