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Submicrometer fluid inclusions in turbid-diamond coats

Guthrie, George D., Jr. and Veblen, David R. and Navon, Oded and Rossman, George R. (1991) Submicrometer fluid inclusions in turbid-diamond coats. Earth and Planetary Science Letters, 105 (1-3). pp. 1-12. ISSN 0012-821X. doi:10.1016/0012-821X(91)90116-Y.

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Transmission and analytical electron microscopies were used to characterize the turbid coats on two diamonds from Zaire. The coats contained euhedral cavities (generally ≤ 0.5 μm) that are believed to represent decrepit fluid inclusions. Crystals (generally ≤ 0.2 μm) were sometimes found in the cavities, but they were never observed to fill the cavities entirely. Cavities that appeared to be intact typically contained several solid inclusions and an amorphous material with a low average atomic weight. The crystals in such cavities were able to move under a condensed electron beam, suggesting that the amorphous material was a liquid and not a glass. Using compositional analysis and electron diffraction, five minerals were identified as daughter crystals in the cavities: apatite, high-Ca carbonate, low-Ca carbonate, mica, and quartz. Coesite and olivine were not observed in any of the cavities. Compositional analysis of some crystals indicated that other minerals (e.g., amphibole) were present as daughter crystals; however, electron diffraction data were insufficient to identify them unambiguously. Since these inclusions are believed to have been trapped during the growth of the diamond coats [1], it may be possible to constrain the environment under which the coast grew, assuming that the daughter minerals precipitated from the trapped fluid and that the fluid inclusions have not re-equilibrated. Coexisting magnesite-like and dolomite-like carbonates and silica constrain X_(CO2) of the fluid to greater than 0.4. The presence of quartz is consistent with the coats developing at lower pressures and temperatures than the cores they surround; alternatively, quartz grew from a glass or high-P, high-T silica polymorph (coesite) when the inclusions re-equilibrated in the quartz stability field.

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Rossman, George R.0000-0002-4571-6884
Additional Information:© 1991 Elsevier Science. Received May 20, 1990; revision accepted April 29, 1991. We would like to thank S. Olsen, L. Baumgartner, D. Sverjensky, J. Ferry, I. Hutcheon, and G. Wasserburg for helpful discussions. The original manuscript benefitted from comments by S. Olsen, D. Bish, S. Baldridge, and an anonymous reviewer. This electron microscopy was performed at the Center for HRTEM at The Johns Hopkins University, established in part with NSF grant EAR8300365; research was supported by NSF grants EAR8609277 (to DRV), EAR8903630 (to DRV), EAR8618200 (to GRR), and EAR8816936 (to G. Wasserburg).
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Issue or Number:1-3
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Official Citation:George D. Guthrie Jr., David R. Veblen, Oded Navon, George R. Rossman, Submicrometer fluid inclusions in turbid-diamond coats, Earth and Planetary Science Letters, Volume 105, Issues 1–3, July 1991, Pages 1-12, ISSN 0012-821X, 10.1016/0012-821X(91)90116-Y. (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37957
Deposited By: Ruth Sustaita
Deposited On:16 Apr 2013 15:43
Last Modified:09 Nov 2021 23:32

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