Some statistical analyses of Cu and Mo variates and geological interpretations for Parkam porphyry copper system, Kerman, Iran

Precise calculation of statistical characteristics of Cu- and Mo-grade datasets was performed and results were interpreted geologically. The nature of Cu and Mo distributions were initially identified and the distributions were normalized through statistical treatment. Subsequently, the variograms were calculated for each exploration borehole and showed that both Cu and Mo geochemical variates have a spatial correlation, the result upon which the k-means clustering analysis for the whole Cu- and Mo-grade values in the area (see the text) became feasible. Based on the different geochemical behaviors of Mo and Cu, pervasive secondary hydrothermal activity which may exist for long periods, can remobilize Cu from deep parts of mineralization to the shallower levels while Mo is not remobilized significantly. However, in this paper, statistical analysis suggested that hydrothermal activity associated with secondary waters in Parkam was not effective enough to remobilize and enrich Cu. Yet the lower variation (variance) of Cu may indicate some sort of remobilization and enrichment of this element in the system (compared to Mo with higher variance); however, the process did not make the system evolve economically

Orebody modelling for exploration: the Western Mineralisation, Broken Hill, NSW

The Western Mineralisation in the Broken Hill deposit was studied to identify the zonation sequence of lithogeochemical haloes along and across the strike of the orebody. Samples used are from 77 drill holes and the samples were assayed for Pb, Zn, Fe, S, Cu, Ag, Cd, Sb, Bi and As. Variogram analyses were calculated for all the elements and kriging was used to construct the 3D block model. Analysis of cross sections along and across the strike of the orebody shows that Bi and Sb form broader halos around sulphide masses and this suggests that they are pathfinder elements for the Pb and Zn elements of this orebody. The threshold concentrations (minimum anomaly) of the 10 elements were determined using the concentration-area analysis. On east–west vertical cross sections, the values of linear productivity, variability gradient and zonality index were calculated for each element. Based on the maximum zonality index of each element, the sequence of geochemical zonation pattern was determined from top to bottom of the orebody. The result shows that S, Pb, Zn and Cd tend to concentrate in the upper part of the mineralisation whereas Ag, Cu, Bi and As have a tendency to concentrate in the lower part of the mineralised rocks. Also, an empirical product ratio index was developed based on the position of the elements in the zonation sequence. The methods and results of this research are applicable to exploration of similar Zn and Pb sulphide ore deposits.Mohammad Lotfolah Hamedani, Ian Rutherford Plimer, and Chaoshui X