Low-sulfidation epithermal Au-Ag mineralization in the Sındırgı District, Balıkesir Province, Turkey

The Sindirgi District (Balikesir, western Turkey) lies within the Western Anatolian volcanic and extensional province, adjacent to the WNW-trending Simav graben, approximately 130 km NE of Izmir. The Sindirgi mining district is underlain mainly by Miocene volcanic rocks and hosts several low-sulfidation epithermal Au-Ag deposits and prospects located near the towns of Sindirgi and Bigadic. The Kiziltepe low-sulfidation epithermal gold-silver deposit is located southeast of Yusufcam village (Sindirgi, Balikesir), and other prospects, including the Kepez, Kavakliduz, and Karaduz prospects, are located northeast of Kiziltepe. Potentially economic grades occur at Kiziltepe, which contains a measured and indicated resource of 1.754.790 Mt @3.0 g/t Au, 44 g/t Ag, hosted by quartz veins showing colloform/crustiform banding, quartz pseudomorphs after bladed calcite, and multiphase brecciations, all typical textures noted in low-sulfidation epithermal deposits. Alteration minerals include mixed-layer illite/smectite, high-crystallinity illite, and kandite group minerals (dickite and nacrite). Precious metal minerals include traces of electrum, acanthite, Au-rich acanthite, and Ag-Hg-Au-Tl-Pb series, occurring mainly within quartz. Pyrite is the most common opaque mineral at Kiziltepe. 40Ar/39Ar dating of adularia from the quartz veins indicates an age of mineralization of 18.3 ± 0.2 Ma. The ore mineralization is divided into three main phases. These comprise the deposition of: coarse-grained quartz, illite, pyrite, and minor precious metals (Phase I); major gold–silver-bearing medium-grained quartz, which commonly exhibits crustiform banding, carbonate replacement, and hydrothermal breccia textures (Phase II); and fine-grained chalcedonic quartz with colloform/crustiform banding (Phase III). Phase II is economically the most important in terms of precious metal content. Phase II quartz contains fluid inclusions, which range from predominantly vapor-rich to predominantly liquid-rich with homogenization temperatures (Th) varying from 157 to 330 °C, showing a cluster between 190 and 300 °C, and ice-melting temperatures (Tm) ranging from -0.2 to -2.9 °C (salinity from 0.5-4.8 wt.% NaCl equiv.). Moderate to strong positive correlations occur between Au-Ag (R = 0.8) and Au-Cu (R = 0.5), whereas there is no correlation between As and Au or Ag.