Temperature and pressure dependence of Fe-Mg partitioning between garnet and phengite, with particular reference to eclogites

Krogh, Erling; Råheim, A.

doi:10.1007/bf00376087

Cited by 128 publications

(57 citation statements)

References 21 publications

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“…On the ACF-deluxe chemography in Figure 6 (Thompson 1982), where the composition of calculated pre-Alpine amphibolite-facies minerals is reported, bulk Mineral abbreviations are as proposed by Kretz (1983). O = Ti content in amphibole according to Otten (1984); P = garnet/amphibole Fe-Mg exchange according to Perchuk (1991); GP = garnet/amphibole Fe-Mg exchange according to Graham and Powell (1984); EGP = garnet/clinopyroxene Fe-Mg exchange according to Ellis and Green (1979) after (Powell 1985); K = garnet/clinopyroxene Fe-Mg exchange according to Krogh Ravna (2000); K&R = garnet/white mica Fe-Mg exchange according to Krogh and Råheim (1978); PS = amphibole compositions experimentally determined during amphibolites-to-eclogite transition according to Poli (1993) and Schmidt (1993); S = white mica compositions experimentally determined during amphibolites-to-eclogite transition according to Schmidt (1993); HZ, H, JR = Al tot content in amphibole according to Hammarstrom and Zen (1986), Hollister et al (1987), and Johnson and Rutherford (1989), respectively. compositions are aligned along the join between plagioclase and hornblende, as expected for amphibolite-facies metabasites. This suggests that different modal amounts of hornblende and plagioclase, and the accompanying minerals diopside, orthopyroxene, biotite, and quartz, characterized the pre-eclogitic assemblage.…”

Section: Bulk Chemistry Versus Modal Compositionmentioning

confidence: 99%

Interplay between deformation and metamorphism during eclogitization of amphibolites in the Sesia–Lanzo Zone of the Western Alps

Gosso

Messiga

Rebay

et al. 2010

International Geology Review

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Interactions of fabric evolution and chemical parameters driving reaction progress during the amphibolite-to-eclogite transition were investigated in eclogitized amphibolites of the Western Alps. In the Sesia-Lanzo Zone (SLZ), mafic rocks ranging from eclogitized hornblendites to true eclogites occur as layers and boudins within micaschists and are characterized by different modal amounts of amphibole, omphacite, zoisite, garnet, and phengite, constituting the Alpine HP assemblage. Across narrow zones, this array of lithologies displays gradients in planar fabrics characterized by coronitic, S-tectonitic, and mylonitic textures with different extents of eclogitization. Eclogitic parageneses are controlled not only by the bulk rock composition of the protoliths but also by the degree of fabric evolution. This is the case for omphacite occurrence, which is constrained by plagioclase composition and modal amount (NK parameter) in the protoliths, whereas the increase in modal omphacite and the concomitant decrease in modal amphibole in rocks with high NK are controlled by the strain rate. Protoliths with a low NK content develop the amphibole + garnet + epidote assemblage in eclogitized hornblendites. In protoliths with higher NK values, the co-existence of amphibole with garnet, omphacite, and epidote occurs only for low-to-medium strain textures (e.g. coronites and S-tectonites), whereas an amphibole-free assemblage defines a mylonitic foliation; in this case, amphibole relics are present exclusively as armoured inclusions in garnets and omphacite porphyroclasts. Thus, amphibole persists in the eclogitic assemblage at pressures exceeding the experimentally determined amphibole stability field. Values of confining pressure under which Sesia-Lanzo mafic rocks re-equilibrated during Alpine subduction were estimated, through equilibrium assemblage modelling, at 2.2-2.7 GPa. The amphibole-bearing eclogites of the SLZ show that large volumes of amphibole-bearing rocks can be exhumed from a depth exceeding 75 km without dehydration reactions running to completion. Petrological estimates in orogenic zones may help constrain geological and tectonic conclusions when selection of laboratory samples is assisted even by simple microstructural evaluation of planar fabric development.

