Continental subduction and exhumation: an example from the Ulten Unit, Tonale Nappe, Eastern Austroalpine

Ranalli, Giorgio; Martin, Silvana; Mahatsente, R.

doi:10.1144/gsl.sp.2005.243.01.12

Cited by 14 publications

(14 citation statements)

References 56 publications

(81 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similarly to old UHP belts, such as those of the Variscan and Alpine orogens (Spalla et al, 1996;Duchêne et al, 1997;Ranalli et al, 2005) and younger HP terranes in SWPacific-style orogenic belts (Lister and Forster, 2002), the fast exhumation of the Lanterman Range HP/UHP rocks can be related to buoyancy-driven extrusion (Chemenda et al, 1995(Chemenda et al, , 1996Ernst et al, 1997;Ranalli et al, 2005) during the early, nearly isothermal, decompression and to extensional tectonics in the super-subduction domain of the overriding plate resulting from rollback of the hinge of the subducting oceanic lithosphere.…”

Section: P-t Paths and Geodynamic Implicationsmentioning

confidence: 99%

Ultrahigh‐pressure metamorphism at the Lanterman Range (northern Victoria Land, Antarctica)

2011

View full text Add to dashboard Cite

Northern Victoria Land is a key area for the Ross Orogen-a Palaeozoic fold belt formed at the palaeo-Pacific margin of Gondwana and also known as the Delamerian and Tyennan Orogeny in southern Australia, and Tasmania, respectively. A narrow and discontinuous high-to ultrahigh-pressure (HP/UHP) belt, consisting of mafic and ultramafic rocks (including garnet-bearing types) within a metasedimentary sequence of gneisses and quartzites, is exposed at the Lanterman Range (northern Victoria Land), at the boundary between two main lithotectonic terranes (the Wilson and Bowers terranes). Mesostructural and microstructural relations between eclogitic boudins and country gneisses are, in some areas, characterized by interlayering with sharp contacts on a cm scale. Geological, petrological and geochronological studies indicate that mafic, ultramafic and felsic host rocks underwent a common metamorphic evolution with an UHP eclogite-facies stage % 500 Ma ago at temperatures of up to % 8508C and pressures up to 3.3 GPa. The retrograde P-T path is similar and, indeed, it overlaps in every lithology; it is a nearly isothermal path from UHP conditions up to deep crustal levels, and becomes a cooling-unloading path from intermediate to shallow levels. The discovery of UHP rocks at the Lanterman Range yields eclogite-facies rocks of this area among the rare UHP rocks of the world and represents the only known locality in Antarctica and along the entire palaeo-Pacific margin of Gondwana during the Ross-Delamerian-Tyennan Orogen.

show abstract

Section: P-t Paths and Geodynamic Implicationsmentioning

confidence: 99%

Ultrahigh‐pressure metamorphism at the Lanterman Range (northern Victoria Land, Antarctica)

2011

View full text Add to dashboard Cite

show abstract

“…The total buoyancy is obtained from the density anomalies by integration (for details see Mahatsente and Ranalli, 2004). This model has been extended to subduction of continental lithosphere (Ranalli et al, 2005), assuming that continental material arrives at the subduction zone at a specified time after the beginning of subduction. The resulting total buoyancy (algebraic sum of negative thermal buoyancy due to temperature anomalies, positive and negative buoyancies related to phase changes, and positive compositional buoyancy of the continental crust) is obtained as a function of time since the beginning of subduction.…”

Section: Models For Slab Detachmentmentioning

confidence: 99%

“…However, the width of the plume is not an important factor in the present first-order model, as the total strength of the slab is estimated along 1-D profiles across the slab above the plume head. The temperature distribution within the slab at the beginning of slab-plume interaction is obtained from the thermal models of Mahatsente and Ranalli (2004) and Ranalli et al (2005). The plume head is assumed to be at T = 1900 K, that is, approximately 300 K hotter than the surrounding mantle.…”

Section: Models For Slab Detachmentmentioning

confidence: 99%

Slab detachment and mantle plume upwelling in subduction zones: An example from the Italian South-Eastern Alps

