P–T evolution of ‘crustal’ garnet peridotites and included pyroxenites from Nonsberg area (upper Austroalpine), NE Italy: from the wedge to the slab

Nimis, Paolo; Morten, Lauro

doi:10.1016/s0264-3707(99)00029-0

Cited by 64 publications

(50 citation statements)

References 42 publications

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“…Obata & Morten 1987;Nimis & Morten 2000;Tumiati 2002;Tumiati et al 2003). The protogranular coarse-grained spinel peridotites equilibrated at P c. 1.5 GPa, T c. 1250 ~ (Nimis & Morten 2000), at an uncertain but in any case old age (t > 500 Ma ;Ntaflos et al 1993;Th6ni 1999).…”

Section: Ptt-pathmentioning

confidence: 98%

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

Ranalli

Martin

Mahatsente

2005

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Section: Ptt-pathmentioning

confidence: 98%

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

Ranalli

Martin

Mahatsente

2005

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“…Orogenic peridotites are common in many UHP terranes (Brueckner and Medaris 2000;Nimis and Morten 2000;Zhang et al 2000), providing us with an excellent target to study the reaction of subduction-zone fluids with the mantle wedge at the slab-mantle interface in subduction channels (Scambelluri et al 2007;Zheng 2012). According to the occurrence of crustal derivatives in the orogenic peridotites, two types of crustal metasomatism may take place at mantle depths (Zheng 2012).…”

Section: Crust-mantle Interaction In Subduction Channelmentioning

confidence: 99%

Geochemistry of continental subduction-zone fluids

2014

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The composition of continental subduction-zone fluids varies dramatically from dilute aqueous solutions at subsolidus conditions to hydrous silicate melts at supersolidus conditions, with variable concentrations of fluid-mobile incompatible trace elements. At ultrahigh-pressure (UHP) metamorphic conditions, supercritical fluids may occur with variable compositions. The water component of these fluids primarily derives from structural hydroxyl and molecular water in hydrous and nominally anhydrous minerals at UHP conditions. While the breakdown of hydrous minerals is the predominant water source for fluid activity in the subduction factory, water released from nominally anhydrous minerals provides an additional water source. These different sources of water may accumulate to induce partial melting of UHP metamorphic rocks on and above their wet solidii. Silica is the dominant solute in the deep fluids, followed by aluminum and alkalis. Trace element abundances are low in metamorphic fluids at subsolidus conditions, but become significantly elevated in anatectic melts at supersolidus conditions. The compositions of dissolved and residual minerals are a function of pressure-temperature and whole-rock composition, which exert a strong control on the trace element signature of liberated fluids. The trace element patterns of migmatic leucosomes in UHP rocks and multiphase solid inclusions in UHP minerals exhibit strong enrichment of large ion lithophile elements (LILE) and moderate enrichment of light rare earth elements (LREE) but depletion of high field strength elements (HFSE) and heavy rare earth elements (HREE), demonstrating their crystallization from anatectic melts of crustal protoliths. Interaction of the anatectic melts with the mantle wedge peridotite leads to modal metasomatism with the generation of new mineral phases as well as cryptic metasomatism that is only manifested by the enrichment of fluid-mobile incompatible trace elements in orogenic peridotites. Partial melting of the metasomatic mantle domains gives rise to a variety of mafic igneous rocks in collisional orogens and their adjacent active continental margins. The study of such metasomatic processes and products is of great importance to understanding of the mass transfer at the slab-mantle interface in subduction channels. Therefore, the property and behavior of subduction-zone fluids are a key for understanding of the crust-mantle interaction at convergent plate margins.

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“…Off-craton Basalt Cenozoic Proterozoic Henjes Kunst and Altherr (1992) Lashaine and Labait, Tanzania Craton Ankaramite and carbonitite Cenozoic Proterozoic Reid et al (1975), Rhodes and Dawson (1975), Ridley and Dawson (1975), Bishop et al (1978), Henjes Kunst and Altherr (1992) Hunter and Smith (1981), Ehrenberg (1982), Smith and Ehrenberg (1984), Smith et al (1991), Roden Song et al (2004Song et al ( , 2005Song et al ( , 2007 Dabie-Sulu, China Massif Eclogite and gneiss Mesozoic Mesozoic Zhang et al (1994Zhang et al ( , 2000bZhang et al ( , 2003Zhang et al ( , 2004aZhang et al ( , b, 2005Zhang et al ( , 2007c, Zhang and Liou (1998), Liu et al (1995), Hacker et al (1997), Liou and Zhang (1998), Yang and Jahn (2000), You et al (2000), Yang (2003) (1987), Godard et al (1996), Rampone and Morten (2001), Godard and Martin (2000), Nimis and Morten (2000) Scandian, Sweden Lens Gneiss and schist Paleozoic Archean Brueckner et al (2004) Bohemian, Austria and Czech…”

