Multi-stage exhumation of young UHP–HP rocks: Timescales of melt crystallization in the D’Entrecasteaux Islands, southeastern Papua New Guinea

Gordon, Stacia M.; Little, Timothy A.; Hacker, Bradley R.; Bowring, Samuel A.; Korchinski, Megan; Baldwin, Suzanne L.; Kylander-Clark, Andrew R.C.

doi:10.1016/j.epsl.2012.07.014

Cited by 68 publications

(153 citation statements)

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“…Recent highprecision geochronological and geochemical data from the Western Gneiss Region in Norway suggest that melting initiated during high-pressure metamorphism and continued during exhumation-related decompression (Labrousse et al, 2002(Labrousse et al, , 2011. However, data from the D'Entrecasteaux Islands UHP terrane suggests that melting took place after exhumation to lower crustal levels, rather than during UHP metamorphism (Gordon et al, 2012). These data suggest that, at least in this region, melting was a consequence of decompression rather than a driver of exhumation.…”

Section: J Warren: Exhumation Of (Ultra-)high-pressure Terranes 3mentioning

confidence: 50%

“…Many continental UHP terranes show evidence for migmatization in the mafic eclogite bodies as well as their host rocks, suggesting bulk weakening on a regional scale: see, for example, data from the Western Gneiss Region in Norway (Labrousse et al, 2002(Labrousse et al, , 2011, the Woodlark Basin (Hill et al, 1995;Gordon et al, 2012), the Dabie Sulu region (Wallis et al, 2005), the Kokchetav Massif (Ragozin et al, 2009) and the Greenland Caledonides (Lang and Gilotti, 2007). These studies suggest that conditions suitable for partial melting during the attainment of peak conditions or during exhumation are commonly experienced by UHP terranes.…”

Section: J Warren: Exhumation Of (Ultra-)high-pressure Terranes 3mentioning

confidence: 99%

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Exhumation of (ultra-)high-pressure terranes: concepts and mechanisms

Warren

2013

Solid Earth

111

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Abstract. The formation and exhumation of high and ultrahigh-pressure, (U)HP, rocks of crustal origin appears to be ubiquitous during Phanerozoic plate subduction and continental collision events. Exhumation of (U)HP material has been shown in some orogens to have occurred only once, during a single short-lived event; in other cases exhumation appears to have occurred multiple discrete times or during a single, long-lived, protracted event. It is becoming increasingly clear that no single exhumation mechanism dominates in any particular tectonic environment, and the mechanism may change in time and space within the same subduction zone. Subduction zone style and internal force balance change in both time and space, responding to changes in width, steepness, composition of subducting material and velocity of subduction. In order for continental crust, which is relatively buoyant compared to the mantle even when metamorphosed to (U)HP assemblages, to be subducted to (U)HP conditions, it must remain attached to a stronger and denser substrate. Buoyancy and external tectonic forces drive exhumation, although the changing spatial and temporal dominance of different driving forces still remains unclear. Exhumation may involve whole-scale detachment of the terrane from the subducting slab followed by exhumation within a subduction channel (perhaps during continued subduction) or a reversal in motion of the entire plate (eduction) following the removal of a lower part of the subducting slab. Weakening mechanisms that may be responsible for the detachment of deeply subducted crust from its stronger, denser substrate include strain weakening, hydration, melting, grain size reduction and the development of foliation. These may act locally to form narrow high-strain shear zones separating stronger, less-strained crust or may act on the bulk of the subducted material, allowing whole-scale flow. Metamorphic reactions, metastability and the composition of the subducted crust all affect buoyancy and overall strength. Future research directions include identifying temporal and spatial changes in exhumation mechanisms within different tectonic environments, and determining the factors that influence those changes.

