Geological models for the exploration and evaluation of epithermal Au and porphyry Cu-Au deposits rely upon a classification of different deposit styles and an understanding of the evolutionary processes of deposit formation. These models guide the interpretation of subsurface deposit anatomy in order to target drill testing and assist the explorationist to focus on the more prospective projects. It is important for the explorationist to distinguish between different styles of magmatic arc Au deposits as each style displays distinctive characteristics with exploration implications._x000D_
Magmatic arc Au deposits are distinguished as porphyry Cu-Au formed at depths of 1 - 2 km at the apophysis to larger, buried, magmatic sources which are also the ultimate metal sources for the varying styles of shallower level epithermal Au deposits. Low sulfidation epithermal Au deposits characteristically develop from dilute circulating meteoric waters and are distinguished as the group with a closer relationship to intrusive source rocks, and slightly higher sulfide contents (still generally <10 per cent), which are classed with decreasing crustal level as: quartz-sulfide au + cu, carbonate-base metal au (including polymetallic au-ag), and epithermal quartz au-ag, and contrast with the low sulfidation adularia-sericite banded epithermal au-ag quartz veins. sediment hosted replacement au deposits result from the reaction of a quartz-sulfide style fluid with reactive carbonate host rocks. high sulfidation au deposits develop from strongly acidic evolved magmatically-derived fluids with characteristic zoned alteration and pyrite-enargite mineralisation.>