Identification of the anomaly component using BEMD combined with PCA from element concentrations in the Tengchong tin belt, SW China

Concentration of elements or element groups in a geological body is the result of multiple stages of rock-forming and ore-forming geological processes. An ore-forming element group can be identified by PCA (principal component analysis) and be separated into two components using BEMD (bi-dimensional empirical mode decomposition): (1) a high background component which represents the ore-forming background developed in rocks through various geological processes favorable for mineralization (i.e. magmatism, sedimentation and/or metamorphism); (2) the anomaly component which reflects the ore-forming anomaly that is overprinted on the high background component developed during mineralization. Anomaly components are used to identify ore-finding targets more effectively than ore-forming element groups. Three steps of data analytical procedures are described in this paper; firstly, the application of PCA to establish the ore-forming element group; secondly, using BEMD on the ore-forming element group to identify the anomaly components created by different types of mineralization processes; and finally, identifying ore-finding targets based on the anomaly components. This method is applied to the Tengchong tin-polymetallic belt to delineate ore-finding targets, where four targets for Sn (W) and three targets for Pb-Zn-Ag-Fe polymetallic mineralization are identified and defined as new areas for further prospecting. It is shown that BEMD combined with PCA can be applied not only in extracting the anomaly component for delineating the ore-finding target, but also in extracting the residual component for identifying its high background zone favorable for mineralization from its ore-forming element group. Keywords: Bi-dimensional empirical mode decomposition (BEMD), Principal component analysis (PCA), Anomaly components, Ore-forming element groups, Sn (W) and Pb-Zn-Ag-Fe polymetallic deposits, Tengchong tin-polymetallic belt