Experimental Melting of Carbonated Peridotite at 6-10 GPa

Brey, Gerhard P.; Bulatov, Vasily V.; Гирнис, А. В.; Lahaye, Yann

doi:10.1093/petrology/egn002

Cited by 267 publications

(115 citation statements)

References 69 publications

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“…Compared to other studies on carbonated mafic eclogites (Hammouda 2003;Dasgupta et al 2004Dasgupta et al , 2005Yaxley and Brey 2004) and on peridotites Brey et al 2008;Ghosh et al 2009), our pelites exhibit a 100-300°C lower solidus temperature due to the higher alkali (especially K 2 O) and water (AM) content (Fig. 11).…”

Section: Melting Systematics For Carbonated Lithologiescontrasting

confidence: 65%

“…No indication of a miscibility gap has been found (Fig. 7), similar to the C6 GPa melting of carbonated peridotite (Brey et al 2008). Other effects of temperature on melt composition are the decrease in CO 2 and K 2 O through dilution with increasing melt fraction, and a twofold increase in Na 2 O content at 8 GPa, leading to a decrease in K 2 O/Na 2 O with temperature.…”

Section: Resultsmentioning

confidence: 57%

“…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: 76%

“…The SiO 2 and Al 2 O 3 content in the carbonatites of this study remains below 10 wt% even at 400°C above the solidus. Carbonatites derived from peridotitic and basaltic systems at similar pressure (Dalton and Presnall 1998;Dasgupta et al 2004;Brey et al 2008) show much higher SiO 2 and Al 2 O 3 contents up to 25-30 wt% at \200°C above the solidus. The most evident reason for this behaviour is the lower solidus temperature on pelitic alkali-rich systems compared to basaltic or peridotitic lithologies.…”

Section: Melting Systematics For Carbonated Lithologiesmentioning

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 Systematics For Carbonated Lithologiescontrasting

confidence: 65%

Section: Resultsmentioning

confidence: 57%

Section: Melting Reactionsmentioning

confidence: 76%

Section: Melting Systematics For Carbonated Lithologiesmentioning

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 low-degree melts of carbonated assemblages produced at high pressures are expected to be carbonatitic or carbonate rich (Brey et al 2008;Rohrbach and Schmidt 2011). If such melts are highly mobile (Hammouda and Laporte 2000), they will rapidly percolate through the subducting assemblage to the surface of the slab and react with surrounding mantle peridotite.…”

Section: Depth Of Individual Inclusion Formationmentioning

confidence: 99%

Origin of sub-lithospheric diamonds from the Juina-5 kimberlite (Brazil): constraints from carbon isotopes and inclusion compositions

Thomson

Kohn²,

Bulanova

et al. 2014

Contrib Mineral Petrol

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interpreted as evidence of diamond growth from abiotic organic carbon added to the oceanic crust during hydrothermal alteration. The bulk isotopic composition of the oceanic crust, carbonates plus organics, is equal to the composition of mantle carbon (−5 ‰), and we suggest that recycling/mixing of subducted material will replenish this reservoir over geological time. Several exposed, syngenetic inclusions have bulk compositions consistent with former eclogitic magnesium silicate perovskite, calcium silicate perovskite and NAL or CF phases that have reequilibrated during their exhumation to the surface. There are multiple occurrences of majoritic garnet with pyroxene exsolution, coesite with and without kyanite exsolution, clinopyroxene, Fe or Fe-carbide and sulphide minerals alongside single occurrences of olivine and ferropericlase. As a group, the inclusions have eclogitic affinity and provide evidence for diamond formation at pressures extending to Earth's deep transition zone and possibly the lower mantle. It is observed that the major element composition of inclusions and isotopic compositions of host Juina-5 diamonds are not correlated. The diamond and inclusion compositions are intimately related to subducted material and record a polybaric growth history across a depth interval stretching from the lower mantle to the base of the lithosphere. It is suggested that the interaction of slabderived melts and mantle material combined with subsequent upward transport in channelised networks or a buoyant diapir explains the formation of Juina-5 diamonds. We conclude that these samples, despite originating at great mantle depths, do not provide direct information about the ambient mantle, instead, providing a snapshot of the Earth's deep carbon cycle. Keywords Diamonds · Sub-lithospheric mantle · Carbon cycle · SubductionAbstract Forty-one diamonds sourced from the Juina-5 kimberlite pipe in Southern Brazil, which contain optically identifiable inclusions, have been studied using an integrated approach. The diamonds contain <20 ppm nitrogen (N) that is fully aggregated as B centres. Internal structures in several diamonds revealed using cathodoluminescence (CL) are unlike those normally observed in lithospheric samples. The majority of the diamonds are composed of isotopically light carbon, and the collection has a unimodal distribution heavily skewed towards δ 13 C ~ −25 ‰. Individual diamonds can display large carbon isotope heterogeneity of up to ~15 ‰ and predominantly have isotopically lighter cores displaying blue CL, and heavier rims with green CL. The light carbon isotopic compositions are Communicated by O. Müntener. Electronic supplementary materialThe online version of this article

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Numerical modeling of convective erosion and peridotite‐melt interaction in big mantle wedge: Implications for the destruction of the North China Craton

2014

JGR Solid Earth

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The deep subduction of the Pacific Plate underneath East Asia is thought to have played a key role in the destruction of the North China Craton (NCC). To test this hypothesis, this paper presents a new 2-D model that includes an initial stable equilibrated craton, the formation of a big mantle wedge (BMW), and erosion by vigorous mantle convection. The model shows that subduction alone cannot thin the cold solid craton, but it can form a low-viscosity BMW. The amount of convective erosion is directly proportional to viscosity within the BMW (η 0bmw ), and the rheological boundary layer thins linearly with decreasing log 10 (η 0bmw ), thereby contributing to an increase in heat flow at the lithospheric base. This model also differs from previous modeling in that the increase in heat flow decays linearly with t 1/2 , meaning that the overall thinning closely follows a natural log relationship over time. Nevertheless, convection alone can only cause a limited thinning due to a minor increase in basal heat flow. The lowering of melting temperature by peridotite-melt interaction can accelerate thinning during the early stages of this convection. The two combined actions can thin the craton significantly over tens of Myr. This modeling, combined with magmatism and heat flow data, indicates that the NCC evolution has involved four distinct stages: modification in the Jurassic by Pacific Plate subduction and BMW formation, destruction during the Early Cretaceous under combined convective erosion and peridotite-melt interaction, extension in the Late Cretaceous, and cooling since the late Cenozoic.

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Experimental Melting of Carbonated Peridotite at 6-10 GPa

Cited by 267 publications

References 69 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

Origin of sub-lithospheric diamonds from the Juina-5 kimberlite (Brazil): constraints from carbon isotopes and inclusion compositions

Numerical modeling of convective erosion and peridotite‐melt interaction in big mantle wedge: Implications for the destruction of the North China Craton

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