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Section: Bulk Chemistry Versus Modal Compositionmentioning

confidence: 99%

Interplay between deformation and metamorphism during eclogitization of amphibolites in the Sesia–Lanzo Zone of the Western Alps

Gosso

Messiga

Rebay

et al. 2010

International Geology Review

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“…This exchange is inversely correlated with a 0-2 to 0-1 unit exchange of KNa_ ( towards paragonite. The Fe 2 + Mg_, exchange equilibrium between phengite and garnet has been studied experimentally by Krogh & Raheim (1978) and by Green & Hellman (1982) under reducing conditions where Fe 2+ = Fe to1 could be assumed. Natural phengites allow considerable exchange along Fe 3 + Al _,, but since some displacement towards tri-octahedral micas is possible as well, no unambiguous estimation of Fe 2+ /Fe 3+ from microprobe analysis is possible.…”

Section: Mineral Chemistry Of Primary Eclogitic Hydrosilicatesmentioning

confidence: 99%

“…Krogh, 1977;Evans & Trommsdorff, 1978;Evans et al, 1979;Ernst & Dal Piaz, 1978;Rubie, 1984). However, it is not clear whether any of these 'crustal' eclogites have indeed formed by dehydration of more hydrous mafic precursors, or whether they have crystallized under H 2 O-undersaturated conditions from primarily anhydrous protoliths.…”

Section: Introductionmentioning

confidence: 99%

“…However, comparison between eclogites and a more general interpretation of their genesis is hampered by the structural incoherence typical of most terrains, which rarely show regular regional distribution patterns of eclogitic assemblages. The few known exceptions are from SW Norway (Krogh, 1977;Griffin et al, 1984), New Caledonia (Black, 1977), the Adula Nappe (Heinrich, 1982), and from Venezuela, where Maresch (1983) first reported a field example indicating progressive in-situ dehydration of amphibolite to eclogite. Recently, Takasu (1984) presented textural evidence for the transformation of epidote amphibolite to hydrous eclogite, which he ascribed to prograde dehydration metamorphism.…”

Section: Introductionmentioning

confidence: 99%

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Eclogite Facies Regional Metamorphism of Hydrous Mafic Rocks in the Central Alpine Adula Nappe

Heinrich

1986

Journal of Petrology

177

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The Adula Nappe is a slice of Pre-Mesozoic continental basement affected by Early Alpine (Mesozoic or Lower Tertiary) high-pressure metamorphism. Mineral compositions in mafic rocks containing omphacite -I-garnet + quartz record a continuous regional trend of increasing recrystallization temperatures and pressures that can be ascribed to this regional high-pressure metamorphic event. P-T estimates derived from mineral compositions grade from about 12 kb and 500 °C or less in the north of the nappe to more than 20 kb/800 °C in the south.The regional P-T trend is associated with a mineralogical transition from assemblages containing additional albite and abundant amphiboles, epidote minerals, and white micas in the north (omphacite-garnet amphibolites) to kyanite eclogites containing smaller amounts of hornblende and zoisite in the south. Textures and mineral compositional data show that these hydrous and anhydrous silicates associated with omphacite + garnet-I-quartz are primary parts of the high-pressure assemblages. Observed phase relations between these primary silicates, theoretical Schreinemakers analysis, and the thermobarometric results, together indicate that the regional transition from omphacite amphibolites to kyanite eclogites can be described by two simplified reactions: alb + epi + hbl = omp + kya -I-qtz + par (H 2 O-conserving)par + epi + hbl + qtz = omp + kya + H 2 O (dehydration)which have the character of isograd reactions. Local variations of water activity (a H2<3 ) as indicated by isofacial mineral assemblages, and the H 2 O-conserving character of the reaction (15), are interpreted to reflect largely H 2 O-undersaturated and predominantly fluid-absent high-pressure metamorphism within the northern part of the nappe. The omphacite amphibolites and paragonite eclogites in this area are thought to have formed by H 2 O-conserving reactions from Pre-Mesozoic high-grade amphibolites, i.e. from protoliths of similar bulk H 2 O-content.The second 'isograd' (12) is interpreted to mark the regional transition from largely fluid-absent metamorphism in the north to fluid-present metamorphism in the south, where metamorphic pressures and temperatures in excess of 12-15 kb and 500-600 °C were sufficient for prograde in-situ dehydration of similar hydrous protoliths to kyanite eclogites. The observation of abundant veins, filled with quartz + kyanite + omphacite, suggests that a free fluid coexisted locally with the kyanite eclogites of the southern Adula Nappe at some time during progressive dehydration.

