Petrochemistry of the Oyaca–Kedikayası (Ankara) dacites as evidence for the post-collisional tectonic evolution of north-central Anatolia, Turkey
✍ Scribed by Erdin Bozkurt; Ali Koçyiğit; John A. Winchester; Grenville Holland; Ali Beyhan
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 235 KB
- Volume
- 34
- Category
- Article
- ISSN
- 0072-1050
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✦ Synopsis
The Lower Miocene Oyaca and Kedikayasõ dacite stocks, unconformably overlain by Plio-Quaternary sedimentary and volcanic rocks, intrude a southward-verging imbricate thrust zone within the I . zmir±Ankara±Erzincan Suture Zone (I . AESZ), approximately 50 km SW of Ankara. These stocks crop out as two petrographically distinguishable plagioclase, hornblende and biotite±phyric dacites. Xenoliths petrographically similar to the Kedikayasõ dacite occur within the Oyaca stock, suggesting that the Kedikayasõ stock is older; if so, the venting from the magma chamber may have removed the upper, more evolved magma ®rst.
The Oyaca and the Kedikayasõ dacites are chemically distinct but probably were derived from the same magmatic source. Mobilization of alkali metals and some other elements hints at later hydrothermal activity. Discriminant plots tend to place both stocks in collision-related ®elds, but this result must be interpreted carefully in view of the ®eld relations, which suggest an essentially post-collisional setting. However, these stocks do suggest that, in central Anatolia, even after Miocene intracontinental transpression, magmatism with an `arc-related' chemistry continued, with obvious implications for the interpretation of the Tertiary tectonic evolution of Turkey.