Metamorphic evolution of the Gran Paradiso Massif: A case study of an eclogitic metagabbro and a polymetamorphic glaucophane–garnet micaschist

Gasco, Ivano; Borghi, Alessandro; Gattiglio, Marco

doi:10.1016/j.lithos.2009.11.009

Cited by 22 publications

(19 citation statements)

References 40 publications

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“…Maximum pressure estimates for the Lower oceanic Unit (22-24 kbar) can also be compared with those obtained in the underlying Gran Paradiso crystalline massif by previous works: Vidal et al (2001) gave pressure conditions at 18-22 kbar for a metapelitic sample from multi-equilibrium thermobarometry, Gabudianu Radulescu et al (2009) give maximum pressure conditions of 19-27 kbar from pseudosection modelling of a talc-chlorite-chloritoid assemblage and Gasco et al (2010) reported conditions of 23-26 kbar based on pseudosection modelling of an eclogitic assemblage. The extent of these pressure ranges does not firmly constrain the absence or presence of a (small) pressure gap between the Lower Unit and the Gran Paradiso basement.…”

Section: P-t Conditions For the Schistes Lustrés Complex Of Haute Maumentioning

confidence: 81%

“…(2001) gave pressure conditions at 18–22 kbar for a metapelitic sample from multi‐equilibrium thermobarometry, Gabudianu Radulescu et al. (2009) give maximum pressure conditions of 19–27 kbar from pseudosection modelling of a talc–chlorite–chloritoid assemblage and Gasco et al. (2010) reported conditions of 23–26 kbar based on pseudosection modelling of an eclogitic assemblage.…”

Section: Discussionmentioning

confidence: 99%

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How continuous and precise is the record of P–T paths? Insights from combined thermobarometry and thermodynamic modelling into subduction dynamics (Schistes Lustrés, W. Alps)

Plunder

Agard²,

Dubacq

et al. 2012

Journal Metamorphic Geology

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Pressure-temperature (P-T) paths as complete as possible and with a precision on the km-scale or less are needed to further improve the knowledge of deformation, re-equilibration processes and element ⁄ fluid transfer, in particular along subduction zones. This contribution attempts to (i) critically evaluate the precision and continuity with which metamorphic P-T histories are retrieved today and (ii) discuss implications for regional-scale accretionary processes in subduction zones, through application to the Schistes Lustre´s complex (Haute Maurienne, W. Alps). P-T estimates are compared and combined using several independent approaches: (i) from minerals assumed to be in textural equilibrium; (ii) from electron microprobe compositional maps; and (iii) from pseudosection modelling predictions. Multi-equilibrium calculations were performed with TWEEQU and THERMOCALC, and pseudosections were built with PERPLE_X and THERIAK ⁄ DOMINO. These P-T estimates were also compared with maximum temperatures (T max ) deduced from the Raman spectroscopy of carbonaceous matter. The different methods used here yield the peak of pressure for the lower structural unit of the Schistes Lustre´s at 480°C and 23 kbar and document the retrograde path for both the Median and Lower Units. The results show that P-T conditions are recorded almost continuously and can be determined with a precision of ±1 kbar and ±30°C at best. This study underlines the complementarity of the various thermobarometric methods and demonstrates that precision could be increased by improving solid solution models for chlorite. Observed tectonic patterns, major lithological boundaries, pressure-temperature and T max data suggest that underplating processes and early structural development played a key role in the Schistes Lustre´s accretionary complex.

