Metamorphic-hosted Au-Ag mineralizations in Koyluoglu (Esme-Usak) and their significance for further exploration

This study summarizes a gold exploration programme using geological, geochemical and geophysical techniques implemented over an area of 200 km2 in Usak-Esme region.Koyluoglu-Ilikler Au mineralization is located in the micaschists. Mineralization and the dominant structural planes are mostly parallel to graben planes caused by West Anatolian neotectonics.The Au mineralization zones in the study area occur as silicified micashist layers parallel to schistosity planes. Despite lack of significant argillic alteration at the surface, sericitation and chloritization are the dominant alteration types in the area. Locally abundant ironoxide-hydroxide occurrences and gossans are present and thereby pointing to the former location of the sulfide enrichments.One thousand forty nine -80# stream sediment samples with assay values ranging up to 1815 ppb Au were taken from the field during the regional geochemical exploration programme. Ilikler-Kocatepe area with a major Au anomaly were followed up by a collection of 1208 soil samples with a peak Au value of 488 ppb. Rock chip sample results of iron oxide-gossanous zones range up to 3 ppm Au and 80 ppm Ag.Predominant occurrence of sericite and chlorite representing the alteration product of retrograde metamorphism and formation of hydrothermal fluids along with its influence on Au concentration in the silicified metamorphic rocks in shear zones suggest a gold-silver mineralization of metamorphic origin. Moreover, a positive correlation between Au-As and alteration style caused by retrograde metamorphism along with the occurrence of shear- or schistosity-hosted mineralization suggest an orogenic gold deposition at hypozonal levels.