Phase Equilibria in Three Assemblages of Kyanite-Zone Pelitic Schists, Lincoln Mountain Quadrangle, Central Vermont

Albee, A. L.; Bingham, Elizabeth; Chodos, A. A.; Maynes, A. D.

doi:10.1093/petrology/6.2.246

Cited by 57 publications

(14 citation statements)

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“…The method used to estimate Fe 3+ is that which gives the maximum amount consistent with stoichiometry. The assemblages are comparable with those described by Albee et al (1965), but cover a different range of rock types; Albee et al (1965)additionally havekyanite+chloritoid+chlorite, but do not have assemblages with K-feldspar. The alternative calculation, giving the minimum Fe 3+ , gives zero in the present case.…”

Section: Electron Microprobe Analysessupporting

confidence: 68%

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

Ashworth

Evirgen

1984

Geol. Mag.

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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,

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Section: Electron Microprobe Analysessupporting

confidence: 68%

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

Ashworth

Evirgen

1984

Geol. Mag.

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“…11). The garnet-chloritoid-chlorite association is stable from approximately 4 kbar up to 18 kbar, as shown by its common occurrence in medium-pressure metapelites (Albee, 1965;Labotka, 1980;Droop, 1981;Karabinos 1985;Klaper & Bucher-Nurminen, 1987) and in high-pressure metapelites (Brown & Forbes, 1986;Ghent et al, 1987;this paper). Numerous workers have described garnet-chloritoid associations from high-grade blueschists, but phase relations with chlorite and/or glaucophane are generally not well understood.…”

Section: Observed Phase Relationsmentioning

confidence: 86%

“…The garnet-chloritoid-chlorite association is frequently reported from medium-pressure metapelitic rocks (e.g. Albee, 1965;Labotka, 1980;Karabinos, 1985) and is one of the characteristic assemblages of the almandine-low grade zone of Winkler (1979). Phase relations between the AFM-phases garnet, chloritoid, chlorite and staurolite are now clearly established (Harte & Hudson, 1979) and have been experimentally investigated in the simple AFSH system (Richardson, 1968;Ganguly, 1972;Rao & Johannes, 1979).…”

Section: Introductionmentioning

confidence: 95%

Garnet–chloritoid equilibria in eclogitic pelitic rocks from the Sesia zone (Western Alps): their bearing on phase relations in high pressure metapelites

Vuichard

Ballèvre

1988

Journal Metamorphic Geology

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A detailed study of garnet-chloritoid micaschists fom the Sesia zone (Western Alps) is used to constrain phase relations in high pressure (HP) metapelitic rocks. In addition to quartz, phengite, paragonite and rutile, the micaschists display two distinct parageneses, namely garnet + chloritoid + chlorite and garnet + chloritoid + kyanite. Talc has never been observed. Garnet and chloritoid are more magnesian when chlorite is present instead of kyanite. The distinction of the two equilibria results from different bulk rock chemistries, not from P-T conditions or redox state. Estimated P-T conditions for the eclogitic metamorphism are 55(Moo°C, 15-18 kbar.The presence of primary chlorite in association with garnet and chloritoid leads us to construct two possible AFM topologies for the Sesia metapelites. The paper describes a W A S H multisystem for HP pelitic rocks, which extends the grid of Harte & Hudson (1979) towards higher pressures and adds the phase talc. Observed parageneses in HP metapelites are consistent with predicted phase relations. Critical associations are Gt-Ctd-Chl and Gt-Ctd-Ky at relatively low temperatures and G1-Chl-Ky and Gt-Tc-Ky at relatively high temperatures.

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“…Studies of partitioning of cations between coexisting minerals in natural rocks by several petrologists such as Albee (1965), Annersten (1968), Binr_s (1962), Butler (1969), Mueller (1960), Kretz (1959), Gorbatschev (1969), flietnan (1971) among many others are attempts to rationalize the concept of metamorphic facies on a mineral-chemical basis. In experimental systems similar attempts = have been made by Nafziger and Muan (1967), Larimer (1968) and Medaris (1969) among others.…”

Section: Distribution Of a Cation Between Two Or More Multicomponent mentioning

confidence: 99%

Thermodynamics of Rock-Forming Crystalline Solutions

Saxena

1973

142

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Phase Equilibria in Three Assemblages of Kyanite-Zone Pelitic Schists, Lincoln Mountain Quadrangle, Central Vermont

Cited by 57 publications

References 0 publications

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

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

Garnet–chloritoid equilibria in eclogitic pelitic rocks from the Sesia zone (Western Alps): their bearing on phase relations in high pressure metapelites

Thermodynamics of Rock-Forming Crystalline Solutions

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