Structural Characteristics And 3D Modeling Of BIF In Anshan-Benxi,Liaoning Province

Anshan-Benxi area is the most important Archean banded iron formation(BIF)iron ore metallogenic centralized region in China,located in the northeastern margin of North China Craton and uplift of the northwestern Jiao-Liao platform.The amount of iron ore resources there accounted for 25% of China.The amount of iron resources in the Anshan ore concentrated area accounted for more than 60% of the study area(Zhou Shitai,1994),there are 23 large-extra large iron deposits,and still there are many middle and small iron deposits.This paper based on the existing work of this area,applying several methods to promote research progress comprehensively,including geological and geophysical data synthetic research;geological 3D modelling in specimenal scale;BIF magnetic susceptibility 3-D inversion method.The most important research pointsin Anshan-Benxi region including 3D geometry morphology of ironbearing metamorphic rock series,method of building geological 3D model in specimenal scale and genesis of rich iron ore are discussed in this paper.Finally revealed the deep geological structure,3D deformation,and exploration prospecting of Anshan-Benxi region.The main achievements as follows:(1)This paper put forward a geological model that BIF deposits in Anshan-Benxi area are controlled by the fold-ductile shear zone,point out a view that the area suffered strong tectonic and ductile deformationis close to Anshan micro continental nucleus,the main factors that controlling the BIF and iron ore distribution is ductile shearing,so the existing layered iron ore is not the original iron-rich layer,but formed through the folds deformation and ductile shearing;The fold deformation are well-developed in the area that far from Anshan micro continental nucleus,folds and ductile shearing developed concomitantly in the middle deformation area that are not very far from Anshan micro continental nucleus,the spatial distribution of BIF and iron ore belt are controlled by the folding and ductile shearing.(2)This paper put forward a method on building 3D model of magnetite quartzite in specimenal scale.This method mainly includes slicing,high-definition picture scanning,feature extraction,modeling.It opens up a new way for the study of the 3D structure of research area in specimenal scale.After slice and scan specimens,high resolution images of rock specimens can be obtained.This method can avoid the defect that microscope cannot obtain the global rock deformation images,3D geological modeling can reveal the deformation characteristics of the internal structure of rock,and show 3D deformation of rock specimens with 3D visualization.It can provide important information for 3D deformation research in specimenal scale.It has important significance to recognize the deformation characteristics and tectonic evolution of general magnetite quartzite.(3)This paper design a 3D geometric model with deformation feature of specimens and found structure has obvious control effect on iron ore in the specimen scale,resulting in uneven distribution of iron ore material.It deepens the understanding of 3D deformation in specimen's scale in Anshan-Benxi area.(4)3D geometric shapes of the several biggest BIF ore-bodies in Anshan Benxi area are calculated by the method of magnetic susceptibility 3-D inversion,and two concealed magnetic bodies in the deep part of Anshan are revealed.(5)Put forward a point of view that tectonic deformation has play a significant role on controlling iron ore concentration.During the process of strong tectonic deformation,the well-developed fold and ductile shearing zone make the replacement effect happened on the magnetite quartzite,and the magnetite enriched again to form the rich layered iron deposit.(6)An assessment of the iron ore prospect of Anshan-Benxi area was carried out.There are two concealed magnetic bodies in the deep part of Anshan quaternary overburden.thus the BIF iron ore potential exploration prospecting in late Archean granite distribute in Qinghecheng Town,Anshan,and concealed BIF prospected under the widely exposed Neoproterozoic-Paleozoic sedimentary cover.