Ophiolite mélange zone records exhumation in a fossil subduction channel

Federico, Laura; Crispini, Laura; Scambelluri, Marco; Capponi, Giovanni

doi:10.1130/g23190a.1

Cited by 152 publications

(137 citation statements)

References 17 publications

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“…During subduction of the Piemont-Ligurian Ocean and Alpine collision, the Voltri Massif ophiolitic rocks underwent an Alpine prograde metamorphism Messiga et al, 1995;Scambelluri et al, 1995;Hermann et al, 2000;Früh-Green et al, 2001;Malatesta et al, 2012a, b). The peak metamorphic conditions of the Alpine metamorphism have been estimated at 1.8-2.5 GPa and 500-650 • C on the basis of the assemblage omphacite + chloritoid + garnet + zoisite ±talc in a mylonitic metagabbro by Messiga et al (1995), which are consistent with the pressure-temperature (P-T) estimates by .…”

Section: Geological Settingsupporting

confidence: 65%

“…Hoogerduijn Strating et al, 1993;Vissers et al, 1991;Rampone et al, 2004Rampone et al, , 2005Piccardo and Vissers, 2007), as well as on the subsequent subduction and exhumation history (e.g. Scambelluri et al, 1991Scambelluri et al, , 1995Scambelluri et al, , 1997Messiga et al, 1995;Hermann et al, 2000;Früh-Green et al, 2001;Malatesta et al, 2012a, b;Piccardo 2013).…”

Section: Introductionmentioning

confidence: 99%

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The microstructural record of porphyroclasts and matrix of partly serpentinized peridotite mylonites – from brittle and crystal-plastic deformation to dissolution–precipitation creep

Bial

Trepmann

2013

Solid Earth

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Abstract. We present microfabrics in high-pressure, metamorphic, partly serpentinized peridotite mylonites from the Voltri Massif, in which porphyroclasts and matrix record independent deformation events. The microfabrics are analysed using polarization microscopy and electron microscopy (SEM/EBSD, EMP). The mylonites contain diopside and olivine porphyroclasts originating from the mantle protolith embedded in a fine-grained matrix consisting mainly of antigorite and minor olivine and pyroxene. The porphyroclasts record brittle and crystal-plastic deformation of the peridotite at upper-mantle conditions and differential stresses of a few hundred MPa. After the peridotites became serpentinized, deformation occurred mainly by dissolutionprecipitation creep resulting in a pronounced foliation of the antigorite matrix, crenulation cleavages and newly precipitated olivine and pyroxene from the pore fluid at sites of dilation, i.e. in strain shadows next to porphyroclasts and folded fine-grained antigorite layers. Antigorite reveals a pronounced associated shape preferred orientation (SPO) and crystallographic preferred orientation (CPO) with the basal (001) cleavage plane oriented in the foliation plane. In monomineralic antigorite aggregates at sites of stress concentration around porphyroclasts, a characteristically reduced grain size and deflecting CPO as well as sutured grain boundaries indicate also some contribution of crystal-plastic deformation and grain-boundary migration of antigorite. In contrast, the absence of any intragranular deformation features in newly precipitated olivine in strain shadows reveals that stresses were not sufficiently high to allow for significant dislocation creep of olivine at conditions at which antigorite is stable. The porphyroclast microstructures are not associated with the microstructures of the mylonitic matrix, but are inherited from an independent earlier deformation. The porphyroclasts record a high-stress deformation of the peridotite with dislocation creep of olivine in the upper mantle probably related to rifting processes, whereas the serpentinite matrix records dominantly dissolution-precipitation creep and low stresses during subduction and exhumation.

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Section: Geological Settingsupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

The microstructural record of porphyroclasts and matrix of partly serpentinized peridotite mylonites – from brittle and crystal-plastic deformation to dissolution–precipitation creep

Bial

Trepmann

2013

Solid Earth

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“…Thus, serpentinites may have enhanced exhumation of HP rocks in the Bantimala Complex (Hermann et al, 2000;Ernst, 2010). Furthermore, the presence of mélange units intercalated with high-pressure metamorphic rocks and the chaotic occurrence of different metamorphic facies (e.g., eclogite, blueschist, greenschist) (Sukamto, 1982) has been proposed for a subduction channel environment (Gerya et al, 2002;Federico et al, 2007).…”

Section: Tectonic Implicationsmentioning

confidence: 99%

Prograde and retrograde evolution of eclogites from the Bantimala Complex in South Sulawesi, Indonesia

Setiawan

Osanai

Nakano

et al. 2016

Journal of Mineralogical and Petrological Sciences

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This contribution reports the metamorphic evolution of the high-pressure metamorphic rocks from the Bantimala Complex, South Sulawesi, Indonesia. Barroisite-bearing and barroisite-free eclogites were examined to assess their metamorphic evolutions, which have implications regarding the tectonic conditions in this region. The eclogites mainly consist of garnet, omphacite, phengite, rutile, and epidote, with or without barroisite. The variations in mineral assemblages are interpreted to depend upon local changes in the bulk chemical composition. The barroisite-bearing eclogites contain two types of euhedral garnet: coarse-(1-1.5 mm) and finegrained (<0.5 mm). Mineral inclusions in the coarse-grained garnet core and mantle show epidote + titanite and glaucophane + epidote assemblages, that stabilized at 0.9-1.5 GPa and 350-550°C within epidote blueschist-facies conditions. Mineral chemistry and chemical-mapping analyses indicate that both fine-grained garnet and the rim of coarse-grained garnet formed at peak P-T conditions, which were estimated as 2.3-2.7 GPa at 615-680°C based on the garnet-omphacite-phengite-quartz equilibrium. Peak P-T conditions for barroisitefree eclogite were similar (2.5-2.7 GPa at 650-690°C) to those for barroisite-bearing eclogite. Actinolite rims overgrowing matrix sodic-calcic amphiboles attest to retrogression at P < 0.5 GPa and T < 350°C in a clockwise P-T path. The very low geothermal gradient experienced during the prograde path (~5°C/km) likely suggests the subduction of an old and cold oceanic crust. The low geothermal gradient on the retrograde path suggests decompressional cooling during exhumation, possibly favored by a serpentinite-dominated matrix within a subduction channel environment.

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“…the Voltri Massif in the Western Alps; Frederico et al, 2007, or the Sierra del Convento in Cuba; Blanco-Quintero et al, 2010). Therefore the EZ represents a specific type of subduction channel, in which the viscous matrix surrounding the eclogite boudins is purely made up of high pressure metasediments.…”

Section: Seismic Imaging Of Subduction Channel Rocksmentioning

confidence: 99%

Crystallographic preferred orientations of exhumed subduction channel rocks from the Eclogite Zone of the Tauern Window (Eastern Alps, Austria), and implications on rock elastic anisotropies at great depths

et al. 2015

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Ophiolite mélange zone records exhumation in a fossil subduction channel

Cited by 152 publications

References 17 publications

The microstructural record of porphyroclasts and matrix of partly serpentinized peridotite mylonites – from brittle and crystal-plastic deformation to dissolution–precipitation creep

The microstructural record of porphyroclasts and matrix of partly serpentinized peridotite mylonites – from brittle and crystal-plastic deformation to dissolution–precipitation creep

Prograde and retrograde evolution of eclogites from the Bantimala Complex in South Sulawesi, Indonesia

Crystallographic preferred orientations of exhumed subduction channel rocks from the Eclogite Zone of the Tauern Window (Eastern Alps, Austria), and implications on rock elastic anisotropies at great depths

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