Dynamics of Saxothuringian subduction channel/wedge constrained by phase‐equilibria modelling and micro‐fabric analysis

Collett, Stephen; Štípská, Pavla; Kusbach, Vladimír; Schulmann, Karel; Marciniak, Gilbert

doi:10.1111/jmg.12226

Cited by 22 publications

(16 citation statements)

References 104 publications

(185 reference statements)

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“…Kyanite is present under similar P-T conditions, hence tiny inclusions of kyanite observed in the cores of garnet are also interpreted as remnants of the prograde assemblage. In contrast to some other eclogites of the Bohemian Massif (e.g., Collett, Štípská, Kusbach, Schulmann, & Marciniak, 2017), garnet does not preserve any zoning in the cores, which points to homogenization at or near the peak conditions. Omphacite and phengite that occur as inclusions in the garnet cores show the highest Jd and Si (apfu), respectively, similar to the cores of omphacite and phengite grains located in the matrix.…”

Section: P-t Evolution Of the Międzygórze Eclogitecontrasting

confidence: 65%

“…The formation of the channels is interpreted as an effect of the partial, fluid-induced dissolution-reprecipitation of the garnet. Such channels in garnet have been previously described by, for example, Faryad, Nahodilova, and Dolejš (2010) and Collett et al (2017). These features together with the zoisite and amphibole bloom (see also Massonne, 2012) are interpreted as independent lines of evidence for H 2 O-dominated fluid infiltration that hydrated the system during decompression.…”

Section: P-t Evolution Of the Międzygórze Eclogitesupporting

confidence: 61%

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Integrating X‐ray mapping and microtomography of garnet with thermobarometry to define the P–T evolution of the (near) UHP Międzygórze eclogite, Sudetes, SW Poland

Majka

Mazur

Młynarska

et al. 2018

Journal Metamorphic Geology

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Detailed X‐ray compositional mapping and microtomography have revealed the complex zoning and growth history of garnet in a kyanite‐bearing eclogite. The garnet occurs as clusters of coalesced grains with cores revealing slightly higher Ca and lower Mg than the rims forming the coalescence zones between the grains. Core regions of the garnet host inclusions of omphacite with the highest jadeite, and phengite with the highest Si, similar to values in the cores of omphacite and phengite located in the matrix. Therefore, the core compositions of garnet, omphacite, and phengite have been chosen for the peak pressure estimate. Coupled conventional thermobarometry, average P–T, and phase equilibrium modelling in the NCKFMMnASHT system yields P–T conditions of 26–30 kbar at 800–930°C. Although coesite is not preserved, these P–T conditions partially overlap the coesite stability field, suggesting near ultra‐high–pressure (UHP) conditions during the formation of this eclogite. Therefore, the peak pressure assemblage is suggested to have been garnet–omphacite–kyanite–phengite–coesite/quartz–rutile. Additional lines of evidence for the possible UHP origin of the Międzygórze eclogite are the presence of rod‐shaped inclusions of quartz parallel to the c‐axis in omphacite as well as relatively high values of Ca‐Tschermak and Ca‐Eskola components. Late zoisite, rare diopside–plagioclase symplectites rimming omphacite, and minor phlogopite–plagioclase symplectites replacing phengite formed during retrogression together with later amphibole. These retrograde assemblages lack minerals typical of granulite facies, which suggests simultaneous decompression and cooling during exhumation before the crustal‐scale folding that was responsible for final exhumation of the eclogite.

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Section: P-t Evolution Of the Międzygórze Eclogitecontrasting

confidence: 65%

Section: P-t Evolution Of the Międzygórze Eclogitesupporting

confidence: 61%

Integrating X‐ray mapping and microtomography of garnet with thermobarometry to define the P–T evolution of the (near) UHP Międzygórze eclogite, Sudetes, SW Poland

Majka

Mazur

Młynarska

et al. 2018

Journal Metamorphic Geology

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“…(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Table 2 ( Abbott and Draper, 2010;Abd El-Naby et al, 2000;Abers et al, 2013;Agard et al, 2002;Agard et al, 2005;Agard et al, 2011;Anczkiewicz et al, 2000;Angiboust et al, 2017;Ao and Bhowmik, 2014;Aoki et al, 2008;Aoya, 2002;Aoya et al, 2013;Aoya et al, 2009;Aoya et al, 2006;Aoya et al, 2003;Aygul and Oberhaensli, 2017;Banno et al, 2000;Blanco-Quintero et al, 2010a;Blanco-Quintero et al, 2010b;Bosch et al, 2002;Bousquet et al, 2002;Bousquet et al, 1998;Brandon and Calderwood, 1990;Bucher et al, 2005;Candan et al, 2005;Carson et al, 1999;Castelli et al, 2002;Clague et al, 1981;Collett et al, 2017;Collins et al, 2015;Cook-Kollars et al, 2014;Cowan et al, 2014;Droop et al, 2005;Ellis et al, 2015;Enami, 1983;Enami et al, 1994;Encarnacion et al, 1995;Escuder-Viruete and Perez-Estaun, 2006;Escuder-Viruete et al, 2011;Escuder-Viruete et al, 2013;…”

