Bi-dimensional Empirical Mode Decomposition(BEMD)for Extraction Of Gravity Anomalies Associated With Cu-polymetallic Mineralization In Zhongdian Area,Yunnan Province,Southwestern China

Superimposition metallogenesis has the characters of nonlinear and non-stationary.Thus,Nonlinear Science in Geoscience attracts more and more attention.The way to extract available prospecting information from nonlinear and non-stationary geological data is one of the important directions of mineral exploration.Using effective methods of information processing extract or separate the useful exception information from complex 2D information can reduce uncertainty of metallogenic prognosis and improve exploration efficiency.It is of a great practical value.In the course of mineral resources exploration,the way to get ore-information is a key of predicting metallogenic target area as well as mineral resources assessment.However,the geologic body is shielded by the factors such as depth and cover,and it causes ore-information became faint and difficult to be identified.Gravity information has characteristic of perspectivity,it can not only reflect the shallow geological phenomena,but also decompose the gravitational field effectively to obtain deep geological structure information.Using the bi-dimensional empirical mode decomposition method in extracting ore-anomalies with Zhongdian area 1:200,000 gravity data,can obtain local ore-anomalies.The methods can narrow the range of prospecting and define the key exploration target areas.The main results of thesis are as follows:1.Employing the bi-dimensional empirical mode decomposition(BEMD)extraction of gravity anomaly,we obtained 3 different space-scale gravity component,BIMF1,BIMF2 and BIMF3,they represent the high-pass filter,band-pass filter and low-pass filter of original gravity respectively.The BIMF3 component has low frequency,reflects two tectonic units in the study area:(I)Zhongzan land block,(II)Zhongdian island arc.The BIMF2 component reflecs the distribution of rock mass in the study area.The BIMF1 component has high frequency,and reflect local structural information in the study area.2.Studies have shown that in Zhongdian island arc Cu-polymetallic deposit in partial negative gravity anomaly caused by neutral and acidic rock mass,it shows that mineralization enrichment associated with the intrusion of the neutral and acidic rock mass.NW-trending faults controlling the neutral and acidic rock mass and Cu-polymetallic ore deposit formation and spatial distribution.3.While metallogenic prognosis in Zhongdian area,While metallogenic prognosis in Zhongdian area,the intermediate-acid intrusive rocks controlled by NW-trending faults are key target areas for prospecting.Intermediate-acid rocks provid the ore-bearing hydrothermal solution and heat,and NW linear tectonic provided a good space for the storage and enrichment of mineral.So,the intermediate-acid rocks controlled by North-West faults has a very good exploration potential.