The Cu-Mo Minerlization And Metallogenic Prognosis Of Xilamulun Metallogenic Belt,Inner Mongolia

The Xilamulun Cu-Mo poly-metal belt located in the Northern margin of North China Craton and Southern Part of Great Khingan,where it is to the Northern part of Chifeng fault,to the southern part of Hegenshan fault,to the western part of Nenjiang fault and along two sides of the Xilamulun fault,is the second large ore-concentrated area of China.Based on mineralization characteristics,the Xilamulun Cu-Mo-polymetallic belt can be divided into two types: porphyry-type(Chehugou Mo-Cu deposit,Laojiagou Mo deposit,Jiguanshan Mo deposit and Aolunhua Cu-Mo deposit),and vein-type deposit(Nianzigou Mo deposit and Bianbianshan Cu-polymetallic deposit).From fluid inclusions study and H-O-S-Pb analysis,we assume that the ore-forming material of the porphyry deposits in this area was mainly originated from magmatic intrusion activity and the ore-forming fluid was attributed to a moderate-high temperature,moderate-high salinity,and moderate-high density system,where the ore-forming fluid is originated from magmatic water.Fluid boiling caused the phase separation and accelerated metal participation.The ore-forming material of vein-type deposits,which are controlled by faults,was derived from a magma with deep origins that underwent crustal contamination,and ore-forming fluid was originated from magmatic water initially then mixed with meteoric water.Fluid immiscibility/boiling caused the phase separation and drove metal participation.Zircon U-Pb analysis suggests that Chehugou porphyry Cu-Mo deposit was related to Late Permian to Early Triassic magmatic intrusion(~257?3.8Ma),Nianzigou vein-type Cu-Mo deposit was related to middle-late Jurassic magmatic intrusion(~154?1.8Ma),and Aolunhua porphyry Cu-Mo was related to Early Cretaceous magmatic intrusion(~134?1.8 Ma).Based on the tectonic and magmatic activities,the mineralization can be divided into three periods: 1)during the Late Permian to Early Triassic Mo-Cu mineralization period(259-210Ma),typical deposits are Chehugou Mo-Cu deposit and Laojiagou Mo deposit;2)the middle-late Jurassic(185-142Ma)Mo mineralization period,typical deposits are Jiguanshan Mo deposit and Nianzigou Mo deposit,3)and the Early cretaceous Cu-Mo poly-metal mineralization period(~139-109Ma),typical deposits are Aolunhua Cu-Mo deposit and Bianbianshan Cu-polymetal deposit.According to the systematic geochemistry and zircon U-Pb dating geochronology,it suggests that during the Late Permian to Early Triassic,the geodynamic setting was related to the closure of Palo-Asian ocean-collision-extension;the middle-late Jurassic was related to the tectonic stress transformation from NS to EW;and the Early cretaceous was closely related to the lithosphere thinning and palo-Pacifc ocean subduction.Xilamulun Cu-Mo poly-metallic belt can be divided into three sub-metallogenic series:(I)related to the Early Triassic intermediate-acidic magmatic activities Mo-Cu sub-metallogenic series,(II)related to the middle-late Jurassic intermediate-acidic magmatic activities Cu-Mo sub-metallogenic series,(III)related to the Early Cretaceous intermediate-acidic magmatic activities Cu-Mo-Pb-Zn sub-metallogenic series.Additionally,different mineralization was closely associated with the stratiform,tectonism and magmatism.In our study,according to the 1:200,000 scale sedimentary geochemistry data,we redefine the geochemical anomaly thresholds.Synchronously,with efficient geophysics information and data weight-based value system(MRAS),we use evidence weight model to make a prospecting analysis and define five targets for exploration in the future,which can promote further exploration.