Section: Further Evidence From Diagnostic Fossil Exposuresmentioning

confidence: 99%

The subduction plate interface: rock record and mechanical coupling (from long to short timescales)

Agard

Plunder

Angiboust

et al. 2018

Lithos

216

294

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Short-and long-term processes at or close to the subduction plate interface (e.g.,mineral transformations, fluid release, seismicity and more generally deformation) might be more closely related than previously thought. Increasing evidence from the fossil rock record suggests that some episodes of their long geological evolution match or are close to timescales of the seismic cycle. This contribution uses rocks recovered (episodically) from subduction zones, together with insights from thermomechanical modelling, to provide a new dynamic vision of the nature, structure and properties of the plate interface and to bridge the gap between the mechanical behavior of active subduction zones (e.g.,coupling inferred from geophysical monitoring) and fossil ones (e.g., coupling required to detach and recover subducted slab fragments). Based on critical observations and an exhaustive compilation of worldwide subducted oceanic units (for which the presence near the plate interface, rock types, pressure, temperature, T/P gradients, thickness and timing of detachment can be assessed), the present study demonstrates how long-term mechanical coupling exerts a key control on detachment from the slab and potential rock recovery. Critical assessment of rock T/P characteristics indicates that these fragments can indeed be used as natural probes and provide reliable information on subduction interface dynamics down to~2.8 GPa. Rock clusters are identified at depths of 30, 55-60 and 80 km, with some differences between rock types. Data also reveal a first-order evolution with subduction cooling (in the first~5 Myr), which is interpreted as reflecting a systematic trend from strong to weak mechanical coupling, after which subduction is lubricated and mostly inhibits rock recovery. This contribution places bounds on the plate interface constitution, regular thickness (b300 m; i.e. where/when there is no detachment), changing geometry and effective viscosity. The concept of 'coupled thickness' is used here to capture subduction interface dynamics, notably during episodes of strong mechanical coupling, and to link long-and short-term deformation. Mechanical coupling depends on mantle wedge rheology, viscosity contrasts and initial structures (e.g.,heterogeneous lithosphere, existence of décollement horizons, extent of hydration, asperities) but also on boundary conditions (convergence rates, kinematics), and therefore differs for warm and cold subduction settings. Although most present-day subduction zone segments (both along strike and downdip) are likely below the detachment threshold, we propose that the most favorable location for detachment corresponds to the spatial transition between coupled and decoupled areas. Effective strain localization involves dissolution-precipitation and dislocation creep but also possibly brittle fractures and earthquakes, even at intermediate depths.

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“…Within the European Variscides, the Saxothuringian Domain preserves numerous occurrences of blueschists, eclogite facies rocks, and UHP relics clearly pointing to a subduction‐related environment (e.g., Collett et al, 2017; Faryad & Kachlík, 2013; Massonne, 2001; Massonne & Nasdala, 2003). Structurally, the high‐grade ( U ) HP ‐ HT rocks crop out in the centre of a domal structure in the footwall of the lower‐grade HP ‐ LT metasediments creating apparent normal metamorphic zoning.…”

Section: Introductionmentioning

confidence: 99%

New constraints on the tectonometamorphic evolution of the Erzgebirge orogenic wedge (Saxothuringian Domain, Bohemian Massif)

Jouvent

Lexa

Peřestý

et al. 2021

Journal Metamorphic Geology

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In contrast to well-documented (U)HP rocks of the Erzgebirge crystalline complex (Saxothuringian Domain, Bohemian Massif), the surrounding mediumto low-grade metasediments are scarcely studied, although they provide an important link between deep subduction and mid-crustal processes. To constrain the Variscan evolution from continental subduction to orogenic wedge, the transition from the low-grade phyllites to the footwall medium-grade micaschists was investigated. We used thermodynamic modelling to constrain the P-T conditions of four deformation fabrics (D1-D4) identified by the structural analysis. The studied area was first affected by the M1-D1 event characterized by HP-LT minerals (garnet, chloritoid, phengite, paragonite, and rutile)

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Dynamics of Saxothuringian subduction channel/wedge constrained by phase‐equilibria modelling and micro‐fabric analysis

Abstract: International audienc

Cited by 22 publications

References 104 publications

Integrating X‐ray mapping and microtomography of garnet with thermobarometry to define the P–T evolution of the (near) UHP Międzygórze eclogite, Sudetes, SW Poland

Integrating X‐ray mapping and microtomography of garnet with thermobarometry to define the P–T evolution of the (near) UHP Międzygórze eclogite, Sudetes, SW Poland

The subduction plate interface: rock record and mechanical coupling (from long to short timescales)

New constraints on the tectonometamorphic evolution of the Erzgebirge orogenic wedge (Saxothuringian Domain, Bohemian Massif)

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