Metallogenic Regularities Of Fenghuangshan Ore Field At Tongling,Anhui Province And Its Prospecting

Fenghuangshan ore field in Tongling is one of the main ore fields in Tongling ore gathering area.It is located in the middle of the near-east-west Tongling-Daijiahui tectonic-magmatic-metallogenic belt.The geotectonic evolution of study area can be summarized as three stages including activity,stability and reactivity.From Paleozoic to early Triassic,Marine facies,littoral-shallow Marine facies,clastic rocks,carbonate rocks and siliceous rock formations were deposited.Because of strong magmatism and mineralization,metallogenic series related to magmatic intrusion was formed during Yanshan movement.By taking Fenhuangshan ore field as a whole,a large variety of experiment has been carried out.Such as geological survey,typical ore deposit analysis,rock zircon U-Pb isotope precise dating,rock mass principal element and trace element analysis,as well as,mineral fluid inclusion analysis based on C,O,S,Pb isotope,molybdenum ore Re-Os dating and other mainstream research approaches.The main understanding are listed as follows: the rock mass of Fenghuangshan is a series of high potassium calc-alkaline intrusive rocks with high Ba,high Sr,relative loss of Nb and Ta characteristics,and the source rock of the surface rock mass has both crust source components and mantle mixing components,which belong to the crust and mantle mixing source.The isotopic age of rock mass varies from 152.1 to 124.4 Ma,which is consistent with the formation age of main intrusive rock mass in Tongling ore gathering area.The C and O isotopes show that the ore-forming fluid is mainly magmatic water,and the ore-forming fluid has multi-source characteristics,that is,one part comes from magmatic rock and the other part comes from deposit carbonate country rock.The age of the molybdenum Re-Os isotope model is between 140.9 and 142.2 Ma,and the metallogenic age on the surface is basically consistent with the diagenetic age of the Fenghuangshan rock mass.The S and Pb isotope characteristics of minerals indicate that the sulfur in the metallogenic fluid has magmatic origin.Fenghuangshan ore field is formed mainly by magmatic metallogenic series,in detail,contact metasomatic skarn type.The ore deposit surrounding the Fenghuangshan rock mass known as “a circle and a belt”,formed with horizontal and vertical zonation.The main orebodies occur in the contact zone of rock mass.In principle,the outer zone is distributed in the thermal metamorphic circle,with occurrence in capture body and rock fracture belt.Based on the information of geology,geophysics and geochemistry of the Fenghuangshan ore field,7 primary ore prospecting target areas and 5 secondary ore prospecting target areas were identified and evaluated.Potential target area is selected for drilling verification and good prospecting results are obtained.