scholarly journals The crust‐mantle interaction in continental subduction channels: Zircon evidence from orogenic peridotite in the Sulu orogen

2016 ◽  
Vol 121 (2) ◽  
pp. 687-712 ◽  
Author(s):  
Hai‐Yong Li ◽  
Ren‐Xu Chen ◽  
Yong‐Fei Zheng ◽  
Zhaochu Hu
Keyword(s):  
Continental Subduction ◽  
Orogenic Peridotite

Dating the Indian continental subduction and collisional thickening in the northwest Himalaya: Multichronology of the Tso Morari eclogites

Geology ◽  
2000 ◽  
Vol 28 (6) ◽  
pp. 487-490 ◽  
Author(s):  
Julia de Sigoyer ◽  
Valérie Chavagnac ◽  
Janne Blichert-Toft ◽  
Igor M. Villa ◽  
Béatrice Luais ◽  
...  
Keyword(s):  
Northwest Himalaya ◽  
Continental Subduction ◽  
Tso Morari

FAST SUBDUCTION, SLOW EXHUMATION: DATING CONTINENTAL SUBDUCTION BENEATH THE OMAN OPHIOLITE

2016 ◽  
Author(s):  
Joshua M. Garber ◽  
◽  
Matthew Rioux ◽  
Matthew Rioux ◽  
Andrew R.C. Kylander-Clark ◽  
...  
Keyword(s):  
Oman Ophiolite ◽  
Continental Subduction

Subcratonic and tectonic evolution of pyroxenite and eclogite with lamellar inclusions in garnet, Western Gneiss Region, Norway

2021 ◽  
Author(s):  
Dirk Spengler ◽  
Taisia A Alifirova ◽  
Herman L M van Roermund
Keyword(s):  
Stability Field ◽  
Mantle Lithosphere ◽  
Western Gneiss Region ◽  
Data Set ◽  
Entire Area ◽  
Ultra High Pressure ◽  
Planar Structures ◽  
Lamellar Inclusions ◽  
Al2o3 Concentration ◽  
Orogenic Peridotite

Abstract Oriented lamellar inclusions of pyroxene and rutile in mantle garnet often serve as evidence for majoritic and titaniferous precursor garnets, respectively. We investigated ten new such microstructure-bearing samples from six orogenic peridotite bodies in SW Norway, which originated in the E Greenland mantle lithosphere, petrologically and thermobarometrically. All pyroxenite (nine) and eclogite (one) samples have large (mainly porphyroclastic) garnet containing silicate and oxide inclusions with shape-preferred orientation relationship. These inclusions vary – dependent on their size – systematically in shape (acicular to subprismatic), width (∼50 μm to submicron size), spacing (several 100 to ∼10 μm) and phase (pyroxene to Ti-oxide ± pyroxene). Smaller inclusions can fill the space between larger inclusions, which support the idea of consecutive generations. The larger, early formed lamellae occur least frequent and are most poorly preserved. A younger generation of other inclusions decorates healed cracks cutting across cores but not rims of garnet. These inclusions comprise oxides, silicates, carbonates (aragonite, calcite, magnesite) and fluid components (N2, CO2, H2O). The older, homogeneously distributed inclusions comply texturally and stoichiometrically with an origin by exsolution from excess Si- and Ti-bearing garnet. Their microstructural systematic variation demonstrates a similar early evolution of pyroxenite and eclogite. The younger inclusions in planar structures are ascribed to a metasomatic environment that affected the subcratonic lithosphere. The microstructure-bearing garnets equilibrated at ∼3.7 GPa (840 °C) and ∼3.0 GPa (710 °C), at a cratonic geotherm related to 37–38 mW m−2 surface heat flow. Some associated porphyroclastic grains of Mg-rich pyroxene have exsolution lamellae of Ca-rich pyroxene and vice versa that indicate a preceding cooling event. Projected isobaric cooling paths intersect isopleths for excess Si in garnet at ∼1550 °C, if an internally consistent thermodynamic data set in the system Na2O–CaO–MgO–Al2O3–SiO2 (NCMAS) is applied (or ∼1600 °C if using CMAS). This temperature may confine the crystallisation of the unexsolved garnets at 100–120 km depths of the E Greenland subcratonic lithosphere. Tectonism is indicated in coastal and hinterland samples by porphyroclastic orthopyroxene with Al2O3 concentrations showing W-shaped profiles. Cores of associated large (>200 μm) recrystallised grains have low Al2O3 contents (0.18–0.23 wt.%). Both characteristics typify relatively short intracrystalline Al diffusion lengths and a prograde metamorphism into the diamond stability field. We assign this event to subduction during the Scandian orogeny. Porphyroclastic orthopyroxene in other samples shows U-shaped Al2O3 concentration profiles paired with long Al diffusion lengths (several 100 μm) that exceed the radius of recrystallised grains. Their cores contain high Al2O3 contents (0.65–1.16 wt.%), consistent with a diffusional overprint that obliterated prograde and peak metamorphic records. Unlike Al2O3, the CaO content in porphyroclastic orthopyroxene cores is uniform suggesting that early exhumation was subparallel to Ca isopleths in pressure–temperature space. The depth of sample origin implies that rock bodies of Scandian ultra-high pressure metamorphism occur in nearly the entire area between Nordfjord and Storfjord and from the coast towards ∼100 km in the hinterland, i.e. in a region much larger than anticipated from crustal eclogite.

Multi-stage sulfur and carbon mobility in fossil continental subduction zones: new insights from carbonate-bearing orogenic peridotites

2021 ◽  
Author(s):  
Giulia Consuma ◽  
Sonja Aulbach ◽  
Roberto Braga ◽  
Laure A.J. Martin ◽  
Peter Tropper ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Continental Subduction ◽  
Multi Stage

Some elements of continental subduction along the Himalayan front

1984 ◽  
Vol 105 (1-4) ◽  
pp. 263-278 ◽  
Author(s):  
L. Seeber ◽  
J.G. Armbruster
Keyword(s):  
Continental Subduction
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