Diamond growth in mantle fluids - Sorbonne Université Accéder directement au contenu
Article Dans Une Revue Lithos Année : 2016

Diamond growth in mantle fluids

Résumé

In the upper mantle, diamonds can potentially grow from various forms of media (solid, gas, fluid) with a range of compositions (e.g. graphite, C–O–H fluids, silicate or carbonate melts). Inclusions trapped in diamonds are one of the few diagnostic tools that can constrain diamond growth conditions in the Earth's mantle. In this study, inclusion-bearing diamonds have been synthesized to understand the growth conditions of natural diamonds in the upper mantle. Diamonds containing syngenetic inclusions were synthesized in multi-anvil presses employing starting mixtures of carbonates, and silicate compositions in the presence of pure water and saline fluids (H2O–NaCl). Experiments were performed at conditions compatible with the Earth's geotherm (7 GPa, 1300–1400 °C). Results show that within the timescale of the experiments (6 to 30 h) diamond growth occurs if water and carbonates are present in the fluid phase. Water promotes faster diamond growth (up to 14 mm/year at 1400 °C, 7 GPa, 10 g/l NaCl), which is favorable to the inclusion trapping process. At 7 GPa, temperature and fluid composition are the main factors controlling diamond growth. In these experiments, diamonds grew in the presence of two fluids: an aqueous fluid and a hydrous silicate melt. The carbon source for diamond growth must be carbonate (CO32) dissolved in the melt or carbon dioxide species in the aqueous fluid (CO2aq). The presence of NaCl affects the growth kinetics but is not a prerequisite for inclusion-bearing diamond formation. The presence of small discrete or isolated volumes of water-rich fluids is necessary to grow inclusion-bearing peridotitic, eclogitic, fibrous, cloudy and coated diamonds, and may also be involved in the growth of ultradeep, ultrahigh-pressure metamorphic diamonds.

Domaines

Chimie
Fichier principal
Vignette du fichier
Bureau_Diamond_growth_in.pdf (760.13 Ko) Télécharger le fichier
Origine : Fichiers produits par l'(les) auteur(s)
Loading...

Dates et versions

hal-01504562 , version 1 (10-04-2017)

Identifiants

Citer

Hélène Bureau, Daniel J. Frost, Nathalie Bolfan-Casanova, Clémence Leroy, Imène Esteve, et al.. Diamond growth in mantle fluids. Lithos, 2016, 265, pp.4 - 15. ⟨10.1016/j.lithos.2016.10.004⟩. ⟨hal-01504562⟩
523 Consultations
509 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More