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Section: P-t Conditions For the Schistes Lustrés Complex Of Haute Maumentioning

confidence: 81%

Section: Discussionmentioning

confidence: 99%

How continuous and precise is the record of P–T paths? Insights from combined thermobarometry and thermodynamic modelling into subduction dynamics (Schistes Lustrés, W. Alps)

Plunder

Agard²,

Dubacq

et al. 2012

Journal Metamorphic Geology

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“…This unit is characterized by a polymetamorphic history, best recorded in multistage garnets Gasco et al, 2010;Gabudianu Radulescu et al, 2011). Pre-Alpine garnet occurs as large (to ~2 cm) rounded inclusion-rich grains, recording relatively low pressure and high temperature conditions.…”

Section: Geological Settingmentioning

confidence: 99%

“…The occurrence of multistage garnet crystals has been documented in different mountain belts and it has been interpreted as evidence of (1) successive metamorphic stages, associated with two orogenic cycles (Compagnoni, 1977;Karabinos, 1984;Lardeaux and Spalla, 1991;Bouffette et al, 1993;Vance et al, 1998;Faryad and Hoinkes, 2003;Zeh et al, 2004;Feenstra et al, 2007;Manzotti et al, 2012); (2) contact metamorphism followed by regional metamorphism (Le Bayon and Ballèvre, 2004;Jerabek et al, 2008;Thöni and Miller, 2009); and (3) successive regional metamorphism stages associated with a single orogenic cycle (e.g., Baxter et al, 2002;Gasco et al, 2010;Zulbati, 2011).…”

Section: Introductionmentioning

confidence: 99%

Multistage garnet in high-pressure metasediments: Alpine overgrowths on Variscan detrital grains

Manzotti

Ballèvre

2013

Geology

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International audienceGarnet is commonly found in metamorphic and magmatic rocks, where its growth records the pressure-temperature history of the rock. Petrologists pay particular attention to multistage garnets, because they document the superposition of successive metamorphic stages and/or cycles in orogenic belts. Due to its considerable resistance to mechanical and chemical weathering, garnet is also commonly present as detrital grains in modern and ancient sediments. Therefore, some multistage garnets could potentially result from overgrowths on detrital grains. We report the first discovery of this type of metamorphic overgrowth on detrital garnet grains in a high-pressure metasediment (Money Unit, western Alps). The studied garnet crystals are found in metamorphic rocks derived from matrix-supported conglomerates. Garnet cores display morphological characteristics of the detrital grains and testify that crystals have been corroded as a consequence of abrasion and dissolution. Furthermore, they display a range of compositions incompatible with their growth in a single rock type, implying their provenance from diverse sources. Garnet overgrowths developed on detrital grains during a blueschist facies event, as indicated by chloritoid and rutile inclusions

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“…Lenses of mafic rocks, derived from pre-Alpine amphibolites (Ballèvre, 1988;Battiston et al, 1984;Benciolini, Martin, & Tartarotti, 1984;Brouwer, Vissers, & Lamb, 2002;Dal Piaz & Lombardo, 1986) or from Late Palaeozoic gabbros (Gasco, Borghi, & Gattiglio, 2010;Pognante, Talarico, Rastelli, & Ferrati, 1987) occur in the paragneisses. Remnants of a thin Mesozoic metasedimentary cover lay over this pre-Triassic basement (Elter, 1960(Elter, , 1972Polino & Dal Piaz, 1978).…”

Section: Gran Paradiso Unitmentioning

confidence: 99%

Petro-structural map of the Money Unit (Gran Paradiso Massif, Valnontey valley, Western Alps)

et al. 2013

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Metamorphic evolution of the Gran Paradiso Massif: A case study of an eclogitic metagabbro and a polymetamorphic glaucophane–garnet micaschist

Cited by 22 publications

References 40 publications

How continuous and precise is the record of P–T paths? Insights from combined thermobarometry and thermodynamic modelling into subduction dynamics (Schistes Lustrés, W. Alps)

How continuous and precise is the record of P–T paths? Insights from combined thermobarometry and thermodynamic modelling into subduction dynamics (Schistes Lustrés, W. Alps)

Multistage garnet in high-pressure metasediments: Alpine overgrowths on Variscan detrital grains

Petro-structural map of the Money Unit (Gran Paradiso Massif, Valnontey valley, Western Alps)

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