Exhumation of oceanic blueschists and eclogites in subduction zones: Timing and mechanisms

Agard, Philippe; Yamato, Philippe; Jolivet, Laurent; Burov, Evgenii

doi:10.1016/j.earscirev.2008.11.002

Cited by 538 publications

(466 citation statements)

References 250 publications

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“…The serpentinites are extremely buoyant with respect to the oceanic crust that mainly consists of mafic rocks that have been transformed to eclogites during subduction, increasing their density so that they are denser than average mantle rocks (Hermann et al, 2000). Our P-T estimates (2.3-2.7 GPa at 615-680°C for barroisite-bearing and 2.5-2.7 GPa at 650-690°C for barroisite-free eclogites) fit the stability field of antigorite along subduction zone gradients, i.e.~650°C at 2.7 GPa (Wunder and Schreyer, 1997;Agard et al, 2009). Thus, serpentinites may have enhanced exhumation of HP rocks in the Bantimala Complex (Hermann et al, 2000;Ernst, 2010).…”

Section: Tectonic Implicationsmentioning

confidence: 83%

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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Section: Tectonic Implicationsmentioning

confidence: 83%

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 mélange may include high-pressure rocks but not necessarily exclusively, such as in the case of the Franciscan complex (e.g. Agard et al, 2009). The distribution of metamorphic grade in the allochthonous units is thus an important criterion to distinguish between the two models.…”

Section: Metamorphic Gradementioning

confidence: 99%

Tectonic evolution and high-pressure rock exhumation in the Qiangtang terrane, central Tibet

et al. 2015

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Abstract. Conflicting interpretations of the > 500 km long, east-west-trending Qiangtang metamorphic belt have led to very different and contradicting models for the PermoTriassic tectonic evolution of central Tibet. We define two metamorphic events, one that only affected pre-Ordovician basement rocks and one subduction-related Triassic highpressure metamorphism event. Detailed mapping and structural analysis allowed us to define three main units that were juxtaposed due to collision of the north and south Qiangtang terranes after closure of the Ordovician-Triassic ocean that separated them. The base is formed by the Precambrian-Carboniferous basement, followed by nonmetamorphic ophiolitic mélange containing mafic rocks that range in age from the Ordovician to Middle Triassic. The top of the sequence is formed by strongly deformed sedimentary mélange that contains up to > 10 km size rafts of both unmetamorphosed Permian sediments and highpressure blueschists. We propose that the high-pressure rocks were exhumed from underneath the south Qiangtang terrane in an extensional setting caused by the pull of the northward subducting slab of the Shuanghu-Tethys. Highpressure rocks, sedimentary mélange and margin sediments were thrust on top of the ophiolitic mélange that was scraped off the subducting plate. Both units were subsequently thrust on top of the south Qiantang terrane continental basement. Onset of Late Triassic sedimentation marked the end of the amalgamation of both Qiangtang terranes and the beginning of spreading between Qiantang and north Lhasa to the south, leading to the deposition of thick flysch deposits in the Jurassic.

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“…Gerya et al 2002;Gorczyk et al 2006Gorczyk et al , 2007Yamato et al 2007;Ernst & Liou 2008;Agard et al 2009;Meda et al 2010;Roda et al 2010Roda et al , 2012Le Voci et al 2014). In ocean-continent sub-Q3 Q4 duction systems, low viscosity hydrated mantle facilitates the exhumation and underplating of subducted oceanic and continental material at the base of the crust of the upper plate (Billen & Gurnis 2001;Hirth & Kohlstedt 2003;Billen 2008;Hirth & Guillot 2013;Nagaya et al 2016).…”

Section: Introductionmentioning

confidence: 99%

2-D numerical study of hydrated wedge dynamics from subduction to post-collisional phases

Regorda¹,

Roda²,

Marotta³

et al. 2017

Geophysical Journal International

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S U M M A R YWe developed a 2-D finite element model to investigate the effect of shear heating and mantle hydration on the dynamics of the mantle wedge area. The model considers an initial phase of active oceanic subduction, which is followed by a post-collisional phase characterized by pure gravitational evolution. To investigate the impact of the subduction velocity on the thermomechanics of the system, three models with different velocities prescribed during the initial subduction phase were implemented. Shear heating and mantle hydration were then systematically added into the models. We then analysed the evolution of the hydrated area during both the subduction and post-collisional phases, and examined the difference in P max -T (maximum pressure-temperature) and P-T max (pressure-maximum temperature) conditions for the models with mantle hydration. The dynamics that allow for the recycling and exhumation of subducted material in the wedge area are strictly correlated with the thermal state at the external boundaries of the mantle wedge, and the size of the hydrated area depends on the subduction velocity when mantle hydration and shear heating are considered simultaneously. During the post-collisional phase, the hydrated portion of the mantle wedge increases in models with high subduction velocities. The predicted P-T configuration indicates that contrasting P-T conditions, such as Barrovian-to Franciscan-type metamorphic gradients, can contemporaneously characterize different portions of the subduction system during both the active oceanic subduction and post-collisional phases and are not indicative of collisional or subduction phases.

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Exhumation of oceanic blueschists and eclogites in subduction zones: Timing and mechanisms

Cited by 538 publications

References 250 publications

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

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

Tectonic evolution and high-pressure rock exhumation in the Qiangtang terrane, central Tibet

2-D numerical study of hydrated wedge dynamics from subduction to post-collisional phases

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