Phase relations of carbonate-bearing eclogite assemblages from 2.5 to 5.5�GPa: implications for petrogenesis of carbonatites

Yaxley, Gregory M.; Brey, Gerhard P.

doi:10.1007/s00410-003-0517-3

Cited by 296 publications

(205 citation statements)

References 56 publications

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“…The generation of first highly potassic carbonatite melt at 8 GPa is controlled by a melting out of carbonates and K-phases. The melting reaction is similar for all three bulk (Yaxley and Brey 2004;Dasgupta et al 2004Dasgupta et al , 2005, peridotites (Brey et al 2008(Brey et al , 2009Ghosh et al 2009), and sediments (Thomsen and Schmidt 2008b). Note the correlation between carbonate and bulk composition, in particular of the Mg# of magnesite and the bulk.…”

Section: Melting Reactionsmentioning

confidence: 74%

“…b Compositions of carbonatite melts projected in the Na 2 CO 3 -K 2 CO 3 -(Mg,Ca,Fe)CO 3 space. The carbonatite melts of this study have much higher amounts of K 2 O and Na 2 O compared to melts from carbonated mafic eclogites (3-8 GPa, Hammouda 2003; Yaxley and Brey 2004;Dasgupta et al 2004), peridotites (2-10 GPa, Wallace and Green 1988;Yaxley and Green 1996;Ghosh et al 2009), and pelites at p B 5 GPa (Thomsen and Schmidt 2008b). With increasing pressure, the K 2 O/Na 2 O ratio decreases.…”

Section: Textures and Mineral Compositionsmentioning

confidence: 95%

“…Nevertheless, the large amounts of K-hollandite, jadeitic cpx and carbonates observed in BSE images of the subsolidus Fig. 7 Pseudo-ternary projection of carbonatite and silicate melts after Freestone and Hamilton 1980), defining a silicate-carbonatite liquid miscibility gap at 1,100°C, 3.7-5 GPa for the AM composition (Thomsen and Schmidt 2008b) compared to the miscibility gap after (dashed line) and the carbonatites of Yaxley and Brey (2004). At 8-13 GPa, there is a continuum from carbonatite melts towards more silica-rich melts, and no solvus has been observed.…”

Section: Melting Reactionsmentioning

confidence: 99%

“…Although there are a large number of studies on carbonated mafic eclogites (Yaxley and Green 1994;Hammouda 2003;Yaxley and Brey 2004;Dasgupta et al 2004Dasgupta et al , 2005Litasov and Ohtani 2009;Keshav and Gudfinnsson 2010), there are only three studies on carbonated pelites at upper mantle conditions (Domanik and Holloway 1998;Thomsen and Schmidt 2008a, b). As has been pointed out (Dasgupta et al 2005;Thomsen and Schmidt 2008b), the melting systematics of peridotites and carbonated K-poor mafic eclogites at 2-7 GPa is similar to the melting relations in the simple CaCO 3 -MgCO 3 ± FeCO 3 system (Irving and Wyllie 1975;Buob et al 2006).…”

mentioning

confidence: 99%

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Melting of carbonated pelites at 8–13 GPa: generating K-rich carbonatites for mantle metasomatism

Grassi

Schmidt

2010

Contrib Mineral Petrol

104

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The melting behaviour of three carbonated pelites containing 0-1 wt% water was studied at 8 and 13 GPa, 900-1,850°C to define conditions of melting, melt compositions and melting reactions. At 8 GPa, the fluidabsent and dry carbonated pelite solidi locate at 950 and 1,075°C, respectively; [100°C lower than in carbonated basalts and 150-300°C lower than the mantle adiabat. From 8 to 13 GPa, the fluid-present and dry solidi temperatures then increase to 1,150 and 1,325°C for the 1.1 wt% H 2 O and the dry composition, respectively. The melting behaviour in the 1.1 wt% H 2 O composition changes from fluid-absent at 8 GPa to fluid-present at 13 GPa with the pressure breakdown of phengite and the absence of other hydrous minerals. Melting reactions are controlled by carbonates, and the potassium and hydrous phases present in the subsolidus. The first melts, which composition has been determined by reverse sandwich experiments, are potassium-rich Ca-FeMg-carbonatites, with extreme K 2 O/Na 2 O wt ratios of up to 42 at 8 GPa. Na is compatible in clinopyroxene with D cpx=carbonatite Na ¼ 10À18 at the solidus at 8 GPa. The melt K 2 O/Na 2 O slightly decreases with increasing temperature and degree of melting but strongly decreases from 8 to 13 GPa when K-hollandite extends its stability field to 200°C above the solidus. The compositional array of the sediment-derived carbonatites is congruent with alkali-and CO 2 -rich melt or fluid inclusions found in diamonds. The fluid-absent melting of carbonated pelites at 8 GPa contrasts that at B5 GPa where silicate melts form at lower temperatures than carbonatites. Comparison of our melting temperatures with typical subduction and mantle geotherms shows that melting of carbonated pelites to 400-km depth is only feasible for extremely hot subduction. Nevertheless, melting may occur when subduction slows down or stops and thermal relaxation sets in. Our experiments show that CO 2 -metasomatism originating from subducted crust is intimately linked with K-metasomatism at depth of [200 km. As long as the mantle remains adiabatic, lowviscosity carbonatites will rise into the mantle and percolate upwards. In cold subcontinental lithospheric mantle keels, the potassic Ca-Fe-Mg-carbonatites may freeze when reacting with the surrounding mantle leading to potassium-, carbonate/diamond-and incompatible element enriched metasomatized zones, which are most likely at the origin of ultrapotassic magmas such as group II kimberlites.

