The Afyon-Bolkardag Zone (ABZ) is made up of two main metamorphic sequences - a Paleozoic sequence and a Mesozoic sequence, both containing metadetrital rocks and metacarbonates. Although the metasediments have similar tectonic settings and sedimentary provenances, the Mesozoic sequence has transgressive characteristics and includes dolomitic metacarbonates and metavolcanics. In the Ilgin (Konya) area, the low-grade metavolcanics were originally rhyolitic lavas and tuffs. Metarhyolites are extensively K-feldspathised. K-metasomatism has produced K-feldspar porphyroblasts, sericitization in the matrix and has modified the K/Na, K/Rb and Rb/Sr ratios. The metarhyolites are extremely K-rich (6-11 wt.% K2O), with one exception that is marginally alkaline. They are subalkaline and calcalkaline in character. The REE data define two groups of metarhyolites having relatively high and low heavy REE abundances. The results indicate an origin of the high-K rhyolites in an extensional tectonic regime during the early-Alpine rifting stage, which could be related to the opening of the northern branch of the Neo-Tethys on the northern margin of Gondwana as a consequence of a southward subduction of the Paleo-Tethys.