THE RADIAL DISTRIBUTION OF IMPLANTED AND TRAPPED 4HE IN SINGLE DIAMOND CRYSTALS AND IMPLICATIONS FOR THE ORIGIN OF CARBONADO
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dc.contributor.author | Shelkov D.A. | |
dc.contributor.author | Verchovsky A.B. | |
dc.contributor.author | Milledge H.J. | |
dc.contributor.author | Pillinger C.T. | |
dc.date.accessioned | 2020-12-29T04:14:51Z | |
dc.date.available | 2020-12-29T04:14:51Z | |
dc.date.issued | 1998 | |
dc.identifier | https://elibrary.ru/item.asp?id=74864 | |
dc.identifier.citation | Chemical Geology, 1998, , 1, 109-116 | |
dc.identifier.issn | 0009-2541 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/21604 | |
dc.description.abstract | We have investigated variations of 4He content in the different zones of single natural diamond crystals using a step combustion technique. The results indicate that some diamonds may be strongly irradiated during their residence in the earth's crust, since concentrations of 4He in the 30-μm outer layer were found to be as high as 0.014 cm3/g. The observation leads to a conclusion that similarly high 4He concentrations in carbonado diamonds do not necessary demand an exotic origin. Previous theoretical estimations of the magnitude of He implantation in diamonds, which use normal U-Th concentrations of ca. 30 ppm in the surrounding rocks, do not agree with experimentally-obtained results. The He concentrations actually found in the `skins' (outer ~30- μm layer of the crystals) of the samples we studied, require concentrations of U and Th in the host rock from 160 ppm to 1000 ppm. The interiors of the samples have also been analysed and exhibited 4He concentrations from 3x10-7 cm3/g to 2x10-5 cm3/g, indicating heterogeneity even within single diamond crystals and arguing for the changes in the growth environment. From 4He zoning within a diamond from the Finsch kimberlite, a maximum 4He diffusion coefficient was estimated to be ~4x10-21 cm2/s, lower than previous estimates, indicating that diamond may retain indigenous 4He in the structure during its residence under mantle PT conditions. | |
dc.subject | DIAMOND | |
dc.subject | HELIUM | |
dc.subject | CARBONADO | |
dc.subject | IMPLANTATION | |
dc.subject | DIFFUSION | |
dc.title | THE RADIAL DISTRIBUTION OF IMPLANTED AND TRAPPED 4HE IN SINGLE DIAMOND CRYSTALS AND IMPLICATIONS FOR THE ORIGIN OF CARBONADO | |
dc.type | Статья |
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