Monazite solubility in hydrous silicic melts at high pressure conditions relevant to subduction zone metamorphism

2012 ◽  
Vol 321-322 ◽  
pp. 104-114 ◽  
Author(s):  
Susanne Skora ◽  
Jon Blundy
Keyword(s):  
High Pressure ◽  
Subduction Zone

scholarly journals Up the down escalator: the exhumation of (ultra)-high pressure terranes during on-going subduction

2012 ◽  
Vol 4 (1) ◽  
pp. 745-781 ◽  
Author(s):  
C. J. Warren
Keyword(s):  
High Pressure ◽  
Subduction Zone ◽  
Continental Crust ◽  
Subduction Zones ◽  
Crustal Material ◽  
Time And Space ◽  
Ultra High Pressure ◽  
Tectonic Environment ◽  
Tectonic Style ◽  
Weak Material

Abstract. The exhumation of high and ultra-high pressure rocks is ubiquitous in Phanerozoic orogens created during continental collisions, and is common in many ocean-ocean and ocean-continent subduction zone environments. Three different tectonic environments have previously been reported, which exhume deeply buried material by different mechanisms and at different rates. However it is becoming increasingly clear that no single mechanism dominates in any particular tectonic environment, and the mechanism may change in time and space within the same subduction zone. In order for buoyant continental crust to subduct, it must remain attached to a stronger and denser substrate, but in order to exhume, it must detach (and therefore at least locally weaken) and be initially buoyant. Denser oceanic crust subducts more readily than more buoyant continental crust but exhumation must be assisted by entrainment within more buoyant and weak material such as serpentinite or driven by the exhumation of structurally lower continental crustal material. Weakening mechanisms responsible for the detachment of crust at depth include strain, hydration, melting, grain size reduction and the development of foliation. These may act locally or may act on the bulk of the subducted material. Metamorphic reactions, metastability and the composition of the subducted crust all affect buoyancy and overall strength. Subduction zones change in style both in time and space, and exhumation mechanisms change to reflect the tectonic style and overall force regime within the subduction zone. Exhumation events may be transient and occur only once in a particular subduction zone or orogen, or may be more continuous or occur multiple times.

High-pressure experimental verification of rutile-ilmenite oxybarometer: Implications for the redox state of the subduction zone

2017 ◽  
Vol 60 (10) ◽  
pp. 1817-1825 ◽  
Author(s):  
RenBiao Tao ◽  
LiFei Zhang ◽  
Vincenzo Stagno ◽  
Xu Chu ◽  
Xi Liu
Keyword(s):  
High Pressure ◽  
Subduction Zone ◽  
Experimental Verification ◽  
Redox State

scholarly journals Carbonation of subduction-zone serpentinite (high-pressure ophicarbonate; Ligurian Western Alps) and implications for the deep carbon cycling

2016 ◽  
Vol 441 ◽  
pp. 155-166 ◽  
Author(s):  
Marco Scambelluri ◽  
Gray E. Bebout ◽  
Donato Belmonte ◽  
Mattia Gilio ◽  
Nicola Campomenosi ◽  
...  
Keyword(s):  
High Pressure ◽  
Carbon Cycling ◽  
Subduction Zone ◽  
Western Alps

Geochemical and Nd isotopic constraints for the origin of eclogite protoliths, northern Cordillera: implications for the Paleozoic tectonic evolution of the Yukon-Tanana terrane

1999 ◽  
Vol 36 (10) ◽  
pp. 1697-1709 ◽  
Author(s):  
Robert A Creaser ◽  
Jo-Anne S Goodwin-Bell ◽  
Philippe Erdmer
Keyword(s):  
High Pressure ◽  
Subduction Zone ◽  
Convergent Margins ◽  
Metasedimentary Rocks ◽  
High Pressure Metamorphism ◽  
Distal Edge ◽  
History Of ◽  
Convergent Plate Margin ◽  
Ocean Ridge ◽  
Subduction Zone Magmatism

On the basis of trace-element data, basaltic protoliths for Paleozoic eclogites from the Yukon-Tanana terrane (YTT) have diverse origins. Eclogites from Stewart Lake and the Simpson Range have characteristics of basaltic protoliths generated by subduction-zone magmatism, are hosted by serpentinitic-gabbroic rocks, and record Mississippian high-pressure metamorphism and cooling. In contrast, eclogites from Faro, Ross River, and Last Peak show either within-plate geochemistry or mid-ocean ridge protolith geochemistry with a small subduction component, are hosted by continental metasedimentary rocks of the Nisutlin assemblage, and record Permian high-pressure metamorphism and cooling. We interpret these results to derive from the following tectonic events in the Paleozoic history of the YTT: (1) activity at a Devonian-Mississippian convergent plate margin at the distal edge of North America, with near-contemporaneous subduction-zone magmatism and high-pressure metamorphism; (2) Mississippian rifting of that margin to form the outboard YTT, the Slide Mountain marginal basin, and the Faro, Ross River, and Last Peak eclogite protoliths; and (3) west-dipping subduction of the Slide Mountain Ocean under the outboard YTT in Permian time, to produce the Faro, Ross River, and Last Peak eclogites and Permian arc magmatism throughout the YTT. The basaltic protoliths of the Paleozoic YTT eclogites bear close similarity to those produced in rifted convergent margins, such as the Miocene Japanese arc - back-arc system.

