Calculated mineral equilibria for eclogites in CaO–Na2O–FeO–MgO–Al2O3–SiO2–H2O: application to the Pouébo Terrane, Pam Peninsula, New Caledonia

Carson, Chris; Powell, Christopher A.; Clarke, Graeme

doi:10.1046/j.1525-1314.1999.00177.x

Cited by 177 publications

(169 citation statements)

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“…To avoid problems of fractionation (Carson et al 1999;2000;Marmo et al 2002), we have chosen to model a mylonitic eclogitized hornblendite (HP mylonitic rock deriving from a hornblendite, sample cc4/4), reasonably representing the most pervasively re-equilibrated mineral association. The sample has been modelled in the NCFMASH (Na 2 O, CaO, FeO, MgO, Al 2 O 3 , SiO 2 , and H 2 O) system; K 2 O and TiO 2 have not been considered as they are present only in phengite and rutile, respectively.…”

Section: P-t Estimatesmentioning

confidence: 99%

Interplay between deformation and metamorphism during eclogitization of amphibolites in the Sesia–Lanzo Zone of the Western Alps

Gosso

Messiga

Rebay

et al. 2010

International Geology Review

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Interactions of fabric evolution and chemical parameters driving reaction progress during the amphibolite-to-eclogite transition were investigated in eclogitized amphibolites of the Western Alps. In the Sesia-Lanzo Zone (SLZ), mafic rocks ranging from eclogitized hornblendites to true eclogites occur as layers and boudins within micaschists and are characterized by different modal amounts of amphibole, omphacite, zoisite, garnet, and phengite, constituting the Alpine HP assemblage. Across narrow zones, this array of lithologies displays gradients in planar fabrics characterized by coronitic, S-tectonitic, and mylonitic textures with different extents of eclogitization. Eclogitic parageneses are controlled not only by the bulk rock composition of the protoliths but also by the degree of fabric evolution. This is the case for omphacite occurrence, which is constrained by plagioclase composition and modal amount (NK parameter) in the protoliths, whereas the increase in modal omphacite and the concomitant decrease in modal amphibole in rocks with high NK are controlled by the strain rate. Protoliths with a low NK content develop the amphibole + garnet + epidote assemblage in eclogitized hornblendites. In protoliths with higher NK values, the co-existence of amphibole with garnet, omphacite, and epidote occurs only for low-to-medium strain textures (e.g. coronites and S-tectonites), whereas an amphibole-free assemblage defines a mylonitic foliation; in this case, amphibole relics are present exclusively as armoured inclusions in garnets and omphacite porphyroclasts. Thus, amphibole persists in the eclogitic assemblage at pressures exceeding the experimentally determined amphibole stability field. Values of confining pressure under which Sesia-Lanzo mafic rocks re-equilibrated during Alpine subduction were estimated, through equilibrium assemblage modelling, at 2.2-2.7 GPa. The amphibole-bearing eclogites of the SLZ show that large volumes of amphibole-bearing rocks can be exhumed from a depth exceeding 75 km without dehydration reactions running to completion. Petrological estimates in orogenic zones may help constrain geological and tectonic conclusions when selection of laboratory samples is assisted even by simple microstructural evaluation of planar fabric development.

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Section: P-t Estimatesmentioning

confidence: 99%

Interplay between deformation and metamorphism during eclogitization of amphibolites in the Sesia–Lanzo Zone of the Western Alps

Gosso

Messiga

Rebay

et al. 2010

International Geology Review

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“…1). Peak metamorphic conditions have been constrained as 1.6-1.9 GPa and 550-600°C (Carson et al 1999;Fitzherbert et al 2003). The belt represents an exhumed package of Cretaceous to Paleocene oceanic crust and continental sediments that was subducted during the middle Eocene (Cluzel et al 2001;Spandler et al 2005).…”

Section: Geological Settingmentioning

confidence: 99%

The importance of talc and chlorite “hybrid” rocks for volatile recycling through subduction zones; evidence from the high-pressure subduction mélange of New Caledonia

