Formation characteristics of newly discovered Akçal (Balıkesir) Au-Ag epithermal mineralization in Extensional Tectonics of Biga Peninsula, Western Tethyan Belt

Akçal Au-Ag mineralization is located in one of the most important metallogenic provinces in Tethys Orogenic Belt, Biga Peninsula. In the study area, widespread argillic alteration is observed and mined in previous years. Recent surface exploration and drillhole operation studies indicate that extensional tectonic-related, structurally-controlled Au-Ag mineralization developed parallel alongE-W, N55-75E and N30W-trending tectonic zones and NE-SW-trending secondary tectonic zones. Based on field observations and mineralogical-petrographic studies, mineralization was formed inŞapçı volcanics where fluids caused widespread advanced argillic, argillic and propylitic alteration in the study area. Fluid inclusion analyses were performed on transparent-semi-transparent (quartz) crystals in the argillic alteration zone. The primary inclusions consist of two-phase (liquid+gas) inclusions. The homogeniSation temperature was determined as 190-240°C and the salinity as 0.7- 2.7% NaCl in the fluid inclusion measurements. Field observations, mineralogical-petrographic studies, and fluid inclusion data indicate that Au-Ag mineralization occurs in an epithermal system and that the mineralization is not eroded. In west-northwest Anatolia, formation temperature and salinities of the Miocene-aged extensional-related Au-Ag deposits are quite compatible with the formation temperature 190-240°C, 0.7-2.7% NaCl salinity of Akçal Au-Ag deposit. Due to this feature, Akçal mineralization is quite similar to low/medium sulfidation epithermal system deposits.

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