Synthesis of cubic diamond in the graphite-magnesium carbonate and graphite-K2Mg(CO3)2 systems at high pressure of 9–10 GPa region

Taniguchi, Takashi; Dobson, David P.; Jones, Adrian P.; Rabe, R.; Milledge, H. J.

doi:10.1557/jmr.1996.0330

Cited by 60 publications

(18 citation statements)

References 20 publications

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“…1). This phase was previously observed as a quench product in some high-pressure experiments on diamond and wadsleyite growth (Shatskiy et al, 2009;Taniguchi et al, 1996) and in experiments on carbonated peridotite (Brey et al, 2011), but was not characterized. The new K-Ca phase is stable over the entire studied pressure range but becomes dominant in the Na carbonatite subsolidus assemblage at 21 GPa only; its structure is yet to be determined.…”

Section: Resultsmentioning

confidence: 92%

Solidus of alkaline carbonatite in the deep mantle

Litasov

Shatskiy

Ohtani

et al. 2013

Geology

147

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Section: Resultsmentioning

confidence: 92%

Solidus of alkaline carbonatite in the deep mantle

Litasov

Shatskiy

Ohtani

et al. 2013

Geology

147

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“…The absence of any evidence for an accumulation of this kind of melts at the base of the lithosphere, where temperatures would be low enough for complete crystallization of the carbonatite melts, suggests that a redox reaction with the reduced mantle (Frost and McCammon 2008;Rohrbach et al 2009) immobilizes these carbonatites. In fact, diamond crystallization has been shown to be favored by the catalytic behaviour of K 2 CO 3 -rich melt and fluid (Taniguchi et al 1996;Palyanov et al 2007;Klein-BenDavid et al 2007).…”

Section: Evidence For Subducted Carbonates and K-rich Metasomatism Inmentioning

confidence: 99%

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

Grassi

Schmidt

2010

Contrib Mineral Petrol

106

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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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“…The fi rst group has been the most extensively explored, with solvents or catalysts (other than transition metal melts) such as kimberlitic melts (Arima et al 1993), solid or liquid carbonate (Akaishi et al 1990;Taniguchi et al 1996;Pal'yanov et al 1999aPal'yanov et al , 1999bPal'yanov et al , 2002aSato et al 1999;Sokol et al 2000Sokol et al , 2001aSpivak and Litvin 2004;Tomlinson et al 2004), sulfi de melts (Pal'yanov et al 2001;Sato and Katsura 2001), and both oxidized (CO 2 -H 2 O) and reduced (CH 4 -H 2 O) fl uids (Yamaoka et al 1992(Yamaoka et al , 2002a(Yamaoka et al , 2002bKumar et al 2000Kumar et al , 2001Sun et al 2000;Akaishi et al , 2001Sokol et al 2001b;Okada et al 2002;Dobrzhinetskaya et al 2004). To the authors' knowledge, no study has reported oxidation of a reduced, carbon-bearing (e.g., CH 4 -rich) fl uid to produce diamond in the absence of graphite or another source of carbon.…”

Section: Introductionmentioning

confidence: 99%

Carbonate reduction by Fe-S-O melts at high pressure and high temperature

Gunn

Luth

2006

American Mineralogist

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Diamond may form in the Earth's mantle by recrystallization of graphite, by precipitation from a C-bearing fl uid, or by reduction of carbonate. The latter mechanism could result from interaction with a reduced fl uid or another phase that would accommodate the oxygen produced by the reduction. One possible such phase is a sulfi de-bearing melt, given that sulfi des are common inclusions in diamond. Experiments at 1300 °C, 6 and 7.5 GPa successfully reduced magnesite in the presence of a eutecticcomposition Fe-S-O melt. Although graphite rather than diamond was produced by this reduction, these experiments demonstrate that this mechanism is a viable mechanism for reducing carbonate to carbon in the Earth's mantle.

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Synthesis of cubic diamond in the graphite-magnesium carbonate and graphite-K₂Mg(CO₃)₂ systems at high pressure of 9–10 GPa region

Cited by 60 publications

References 20 publications

Solidus of alkaline carbonatite in the deep mantle

Solidus of alkaline carbonatite in the deep mantle

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

Carbonate reduction by Fe-S-O melts at high pressure and high temperature

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