Late Paleozoic onset of subduction and exhumation at the western margin of Gondwana (Chilenia Terrane): Counterclockwise P–T paths and timing of metamorphism of deep-seated garnet–mica schist and amphibolite of Punta Sirena, Coastal Accretionary Complex, central Chile (34° S)

Hyppolito, Thaís; García-Casco, Antonio; Juliani, Caetano; Meira, Vinícius Tieppo; Hall, Chris M.

doi:10.1016/j.lithos.2014.07.023

Cited by 30 publications

(26 citation statements)

References 82 publications

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“…The textural features of amphibole suggest a similar deformation history to plagioclase (Figure b). Amp1 (high Mg#) grains are preserved mostly as relict cores and display embayments, lobate edges, and truncated chemical zoning patterns (Figures f and c; Bukovská, Wirth, & Morales, ; Gratier et al., ; Hyppolito, García‐Casco, Juliani, Meira, & Hall, ; Passchier & Trouw, ; Rutter, ; Stokes et al., ; Wassmann & Stöckhert, ; Wintsch & Yi, ). These textural features suggest that Amp1 underwent coupled dissolution and Amp2 precipitated on Amp1.…”

Section: Discussionmentioning

confidence: 99%

Replacement reactions and deformation by dissolution and precipitation processes in amphibolites

Giuntoli

Menegon

Warren

2018

Journal Metamorphic Geology

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The deformation of the middle to lower crust in collisional settings occurs via deformation mechanisms that vary with rock composition, fluid content, pressure, and temperature. These mechanisms are responsible for the accommodation of large tectonic transport distances during nappe stacking and exhumation. Here, we show that fracturing and fluid flow triggered coupled dissolution–precipitation and dissolution–precipitation creep processes, which were responsible for the formation of a mylonitic microstructure in amphibolites. This fabric is developed over a crustal thickness >500 m in the Lower Seve Nappe (Scandinavian Caledonides). Amphibolites display a mylonitic foliation that wraps around albite porphyroclasts appearing dark in panchromatic cathodoluminescence (CL). The albite porphyroclasts were dissected and fragmented by fractures preferentially developed along the (001) cleavage planes and display lobate edges with embayments and peninsular features. Two albite/oligoclase generations, bright in CL, resorbed and overgrew the porphyroclasts, sealing the fractures. Electron backscattered diffraction shows that the two albite/oligoclase generations grew both pseudomorphically and topotaxially at the expense of the albite porphyroclasts and epitaxially around them. These two albite/oligoclase generations also grew as neoblasts elongated parallel to the mylonitic foliation. The amphibole crystals experienced a similar microstructural evolution, as evidenced by corroded ferrohornblende cores surrounded by ferrotschermakite rims that preserve the same crystallographic orientation of the cores. Misorientation maps highlight how misorientations in amphibole are related to displacement along fractures perpendicular to its c‐axis. No crystal plasticity is observed in either mineral species. Plagioclase and amphibole display a crystallographic preferred orientation that is the result of topotaxial growth on parental grains and nucleation of new grains with a similar crystallographic orientation. Amphibole and plagioclase thermobarometry constrains the mylonitic foliation development to the epidote amphibolite facies (˜600°C, 0.75–0.97 GPa). Our results demonstrate that at middle to lower crustal levels, the presence of H2O‐rich fluid at grain boundaries facilitates replacement reactions by coupled dissolution–precipitation and favours deformation by dissolution–precipitation creep over dislocation creep in plagioclase and amphibole.

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Section: Discussionmentioning

confidence: 99%

Replacement reactions and deformation by dissolution and precipitation processes in amphibolites

Giuntoli

Menegon

Warren

2018

Journal Metamorphic Geology

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“…More recently, an age of c . 308 Ma was suggested for the change of the accretion mode, based on the youngest detrital zircon ages from the accreted metasedimentary rocks (Willner et al ., ), also corroborated by 40 Ar– 39 Ar ages in white mica (Willner et al ., ; Hyppolito et al ., ). Willner et al .…”

Section: Geological Settingmentioning

confidence: 97%

“…300 Ma paired metamorphic belt comprising two contrasting lithological/structural/metamorphic series (González‐Bonorino & Aguirre, ; González‐Bonorino, ; Aguirre et al ., ; Hervé et al ., ; Willner, ; Willner et al ., ; Richter et al ., ; Hervé et al ., ; Hyppolito et al ., ). The Western Series comprises strongly deformed oceanic‐derived HP/LT units made of metabasic and metasedimentary rocks related to abyssal and trench environments (Willner, ; Hyppolito et al ., ,b), whereas the Eastern Series is formed by trench‐to‐forearc metasedimentary rocks that are less deformed and were metamorphosed at shallower levels of the accretionary wedge (Hervé et al ., ; Hervé, ; Willner, ). The latter records the thermal effects of subduction‐related granitic magmatism that intruded the wedge (Willner, ; Richter et al ., ) and triggered the LP/HT metamorphism (González‐Bonorino, ; Aguirre et al ., ; Willner, ).…”

Section: Introductionmentioning

confidence: 97%

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LP/HTmetamorphism as a temporal marker of change of deformation style within the Late Palaeozoic accretionary wedge of central Chile

