Gold and silver mineralisation at the Chatree and Chatree North gold deposits is low sulphidation in nature, hosted in andesitic volcanic and volcaniclastic rocks and characterised by multiple hydrothermal alteration assemblages and quartz-carbonate (chlorite-adularia) replacements, veins and breccias.
The deposit is located in the Loei-Phetchabun volcanic belt, composed of remnant oceanic and continental arc complexes that were merged into what is now the Asian plate during the Permian - Triassic Period. A thick Carboniferous to Early Permian sedimentary sequence composed of conglomerate, sandstone, shale and limestone dominates the district-scale geology.
The Chatree deposit is associated with a volcanic centre that spans approximately 7.5 by 2.5km, hosted in Early Triassic intermediate to felsic volcaniclastic rocks that form a coherent andesitic to rhyolitic centre. This volcanic centre interfingers and overlies fine-grained volcaniclastics and epiclastic siltstone, mudstone and fossiliferous limestone. Alteration in the region is associated with volcanic centers and major NE-SW fault systems (Corbett, 2006; Crossing, 2006 - see pdf document for references).
The mineral resource, together with the previously mined ore, totals almost five million ounces of gold, at average grades of 1.2g/t Au (gold) and 12g/t Ag (silver), making it the largest hard-rock gold resource in Thailand. Veins display crustiform to colloform vein textures, typical of low-sulphidation conditions. The age of the host rocks and the mineralisation is similar, at around 250 million years.
Approximately 80% of the region surrounding the deposit is overlain by thick laterite and unconsolidated sediments.