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Section: J Warren: Exhumation Of (Ultra-)high-pressure Terranes 3mentioning

confidence: 50%

Section: J Warren: Exhumation Of (Ultra-)high-pressure Terranes 3mentioning

confidence: 99%

Exhumation of (ultra-)high-pressure terranes: concepts and mechanisms

Warren

2013

Solid Earth

111

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“…Many of the leucocratic melts seen in UHP terranes form by the introduction of hydrous fluid during the later stages of exhumation (Gilotti et al, 2014;Gordon et al, 2012;Labrousse et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Modeling the exhumation path of partially melted ultrahigh-pressure metapelites, North-East Greenland Caledonides

Lang

Gilotti

2015

Lithos

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Pseudosection modeling constrains the pressure-temperature (P-T) exhumation path of partially melted ultrahigh-pressure (UHP) metapelites exposed in the North-East Greenland UHP terrane. A robust peak P and T estimate of 3.6 GPa and 970°C based on mineral assemblages in nearby kyanite eclogites is the starting point for the P-T path. Although the peak assemblage for the metapelite is not preserved, the calculated modeled peak assemblage contained substantial clinopyroxene, garnet, phengite, K-feldspar and coesite with minor kyanite and rutile. Combining the pseudosection and observed textures, the decompression path crosses the coesite-quartz transition before reaching the dry phengite dehydration melting reaction where phengite is abruptly consumed. In the range of 2.5 to 2.2 GPa, clinopyroxene is completely consumed and garnet grows to its maximum volume and grossular content, matching the high grossular rims of relict megacrysts. Plagioclase joins the assemblage and the pseudosection predicts up to 12-13 vol.% melt in the supersolidus assemblage, which contained garnet, liquid, K-feldspar, plagioclase, kyanite, quartz and rutile. At this stage, the steep decompression path flattened out and became nearly isobaric. The melt crystallization assemblage that formed when the path crossed the solidus with decreasing temperature contains phengite, garnet, biotite, 2 feldspars, kyanite, quartz and rutile. Therefore, the path must have intersected the solidus at approximately 1.2 GPa, 825°C. The pseudosection predicts that garnet is consumed on the cooling path, but little evidence of late garnet consumption or other retrograde effects is observed. This may be due to partial melt loss from the rock. Isochemical PT-n and PT-X sections calculated along the P-T path display changes in mineral assemblage and composition that are consistent with preserved assemblages.

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“…Hoskins and Black, 2000), but the fact that there is no age difference between grains with and without oscillatory zoning (Zirakparvar et al, 2014) suggests that such recrystallization is not responsible for the uniformity of zircon U-Pb ages. Instead, the abundant geochronological evidence for the emplacement and deformation of partial melts formed during exhumation (Gordon et al, 2012;Hill et al, 1995) of the PNG (U)HP terrane can be used to confidently interpret 3.66 ± 0.13 Ma zircon age as recording the time when zircon crystallized in one of these exhumation-related partial melts. Because these exhumation related partial melts are not likely to have separated from their parent rocks, they can be classified as anatectic (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…Within the core of one of these domes occurs a mafic coesite-eclogite preserving a 5-8 Ma peak (U)HP metamorphic assemblage (Baldwin et al, 2004;Gordon et al, 2012;Monteleone et al, 2007;Zirakparvar et al, 2011). While it is understood that exhumation of the core zone rocks is intrinsically related to rifting in the Woodlark Rift, there is still some debate over exhumation mechanisms (Little et al, 2011;Martinez et al, 2001;Webb et al, 2008).…”

Section: Tectonic Evolution Of the Woodlark Riftmentioning

confidence: 98%

Cathodoluminescence guided zircon Hf isotope depth profiling: Mobilization of the Lu–Hf system during (U)HP rock exhumation in the Woodlark Rift, Papua New Guinea

Zirakparvar

2015

Lithos

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Multi-stage exhumation of young UHP–HP rocks: Timescales of melt crystallization in the D’Entrecasteaux Islands, southeastern Papua New Guinea

Cited by 68 publications

References 69 publications

Exhumation of (ultra-)high-pressure terranes: concepts and mechanisms

Exhumation of (ultra-)high-pressure terranes: concepts and mechanisms

Modeling the exhumation path of partially melted ultrahigh-pressure metapelites, North-East Greenland Caledonides

Cathodoluminescence guided zircon Hf isotope depth profiling: Mobilization of the Lu–Hf system during (U)HP rock exhumation in the Woodlark Rift, Papua New Guinea

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