Metamorphic and geochronogical study of the Triassic El Oro metamorphic complex, Ecuador: Implications for high-temperature metamorphism in a forearc zone

Riel, Nicolas; Guillot, S.; Jaillard, Étienne; Martelat, Jean-Emmanuel; Paquette, Jean‐Louis; Schwartz, Stéphane; Gonçalves, Philippe; Duclaux, Guillaume; Thébaud, Nicolas; Lanari, Pierre; Janots, Émilie; Yuquilema, Jonatan

doi:10.1016/j.lithos.2012.10.005

Cited by 36 publications

(44 citation statements)

References 67 publications

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“…A similar geotherm was reported by Riel et al (2013), who interpreted such a geothermal gradient to result from buffering of maximum temperature by the latent heat of biotite melting in migmatites according to Thompson & Connolly (1995) and Depine et al (2008). Alternatively, convection in the migmatitic deep crust, might have produced a very hot conductive geotherm in the upper crust and a stable and steep geotherm in the deep migmatitic crust (Riel et al, 2013). However, the heating related to the S1 fabric indicates that the two gradients may be also explained by syn-folding emplacement of granite sills advecting heat and enhancing dehydration melting in the migmatite domaini.e.…”

Section: Significance Of P-t Evolution Of the Horizontal Fabricssupporting

confidence: 87%

“…The two P-T gradients therefore define a non-linear geotherm, which is characterized by two segments: hot in the upper crustal levels and colder in the deep crustal levels. A similar geotherm was reported by Riel et al (2013), who interpreted such a geothermal gradient to result from buffering of maximum temperature by the latent heat of biotite melting in migmatites according to Thompson & Connolly (1995) and Depine et al (2008). Alternatively, convection in the migmatitic deep crust, might have produced a very hot conductive geotherm in the upper crust and a stable and steep geotherm in the deep migmatitic crust (Riel et al, 2013).…”

Section: Significance Of P-t Evolution Of the Horizontal Fabricssupporting

confidence: 68%

“…A similar geotherm was reported by Riel et al . (), who interpreted such a geothermal gradient to result from buffering of maximum temperature by the latent heat of biotite melting in migmatites according to Thompson & Connolly () and Depine et al . ().…”

Section: Discussionmentioning

confidence: 93%

“…(). Alternatively, convection in the migmatitic deep crust, might have produced a very hot conductive geotherm in the upper crust and a stable and steep geotherm in the deep migmatitic crust (Riel et al ., ). However, the heating related to the S1 fabric indicates that the two gradients may be also explained by syn‐folding emplacement of granite sills advecting heat and enhancing dehydration melting in the migmatite domain – i.e.…”

Section: Discussionmentioning

confidence: 99%

“…The evolution of the Chandman massif originated as a metamorphic structure typical of the western Pacific type (Miyazaki, , ). Such a metamorphic environment is characteristic of a suprasubduction setting (Miyashiro, ; Riel et al ., ) and characterizes magmatic recycling of an accretionary system during subduction retreat (e.g. Collins, ).…”

Section: Discussionmentioning

confidence: 99%

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P–T–t–D record of crustal‐scale horizontal flow and magma‐assisted doming in the SW Mongolian Altai

