Regional Geology

          The relatively young geological formation of the İzmir region is attributed to the presence of three interacting paleo-tectonic units.
From east to west, these are: (Şengör and Yılmaz, 1980)
Metamorphites of the Menderes Massive, which qualify as the oldest unit. 
The İzmir-Ankara Ophiolite Zone, formed by the closure of Neo-Tethys ocean and that extends in the NE-SW direction.
The Karaburun Block, which includes platform-type carbonates and is considered to be an extension of the Sakarya Continent.
          In the Early Palaeocene epoch, due to the thrust of the Menderes Massive toward the Sakarya Continent, the Neo-Tethys Ocean formed a regional metamorphism zone and was therefore closed (Şengör-Yılmaz, 1981; Akkök, 1985). The depression zone that later developed in Western Anatolia during the Miocene period resulted in the formation of east-west trending horsts and rift valleys (grabens). Calc-alkaline magmatism that started immediately after this structural formation in the region was followed by trachytes and rhyolitic volcanic activities. 
          The İzmir-Ankara Suture Zone marks the closure point of a subduction zone that separated the Sakarya and Anatolide-Tauride microplates during the late Cretaceous and early Palaeocene Age. As the subduction zone closed, the Neo-Tethyan sea floor between the two microplates was obducted onto the Anatolide-Tauride plate. Lenses of serpentine, often associated with thrust faults and large olistoliths of recrystallized limestone, were caught up in the melange-like complex (mainly flysch) that formed during the suturing process. Regionally extensive volcanism and intrusive activity were also associated with the subduction process. Subsequent mid-Tertiary dilation in western Turkey resulted in block faulting and the formation of the north-south orientated Seferihisar horst. The Efemçukuru mine is situated in the central part of the Seferihisar horst.
Geological Setting

          Efemçukuru is an intermediate sulfidation epithermal gold deposit hosted within Upper Cretaceous phyllite and schist at the western end of the Izmir-Ankara Suture Zone in SW Turkey. The host rocks are locally silicified to hornfels and are cut by moderately N- to NE-dipping faults that are exploited by rhyolite dykes and epithermal veins.


          Two major veins host mineralization, Kestanebeleni and Kokarpinar, with the former containing the bulk of the ore. Vein mineralogy is variable but primarily consists of quartz, rhodonite (commonly replaced by rhodochrosite), adularia, and sulfide assemblages including pyrite, galena, chalcopyrite, and sphalerite.
          Spectacular, high grade banded crustiform-colloform textures characterize the veins in addition to multistage breccias that were likely the result of shallow-level boiling. Most of the gold is very fine (2.5 to 50 microns), occurring as free grains in quartz and carbonate, and as inclusions in sulphide minerals. Lower grade mineralized stockworks occur peripheral to the ore shoots, and are most strongly developed in hangingwall rocks. Most of the current resources are in the Kestane Beleni vein. Both veins strike northwesterly (320°-340°), dip 60°E to 70°E, and can be traced on surface for strike lengths of over a kilometre. The veins commonly have faults with post-mineral movement along either hangingwall or footwall contacts, or within the veins themselves. The Kestane Beleni vein’s three ore shoots (south, middle and north) differ slightly in strike and dip orientation, but the vein and the fault zone is continuous between them.
© TÜPRAG is a subsidiary of Eldorado Gold Co. 2013.