Section: Marsabit and Chyulu Kenyamentioning

confidence: 99%

“…Alps and Sulu-Dabie mountains are the typical and important orogenic garnet peridotite distributing areas (Fig. 1) and have been studied in more detail (e.g., Obata and Morten 1987;Green et al 1997;Nimis and Morten 2000;Li 1994;Zhang et al 1994;Xu et al 2001Xu et al , 2002Yang et al 2007). The TRANSALP Working Group (2002) proposed a crocodile model of the lithospheric structure beneath Eastern Alps.…”

Section: Further Constraints On the Composition Of Lithospheric Mantlementioning

confidence: 99%

Geochemical syntheses among the cratonic, off-cratonic and orogenic garnet peridotites and their tectonic implications

Zhang

Tang

et al. 2010

Int J Earth Sci (Geol Rundsch)

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Garnet-bearing mantle peridotites, occurring as either xenoliths in volcanic rocks or lenses/massifs in high-pressure and ultrahigh-pressure terrenes within orogens, preserve a record of deep lithospheric mantle processes. The garnet peridotite xenoliths record chemical equilibrium conditions of garnet-bearing mineral assemblage at temperatures (T) ranging from *700 to 1,400°C and pressures (P) [ 1. 6-8.9 GPa, corresponding to depths of *52-270 km. A characteristic mineral paragenesis includes Cr-bearing pyropic garnet (64-86 mol% pyrope; 0-10 wt% Cr 2 O 3 ), Cr-rich diopside (0.5-3.5 wt% Cr 2 O 3 ), Al-poor orthopyroxene (0-5 wt% Al 2 O 3 ), high-Cr spinel (Cr/(Cr ? Al) 9 100 atomic ratio = 2-86) and olivine (88-94 mol% forsterite). In some cases, partial melting, re-equilibration involving garnet-breakdown, deformation, and mantle metasomatism by kimberlitic and/or carbonatitic melt percolations are documented. Isotope model ages of Archean and Proterozoic are ubiquitous, but Phanerozoic model ages are less common. In contrast, the orogenic peridotites were subjected to ultrahigh-pressure (UHP) metamorphism at temperature ranging from *700 to 950°C and pressure [3.5-5.0 GPa, corresponding to depths of [110-150 km. The petrologic comparisons between 231 garnet peridotite xenoliths and 198 orogenic garnet peridotites revealed that (1) bulk-rock REE (rare earth element) concentrations in xenoliths are relatively high, (2) clinopyroxene and garnet in orogenic garnet peridotites show a highly fractionated REE pattern and Ce-negative anomaly, respectively, (3) Fo contents of olivines for off-cratonic xenolith are in turn lower than those of orogenic garnet and cratonic xenolith but mgnumber of garnet for orogenic is less than that of offcratonic and on-cratonic xenolith, (4) Al 2 O 3 , Cr 2 O 3 , CaO and Cr# of pyroxenes and chemical compositions of whole rocks are very different between these garnet peridotites, (5) orogenic garnet peridotites are characterized by low T and high P, off-cratonic by high T and low P, and cratonic by medium T and high P and (6) garnet peridotite xenoliths are of Archean or Proterozoic origin, whereas most of orogenic garnet peridotites are of Phanerozoic origin. Taking account of tectonic settings, a new orogenic garnet peridotite exhumation model, crustmantle material mixing process, is proposed. The composition of lithospheric mantle is additionally constrained by comparisons and compiling of the off-cratonic, oncratonic and orogenic garnet peridotite.

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P–T evolution of ‘crustal’ garnet peridotites and included pyroxenites from Nonsberg area (upper Austroalpine), NE Italy: from the wedge to the slab

Cited by 64 publications

References 42 publications

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

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

Geochemistry of continental subduction-zone fluids

Geochemical syntheses among the cratonic, off-cratonic and orogenic garnet peridotites and their tectonic implications

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