Computer Science
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007e%26psl.264...89k&link_type=abstract
Earth and Planetary Science Letters, Volume 264, Issue 1-2, p. 89-103.
Computer Science
7
Scientific paper
Micrometer sized internal cavities in diamonds preserve evidence of diamond dissolution events. Combining the methods of focused ion beam (FIB) sample preparation and transmission electron microscopy (TEM) enables these features to be studied in detail. Micrometer-scale cavities are found in the inner parts of fibrous and cloudy kimberlitic diamonds. Their filling consists of amorphous matrix, secondary nano-crystals, volatiles and in some cases larger resorbed crystals. Trapped minerals include corundum, Kappa-alumina, quartz, olivine, moissanite-6H and Ca Mg carbonates. This is the first observation of Kappa-alumina in nature. Secondary nano-minerals are observed within the amorphous matrix and include carbonates, Al-oxide, fluorite, ilmenite and secondary diamond crystals. The amorphous matrix is spongy and its composition is dominated by amorphous carbon, nitrogen, chlorine and also contains water. When no crystalline phases are observed, the matrix is also enriched in alumina, silica and in some cases calcium. We propose that micrometer scale cavities in diamonds form during dissolution events induced by the introduction of oxidizing hydrous fluids into the diamond growth area. Hydrous fluids are the main dissolving agents for most kimberlitic diamonds [Fedortchouk, Y., Canil, D., Semenets, E., 2007. Mechanisms of diamond oxidation and their bearing on the fluid composition in kimberlite magmas. Am. Mineral. 92, 1200 1212]. At diamond forming conditions silica and alumina are enriched in hydrous fluids that are in equilibrium with eclogites [Kessel, R., Ulmer, P., Pettke, T., Schmidt, M.W., Thompson, A.B., 2005. The water-basalt system at 4 to 6 GPa: Phase relations and second critical endpoint in a K-free eclogite at 700 to 1400 °C. Earth Planet. Sci. Lett. 237, 873 892]; this is consistent with the increased solubility of alumina with increased pressure and temperature in the Na Cl bearing fluids [Manning, C.E., 2006. Mobilizing aluminum in crustal and mantle fluids. J. Geochem. Explor. 89, 251 253; Manning, C.E., 2007. Solubility of corundum + kyanite in H2O at 700C and 10 kbar: evidence for Al Si complexing at high pressure and temperature. Geofluids. 7, 258 269]. Additionally, hydrous fluids may leach grain boundaries that are enriched in alumina in peridotitic environments [Hiraga, T., Anderson, I.M., Kohlstedt, D.L., 2004. Grain boundaries as reservoirs of incompatible elements in the Earth's mantle. Nature. 427, 699 703; Wirth, R., 1996. Thin amorphous films (1 2 nm) at olivine grain boundaries in mantle xenoliths from San Carlos, Arizona. Contrib. Mineral. Petrol. 124, 44 54]. Diamond dissolution will form oxidized carbon species and may decrease the solubility of silica and alumina in the dissolving agent leading to their precipitation. Diamond forming fluids that are trapped in sub-micrometer inclusions in the same fibrous diamonds are the dominant fluid component in the diamond growth area. Corrosive hydrous fluids are less common and appear as short, discrete events, followed by the return of the common diamond forming fluids and continued diamond precipitation.
Klein-BenDavid Ofra
Navon Oded
Wirth Richard
No associations
LandOfFree
Micrometer-scale cavities in fibrous and cloudy diamonds — A glance into diamond dissolution events does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Micrometer-scale cavities in fibrous and cloudy diamonds — A glance into diamond dissolution events, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Micrometer-scale cavities in fibrous and cloudy diamonds — A glance into diamond dissolution events will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1111133