Implanted radiogenic and other noble gases in crustal diamonds from Northern Kazakhstan

A. B. Verchovsky, U. Ott, F. Begemann

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Noble gases were extracted in steps from grain size fractions of microdiamonds ( <100 μm) from the Kokchetav Massif, Northern Kazakhstan, by pyrolysis and combustion. The concentration of 4He in the diamonds proper (liberated by combustion) shows a 1 r dependence on grain size. For grain diameters > 15 μm the concentration also decreases with the combustion step. Both results are clear evidence that 4He has been implanted into the diamonds from α-decaying elements in the surrounding matrix. The saturation concentration of 4He(5.6 × 10-4> cm3 STP/g) is among the very highest observed in any terrestrial diamonds. Fission xenon from the spontaneous fission of 238U accompanies the radiogenic 4He; the 136Xef 4He ratio of (2.5 ± 0.3) × 10-9 agrees well with the production ratio of 2.3 × 10-9 expected in a reservoir where Th U ∼ 3.3. Radiogenic 40Ar is predominantly ( > 90%) set free upon combustion; it also resides in the diamonds and appears to have been incorporated into the diamonds upon their formation. 3He, on the other hand is mainly released during pyrolysis and hence is apparently carried by 'contaminants'. The concentration in the diamonds proper is of the order of 4 × 10-12 cm3 STP/g, with a 3He 4He ratio of 1 × 10-8. Excess 21Ne, similarly, appears to be present in contaminants as well as in diamonds proper. These two nuclides in the contaminants must have a nucleogenic origin, but it is difficult to explain their high concentrations.

Original languageEnglish
Pages (from-to)87-102
Number of pages16
JournalEarth and Planetary Science Letters
Volume120
Issue number3-4
DOIs
Publication statusPublished - 1993

Fingerprint

Kazakhstan
Noble Gases
Diamond
noble gas
diamond
rare gases
diamonds
contaminants
Impurities
fission
pollutant
combustion
Xenon
xenon
nuclides
pyrolysis
Isotopes
Pyrolysis
grain size
saturation

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences(all)
  • Environmental Science(all)

Cite this

Implanted radiogenic and other noble gases in crustal diamonds from Northern Kazakhstan. / Verchovsky, A. B.; Ott, U.; Begemann, F.

In: Earth and Planetary Science Letters, Vol. 120, No. 3-4, 1993, p. 87-102.

Research output: Contribution to journalArticle

@article{442fe8dcb0e843f4803e7dc21f4a301b,
title = "Implanted radiogenic and other noble gases in crustal diamonds from Northern Kazakhstan",
abstract = "Noble gases were extracted in steps from grain size fractions of microdiamonds ( <100 μm) from the Kokchetav Massif, Northern Kazakhstan, by pyrolysis and combustion. The concentration of 4He in the diamonds proper (liberated by combustion) shows a 1 r dependence on grain size. For grain diameters > 15 μm the concentration also decreases with the combustion step. Both results are clear evidence that 4He has been implanted into the diamonds from α-decaying elements in the surrounding matrix. The saturation concentration of 4He(5.6 × 10-4> cm3 STP/g) is among the very highest observed in any terrestrial diamonds. Fission xenon from the spontaneous fission of 238U accompanies the radiogenic 4He; the 136Xef 4He ratio of (2.5 ± 0.3) × 10-9 agrees well with the production ratio of 2.3 × 10-9 expected in a reservoir where Th U ∼ 3.3. Radiogenic 40Ar is predominantly ( > 90{\%}) set free upon combustion; it also resides in the diamonds and appears to have been incorporated into the diamonds upon their formation. 3He, on the other hand is mainly released during pyrolysis and hence is apparently carried by 'contaminants'. The concentration in the diamonds proper is of the order of 4 × 10-12 cm3 STP/g, with a 3He 4He ratio of 1 × 10-8. Excess 21Ne, similarly, appears to be present in contaminants as well as in diamonds proper. These two nuclides in the contaminants must have a nucleogenic origin, but it is difficult to explain their high concentrations.",
author = "Verchovsky, {A. B.} and U. Ott and F. Begemann",
year = "1993",
doi = "10.1016/0012-821X(93)90232-X",
language = "English",
volume = "120",
pages = "87--102",
journal = "Earth and Planetary Sciences Letters",
issn = "0012-821X",
publisher = "Elsevier",
number = "3-4",

}

TY - JOUR

T1 - Implanted radiogenic and other noble gases in crustal diamonds from Northern Kazakhstan

AU - Verchovsky, A. B.

