Geological-geophysical Model And Prediction Of Mesozoic Magmatic Cu-Ni Sulfide Deposits In The Middle East Of Jilin Province

Hongqiling-Piaohechuan-Changren Cu-Ni metallogenic belt,is located in the central of the Jizhong-Yanji active-continental-margin,southeast segment of Central Asian Orogenic Belt.It has been experienced the geological evolution of the Palaeo-Asia ocean tectonic system,the Mongol-Okhotsk ocean tectonic system and the Pacific tectonic system since the Phaneozoic and formed voluminous magmatic Cu-Ni sulfide deposits.Recently,in the west part,a series of large Cu-Ni deposits have been found such as Kelatongke,Huangshan,Poyi and so on.However,there is no great breakthrough in ore-prospecting in the study area.In addition,the ore prospecting research in the study area are mainly focus on the deposit scale.There is no comprehensive evaluation on regional diagenetic-metallogenic dynamics,geochronology,petrogeochemistry and geophysics,which make the above aspects hard to be an organic whole.Based on the systematic collecting the previous studies,we put our focus on three typical deposits: the large-sized Cu-Ni deposit Hongqiling,mid-sized Ni deposit Piaohechuan and mid-sized Cu-Ni deposit Changren-Zhangxiang.Firstly,we study the diagenetic-metallogenic dynamics of the Mesozoic mafic-ultramafic rocks in the Middle East of Jilin Province.We take advantages of the geochronology,petrochemistry,regional geophysics to study the primary magma,magma source,diagenesis and mineralization age and metallogenesis of mafic ultramafic rocks.The results indicate that the diagenetic dynamics of Mesozoic mafic ultramafic intrusions are divided into two stages: Indosinian period(250 ? 204 Ma),the diagenetic and metallogenic dynamics can be described as lithospheric delamination which triggers the upper mantle high degree melting and the metallogenic potential is great.Yanshanian period(191-175 Ma),the diagenetic dynamics can be described as back arc extension.The degree of upper mantle melting is small and the metallogenic potential is poor.Secondly,large scale high-precision gravity,ground magnetic survey,ground transient electromagnetic(TEM)and controllable source audio frequency magnetotelluric survey(CSAMT)are carried on the typical ore deposits to delineate the spatial distribution of mafic ultrairon rocks and ore bodies.The results indicate that the magma conduit in deep is consisted by a single open one while the shallow one is consisted by several secondary magma conduits.In addition,new data processings have bee carried on geophysics.The edge definition(ED)and discrete wavelet transform(DWT)can be used to determine the boundaries among the country rock,mafic-ultramafic intrusions and orebodies.Finally,according to the position of orebodies and the characteristics of their geophysical fields,we established the geophysical prospecting models for different types of orebodies and three grades A and one grade B ore prospecting areas were delineated.