Characteristic Of Primary Halos And Prediction Of Deep Ore-body Of The Huaaobaote Pb-Zn-Ag Polymetallic Deposit, Inner Mongolia, China

The Huaaobaote Pb-Zn-Ag Deposit, tectonically located in the mid-southern segment of Da Hinggan Mountains'Ore-forming Belt of Innermongolia, belonging to the circum-Pacific metallogenetic domain, is a discovered recently buried hydrothermal vein deposit and may be associated with early Cretaceous technomagma activities. Depending on the analysis of anomalies of primary halo, elements of primary halo can be divided into three categories: front elements (Sb, Cd, Ag, Pb), nearby elements of ore body (Zn, Hg, Cu, In), trailing elements (As, Sn, Bi, Mo, W). From head to foot of ore body, the anomalies of front elements of primary halo are becoming smaller while the anomalies of tail elements are becoming bigger, meanwhile, both of axial zoning and transversal zoning are obvious. A detailed zonation sequence of indicator elements is obtained using the Grigorian's method as follows (from up to down): Sb→Pb→Cd→Ag→Zn→Hg→Cu→In→As→Bi→Sn→Mo→W; Based on the analysis of transversal zoning, we can get that the axial zonal sequence is consistent with the transversal zonal sequence. These elements that are at front of the transversal zonal sequence, such as Cd, Pb, Zn and Sb, Ag, are important indicator elements of ore body. Based on cluster analysis, Zn, Cd, Hg, In, Sn and Cu can be put into one group when the level of its correlation coefficient is below 0.73, which represents the combined characteristic of nearby elements of ore body; Pb, Ag and Sb can be put into one group when the level of its correlation coefficient is below 0.62, which represents the combined characteristic of front elements of ore body; Bi, As, Mo and W may be put into one group when the level of correlation coefficient is below 0.4. Furthermore, Mo and W have a little negative correlation with other elements, which reflects that the ore-forming process is a multi-stage process. Three significant ore-forming element associations have been identified from factor analysis basing on 13 kinds of halo-forming elements are as follows. F1[Pb-Zn-Ag-Hg–Cd-Cu -Sb-Sn–In]:association reflects that Pb-Zn-Ag mineralization stage is a main stage. F2 [Bi-Sn-In] association represents sulfides of Bi, In and Sn, which reflects the other hydrothermal mineralization stage; F3 [W-Mo-As] association may reflects another hydrothermal mineralization stage in which the elements of As ,W and Mo are anomalously enriched. These element associations may reflect three different mineralization stages. At the last, a criterion such as (Sb×Pb×Cd×Ag)D /(As×Sn×Mo×W)D can be constructed for evaluating the ore potential in depth. The criterion values are greater than 1.3 on the top portion of the ore deposit, 0.35 in the middle-upper portion, 0.056 in the middle–lower portion and 0.005 at the end portion, which illustrate that these criterion values decrease abruptly with depth and can be used for predicting the potentials of Pb, Zn, and Ag at a given depth.