AU - Ott, U.

AU - Begemann, F.

PY - 1993

Y1 - 1993

N2 - Noble gases were extracted in steps from grain size fractions of microdiamonds ( <100 μm) from the Kokchetav Massif, Northern Kazakhstan, by pyrolysis and combustion. The concentration of 4He in the diamonds proper (liberated by combustion) shows a 1 r dependence on grain size. For grain diameters > 15 μm the concentration also decreases with the combustion step. Both results are clear evidence that 4He has been implanted into the diamonds from α-decaying elements in the surrounding matrix. The saturation concentration of 4He(5.6 × 10-4> cm3 STP/g) is among the very highest observed in any terrestrial diamonds. Fission xenon from the spontaneous fission of 238U accompanies the radiogenic 4He; the 136Xef 4He ratio of (2.5 ± 0.3) × 10-9 agrees well with the production ratio of 2.3 × 10-9 expected in a reservoir where Th U ∼ 3.3. Radiogenic 40Ar is predominantly ( > 90%) set free upon combustion; it also resides in the diamonds and appears to have been incorporated into the diamonds upon their formation. 3He, on the other hand is mainly released during pyrolysis and hence is apparently carried by 'contaminants'. The concentration in the diamonds proper is of the order of 4 × 10-12 cm3 STP/g, with a 3He 4He ratio of 1 × 10-8. Excess 21Ne, similarly, appears to be present in contaminants as well as in diamonds proper. These two nuclides in the contaminants must have a nucleogenic origin, but it is difficult to explain their high concentrations.

AB - Noble gases were extracted in steps from grain size fractions of microdiamonds ( <100 μm) from the Kokchetav Massif, Northern Kazakhstan, by pyrolysis and combustion. The concentration of 4He in the diamonds proper (liberated by combustion) shows a 1 r dependence on grain size. For grain diameters > 15 μm the concentration also decreases with the combustion step. Both results are clear evidence that 4He has been implanted into the diamonds from α-decaying elements in the surrounding matrix. The saturation concentration of 4He(5.6 × 10-4> cm3 STP/g) is among the very highest observed in any terrestrial diamonds. Fission xenon from the spontaneous fission of 238U accompanies the radiogenic 4He; the 136Xef 4He ratio of (2.5 ± 0.3) × 10-9 agrees well with the production ratio of 2.3 × 10-9 expected in a reservoir where Th U ∼ 3.3. Radiogenic 40Ar is predominantly ( > 90%) set free upon combustion; it also resides in the diamonds and appears to have been incorporated into the diamonds upon their formation. 3He, on the other hand is mainly released during pyrolysis and hence is apparently carried by 'contaminants'. The concentration in the diamonds proper is of the order of 4 × 10-12 cm3 STP/g, with a 3He 4He ratio of 1 × 10-8. Excess 21Ne, similarly, appears to be present in contaminants as well as in diamonds proper. These two nuclides in the contaminants must have a nucleogenic origin, but it is difficult to explain their high concentrations.

UR - http://www.scopus.com/inward/record.url?scp=0027841684&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0027841684&partnerID=8YFLogxK

U2 - 10.1016/0012-821X(93)90232-X

DO - 10.1016/0012-821X(93)90232-X

M3 - Article

VL - 120

SP - 87

EP - 102

JO - Earth and Planetary Sciences Letters

JF - Earth and Planetary Sciences Letters

SN - 0012-821X

IS - 3-4

ER -