Mineral chemistry of regional chloritoid assemblages in the Chlorite Zone, Lycian Nappes, South-west Turkey

In the Ören area at the base of the Lycian Nappes, chloritoid is common on a regional scale. Mn and inferred Fe 3+ contents are low. Chloritoid + quartz occur rather than the more hydrous equivalent pyrophyllite + chlorite, Fe/(Fe + Mg) values in chlorite ranging down to 0·27. Calcite and dolomite, which coexist with chloritoid and pyrophyllite, give a temperature estimate of 350± 30°C, implying moderate to high activities of water for pyrophyllite stability. Muscovite-paragonite geothermometry is unreliable. Mg/Fe distribution coefficients between chloritoid and chlorite differ systematically from literature values from higher grades (biotite and garnet zones). Intensity of colour in chloritoid correlates with inferred Fe 3+ content, which decreases outwards in grains showing prograde growth zoning.