Macera¹,

Gasperini²,

Ranalli³

et al. 2008

Journal of Geodynamics

Self Cite

View full text Add to dashboard Cite

The geochemical properties of the South-Eastern Alps volcanics (SEAV, Eocene age) call for a within-plate origin of the most primitive basalts, in contrast to the widespread calc-alkaline magmatism which developed some million years later northwestwards along the Periadriatic Lineament. The two contrasting magmatic suites that coexist in the Alpine area define binary mixing relationships in the Sr-Nd and Sr-Pb isotopic space, the end members of which being a crustal component (e.g. lower continental crust) and a HIMU-DMM component (e.g. the SEAV). The occurrence of a HIMU (high μ = high 238 U/ 204 Pb) component, which normally traces mantle plumes of deep mantle origin, in a tectonic regime dominated by collision tectonics (the tertiary convergence of European and Adriatic plates) can be explained by slab detachment and ensuing upwelling of mantle material through the lithospheric gap. We combine geochemical data and geophysical modelling to unravel the evolution of the Alpine slab after interaction with plume material and the genesis of the Alpine magmatism. The combination of changes in negative buoyancy caused by continental subduction and softening of a part of the slab caused by slab-plume interaction may act as a regulator for the time of slab breakoff and, consequently, for the variations of magmatism in the overriding lithosphere above a subduction zone. The thermal evolution of a subducting slab is modified by contact with the plume material which decreases significantly the total strength of the slab and favours slab detachment. Interactions between the HIMU component and the shallower depleted mantle can account for the geochemical characteristics of the SEAV. Counterflows of plume material towards the top of the subducting slab may also increase heating and partial melting of the overriding mantle wedge, giving rise to the calc-alkaline suite outcropping in the proximity of the Periadriatic Lineament.

show abstract

“…, 1995, 1996; Ernst et al. , 1995, 1997; Ernst, 2001; Ranalli, 2003; Ranalli et al. , 2005) or, in terms of the bulk rheology (effective viscosity) of the exhuming UHP rocks in the subduction channel (Mancktelow, 1995; Burov et al.…”

Section: Mechanics Of Exhumationmentioning

confidence: 99%

“…, 1997; Ernst, 2001; Lardeaux et al. , 2001), the condition for exhumation can be written approximately as (Ranalli, 2003; Ranalli et al. , 2005; only absolute values are considered) where Δ ρ c is the density difference between the exhuming material and the surrounding mantle, g is the acceleration of gravity, D and L respectively the thickness and downdip length of the exhuming slice, δ the subduction dip angle, and τ the resistance to shear detachment along shear zones.…”

Section: Mechanics Of Exhumationmentioning

confidence: 99%

Ultrahigh‐pressure metamorphism and exhumation of garnet‐bearing ultramafic rocks from the Lanterman Range (northern Victoria Land, Antarctica)

Palmeri

Ghiribelli

Ranalli

et al. 2007

Journal Metamorphic Geology

View full text Add to dashboard Cite

Northern Victoria Land is a key area for the Ross Orogen – a Palaeozoic foldbelt formed at the palaeo-Pacific margin of Gondwana. A narrow and discontinuous high- to ultrahigh-pressure (UHP) belt, consisting of mafic and ultramafic rocks (including garnet-bearing types) within a metasedimentary sequence of gneisses and quartzites, is exposed at the Lanterman Range (northern Victoria Land). Garnet-bearing ultramafic rocks evolved through at least six metamorphic stages. Stage 1 is defined by medium-grained garnet + olivine + low-Al orthopyroxene + clinopyroxene, whereas finer-grained garnet + olivine + orthopyroxene + clinopyroxene + amphibole constitutes the stage 2 assemblage. Stage 3 is defined by kelyphites of orthopyroxene + clinopyroxene + spinel ± amphibole around garnet. Porphyroblasts of amphibole replacing garnet and clinopyroxene characterize stage 4. Retrograde stages 5 and 6 consist of tremolite + Mg-chlorite ± serpentine ± talc. A high-temperature (∼950 °C), spinel-bearing protolith (stage 0), is identified on the basis of orthopyroxene + clinopyroxene + olivine + spinel + amphibole inclusions within stage 1 garnet. The P–T estimates for stage 1 are indicative of UHP conditions (3.2–3.3 GPa and 764–820 °C), whereas stage 2 is constrained between 726–788 °C and 2.6–2.9 GPa. Stage 3 records a decompression up to 1.1–1.3 GPa at 705–776 °C. Stages 4, 5 and 6 reflect uplift and cooling, the final estimates yielding values below 0.5 GPa at 300–400 °C. The retrograde P–T path is nearly isothermal from UHP conditions up to deep crustal levels, and becomes a cooling–unloading path from intermediate to shallow levels. The garnet-bearing ultramafic rocks originated in the mantle wedge and were probably incorporated into the subduction zone with felsic and mafic rocks with which they shared the subsequent metamorphic and geodynamic evolution. The density and rheology of the subducted rocks are compatible with detachment of slices along the subduction channel and gravity-driven exhumation

show abstract

Continental subduction and exhumation: an example from the Ulten Unit, Tonale Nappe, Eastern Austroalpine

Abstract: Some exhumed complexes in collisional belts consist of continental basement containing slivers of mafic and ultramafic material showing evidence of UHP metamorph-

Cited by 14 publications

References 56 publications

Ultrahigh‐pressure metamorphism at the Lanterman Range (northern Victoria Land, Antarctica)

Ultrahigh‐pressure metamorphism at the Lanterman Range (northern Victoria Land, Antarctica)

Slab detachment and mantle plume upwelling in subduction zones: An example from the Italian South-Eastern Alps

Ultrahigh‐pressure metamorphism and exhumation of garnet‐bearing ultramafic rocks from the Lanterman Range (northern Victoria Land, Antarctica)

Contact Info

Product

Resources

About