Geochemical haloes surrounding the CSA orebody in Cobar, NSW

Abstract

Geochemical analysis is of great importance to mineral exploration. Ore forming fluids, by definition, change the fresh rock chemistry by introducing and depleting elements. This can be achieved by dilution, element substitution and transportation in the process known as metasomatism. At the copper producing CSA mine in Cobar, New South Wales, previous researchers have identified depletion haloes for alkali and alkali earth elements around the pipe-like shear structures known to host ore. These haloes have been proposed to aid in targeting orebodies by drilling. This study aimed to investigate the presence of these haloes by using new sample data and 3D modelling techniques. As the samples used were of limited depth, an analysis of the relationship between Ba, Sr, Li and Rb with Fe was conducted to deduce any influence of weathering on depletion haloes. The conclusions of this study are that significant depletion haloes for Sr and Ba exist in close spatial and geometrical proximity to the known ore body. It was also concluded that Strontium displayed a mobilisation behaviour independent of iron concentration and could be an ideal starting point for analysis when conducting exploration of economic minerals in the area.