Uranium and boron distributions in some oceanic ultramafic rocks
Journal Article
·
· Earth Planet. Sci. Lett., v. 21, no. 1, pp. 97-107
From mica fission-track maps the serpentinized and weathered portions of four ultramafic rocks from oceanic ridge systems contained 0.5 to 2.4 ppM U compared to only 2.5 ppB in clinopyroxene, 0.6 ppB in chromite and < 7.0 ppB in olivine. Orthopyroxene grains contained 0.4 ppB U which is three orders of magnitude lower than had previously been reported. Long thin tracks from (n, alpha ) reactions with boron were recorded in cellulose nitrate plastic and were counted like fission tracks. The track density from boron was 2 x 10/sup 4/ times higher than that from uranium fission alone. Boron in serpentine was variable on a 50- mu m scale attaining 155 ppM concentrations. Orthopyroxene grains, in contrast, had maximum concentrations of 0.8 ppM. Most of the uranium and boron in the rocks is believed to have been introduced during serpentinization. From known crystal-melt partitioning ratios the uranium and boron distributions are consistent with the ultramafic rocks being cumulates or residues from partial melting events. (auth)
- Research Organization:
- Carnegie Institution of Washington, DC
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-29-018316
- OSTI ID:
- 4344569
- Journal Information:
- Earth Planet. Sci. Lett., v. 21, no. 1, pp. 97-107, Journal Name: Earth Planet. Sci. Lett., v. 21, no. 1, pp. 97-107; ISSN EPSLA
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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