ÇAĞRILI KONUŞMALAR / KEYNOTES Invited Speeches ... - TPJD

Mineralogical and Petrographic Features of the Hydrothermal Alteration
Around Sandıklı (Afyon) Geothermal Field
Duygu Okur 1 , İbrahim Gündoğan 2 , İsmail Hakkı Kahramanderesi 1 , Yeşim Yücel-Öztürk 2 ,
Cahit Helvacı 2 , Eşref Kanlı 1
1 JEM, Geological Investigations and Consultancy Office, İzmir
2 Dokuz Eylül University, Department of Geological Engineering, İzmir
The study area is located in the Sandıklı district, 40 km southwest of Afyon city. The area was
intensely affected by hydrothermal alteration and geothermal systems related to tectonic and
volcanic activities during the western Anatolian Neo-tectonic period. Miocene volcanic activity
in the Sandıklı district produced alkaline lavas and calc-alkaline pyroclastic rocks. There are many
examples of hydrothermal alteration and mineralization occurrences within the investigated area.
The basement rocks consist of low-grade metamorphic rocks of the Afyon zone. The hydrothermal
alteration can be traced from Hüdai thermal water to the north and east in the Sandıklı volcanic
rocks. The borehole data indicate that the effects of hydrothermal alterations continue further
depths. Mineral paragenesis of the alteration is studied and revealed by mineralogical and
petrographic studies from the borehole samples. Silicification and chalcedony plus hematite
occurrences are extensive at the depth of 50-60 meters of AFS 12 and 13. Marcasite and sericite
with pyrite and hematite abundances increases further depths. Euhedral Fe-Ti oxides are seen at
the interval of 110-180 m interval. In addition to these, sanidine and euhedral pyroxene (augite)
with primary apatite and titanomagnetite minerals are also observed. The Seydişehir formation
is cut at the depth of 316 m of AFS 15. Furthermore, fractured and sulfured zones are cut at the
depth of 136, 179, 217, 452, 484 and 598 meters, respectively. The Seydişehir formation is cut
at the depth of 312 m of AFS 16, and fractured and sulfured zones are cut at the depth of 244,
246, 396, 478, 634, 638, 654, 678, 916 and 920 meters, respectively. In the AFS 17, the Seydişehir
formation is cut at 332 m and sulfured zones are observed at the depth of 156, 260, 304, 380, 762
and 960 meters. The borehole data indicate that Hüdai quartzite is second reservoir rock. Hüdai
quartzite is observed at 500 meter. The project aims are targeted to obtain higher temperatures
at 7 holes studied, in addition to the previous bore holes. The basement rocks show different
sequences in these 7 holes. Main production zone is revealed from Hüdai quartzite. In the Hüdai
quartzite, hydrothermal mineralization riches and thermal water temperature increases with
depth. Production temperatures are given depend on productions. The study is still on progress
in order to obtain further data from the geothermal field. Key words: Hydrothermal alteration,
Alteration mineralogy, Geothermal resources, Western Anatolia, Sandıklı geothermal field.
Keywords: Hydrothermal alteration, Alteration mineralogy, Geothermal resources, Western
Anatolia, Sandıklı geothermal field
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