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Section: Melting Reactionsmentioning

confidence: 74%

Section: Textures and Mineral Compositionsmentioning

confidence: 95%

Section: Melting Reactionsmentioning

confidence: 99%

mentioning

confidence: 99%

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Melting of carbonated pelites at 8–13 GPa: generating K-rich carbonatites for mantle metasomatism

Grassi

Schmidt

2010

Contrib Mineral Petrol

104

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“…Estimates of the amounts of carbonate subducted into the mantle range from 2.4 to 4.8 x 10 13 g of C per year (Dasgupta and Hirschmann, 2010) and numerous studies have indicated that most carbonate survives this process, carrying a characteristic isotopic signature into the deeper mantle (e.g., Kerrick and Connolly, 2001;Yaxley and Brey, 2004). Based initially on density considerations and later on oxygen thermobarometry of garnet peridotites, however, Wood et al (1990Wood et al ( , 1996 Woodland and Koch, 2003) support this hypothesis of increasing stability of diamond relative to carbonate with increasing depth.…”

Section: Lettermentioning

confidence: 99%

The pyroxenite-diamond connection

Kiseeva¹,

Wood²,

Ghosh³

et al. 2015

Geochem. Persp. Let.

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Light Stable Isotopic Compositions of Enriched Mantle Sources: Resolving the Dehydration Paradox

Dixon

Bindeman

Kingsley

et al. 2017

Geochem Geophys Geosyst

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Volatile and stable isotope data provide tests of mantle processes that give rise to mantle heterogeneity. New data on enriched mid‐oceanic ridge basalts (MORB) show a diversity of enriched components. Pacific PREMA‐type basalts (H2O/Ce = 215 ± 30, δDSMOW = −45 ± 5 ‰) are similar to those in the northern Atlantic (H2O/Ce = 220 ± 30; δDSMOW = −30 to −40 ‰). Basalts with EM‐type signatures have regionally variable volatile compositions. Northern Atlantic EM‐type basalts are wetter (H2O/Ce = 330 ± 30) and have isotopically heavier hydrogen (δDSMOW = −57 ± 5 ‰) than northern Atlantic MORB. Southern Atlantic EM‐type basalts are damp (H2O/Ce = 120 ± 10) with intermediate δDSMOW (−68 ± 2 ‰), similar to δDSMOW for Pacific MORB. Northern Pacific EM‐type basalts are dry (H2O/Ce = 110 ± 20) and isotopically light (δDSMOW = −94 ± 3 ‰). A multistage metasomatic and melting model accounts for the origin of the enriched components by extending the subduction factory concept down through the mantle transition zone, with slab temperature a key variable. Volatiles and their stable isotopes are decoupled from lithophile elements, reflecting primary dehydration of the slab followed by secondary rehydration, infiltration, and re‐equilibration by fluids derived from dehydrating subcrustal hydrous phases (e.g., antigorite) in cooler, deeper parts of the slab. Enriched mantle sources form by addition of <1% carbonated eclogite ± sediment‐derived C‐O‐H‐Cl fluids to depleted mantle at 180–280 km (EM) or within the transition zone (PREMA).

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Phase relations of carbonate-bearing eclogite assemblages from 2.5 to 5.5�GPa: implications for petrogenesis of carbonatites

Cited by 296 publications

References 56 publications

Melting of carbonated pelites at 8–13 GPa: generating K-rich carbonatites for mantle metasomatism

Melting of carbonated pelites at 8–13 GPa: generating K-rich carbonatites for mantle metasomatism

The pyroxenite-diamond connection

Light Stable Isotopic Compositions of Enriched Mantle Sources: Resolving the Dehydration Paradox

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