Broussolle

Štípská

Lehmann

et al. 2015

Journal Metamorphic Geology

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The Chandman massif, a typical structure of the Mongolian Altai, consists of a migmatitemagmatite core rimmed by a lower-grade metamorphic envelope of andalusite and cordieritebearing schists. The oldest structure in the migmatite-magmatite core is a sub-horizontal migmatitic foliation S1 parallel to rare granitoid sills. This fabric is folded by upright folds F2 and transposed into a vertical migmatitic foliation S2 that is syn-tectonic, with up to several tens of metres thick granitoid sills. Sillimanite-ilmenite-magnetite S1 inclusion trails in garnet constrain the depth of equilibration during the S1 fabric to 6-7 kbar at 710-780°C. Reorientation of sillimanite into the S2 fabric indicates that the S1-S2 fabric transition Accepted ArticleThis article is protected by copyright. All rights reserved. occurred in the sillimanite stability field. The presence of cordierite, and garnet rim chemistry point to decompression to 3-4 kbar and 680-750°C during development of the S2 steep fabric, and postectonic andalusite indicates further decompression to 2-3 kbar and 600-650°C. Widespread crystallization of post-tectonic muscovite is explained by the release of H 2 O from crystallizing partial melt. In the metamorphic envelope the subhorizontal metamorphic schistosity S1 is heterogeneously affected by upright F2 folds and axial planar subvertical cleavage S2. In the north, the inclusion trails in garnet are parallel to the S1 foliation, and the garnet zoning indicates nearly isobaric heating from 2.5-3 kbar and 500-530°C. Cordierite contains crenulated S1 inclusion trails and has pressure shadows related to the formation of the S2 fabric. The switch from the S1 to the S2 foliation occurred near 2.5-3 kbar and 530-570°C; replacement of cordierite by fine-grained muscovite and chlorite indicates further retrogression and cooling. In the south, andalusite containing crenulated inclusion trails of ilmenite and magnetite indicates heating during the D2 deformation at 3-4 kbar and 540-620°C. Monazite from a migmatite analyzed by LASS yielded elevated HREE concentrations. The grain with the best-developed oscillatory zoning is 356±1. Pb), considered to date the crystallization from melt in the cordierite stability around 680°C and 3.5 kbar, whereas the patchy BSE-dark domains give a date of 347±4.2 [±7] Ma interpreted as recrystallization at subsolidus conditions. The earliest subhorizontal fabric is associated with the onset of magmatism and peak of P-T conditions in the deep crust, indicating important heat input associated with lower crustal horizontal flow. The paroxysmal metamorphic conditions are connected with collapse of the metamorphic structure, an extrusion of the hot lower crustal rocks associated with vertical magma transfer and a juxtaposition of the hot magmatite-migmatite core with supracrustal rocks. This study provides information about tectono-thermal history and time scales of horizontal flow and vertical mass and heat transfer in the Altai orogen. It is shown that, similar to collisional orogens, ...

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Section: Significance Of P-t Evolution Of the Horizontal Fabricssupporting

confidence: 87%

Section: Significance Of P-t Evolution Of the Horizontal Fabricssupporting

confidence: 68%

Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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P–T–t–D record of crustal‐scale horizontal flow and magma‐assisted doming in the SW Mongolian Altai

Broussolle

Štípská

Lehmann

et al. 2015

Journal Metamorphic Geology

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Fore arc tectonothermal evolution of the El Oro metamorphic province (Ecuador) during the Mesozoic

et al. 2014

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The El Oro metamorphic province of SW Ecuador is a composite massif made of juxtaposed terranes of both continental and oceanic affinity that has been located in a fore-arc position since Late Paleozoic times. Various geochemical, geochronological, and metamorphic studies have been undertaken on the El Oro metamorphic province, providing an understanding of the origin and age of the distinct units. However, the internal structures and geodynamic evolution of this area remain poorly understood. Our structural analysis and thermal modeling in the El Oro metamorphic province show that this fore-arc zone underwent four main geological events. (1) During Triassic times (230-225 Ma), the emplacement of the Piedras gabbroic unit at crustal-root level (~9 kbar) triggered partial melting of the metasedimentary sequence under an E-W extensional regime at pressure-temperature conditions ranging from 4.5 to 8.5 kbar and from 650 to 900°C for the migmatitic unit. (2) At 226 Ma, the tectonic underplating of the Arenillas-Panupalí oceanic unit (9 kbar and 300°C) thermally sealed the fore-arc region. (3) Around the Jurassic-Cretaceous boundary, the shift from trench-normal to trench-parallel subduction triggered the exhumation and underplating of the high-pressure, oceanic Raspas Ophiolitic Complex (18 kbar and 600°C) beneath the El Oro Group (130-120 Ma). This was followed by the opening of a NE-SW pull-apart basin, which tilted the massif along an E-W subhorizontal axis (110 Ma). (4) In Late Cretaceous times, an N-S compressional event generated heterogeneous deformation due to the presence of the Cretaceous Celica volcanic arc, which acted as a buttress and predominantly affected the central and eastern part of the massif.

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Multi-phase quantitative compositional mapping by LA-ICP-MS: Analytical approach and data reduction protocol implemented in XMapTools

Markmann,

Lanari,

Piccoli

et al. 2024

Chemical Geology

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Metamorphic and geochronogical study of the Triassic El Oro metamorphic complex, Ecuador: Implications for high-temperature metamorphism in a forearc zone

Cited by 36 publications

References 67 publications

P–T–t–D record of crustal‐scale horizontal flow and magma‐assisted doming in the SW Mongolian Altai

P–T–t–D record of crustal‐scale horizontal flow and magma‐assisted doming in the SW Mongolian Altai

Fore arc tectonothermal evolution of the El Oro metamorphic province (Ecuador) during the Mesozoic

Multi-phase quantitative compositional mapping by LA-ICP-MS: Analytical approach and data reduction protocol implemented in XMapTools

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