| The Benxi Area of Liaoning Province is located in Taizihe-Hunjiang depression of Jiaoliao platform uplift of Sino-Korean paraplatform.It is an important production area of Banded Iron Formation(BIF)in China.It has a long history of iron deposit exploration and mining.The proven reserves account for a large proportion of the same type of proven reserves in China.In recent years,with the rapid development of China's economy,the proven iron deposit reserves in this area have been difficult to meet the needs of economic development.Mining enterprises and scientific research workers have gradually shifted the target of resource prospecting from the surface to the underground,and the exploration of the second space for ore prospecting has gradually become the main trend of the development of mineral resources.At present,mining enterprises and scientific research institutions have mastered a large amount of geological data such as geology,geophysics,geochemistry,remote sensing,etc.How to use scientific spatial analysis technology to mine the hidden mineral resources behind these data and provide scientific basis for spatial prediction of mineral resources has become a scientific problem for geoscientists to solve.In this paper,the method of three-dimensional geological survey divided into blocks is adopted,based on the comprehensive analysis of geological data of strata,deposits and structures in the study area,combined with the non-seismic geophysical profile data(gravity,geomagnetic,magnetotelluric)and regional gravity and magnetic data processing and interpretation,completed the deep geological structure survey of the Benxi Area.The 3D underground geological model of the Benxi Area was established by using the section-based 3D modeling method,which is based on section,supplemented by surface attitude and field observation,and constrained by borehole verification.This paper reveals the deep geological structure and spatial distribution law of BIF iron deposit in the Benxi Area,expounds the spatial relationship between deep geological structure and BIF iron deposit distribution,finds out the influence of late geological structural activities such as intrusive rock mass,fold and fault on the spatial development and distribution of iron deposit,and points out the target areas for deep prospecting.The paper has mainly obtained the following research results and understandings:(1)The idea of three-dimensional geological research is put forward,which is guided by geological model,constrained by multi-level sections,investigated and studied by sub-blocks,unified integration and gradually improved;the deep geological structure survey procedures centered on research methods and models have been established respectively.It provides a feasible reference plan for the deep geological survey in the ore concentration area.(2)Designed 5 trunk profiles through the study area and measured non-seismic geophysical data on the profiles,use inversion software to invert the gravity,magnetic and electrical data on the profile,draw 5 non-seismic geophysical profiles,comprehensively explain the non-seismic profiles,and get the deep geological structure on the trunk profiles.Using the inversion software based on the regional gravity and magnetic data and the trunk profile as the constraint,the gravity and magnetic joint inversion of the 12 gravity and magnetic properties profiles that divide the study area evenly is performed,the deep geological structure on the gravity and magnetic properties profile is obtained.(3)Using the section-based 3D modeling method,the profiles are given priority to,and the DEM data,borehole data,occurrence data,etc.are supplemented,combined with the geological data of strata,deposits and structures,the underground three-dimensional geological model of the Benxi area is established,and the deep geological structure of the Benxi area is elaborated.According to the different characteristics,the deep geological structure of the Benxi area is divided into three types,Paleoproterozoic dominated,Mesozoic granite intrusive,Archean crystalline basement and sedimentary cover double-layer structure,and six sub-types.According to the deep geological structure types of the Benxi area,the Benxi area can be divided into three large deep structural units: Longgang block,Liaoji rift,the transition zone of Liaoji rift and Longgang block,and six small deep structural units.There is an important relationship between the spatial distribution of iron deposits and the deep geological structure in the Benxi area.(4)A three-dimensional spatial model of the main iron ore deposits in the Benxi area was established,combined with the deep geological structure of the area,the spatial distribution law of iron deposits in the Benxi area is pointed out: The iron deposits in the Benxi area are mainly NW trending;From the south to the north,the sedimentary cover gradually thinned and the denudation was strengthened gradually;The iron bearing formations in the northern part are mostly complex folds,while the iron bearing formations in the southern part are mostly expressed plate-shaped.The existing spatial distribution of iron deposits in the Benxi area is the result of the comprehensive geological process of fold,fault and intrusion of rock mass.Folds and faults change the spatial shape of iron deposit,affect the scale of iron deposit development and promote the formation of rich iron deposit.On the one hand,the intrusion of rock mass has caused erosion to iron bearing formation and affected the scale of iron deposit,on the other hand,the metasomatic reaction between the hydrothermal fluid provided by the intrusion of the rock mass and the poor iron deposit promotes the development of the rich iron deposit.(5)Point out the deep prospecting area,according to the deep geological structure of the Benxi Area and the spatial distribution of iron deposit,combined with regional gravity and magnetic anomalies,it is inferred that there are concealed iron deposit buried under the Neoproterozoic-Paleozoic sedimentary cover in the Tianshifu Basin in the east of the study area,the prospect of deep prospecting is better. |
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