The growth of fibrous, cloudy and polycrystalline diamonds

Bureau, Hélène; Langenhorst, F.; Auzende, Anne-Line; Frost, Daniel J.; Estève, Imène; Siebert, J.

doi:10.1016/j.gca.2011.11.016

Cited by 35 publications

(23 citation statements)

References 87 publications

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“…Diamond occurs on the high-temperature side, and the apparent diamond-graphite boundary has a negative slope. Similar conditions for homogeneous diamond nucleation from a fluid or melt were reported by Bureau et al (2012). 2.…”

Section: Diamond Nucleationsupporting

confidence: 70%

Reduced sediment melting at 7.5–12 GPa: phase relations, geochemical signals and diamond nucleation

Brey

Гирнис

Bulatov

et al. 2015

Contrib Mineral Petrol

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garnet. Clinopyroxene stability depends strongly on the Na content in the starting mixture; it remains in the Na-gloss composition up to 1600 °C at 12 GPa, but was not observed in K-gloss experiments above 1200 °C. The composition of melt or fluid changes gradually with increasing temperature from hydrous carbonate-rich (<10 wt% SiO 2 ) at 800-1000 °C to volatile-rich silicate liquids (up to 40 wt% SiO 2 ) at high temperatures. Trace elements were analyzed in melts and crystalline phases by LA ICP MS. The garnetmelt and clinopyroxene-melt partition coefficients are in general consistent with results from the literature for volatile-free systems and silicocarbonate melts derived by melting carbonated peridotites. Most trace elements are strongly incompatible in kyanite and silica polymorphs (D < 0.01), except for V, Cr and Ni, which are slightly compatible in kyanite (D > 1). Aragonite and Fe-Mg carbonate have very different REE partition coefficients (D Mst-Sd/L ~ 0.01 and D Arg/L ~ 1). Nb, Ta, Zr and Hf are strongly incompatible in both carbonates. The bearthite/melt partition coefficients are very high for LREE (>10) and decrease to ~1 for HREE. All HFSE are strongly incompatible in bearthite. In contrast, Ta, Nb, Zr and Hf are moderately to strongly compatible in ZrSiO 4 and TiO 2 phases. Based on the obtained partition coefficients, the composition of a mobile phase derived by sediment melting in deep subduction zones was calculated. This phase is strongly enriched in incompatible elements and displays a pronounced negative Ta-Nb anomaly but no Zr-Hf anomaly. Although all experiments were conducted in the diamond stability field, only graphite was observed in low-temperature experiments. Spontaneous diamond nucleation and the complete transformation of graphite to diamond were observed at temperatures above 1200-1300 °C. We speculate that the observed character of graphite-diamond transformation is controlled by relationships between the kinetics of metastable graphite Abstract Melting of carbonated sediment in the presence of graphite or diamond was experimentally investigated at 7.5-12 GPa and 800-1600 °C in a multianvil apparatus. Two starting materials similar to GLOSS of Plank and Langmuir (Chem Geol 145:325-394, 1998) were prepared from oxides, carbonates, hydroxides and graphite. One mixture (Na-gloss) was identical in major element composition to GLOSS, and the other was poorer in Na and richer in K (K-gloss). Both starting mixtures contained ~6 wt% CO 2 and 7 wt% H 2 O and were doped at a ~100 ppm level with a number of trace elements, including REE, LILE and HFSE. The near-solidus mineral assemblage contained a silica polymorph (coesite or stishovite), garnet, kyanite, clinopyroxene, carbonates (aragonite and magnesite-siderite solid solution), zircon, rutile, bearthite and hydrous phases (phengite and lawsonite at <9 GPa and the hydrous aluminosilicates topaz-OH and phase egg at >10 GPa). Hydrous phases disappear at ~900 °C, and carbonates persist up to 1000-1100 °C. At temperatures >1200 °C, the ...

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Section: Diamond Nucleationsupporting

confidence: 70%

Reduced sediment melting at 7.5–12 GPa: phase relations, geochemical signals and diamond nucleation

Brey

Гирнис

Bulatov

et al. 2015

Contrib Mineral Petrol

View full text Add to dashboard Cite

show abstract

“…Further studies have shown nucleation and growth to be greatly promoted by the presence of H 2 O. [135][136][137] There is further evidence that NaCl may act to reduce the growth rate. 132,136 Experiments to synthesize diamonds from reduced C-H-O fluids have been less successful.…”

Section: Experiments To Study Diamond Formation and Inclusion Entrapmentmentioning

confidence: 98%

“…47 This may explain why diamond growth is promoted in experiments with high H 2 O concentrations. 136,137 One problem with this occurring in the mantle is that the H 2 O contents of mineral inclusions such as olivine trapped in diamonds should be near H 2 O saturation, which seems not to be the case for the lithospheric diamonds measured to date. 140 Reduced CH 4 -rich fluids, on the other hand, experience relatively small changes in carbon solubility with temperature, but much larger changes with pressure.…”

Section: Experiments To Study Diamond Formation and Inclusion Entrapmentmentioning

confidence: 99%

“…Experiments using water-rich mixtures containing carbonates and silicates have successfully produced a broad range of mineral, melt, and fluid inclusions at 6-7 GPa and 1300-1400 C ( Figure 5.7). 136,137 Starting compositions were based on fluid inclusion analyses of fibrous diamonds, 61 and polycrystalline and fibrous growth textures were reproduced, which tended toward monocrystalline growth at higher temperatures. Bureau et al 137 used observations of coexisting melt and fluid inclusions to infer the temperature where the two phases become miscible in the system examined.…”

Section: Experiments To Study Diamond Formation and Inclusion Entrapmentmentioning

confidence: 99%

“…136,137 Starting compositions were based on fluid inclusion analyses of fibrous diamonds, 61 and polycrystalline and fibrous growth textures were reproduced, which tended toward monocrystalline growth at higher temperatures. Bureau et al 137 used observations of coexisting melt and fluid inclusions to infer the temperature where the two phases become miscible in the system examined. Bataleva et al 141 also captured inclusions in monocrystalline diamonds grown from SiO 2 -(Mg,Ca)CO 3 -(Fe,Ni)S mixtures at 6.3 GPa and 1650-1750 C. The inclusions, which encompassed quenched carbonate-silicate melts, sulfide melts, and CO 2 fluid, reflected, in part, the growth medium that is generally assumed for natural diamond inclusions, but Bureau et al 136 demonstrated that carbonate minerals are readily trapped in diamonds that are actually growing from H 2 O-dominated liquids.…”

Section: Experiments To Study Diamond Formation and Inclusion Entrapmentmentioning

confidence: 99%

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