The petrogenesis of Mg-Cr garnet peridotites in European metamorphic belts

Medaris, L. Gordon; Carswell, D. A.

doi:10.1007/978-94-010-9263-0_11

Cited by 86 publications

(78 citation statements)

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“…1000 C). This independent temperature estimate is, however, at least 200 C higher than that derived by standard thermobarometric methods using garnet, olivine and pyroxene mineral compositions (Medaris and Carswell 1990;Krogh and Carswell 1995;Brueckner and Medaris 1998;Medaris 1999). The latter methods consistently yield P±T estimates around 750±820 C and 28±32 kbar, which were interpreted by these authors to represent the peak-metamorphic P±T conditions for the formation of protogranular, porphyroclastic and equigranular garnets (box II in Figure 1).…”

Section: Discussionmentioning

confidence: 83%

“…The WGR (Mg-Cr type) garnet peridotites have been treated as a uniform group (Medaris and Carswell 1990;Krogh and Carswell 1995;Medaris 1998, 2000). The P±T conditions of the garnet±olivine assemblages, derived by standard thermobarometric methods, are characterized by: (a) upper mantle re-equilibration conditions (Medaris and Carswell 1990;Krogh and Carswell 1995;Van Roermund and Drury 1998;Medaris 1999); and (b) a P±T array that is consistent with a geothermal gradient of a cold continental lithosphere (Medaris and Carswell 1990;Krogh and Carswell 1995;Brueckner and Medaris 1998;Medaris 1999). In addition, Carswell (1986), Medaris and Carswell (1990) and Krogh and Carswell (1995) established a seven-stage tectonometamorphic evolution for the WGR Mg-Cr type garnet peridotites.…”

Section: Discussionmentioning

confidence: 99%

“…Accretion was followed by isobaric cooling towards cratonic lithosphere conditions (c. 3 GPa/800 C). The latter is re¯ected by the current mineral chemistries of garnet-bearing assemblages (Medaris and Carswell 1990;Krogh and Carswell 1995;Van Roermund et al 2000a). Final exhumation of the garnet peridotites occurred during the Scandian phase of the Caledonian Orogeny (420±390 Ma) together with the surrounding (U)HP gneisses.…”

Section: Introductionmentioning

confidence: 97%

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Non‐silicate inclusions in garnet from an ultra‐deep orogenic peridotite

et al. 2000

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Non-silicate solid inclusions in garnet from ultra-deep garnet peridotites, Otrùy, Western Gneiss Region, Norway, have been studied using light-optical, scanning and analytical electron microscopic techniques. Texturally, the investigated garnets reveal protogranular, porphyroclastic and equigranular microstructures. Protogranular and porphyroclastic garnets contain microstructural evidence of the former existence of`super-titanic' garnet. The microstructural evidence consists of exsolution textures involving rutile and ilmenite needles //`111b Grt as well as interstitial rutile grains. This exsolution microstructure is similar to the relict majoritic garnet microstructures found in the same peridotite. Some garnets contain both pyroxene and rutile exsolution.Other non-silicate mineral inclusions in protogranular and porphyroclastic garnet consist of nickel-iron alloys (Ni 99 Fe 01 ) and Cr-rich spinel. In addition, some protogranular, porphyroclastic and equigranular garnets contain composite Ni-Fe-Cu sulphide inclusions. The latter represent immiscible sulphide melt trapped within cracks that have healed.The original melting temperature of Ni-Fe-Cu sulphides was determined as being !1000 C and contrasts with temperatures derived from garnet±olivine±pyroxene mineral compositions using conventional geothermobarometry (c. 800 C/3 GPa). This contradiction is explained by the decoupling of microstructures and mineral chemistry; the microstructures were formed at higher temperatures than indicated by the current mineral chemistry. The decoupling of microstructures and current mineral chemistry has important applications for geodynamic models.

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Section: Discussionmentioning

confidence: 83%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Non‐silicate inclusions in garnet from an ultra‐deep orogenic peridotite

et al. 2000

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“…German, Austrian, Polish, and Czech parts of the Bohemian Massif; Black Forest in Germany, Vosges Mountains and Massif Central in France-as well as in the Variscan basement of the Alps (Medaris & Carswell, 1990;O'Brien & Rötzler, 2003;Massonne & O'Brien, 2003).…”

Section: A Model Of Geologic Evolution Of the Area From The Palaeozoicmentioning

confidence: 99%

“…Consequently, they are unique objects for realistic large-scale models of the Earth's geochemical and tectonic evolution (Griffin et al, 1999) as well as for interpreting the tectonic evolution of particular orogens (Liou et al, 2007 and references therein). Examples include the Caledonian, Variscan, and Alpine orogens of Europe, the Kokchetav Massif of Kazakhstan, and the Triassic Dabie-Sulu terrane in east-central China (for reviews, see Medaris, 1990;Brueckner & Medaris, 2000;O'Brien, 2000;Liou et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Late Palaeozoic to Triassic formations unconformably deposited over the Ronda peridotites (Betic Cordilleras): Evidence for their Variscan time of crustal emplacement

Galdeano

Cruz

2016

Estud. geol.

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The crust‐mantle interaction in continental subduction channels: Zircon evidence from orogenic peridotite in the Sulu orogen

Chen

Zheng

et al. 2016

JGR Solid Earth

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A combined secondary ion mass spectrometer and laser ablation‐(multicollector)‐inductively coupled plasma mass spectrometer study of zircon U‐Pb ages, trace elements, and O and Hf isotopes was carried out for orogenic peridotite and its host gneiss in the Sulu orogen. Newly grown zircon domains exhibit weak zoning or no zoning, relatively low Th/U ratios (<0.1), low heavy rare earth element (HREE) contents, steep middle rare earth element‐HREE patterns, negative Eu anomalies, and negative to low δ18O values of −11.3 to 0.9‰ and U‐Pb ages of 220 ± 2 to 231 ± 4 Ma. Thus, these zircons would have grown from metasomatic fluids during the early exhumation of deeply subducted continental crust. The infiltration of metasomatic fluids into the peridotite is also indicated by the occurrence of hydrous minerals such as amphibole, serpentine, and chlorite. In contrast, relict zircon domains exhibit magmatic zircon characteristics. Their U‐Pb ages and trace element and Hf‐O isotope compositions are similar to those for protolith zircons from ultrahigh‐pressure metamorphic rocks in the Dabie‐Sulu orogenic belt. Thus, these relict magmatic zircons would be physically transported into the peridotite by metasomatic fluids originated from the deeply subducted continental crust. Therefore, the peridotite underwent metasomatism by aqueous solutions derived from dehydration of the deeply subducted continental crust during the early exhumation. It is these crustally derived fluids that would have brought not only such chemical components as Zr and Si but also tiny zircon grains from the deeply subducted crustal rocks into the peridotite at the slab‐mantle interface in continental subduction channels. As such, the orogenic peridotite records the crust‐mantle interaction at the deep continental subduction zone.

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The petrogenesis of Mg-Cr garnet peridotites in European metamorphic belts

Cited by 86 publications

References 0 publications

Non‐silicate inclusions in garnet from an ultra‐deep orogenic peridotite

Non‐silicate inclusions in garnet from an ultra‐deep orogenic peridotite

Late Palaeozoic to Triassic formations unconformably deposited over the Ronda peridotites (Betic Cordilleras): Evidence for their Variscan time of crustal emplacement

The crust‐mantle interaction in continental subduction channels: Zircon evidence from orogenic peridotite in the Sulu orogen

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