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

Authors: HÜSEYİN YILMAZ, FATMA NURAN SÖNMEZ, ERHAN AKAY, AHMET KERİM ŞENER, SEDA TUFAN

Abstract: The Sındırgı District (Balıkesir, western Turkey) lies within the Western Anatolian volcanic and extensional province, adjacent to the WNW-trending Simav graben, approximately 130 km NE of İzmir. The Sındırgı 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 Sındırgı and Bigadiç. The Kızıltepe low-sulfidation epithermal gold-silver deposit is located southeast of Yusufçam village (Sındırgı, Balıkesir), and other prospects, including the Kepez, Kavaklıdüz, and Karadüz prospects, are located northeast of Kızıltepe. Potentially economic grades occur at Kızıltepe, 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 Kızıltepe. ^{40}Ar/^{39}Ar 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.

Keywords: Gold, hydrothermal alteration, geochronology, fluid inclusions, Sındırgı

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