Assemblages with muscovite +quartz show a regular increase in grade from the Chlorite Zone at the base of the Lycian Nappe Complex to the Garnet Zone within the structurally underlying Menderes Massif. Biotite enters before garnet, which precedes oligoclase. Garnet-bearing assemblages in pelites are compared with those in re-equilibrated quartzofeldspathic gneisses, where garnet is unusually calcic (in one case approaching Gross 60 Alm 50 ). Local retrograde effects are noted but no evidence is found for a polymetamorphic record in the mineral compositions. Garnet zoning, with Mn decreasing outwards, is interpreted as growth zoning; Ca decreases outwards in pelite garnets but shows the reverse effect in the gneisses. Chloritoid is common but rarely coexists with biotite, and garnet + chlorite + paragonite is found rather than chloritoid+ albite. Garnet-biotite geothermometry, corrected for the effect of Ca in garnets with up to 29 mole % grossular, indicates temperatures of 53O±5O°C near the garnet isograd. As in other areas, an attempt at muscovite-paragonite geothermometry gives an anomalous result. Metamorphic pressure isconsidered in the light of (i) M n/Fe partition between garnet and biotite, (ii) Ca content of garnet coexisting with plagioclase + muscovite +biotite, (iii) Na in actinolite coexisting with albite +chlorite + magnetite, and (iv) celadonite content of muscovite which, however, shows variation due to disequilibrium within a specimen and does not provide an accurate geobarometer. Comparisons with published studies indicate a strong similarity to the Barrovian Dalradian of Scotland and lead to a tentative pressure estimate of approximately 5 kbar. J. R. ASHWORTH& M. M. EVIRGEN \ \ metamorphosed platform carbonates, not tectonised before the Middle Eocene, and subjacent pelites metamorphic |sch!stose) basement augen gneiss within Mendere/ Massif V/ r-r nappe complexes ophiolites platform not tectonised before Upper Eocene-Oligocene A A A,

Activity-composition relations in oligoclase near the peristerite gap are investigated in pelites from the Central Menderes Massif. The pressure of metamorphism is estimated independently, from garnet-rutile-ilmenite-kyanitequartz, as being in the range 4-7 kbar. In the temperature range, 450 -600°C approximately, both the Newton-Haselton calibration of the garnet-plagioclase-kyanite-quartz geobarometer and a related simple treatmeht of garnetplagioclase-muscovite-biotite give a wide range of apparent pressures, correlated with plagioclase composition and ranging up to 11-12 kbar where the plagioclase is most sodic. This effect is attributed to failure of the activity model for plagioclase used in the Newton-Haselton treatment. It is inferred that, in the present area, y : : * decreases with increasing XI? in the range An,,-An,,. The data can be interpreted in terms of high yf;',"g in the high-albite structure at these temperatures, modified to lower values by 'e' ordering in the more calcic oligoclases. The ordering appears to be independent of the peristerite gap, and the data d o not support the interpretation of the gap as a solvus. Garnetplagioclase assemblages are unreliable as geobarometers where the plagioclase is more sodic than approximately An,, and T < 700°C.' and should instead be used to investigate the y-X behaviour of the plagioclase where independent geobarometry can be used as a constraint.

In pelites of the central Menderes iMassif, albite and oligoclase with only slight chemical zoning coexist in apparent textural equilibrium in the garnet zone, staurolite zone, and staurolite + kyanite transition zone. The metamorphic temperature range is estimated as approximately 440-550°C (from the Hodges-Spear calibration of the garnet-biotite geothermometer), or 440-500 "C (Ganguly-Saxena calibration). While oligoclase composition at the peristerite gap changes from An,, t o An,,, albite also becomes more sodic (Ani,,-An0,,). The slope of the albite limb is thus the reverse of that reported in other areas, and may not be a true equilibrium feature. Occurrence of kyanite, at temperatures below the crest of the gap, is due to low water activity in the presence of graphite: is estimated at approximately 0.1-0.2 from the Na content of muscovite coexisting with albite + kyanite +quartz.

ABSTRACT. In the Oren 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~ 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.

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