| Abstrakt: |
The Lower Miocene Oyaca and Kedikayası dacite stocks, unconformably overlain by Plio-Quaternary sedimentary and volcanic rocks, intrude a southward-verging imbricate thrust zone within the İzmirAnkaraErzincan Suture Zone (İAESZ), approximately 50 km SW of Ankara. These stocks crop out as two petrographically distinguishable plagioclase, hornblende and biotitephyric dacites. Xenoliths petrographically similar to the Kedikayası dacite occur within the Oyaca stock, suggesting that the Kedikayası stock is older; if so, the venting from the magma chamber may have removed the upper, more evolved magma first. The Oyaca and the Kedikayası 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 fields, but this result must be interpreted carefully in view of the field 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. Copyright © 1999 John Wiley & Sons, Ltd. |
Plný text