Garnet and associated minerals in the southern margin of the Menderes Massif, southwest Turkey

Abstract

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,

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

“…The Na/(Na + K) values in paragonite (0.95: Table III) and muscovite (0.16: Evirgen and Ashworth, 1983) both give unrealistically high T estimates from available calibrations (Eugster et al, 1972;Chatterjee and Froese, 1975): in other areas, the two limbs give mutually inconsistent results (e.g. Eugster et al, 1972;Mposkos and Perdikatzis, 1981;Ashworth and Evirgen, 1983). Evidently this solvus is sensitive to minor components and cannot yet provide a useful geothermometer.…”

“…5). The Fox (1971); 3, ; 4, Kramm (1973);5, H6ck (1974);6, Fox (1975);7, Cruickshank and Ghent (1978); 8, Liou and Chen (1978);9, Rumble (1978); 10, Baltatzis (1979);11, Plimer and Moazez-Lesco (1979); 12, Droop (1981); 13, Ashworth and Evirgen (1983). curve is calculated by the method of Powell (1978, p. 246) from thermochemical data of Helgeson et al (1978).…”

Exhumation with a twist: Paleomagnetic constraints on the evolution of the Menderes metamorphic core complex, western Turkey

“…The Menderes Massif is intensely sheared during hightemperature and medium-pressure (Barrovian) metamorphism (the so-called Main Menderes Metamorphism, or MMM [Akkök, 1983;Ashworth and Evirgen, 1984;Sengör et al, 1984;Satir and Friedrichsen, 1986;Bozkurt and Park, 1999;Whitney and Bozkurt, 2002;Sengün et al, 2006]. This MMM postdates a phase of HP metamorphism and eclogite formation in mafic pockets in the Pan-African orthogneisses Candan et al, 2001] and also postdates HP metamorphism [Régnier et al, 2007] under blueschist facies conditions Oberhänsli et al, 1998;Rimmelé et al, 2003b;Whitney et al, 2008] in the Paleozoic to Eocene sedimentary cover.…”

Stratigraphic and metamorphic inversions in the central Menderes massif. A new structural model

“…Ashworth and Evirgen (1984), which they cite in support of their statement, write in their abstract "Local retrograde effects are noted but no evidence is found for a polymetamorphic record in the mineral compositions". Hetzel et al (1998) and Ring et al (1999) refer to Pan-African, Cimmerian and Alpide deformation and metamorphism in the Menderes Massif.…”