Hyppolito

Juliani

Garcia‐Casco

et al. 2015

Journal Metamorphic Geology

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A Late Palaeozoic accretionary prism, formed at the southwestern margin of Gondwana from Early Carboniferous to Late Triassic, comprises the Coastal Accretionary Complex of central . This fossil accretionary system is made up of two parallel contemporaneous metamorphic belts: a high-pressure/low temperature belt (HP/LT -Western Series) and a low pressure/high temperature belt (LP/HT -Eastern Series). However, the timing of deformation events associated with the growth of the accretionary prism (successive frontal accretion and basal underplating) and the development of the LP/HT metamorphism in the shallower levels of the wedge are not continuously observed along this paired metamorphic belt, suggesting the former existence of local perturbations in the subduction regime. In the Pichilemu region, a well-preserved segment of the paired metamorphic belt allows a first order correlation between the metamorphic and deformational evolution of the deep accreted slices of oceanic crust (blueschists and HP greenschists from the Western Series) and deformation at the shallower levels of the wedge (the Eastern Series). LP/HT mineral assemblages grew in response to arc-related granitic intrusions, and porphyroblasts constitute time markers recording the evolution of deformation within shallow wedge material. Integrated P-T-t-d analysis reveals that the LP/HT belt is formed between the stages of frontal accretion (D 1 ) and basal underplating of basic rocks (D 2 ) forming blueschists at c. 300 Ma. A timeline evolution relating the formation of blueschists and the formation and deformation of LP/HT mineral assemblages at shallower levels, combined with published geochronological/thermobarometric/geochemistry data suggests a cause-effect relation between the basal accretion of basic rocks and the deformation of the shallower LP/HT belt. The S 2 foliation that formed during basal accretion initiated near the base of the accretionary wedge at~30 km depth at c. 308 Ma. Later, the S 2 foliation developed at c. 300 Ma and 15 km depth shortly after the emplacement of the granitoids and formation of the (LP/HT) peak metamorphic mineral assemblages. This shallow deformation may reflect a perturbation in the longterm subduction dynamics (e.g. entrance of a seamount), which would in turn have contributed to the coeval exhumation of the nearby blueschists at c. 300 Ma. Finally, 40 Ar-39 Ar cooling ages reveal that foliated LP/HT rocks were already at~350°C at c. 292 Ma, indicating a rapid cooling for this metamorphic system. Key words: accretionary prism; central Chile; paired metamorphic belt; P-T-t-d path. INTRODUC TIONThe temporal and spatial relationships of thermal and mechanical processes in orogens have been a topic of debate for the past 40 years. Our understanding of accretionary wedge dynamics remains incomplete. More specifically the relation between the two main geodynamic processes, namely (i) the formation of thermally-contrasted (pene-) contemporaneous metamorphic belts (sensu Miyashiro, 1961;Maruyama, 1997; and...

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“…The Late Devonian-Mississippian (Lower Carboniferous) tectonics of Gondwana has been strongly debated, with particular focus on its western margin (Ramos et al, 1998;Davis et al, 1999;H€ ockenreiner et al, 2003;Dahlquist et al, 2010Dahlquist et al, , 2015Martina et al, 2011;Willner et al, 2011;Alasino et al, 2012;Hyppolito et al, 2014). Most tectonic models (Bahlburg and Herv e, 1997;Ramos, 1988), supported by U-Pb provenance studies in detrital zircon (Willner et al, 2008;Bahlburg et al, 2009;Maksaev et al, 2015;Einhorn et al, 2015) indicated that Gondwana passed through a transitional stage between two clear subducting-driven settings: early-middle Paleozoic with terrane accretions and latest Mississippian~330 Ma-with arc magmatism, accretionary prism formation and thrusting.…”

Section: Introductionmentioning

confidence: 99%

Mississippian lamprophyre dikes in western Sierras Pampeanas, Argentina: Evidence of transtensional tectonics along the SW margin of Gondwana

Martina

Canelo

Dávila

et al. 2018

Journal of South American Earth Sciences

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a b s t r a c tIn the Famatina range, Sierras Pampeanas of Argentina (SW Gondwana), subvertical calc-alkaline lamprophyric dike swarms crop out through >300 km. The dikes cut Ordovician units with a prominent NW-SE trending and are covered by continental sedimentary successions of Pennsylvanian to Permian age. The dikes show a strong structural control associated with Riedel fault systems. Detailed field analysis suggested a~N-S opening direction oblique to the attitude of dike walls and a left-lateral transtensional tectonics during the emplacement. 40 Ar/ 39 Ar geochronology of a lamprophyric sample defined a crystallization age (plateau; whole rock) of 357.1 ± 7.1 Ma (MSWD ¼ 2.3). Coetaneous ductile zones with dominant strikeslip motion, documented along western Argentina for >600 km, suggest a regional event in SW Gondwana during the Mississippian. We propose that this deformation was the result of the counterclockwise fast rotation of Gondwana between 365 and 345 Ma, when the Famatina range and western Argentina occupied a sub-polar position. A transform margin along SW Gondwana better explains our (and others) data rather than a subduction margin. This scenario is also consistent with the occurrence of A-type granites and normal-fault basins within the foreland as well as bimodal volcanics.

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Late Paleozoic onset of subduction and exhumation at the western margin of Gondwana (Chilenia Terrane): Counterclockwise P–T paths and timing of metamorphism of deep-seated garnet–mica schist and amphibolite of Punta Sirena, Coastal Accretionary Complex, central Chile (34° S)

Cited by 30 publications

References 82 publications

Replacement reactions and deformation by dissolution and precipitation processes in amphibolites

Replacement reactions and deformation by dissolution and precipitation processes in amphibolites

LP/HTmetamorphism as a temporal marker of change of deformation style within the Late Palaeozoic accretionary wedge of central Chile

Mississippian lamprophyre dikes in western Sierras Pampeanas, Argentina: Evidence of transtensional tectonics along the SW margin of Gondwana

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