Eclogites of the D'Entrecasteaux Islands

Davies, H. L.; Warren, R.W.

doi:10.1007/bf00310778

Cited by 57 publications

(46 citation statements)

References 23 publications

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“…1b) and provide constraints on the timing of collision and obduction events, and the duration and polarity of subduction preceding obduction. Structural investigations of the largest ophiolite unit in New Guinea (the Papuan Ultramafic belt) imply southwest-directed obduction on top of the Emo metamorphics, whose geochemistry points to a backarc origin (Worthing and Crawford, 1996), during the terminal stage of a northeast-dipping subduction zone (Davies and Warren, 1992;Davies, 2012). Additional evidence for this fossil subduction zone is represented by the Pocklington Trough ( Fig.…”

Section: Geological and Tectonic History Of New Guinea Regionmentioning

confidence: 96%

“…The supra-subduction zone (forearc) origin of (part of) the ophiolites and their Maastrichtian age (based on microfossils; Belford, 1976) imply northeast-directed subduction initiation at ∼71-65 Ma. Furthermore, Paleocene metamorphics of the subduction complex (Davies and Warren, 1992) and ∼59 Ma arc volcanics at Cape Vogel (Walker and McDougall, 1982) imply north to northeast-dipping Paleocene subduction.…”

Section: Geological and Tectonic History Of New Guinea Regionmentioning

confidence: 99%

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Australian plate motion and topography linked to fossil New Guinea slab below Lake Eyre

Schellart

Spakman

2015

Earth and Planetary Science Letters

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Unravelling causes for absolute plate velocity change and continental dynamic topography change is challenging because of the interdependence of large-scale geodynamic driving processes. Here, we unravel a clear spatio-temporal relation between latest Cretaceous-Early Cenozoic subduction at the northern edge of the Australian plate, Early Cenozoic Australian plate motion changes and Cenozoic topography evolution of the Australian continent. We present evidence for a ∼4000 km wide subduction zone, which culminated in ophiolite obduction and arc-continent collision in the New Guinea-Pocklington Trough region during subduction termination, coinciding with cessation of spreading in the Coral Sea, a ∼5 cm/yr decrease in northward Australian plate velocity, and slab detachment. Renewed northward motion caused the Australian plate to override the sinking subduction remnant, which we detect with seismic tomography at 800-1200 km depth in the mantle under central-southeast Australia at a position predicted by our absolute plate reconstructions. With a numerical model of slab sinking and mantle flow we predict a long-wavelength subsidence (negative dynamic topography) migrating southward from ∼50 Ma to present, explaining Eocene-Oligocene subsidence of the Queensland Plateau, ∼330 m of late Eocene-early Oligocene subsidence in the Gulf of Carpentaria, Oligocene-Miocene subsidence of the Marion Plateau, and providing a first-order fit to the present-day, ∼200 m deep, topographic depression of the Lake Eyre Basin and Murray-Darling Basin. We propound that dynamic topography evolution provides an independent means to couple geological processes to a mantle reference frame. This is complementary to, and can be integrated with, other approaches such as hotspot and slab reference frames.

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Section: Geological and Tectonic History Of New Guinea Regionmentioning

confidence: 96%

Section: Geological and Tectonic History Of New Guinea Regionmentioning

confidence: 99%

Australian plate motion and topography linked to fossil New Guinea slab below Lake Eyre

Schellart

Spakman

2015

Earth and Planetary Science Letters

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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%

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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“…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: 94%

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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Eclogites of the D'Entrecasteaux Islands

Cited by 57 publications

References 23 publications

Australian plate motion and topography linked to fossil New Guinea slab below Lake Eyre

Australian plate motion and topography linked to fossil New Guinea slab below Lake Eyre

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

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