sup 3 He in diamonds: The cosmogenic component

Journal Article · Wed Feb 01 00:00:00 EST 1989 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(89)90408-0· OSTI ID:5127424

Lal, D; Craig, H; Wacker, J F; Poreda, R ^[1]

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1. Univ. of California, San Diego, La Jolla (USA)

The authors have measured {sup 3}He and {sup 4}He concentrations in a number of diamonds received directly from mines as well as in industrial samples. None of the authors diamonds recovered from underground mining has a {sup 3}He/{sup 4}He ratio, R, exceeding 3 R{sub A}. One of the five diamonds from the Consolidated Diamond mine has a ratio of 142 R{sub A}. Based on a number of facts: (i) the Zaire alluvial diamonds have >29% cosmogenic {sup 3}He; (ii) some documented high {sup 3}He/{sup 4}He ratio diamonds are from alluvial mines, and (iii) the apparent diffusion coefficients of {sup 3}He and {sup 4}He in diamonds are ten orders of magnitude too large to preserve diamond helium ratios in the mantle. They conclude that Ozima's hypothesis of high primordial {sup 3}He/{sup 4}He ratios in diamonds exceeding MORB ratios is not required. The present data are readily explainable as the result of cosmogenic and nucleogenic production of {sup 3}He within the diamonds.

• OSTI ID: 5127424
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Vol. 53:2; ISSN 0016-7037
• Country of Publication: United States
• Language: English

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EARTH MANTLE
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580000* - Geosciences