Comprehensive Study Of Geophysical Methods To The Deep Prospecting Of Tungsten-copper Polymetallic Ore In Zhuxi Area Of Jiangxi

With the rapid decline in the discovery rate of near-surface deposits,the exploration of mineral resources into the deep is the trend of global mining development,but also an important part of China's scientific and technological innovation strategy.In recent years,China's deep prospecting made gratifying progress,which,Zhuxi Jiangxi tungsten-copper polymetallic ore found thick ore body in 42 exploration line in the depth of 1000 meters,which is a typical deep prospecting case.Before this study work,the newly discovered thick ore body in deep area of Zhuxi is only which is controlled by a few exploration lines and engineering.In order to achieve a breakthrough in ore prospecting,there is an urgent need to solve three problems: first,the depth and the direction of extension of the ore body? What is the change of the depth of the ore body on the surface? Where is the mineralization center? Second,the area of hidden granite is “mineralization geological body”(provide heat and material sources),but whether the hidden granite deposit exist or not.If does,what's the depth,occurrence and range? Third,is there this type of orebody in the mineralization zones(Taqian-Fuchun)of Zhuxi tungsten-coppe polymetallic ore? What methods to rely on to predict?It is worthy of consideration to tackle these proposed questions.In the geology area,searching for minerals is often carried out around the known mining areas which are quite monotonous.The ore body often buried quite deep,and drilling is the most obvious way in accessing such information.With such a high cost and great risk,the information we contained from few drill may be incomplete.Thus,geophysical methods become essential technics to solve such problems.The past survey work in the exploration of Zhuxi tungsten-copper polymetallic ore is mainly focus on geological survey,surface trench exposed and drilling.Less geophysical measurements are carried out,mainly about regional gravity and aeromagnetic measurement.There are some work in measuring ?Z magnetic profiles and IP intermediate gradient on large-scale in some region.Exploration agency regarded the geophysical anomaly didn't match the ore position and didn't work well in exploration.Hence,the geophysical research work becomes quite difficult in this area.In this research,on the basis of a large number of acquisition and measurement of samples and analyzed the physical characteristics,selects exploration line 42 to discuss on the effectiveness.Large scale gravity,magnetic,IP,CSAMT and other geophysical methods have been set up;advanced and effective data processing techniques have been adopted to perform inversion.According to gradual stripping method,we use the gravity data to perform 2.5D interactive inversion;To obtain the initial model of the magnetic body we use Europe lacy equation model,power spectrum analysis and physical property inversion method,then the 2.5D interactive inversion is performed according to the initial model.We use advanced two-dimensional inversion algorithm with topography to invers the bidirectional triode IP sounding data;We also invers CSAMT data using 3D conjugate gradient inversion with topography,which has solved the influence of CSAMT source and the true three-dimensional distribution of ore bodies.To process the gravity and magnetic data in Zhuxi ore area,we extract the northeast local gravity anomalies area using the directional filter with 1:20 million gravity data;forward strip T,P and C strata in 3D to eliminate the effects of formation and obtain 3D gravity inversion which is caused by the local gravity anomaly of the rock mass.We also process the gravity and magnetic data using the wavelet analysis method.In this paper,combined with the demand of deep prospecting of Zhuxi tungsten copper polymetallic ore,the most commonly used method of deep prospecting method CSAMT,for example,we carry out geophysical exploration ability research.Two kinds of typical 3D models(low-resistance cover layer and no low-resistance cover layer)are designed.Then,the three-dimensional model CSAMT forward modeling is carried out to analyze the response characteristics.On this basis,we also carry out a typical 3D CSAMT model inversion calculation to analysis the deep resolution.The technical means of the study is based on source effect of the 3D numerical simulation technology of the controllable source ground electromagnetic exploration and the 3D inversion use finite memory quasi-Newton method.In the process of the inversion,the 3D ground controlled source frequency domain response forward to solve the Helmholtz equation based on the secondary electric field using the staggered-grid finite difference method.The main achievements and knowledge are as follows:1.Through the processing and fine inversion of the gravity and magnetic data of 42 lines in Zhuxi mining area,Combined with geological data for comprehensive analysis and interpretation,for the first time formed effective technology method combination for the Zhuxi ore area.(1)The ground high-precision gravity(dot pitch 40 meters,total accuracy 0.1 mGal)can effectively detect the gravity anomalies generated by deep granite bodies.Through the 2.5D inversion,we infer its depth is about 1800 meters,down about 3500-4000 meters and its width is about 3300 meters.(2)The ground high-precision magnetic measurement(dot pitch 20 m,total accuracy 5 nT)can detect the mineralized crater and the magnetic mineralization strata in the south east side in Zhuxi.Among them,the south-east magnetic mineralization stratigraphy is mainly caused by estrogen in the Mesoproterozoic metamorphic sandstone and the IP method also shows high polarization characteristics.The combination of magnetic method and IP can exclude non-mineralization anomalies caused by carbonaceous formation.(3)The induced polarization anomalies at the new layer are considered to be caused by shallow hydrothermal vein orebodies.The CSAMT method can reflect the deep thick ore body;the low resistivity layer between 1000-2000 m is inferred to be caused by the ore body.The depth below 2000 m is a high-impedance anomaly,which is caused by the rock mass,which is consistent with the gravitational inference result.The technical combination of the above effective methods provides advanced geophysical techniques to address these three problems.We carry out large-scale area of gravity,magnetic and CSAMT exploration in the vicinity of the Zhuxi mining area.Gravity exploration can infer the three-dimensional morphology of deep rock mass.Combined with magnetic exploration and CSAMT method,we can infer the ore body space structure.In the region,we mainly using the gravity and magnetic data to prospecting,the low gravity anomaly and magnetic anomaly is a favorable place for prospecting.2.We build the underground three-dimensional structure of major hidden rock bodies of this region,through a series of processing and interpretation to Zhuxi ore district area's gravity and magnetic data.It turns out that: Zhuixi rock body(Zhuxi low gravity anomaly)and Zhenzhu Mountaiun rock body(Zhenzhu Moutaiun low gravity anomaly)are joined in the deep.In the past,geologists believed that Zhuxi was diorite-porphyrite vein,and Zhenzhu Mountaiun was granite porphyry.According to the deduction of gravity,it was deeply connected and lithology should be consistent.3.Many factors affecting geophysical methods are systematically analyzed.And taking CSAMT as an example,the resolution study on deep underground is carried out,and the abnormal detectability index and abnormal resolvability index are defined.For the two types of low-resistance covering and uniform half-space model,respectively,theoretical calculation is made by changing resistivity and depth of the objective.Finally many useful understanding and conclusions is obtained.