The genesis of low-N diamonds

Chepurov, A. I.; Жимулев, Е. И.; Eliseev, A. P.; Сонин, В. М.; Fedorov, I. I.

doi:10.1134/s0016702909050085

Cited by 6 publications

(6 citation statements)

References 10 publications

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“…At high P–T Ti binds oxygen and, therefore, restores metallic Fe and Ni from FeO and NiO oxides, as followed from the fugacity values of O 2 in equilibrium buffer reactions (Supplementary Fig. S10 ) 11 , 51 . On the one hand, the reactions increase hydrogen solubility in the melt.…”

Section: Discussionmentioning

confidence: 99%

“…It is proposed that an extremely high reactivity of metallic Ti is a key factor that leads to crystallization of low-nitrogen diamond. Also, that is the reason why introduction of Ti in the form of oxide with a maximum degree oxidation (TiO 2 ) did not affect the N-state: metallic Ti extracts oxygen from Fe–Ni melt, but TiO 2 does not 11 . Nevertheless, crystallization of low-nitrogen diamond is related rather to the behavior of hydrogen, than oxygen.…”

Section: Discussionmentioning

confidence: 99%

“…The experiments were carried out at pressures 5.5–6.0 GPa and temperatures 1350–1400 °C with duration over 45 h in the diamond stability field 56 . The details of the procedure are described in 11 , 15 , 57 . The measurement errors were ± 0.2 GPa and ± 25 °C.…”

Section: Methodsmentioning

confidence: 99%

“…The other hypothesis is based on the experimental fact of crystallization of nitrogen-rich diamond if Ti is added in the form of TiO 2 . The introduction of metallic Ti reduces oxygen concentration in the melt, because metallic Ti acts as a strong reducing agent: oxygen fugacity (ƒ O2 ) that corresponds to Ti-TiO 2 equilibrium at 5.0 GPa and 1400 °C is 10 orders of magnitude lower than that of Fe-FeO 11 . Fe is reduced from Fe-bearing oxides and silicates in the presence of metallic Ti at high pressure and temperatures 12 .…”

Section: Introductionmentioning

confidence: 99%

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The composition of the fluid phase in inclusions in synthetic HPHT diamonds grown in system Fe–Ni–Ti–C

Сонин

Томиленко

Жимулев

et al. 2022

Sci Rep

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Diamonds grown by high pressure high temperature process (HPHT) are usually characterized by yellow color and high contents of nitrogen. Introduction of Ti decreases nitrogen content in diamond. Understanding the formation of nitrogen-poor diamond is very important not for the progress of HPHT process only, but because these diamond varieties represent the rare natural stones, although their crystallization conditions have not been clarified yet. Here we studied the composition of fluid phase in synthetic diamonds. The experiments were performed using a high-pressure apparatus BARS at pressures 5.5–6.0 GPa and temperatures 1350–1400 °C. It was found that introduction of metallic Ti leads to concentration of nitrogen mainly as nitrogenated hydrocarbons. The hypothesis that elucidates the formation of low-nitrogen diamond in Fe–Ni is proposed: the presence of Ti leads to an increase of hydrogen fugacity in the metal melt which drastically reduces the nitrogen solubility. As a result, nitrogen concentrates in the form of complex hydrocarbon compounds, while diamond grows colorless and characterized by very low nitrogen content. It is suggested that the proposed mechanism acts the same way in the presence of other metals which are strong reducing agents.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The composition of the fluid phase in inclusions in synthetic HPHT diamonds grown in system Fe–Ni–Ti–C

Сонин

Томиленко

Жимулев

et al. 2022

Sci Rep

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“…It is indicative that the metallic Ti creates a strongly reducing medium that is corresponding to fugacity , that is 15 orders of mag nitude lower relative to the Fe-FeO buffer equilibrium [12]. The СаСО 3 -Ti interaction is not recorded, probably due to the relatively short duration of the experiment.…”

Section: On the Formation Of Element Carbon During Decomposition Of Cmentioning

confidence: 94%

On the formation of element carbon during decomposition of CaCO3 at High P-T parameters under reducing conditions

et al. 2011

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This work presents data on the experimental study of CaCO 3 stability (3.0-5.5 GPa; 1300 1400°C) under reducing conditions modeling the presence of metallic iron. It is established that CaCO 3 is stable at the above P-T parameters under reducing conditions (in the presence of metallic Ti). CaCO 3 decomposed only when it chemically interacted with iron, forming Ca-ferrites and releasing solid carbon in the form of graphite in the closed system (in sealed Pt ampoules).

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Characterization of the nitrogen state in HPHT diamonds grown in an Fe–C melt with a low sulfur addition

et al. 2022

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The genesis of low-N diamonds

Cited by 6 publications

References 10 publications

The composition of the fluid phase in inclusions in synthetic HPHT diamonds grown in system Fe–Ni–Ti–C

The composition of the fluid phase in inclusions in synthetic HPHT diamonds grown in system Fe–Ni–Ti–C

On the formation of element carbon during decomposition of CaCO3 at High P-T parameters under reducing conditions

Characterization of the nitrogen state in HPHT diamonds grown in an Fe–C melt with a low sulfur addition

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