scholarly journals Accretion-controlled forearc deformation pulses recorded by high-pressure paleo-accretionary wedges: the example of the Hellenic subduction zone

2021 ◽  
Author(s):  
Armel Menant ◽  
Onno Oncken ◽  
Johannes Glodny ◽  
Samuel Angiboust ◽  
Laurent Jolivet ◽  
...  
Keyword(s):  
High Pressure ◽  
Subduction Zone ◽  
Numerical Models ◽  
Carbonaceous Material ◽  
Plate Interface ◽  
Stress Regime ◽  
Hellenic Subduction Zone ◽  
Driving Mechanisms ◽  
Wide Range

<p>Subduction margins are the loci of a wide range of deformation processes occurring at different timescales along the plate interface and in the overriding forearc crust. Whereas long-term deformation is usually considered as stable over Myr-long periods, this vision is challenged by an increasing number of observations suggesting a long-term pulsing evolution of active margins. To appraise this emerging view of a highly dynamic subduction system and identify the driving mechanisms, detailed studies on high pressure-low temperature (HP-LT) exhumed accretionary complexes are crucial as they open a window on the deformation history affecting the whole forearc region.</p><p>In this study, we combine structural and petrological observations, Raman spectroscopy on carbonaceous material, Rb/Sr multi-mineral geochronology and thermo-mechanical numerical models to unravel with an unprecedented resolution the tectono-metamorphic evolution of the Late-Cenozoic HP-LT nappe stack cropping out in western Crete (Hellenic subduction zone). A consistent decrease of peak temperatures and deformation ages toward the base of the nappe pile allows us to identify a minimum of three basal accretion episodes between ca. 24 Ma and ca. 15 Ma. On the basis of structural evidences and pressure-temperature-time-strain predictions from numerical modeling, we argue that each of these mass-flux events triggered a pulse in the strain rate, sometimes associated with a switch of the stress regime (i.e., compressional/extensional). Such accretion-controlled transient deformation episodes last at most ca. 1-2 Myr and may explain the poly-phased structural records of exhumed rocks without involving changes in far-field stress conditions. This long-term background tectonic signal controlled by deep accretionary processes plays a part in active deformations monitored at subduction margins, though it may remain blind to most of geodetic methods because of superimposed shorter-timescale transients, such as seismic-cycle-related events.</p>

scholarly journals Deeply subducted continental fragments – Part 2: Insight from petrochronology in the central Sesia Zone (western Italian Alps)

Solid Earth ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 191-222 ◽  
Author(s):  
Francesco Giuntoli ◽  
Pierre Lanari ◽  
Marco Burn ◽  
Barbara Eva Kunz ◽  
Martin Engi
Keyword(s):  
High Pressure ◽  
Subduction Zone ◽  
Driving Forces ◽  
Microstructural Analysis ◽  
Age Dating ◽  
Subduction Channel ◽  
Mineral Growth ◽  
Pressure Peak ◽  
Nw Italy ◽  
Temperature Time

Abstract. Subducted continental terranes commonly comprise an assembly of subunits that reflect the different tectono-metamorphic histories they experienced in the subduction zone. Our challenge is to unravel how, when, and in which part of the subduction zone these subunits were juxtaposed. Petrochronology offers powerful tools to decipher pressure–temperature–time (P–T–t) histories of metamorphic rocks that preserve a record of several stages of transformation. A major issue is that the driving forces for re-equilibration at high pressure are not well understood. For example, continental granulite terrains subducted to mantle depths frequently show only partial and localized eclogitization. The Sesia Zone (NW Italy) is exceptional because it comprises several continental subunits in which eclogitic rocks predominate and high-pressure (HP) assemblages almost completely replaced the Permian granulite protoliths. This field-based study comprises both main complexes of the Sesia terrane, covering some of the recently recognized tectonic subunits involved in its assembly; hence our data constrain the HP tectonics that formed the Sesia Zone. We used a petrochronological approach consisting of petrographic and microstructural analysis linked with thermodynamic modelling and U–Th–Pb age dating to reconstruct the P–T–t trajectories of these tectonic subunits. Our study documents when and under what conditions re-equilibration took place. Results constrain the main stages of mineral growth and deformation, associated with fluid influx that occurred in the subduction channel. In the Internal Complex (IC), pulses of fluid percolated at eclogite facies conditions between 77 and 55 Ma with the HP conditions reaching  ∼  2 GPa and 600–670 °C. By contrast, the External Complex (EC) records a lower pressure peak of  ∼  0.8 GPa for 500 °C at  ∼  63 Ma. The juxtaposition of the two complexes occurred during exhumation, probably at  ∼  0.8 GPa and 350 °C; the timing is constrained between 46 and 38 Ma. Mean vertical exhumation velocities are constrained between 0.9 and 5.1 mm year−1 for the IC, up to its juxtaposition with the EC. Exhumation to the surface occurred before 32 Ma, as constrained by the overlying Biella Volcanic Suite, at a mean vertical velocity between 1.6 and 4 mm year−1. These findings constrain the processes responsible for the assembly and exhumation of HP continental subunits, thus adding to our understanding of how continental terranes behave during subduction.

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