Late Miocene coesite-eclogite exhumed in the Woodlark Rift

Baldwin, Suzanne L.; Webb, Laura E.; Monteleone, B. D.

doi:10.1130/g25144a.1

Cited by 112 publications

(178 citation statements)

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“…Much of the mafic material is amphibolite, but variably retrogressed eclogite is widely distributed. Metamorphic conditions during the peak of subduction reached ∼700-750°C and >3.0-3.6 GPa, based on mineral compositions from a coesitebearing eclogite [Davies and Warren, 1992;Monteleone et al, 2007;Baldwin et al, 2008]. The exhumation path is partly constrained by amphibolite-facies metamorphic overprinting at pressures of ∼1 GPa down to 0.5 GPa at maximum temperatures of 700°C [Hill and Baldwin, 1993].…”

Section: D'entrecasteaux Islandsmentioning

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%

“…The amphibolite samples have a moderate-to well-developed foliation and lineation defined by hornblende. Sample PNG/08-10 is from the coesite-bearing eclogite of Baldwin et al [2008]. The eclogite has a moderately developed foliation and lineation defined by pyroxene.…”

Section: Sample Locations Mineralogy and Microstructurementioning

confidence: 99%

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

et al. 2011

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“…The coesite eclogite studied (sample 89321) is the youngest known exhumed UHP rock on Earth, and it was sampled from Tomabaguna Island in eastern Papua New Guinea (22). 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).…”

Section: Geologic Setting and Sample Descriptionmentioning

confidence: 99%

“…One objective was to assess whether results could be interpreted within a geologic and tectonic context or yielded anomalously old 40 (22). Timing of peak metamorphism based on 40 Ar/ 39 Ar phengite (this study), Lu-Hf garnet (27), and U-Pb zircon (31) ages.…”

Section: Geologic Setting and Sample Descriptionmentioning

confidence: 99%

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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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Zircon growth in (U)HP quartzo-feldspathic host gneisses exhumed in the Woodlark Rift of Papua New Guinea

Zirakparvar

Baldwin

Schmitt

2014

Geochem. Geophys. Geosyst.

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Late Miocene coesite-eclogite exhumed in the Woodlark Rift

Cited by 112 publications

References 1 publication

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

Zircon growth in (U)HP quartzo-feldspathic host gneisses exhumed in the Woodlark Rift of Papua New Guinea

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