The pyrope-coesite rocks and their country rocks at Parigi, Dora Maira Massif, Western Alps: detailed petrography, mineral chemistry and PT-path

Schertl, Hans‐Peter; Schreyer, Werner; Chopin, Christian

doi:10.1007/bf00307322

Cited by 271 publications

(127 citation statements)

References 33 publications

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“…Chopin, 1984;Chopin et al, 1991;Schertl et al, 1991). These assemblages include talc + kyanite + pyrope + coesite, talc + phengite (Si > 3.5) + kyanite + coesite, and talc + jadeite.…”

Section: Discussionmentioning

confidence: 99%

Significance of ultrahigh-P talc-bearing eclogitic assemblages

Liou

Zhang

1995

Mineral. mag.

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Talc was identified as an equilibrium associate of omphacite, kyanite, zoisite, and garnet in some coesitebearing eclogites and as a retrograde phase in associated garnet peridotite from the Bixiling mafic-ultramafic complex in the Dabie ultrahigh-P metamorphic terrane, central China. Observed talc-and tremolite-bearing assemblages within the coexisting mafic and ultramafic rocks together with established phase relations for the simple system CaO-MgO-A12Oa-SiO2-H20 constrain the P-T path for retrograde metamorphism. This, together with reported talc occurrences from the Dora Maira massif, leads to the conclusion that UHP talc assemblages are confined to mafic and pelitic rocks of unusual chemistry, and are not stable at ultrahigh pressures in ultramafic rocks. Thus, talc cannot be an important H20-bearing phase in deep mantle ultramafic rocks.

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“…Chopin, 1984;Chopin et al, 1991;Schertl et al, 1991). These assemblages include talc + kyanite + pyrope + coesite, talc + phengite (Si > 3.5) + kyanite + coesite, and talc + jadeite.…”

Section: Discussionmentioning

confidence: 99%

Significance of ultrahigh-P talc-bearing eclogitic assemblages

Liou

Zhang

1995

Mineral. mag.

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“…The Ti0 2 content ranges between <0.1 and 0.4wt.% (Table 2). Schertl et al (1991) and Harley & Buick (1992) describe garnets with similar high Ti0 2 contents in eclogite facies metasediments belonging to the Dora Maira massif (Western Alps) and in granulite facies calc-silicates in the Rauer Group (Antarctica), respectively. No systematic zoning was observed in the porphyroblastic garnets, but Ca A younger generation of garnets forms coronas between alteration products (zoisite or quartz and calcite) of the older, porphyroblastic garnet (Fig.…”

Section: Petrography and Mineral Chemistry Of Calc-silicate Lensesmentioning

confidence: 99%

Reaction textures and fluid behaviour in very high pressure calc‐silicate rocks of the Münchberg gneiss complex, Bavaria, Germany

Klemd

Matthes

Schüssler

1994

Journal Metamorphic Geology

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Reaction textures and fluid behaviour in very highABSTRACT Calc-silicate rocks occur as elliptical bands and boudins intimately interlayered with eclogites and high-pressure gneisses in the Munchberg gneiss complex of NE Bavaria. Core assemblages of the boudins consist of grossular-rich garnet, diopside, quartz, zoisite, clinozoisite, calcite, rutile and titanite. The polygonal granoblastic texture commonly displays mineral relics and reaction textures such as postkinematic grossular-rich garnet coronas. Reactions between these mineral phases have been modelled in the CaO-Al 2 0 3 -Si02-C02-H 2 0 system with an internally consistent thermodynamic data base. High-pressure metamorphism in the calc-silicate rocks has been estimated at a minimum pressure of 31 kbar at a temperature of 630°C with X^oSQ.Gi. Small volumes of a C0 2 -N 2 -rich fluid whose composition was buffered on a local scale were present at peak-metamorphic conditions. The P-T conditions for the onset of the amphibolite facies overprint are about 10 kbar at the same temperature. A'co., of the H 2 0-rich fluid phase is regarded to have been <0.03 during amphibolite facies conditions. These P-T estimates are interpreted as representing different stages of recrystallization during isothermal decompression. The presence of multiple generations of mineral phases and the preservation of very high-pressure relics in single thin sections preclude pervasive post-peak metamorphic fluid flow as a cause of a re-equilibration within the calc-silicates. The preservation of eclogite facies, very high-pressure relics as well as amphibolite facies reactions textures in the presence of a fluid phase is in agreement with fast, tectonically driven unroofing of these rocks.

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“…Pseudotachylyte veins formed in the chloritoid-talc-kyanitepyrope-coesite gneiss-mylonite unit of Val Gilba (Unit I in Figure 1c) [Zechmeister et al, 2007]. The host rock assemblages indicate peak pressures of 3.0 to 3.4 GPa [Schertl et al, 1991;Sharp et al, 1993] and even up to 4.2 GPa [Chopin and Schertl, 1999]. The age of metamorphism is estimated at about 35.4 AE 1.0 Ma on the basis of U-Pb SHRIMP determinations on metamorphic zircons [Gebauer et al, 1997], with peak temperatures around 800°C.…”

Section: Geology Of the Sampling Localitiesmentioning

confidence: 99%

Magnetic properties of fault pseudotachylytes in granites

Ferré¹,

Geissman²,

Zechmeister³

2012

J. Geophys. Res.

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[1] We investigate the petrographic, geochemical and magnetic properties of fault pseudotachylytes formed by frictional melting in granitic rocks from Southern California, the Italian Alps and Kyushyu, Japan. The main magnetic remanence carriers are mixtures of grain sizes of fine grained magnetite. These ferrimagnetic grains record a stable, multicomponent magnetization that consists of one or more of the following: coseismic thermal remanent magnetization, coseismic lightning isothermal remanent magnetization and post-seismic chemical remanent magnetization. Fault pseudotachylytes from the three localities display contrasting magnetic properties, which suggests that oxygen fugacity and host rock composition ultimately control the magnetic assemblage.

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The pyrope-coesite rocks and their country rocks at Parigi, Dora Maira Massif, Western Alps: detailed petrography, mineral chemistry and PT-path

Cited by 271 publications

References 33 publications

Significance of ultrahigh-P talc-bearing eclogitic assemblages

Significance of ultrahigh-P talc-bearing eclogitic assemblages

Reaction textures and fluid behaviour in very high pressure calc‐silicate rocks of the Münchberg gneiss complex, Bavaria, Germany

Magnetic properties of fault pseudotachylytes in granites

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