Geology and Mineralisation of the Chatree Epithermal Gold-Silver Deposit, Petchabun Province, Central Thailand Grace Cumming¹, Ron James 2 , Abhisit Salam 3 , Khin Zaw 4 , Sebastien Meffre 4 , Weerasak Lunwongsa 5 , Saranya Nuanla-ong 6 1 Consulting Geologist for Akara Mining Limited (Exploration), Research Assistant, CODES ARC Centre for Excellence in Ore Deposits, University of Tasmania, 7001 Hobart, Australia, gcumming@utas.edu.au, 2 General Manager Exploration, Kingsgate Consolidated Limited, Suite 801, Level 8, 14 martin Place, Sydney, NSW, Australia, 2000, rjames@issaramining.com, 3 PhD Candidate, CODES ARC Centre of Excellence in Ore Deposits, University of Tasmania, Hobart, Australia 7001, asalam@postoffice.utas.edu.au, 4 Associate Professor, CODES ARC Centre of Excellence in Ore Deposits, University of Tasmania, Hobart, Australia 7001, Khin.Zaw@utas.edu.au, 5 Senior Exploration Geologist, Issara Mining Limited, 156/9 – 10 Moo 11 T. Dongkui, A. Chondan, Petchabun 67190, Thailand, weerasak@issaramining.com 6 Senior Exploration Geologist, Issara Mining Limited, 156/9 – 10 Moo 11 T. Dongkui, A. Chondan, Petchabun 67190, Thailand, saranya@issaramining.com ABSTRACT Gold and silver mineralisation at the Chatree low sulphidation deposit is hosted in andesitic volcanic and volcaniclastic rocks and characterised by multiple hydrothermal alteration assemblages and quartz-carbonate (chlorite-adularia) replacements, veins and breccias. The ore-bearing veins are influenced by intersecting structures and host rock lithologies. Emplacement of the host succession occurred at 250 ± 6 Ma (dated with Laser Ablation ICP-MS U-Pb zircon techniques), which was closely followed by mineralisation at 250.9 ± 0.8 Ma based on the analysis of adularia from coarse-grained quartz-sulphide (chalcopyrite-pyrite- sphalerite) veins using laser ablation Ar-Ar methods. INTRODUCTION The Chatree epithermal gold-silver deposit, central Thailand, is associated with a volcanic centre that spans approximately 7.5 by 2.5 km. The deposit consists of seven defined prospect areas and multiple open cut pits. The mineral resource contains 1.6 g/t of Au and 13 g/t of Ag, and together with the previously mined ore, totals almost five million ounces of gold, making it the largest hard-rock Au resource in Thailand. Studies of the sulphide mineral assemblages have classified the deposit as low sulphidation epithermal (based on Heald, Foley and Hayba, 1987) with sulphide content generally less than 3 % and low base metal contents (<300 ppm of copper, zinc, and lead). Veins display crustiform to colloform vein textures, typical of low-sulphidation conditions. Gold–silver ratios vary between prospect areas and are in the range of 5:1 to 20:1. Chatree is an unusual epithermal deposit due to the association of Au with chlorite-bearing veins. This extended abstract explains the regional and deposit geology and describes the timing and nature of host volcanic succession, alteration and mineralisation.