Diapiric exhumation of Earth's youngest (UHP) eclogites in the gneiss domes of the D'Entrecasteaux Islands, Papua New Guinea

Little, Tim; Hacker, Bradley R.; Gordon, Stacia M.; Baldwin, Suzanne L.; Fitzgerald, Paul G.; Ellis, Susan; Korchinski, Megan

doi:10.1016/j.tecto.2011.06.006

Cited by 161 publications

(382 citation statements)

References 133 publications

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“…[3] The D'Entrecasteaux Islands ultrahigh-pressure terrane in Papua New Guinea, like most UHP terranes, consists dominantly of quartzofeldspathic gneiss with 5-10% mafic and minor ultramafic blocks of chiefly meter to decameter scale Little et al, 2011]. Much of the mafic material is amphibolite, but variably retrogressed eclogite is widely distributed.…”

Section: D'entrecasteaux Islandsmentioning

confidence: 99%

“…For example, if the terrane is exhuming as a diapiric sheet [Little et al, 2011], with gently dipping foliations at Earth's surface and near-vertical foliations at depth, the slow axis of anisotropy should change downward from vertical to horizontal. If the terrane is exhuming as an axially symmetric diapir with a constrictional flow field, we expect a vertically plunging unique fast axis of anisotropy.…”

Section: Comparison With Seismic Observationsmentioning

confidence: 99%

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Predicted velocity and density structure of the exhuming Papua New Guinea ultrahigh-pressure terrane

et al. 2011

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[1] New electron backscatter diffraction measurements show that the Papua New Guinea (PNG) ultrahigh-pressure (UHP) terrane is dominated by rocks with weakly oriented quartz and feldspar and less abundant strongly oriented hornblende, clinopyroxene, and mica. Velocities measured at high pressures (600 MPa) show that V P is 5.8-6.3 km/s for gneiss samples, 6.5-7.7 km/s for amphibolite, and 7.7-8.2 km/s for eclogite and V S is 3.4-3.9 km/s for gneiss, 4.0-4.4 km/s for amphibolite, and 4.5-4.6 km/s for eclogite. Velocities and anisotropies calculated from mineral crystal preferred orientations (CPOs) are equivalent to within 5% of the measured values. The highest seismic anisotropy for the PNG terrane is in amphibolite at 8% and 7% for V P and V S , respectively. Calculations of seismic velocities at depth based on predicted mineral assemblages indicate that the exhuming UHP terrane is of dominantly mafic composition below ∼20 km depth. Anisotropy in the PNG terrane is expected to be quite low and is controlled by the orientation of the foliation. If observable, changes in anisotropy across the exhuming body may be used to differentiate among the different proposed mechanisms of UHP exhumation.

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Section: D'entrecasteaux Islandsmentioning

confidence: 99%

Section: Comparison With Seismic Observationsmentioning

confidence: 99%

Predicted velocity and density structure of the exhuming Papua New Guinea ultrahigh-pressure terrane

et al. 2011

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“…Mafic eclogites are inferred to have originated as dikes that were metamorphosed in situ and now occur as eclogite boudins within strongly folded and isoclinally folded garnet-bearing quartzofeldspathic host gneisses (23)(24)(25)(26). Foliation in the mafic eclogites is roughly concordant with that in the host gneiss.…”

Section: Geologic Setting and Sample Descriptionmentioning

confidence: 95%

“…Apatite fission track ages for the coesite eclogite host gneiss (0.6 ± 0.2 Ma) indicate exhumation to shallow crustal levels by the middle Pleistocene (27). Geologic and structural data (25), electron backscatter diffraction measurements, and phase relations (28) provide additional outcrop and regional-scale geochemical (29) and P-T-t-D constraints for the UHP terrane (30). These studies provide the context for interpretation of the coesite eclogite Ar and Ne data presented here.…”

Section: Geologic Setting and Sample Descriptionmentioning

confidence: 96%

Atmospheric Ar and Ne returned from mantle depths to the Earth’s surface by forearc recycling

Baldwin¹,

Das²

2015

Proc. Natl. Acad. Sci. U.S.A.

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In subduction zones, sediments, hydrothermally altered lithosphere, fluids, and atmospheric gases are transported into the mantle, where ultrahigh-pressure (UHP) metamorphism takes place. However, the extent to which atmospheric noble gases are trapped in minerals crystallized during UHP metamorphism is unknown. We measured Ar and Ne trapped in phengite and omphacite from the youngest known UHP terrane on Earth to determine the composition of Ar and Ne returned from mantle depths to the surface by forearc recycling. An 40 Ar/ 39 Ar age [7.93 ± 0.10 My (1σ)] for phengite is interpreted as the timing of crystallization at mantle depths and indicates that 40 Ar/ 39 Ar phengite ages reliably record the timing of UHP metamorphism. Both phengite and omphacite yielded atmospheric 38 Ar/ 36 Ar and 20 Ne/ 22 Ne. Our study provides the first documentation, to our knowledge, of entrapment of atmospheric Ar and Ne in phengite and omphacite. Results indicate that a subduction barrier for atmosphericderived noble gases does not exist at mantle depths associated with UHP metamorphism. We show that the crystallization age together with the isotopic composition of nonradiogenic noble gases trapped in minerals formed during subsolidus crystallization at mantle depths can be used to unambiguously assess forearc recycling of atmospheric noble gases. The flux of atmospheric noble gas entering the deep Earth through subduction and returning to the surface cannot be fully realized until the abundances of atmospheric noble gases trapped in exhumed UHP rocks are known.subduction | UHP metamorphism | geochronology | noble gas | atmosphere

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“…19), in which the Taurus-Zagros Mountains of Iran and Turkey refl ect the active continental margin (Turkey, Iran, Afghanistan) colliding with the passive margin (Arabia), and the Greater Caucasus represents an early stage of this collision (Forte et al, 2012); (7) the Eratosthenes seamount-Cyprus collision is an active continental arc (Anatolia-Cyprus) and a passive margin (Eratosthenes seamount-Africa); (8) an ongoing collision exists between the Australian continent and the north-dipping Banda-New Britain subduction zone, with the polarity of subduction undergoing a change from north to south dipping in New Guinea (type A, Fig. 19; Schellart et al, 2006;Little et al, 2011); and (9) in addition, Hall (2002) and Schellart et al (2006) document several recent arc-arc and arc-microcontinent collisions in the complex marginal basin region of the SW Pacifi c.…”

Section: Collisionsmentioning

confidence: 99%

Tectonics: 50 years after the Revolution

Moores

Yıkılmaz

Kellogg

2013

The Web of Geological Sciences: Advances, Impacts, and Interactions

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Diapiric exhumation of Earth's youngest (UHP) eclogites in the gneiss domes of the D'Entrecasteaux Islands, Papua New Guinea

Cited by 161 publications

References 133 publications

Predicted velocity and density structure of the exhuming Papua New Guinea ultrahigh-pressure terrane

Predicted velocity and density structure of the exhuming Papua New Guinea ultrahigh-pressure terrane

Atmospheric Ar and Ne returned from mantle depths to the Earth’s surface by forearc recycling

Tectonics: 50 years after the Revolution

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