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“…Experimental determined reactions: [1] Lws + Jd = Pg + Ep/Zo + Qz + Vapor (Heinrich and Althaus, 1988) [2] maximum stability field of glaucophane (Maresch, 1997), [3] Ep + Ttn = Grt + Rt + Qz + H2O (Manning and Bohlen, 1991), and [4] amphiboles solid-solution (Otsuki and Banno, 1990). Garnet-phengite geothermometry: open square from Krogh and Raheim (1978) and open circle from Green and Hellman (1982). Geobarometry of phengite from Massonne and Schreyer (1987).…”

Section: J O Gmentioning

confidence: 99%

Metamorphic Evolution of Garnet-bearing Epidote-Barroisite Schist from the Meratus Complex in South Kalimantan, Indonesia

Setiawan¹,

Osanai²,

Nakano³

et al. 2015

Indonesian J. Geosci.

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-This paper presents metamorphic evolution of metamorphic rocks from the Meratus Complex in South Kalimantan, Indonesia. Eight varieties of metamorphic rocks samples from this location, which are garnet-bearing epidote-barroisite schist, epidote-barroisite schist, glaucophane-quartz schist, garnet-muscovite schist, actinolite-talc schist, epidote schist, muscovite schist, and serpentinite, were investigated in detail its petrological and mineralogical characteristics by using polarization microscope and electron probe micro analyzer (EPMA). Furthermore, the pressure-temperature path of garnet-bearing epidote-barroisite schist was estimated by using mineral parageneses, reaction textures, and mineral chemistries to assess the metamorphic history. The primary stage of this rock might be represented by the assemblage of glaucophane + epidote + titanite ± paragonite. The assemblage yields 1.7 -1.0 GPa in assumed temperature of 300 -550 °C, which is interpreted as maximum pressure limit of prograde stage. The peak P-T condition estimated on the basis of the equilibrium of garnet rim, barroisite, phengite, epidote, and quartz, yields 547 -690 °C and 1.1 -1.5 GPa on the albite epidote amphibolite-facies that correspond to the depth of 38 -50 km. The retrograde stage was presented by changing mineral compositions of amphiboles from the Si-rich barroisite to the actinolite, which lies near 0.5 GPa at 350 °C. It could be concluded that metamorphic rocks from the Meratus Complex experienced low-temperature and high-pressure conditions (blueschist-facies) prior to the peak metamorphism of the epidote amphibolite-facies. The subduction environments in Meratus Complex during Cretaceous should be responsible for this metamorphic condition.

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Temperature and pressure dependence of Fe-Mg partitioning between garnet and phengite, with particular reference to eclogites

Cited by 128 publications

References 21 publications

Interplay between deformation and metamorphism during eclogitization of amphibolites in the Sesia–Lanzo Zone of the Western Alps

Interplay between deformation and metamorphism during eclogitization of amphibolites in the Sesia–Lanzo Zone of the Western Alps

Eclogite Facies Regional Metamorphism of Hydrous Mafic Rocks in the Central Alpine Adula Nappe

Metamorphic Evolution of Garnet-bearing Epidote-Barroisite Schist from the Meratus Complex in South Kalimantan, Indonesia

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