Spandler

Hermann

Faure

et al. 2007

Contrib Mineral Petrol

161

111

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The transfer of fluid and trace elements from the slab to the mantle wedge cannot be adequately explained by simple models of slab devolatilization. The eclogite-facies mélange belt of northern New Caledonia represents previously subducted oceanic crust and contains a significant proportion of talc and chlorite schists associated with serpentinite. These rocks host large quantities of H 2 O and CO 2 and may transport volatiles to deep levels in subduction zones. The bulk-rock and stable isotope compositions of talc and chlorite schist and serpentinite indicate that the serpentinite was formed by seawater alteration of oceanic lithosphere prior to subduction, whereas the talc and chlorite schists were formed by fluid-induced metasomatism of a mélange of mafic, ultramafic and metasedimentary rocks during subduction. In subduction zones,

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“…Extensive retrogression may occur due to external fluids infiltration (Heinrich 1982;Carson et al 1999;Guiraud et al 2001). These circumstances may explain the breakdown of the eclogitic assemblage in the investigated rocks.…”

Section: Discussionmentioning

confidence: 88%

“…For thermodynamic calculations, bulk rock composition of sample J-257 (Table 1) was used in the simplified system NCFMASH (Na 2 O-CaO-FeO-MgO-Al 2 O 3 -SiO 2 -H 2 O), with water content in excess to model the water-saturated conditions (e.g. Carson et al 1999;Guiraud et al 2001). We assume that effective bulk composition (e.g.…”

Section: P-t Evolutionmentioning

confidence: 99%

Eclogites overprinted in the granulite facies from the Ďumbier Crystalline Complex (Low Tatra Mountains, Western Carpathians)

Janák¹,

Mikuš²,

Pitoňák³

et al. 2009

Geologica Carpathica

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Abstract:Metabasites with evidence for breakdown of former eclogites and recrystallization under granulite facies conditions occur in the Ďumbier Crystalline Complex of the Low Tatra Mountains, Central Western Carpathains. Textural relationships, phase equilibrium modelling and thermobarometry have been used to determine the P-T evolution of these rocks. Omphacite diagnostic for the eclogites facies stage is absent but its former presence is inferred from the symplectitic intergrowths of clinopyroxene +plagioclase. The re-equilibration in high-pressure granulite facies conditions is demonstrated by the assemblage garnet + clinopyroxene (< 10 % Jd) + plagioclase + quartz. The phase equilibrium modelling using THERIAK-DOMINO program and conventional geothermobarometry suggest the P-T conditions of 750-760 °C and 1.1-1.5 GPa for the high-pressure granulite stage. Orthopyroxene formed in the clinopyroxene + plagioclase symplectites and kelyphites and coronas around garnet at P-T conditions of ca. 0.7-1.0 GPa and 650-700 °C. P-T evolution of granulitized eclogites is interpreted as the result of two metamorphic events; early Variscan eclogite facies metamorphism was followed by granulite facies thermal overprint in the Carboniferous time. The second metamorphic event was crucial for breakdown of eclogites, these are only seldom preserved in the pre-Alpine basement of the Western Carpathians.

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Calculated mineral equilibria for eclogites in CaO–Na₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O: application to the Pouébo Terrane, Pam Peninsula, New Caledonia

Cited by 177 publications

References 4 publications

Interplay between deformation and metamorphism during eclogitization of amphibolites in the Sesia–Lanzo Zone of the Western Alps

Interplay between deformation and metamorphism during eclogitization of amphibolites in the Sesia–Lanzo Zone of the Western Alps

The importance of talc and chlorite “hybrid” rocks for volatile recycling through subduction zones; evidence from the high-pressure subduction mélange of New Caledonia

Eclogites overprinted in the granulite facies from the Ďumbier Crystalline Complex (Low Tatra Mountains, Western Carpathians)

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