Accretion rate of extraterrestrial particles determined from osmium isotope systematics of pacific pelagic clay and manganese nodules

Conference · Wed Jun 01 00:00:00 EDT 1988 · Geochimica et Cosmochimica Acta; (USA)

OSTI ID:5557526

Esser, B K; Turekian, K K ^[1]

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1. Yale Univ., New Haven, CT (USA)

Pelagic clay and Mn nodules from DOMES sites in the North Pacific and a varved glacial lake deposit from Connecticut were analyzed for Os concentration and isotopic composition by isotope-dilution secondary ion mass spectrometry after treatment by NiS fusion of oxalic acid leaching. Bulk pelagic clay from DOMES site C has {sup 187}Os/{sup 186}Os = 6.5 and Os = 0.14 ng/g. Oxalic acid leaches of this same sediment and of Mn nodules for DOMES sites A and C have more radiogenic {sup 187}Os/{sup 186}Os ratios which average 8.3. Bulk glacial Lake Hitchcock sediment has {sup 187}Os/{sup 186}Os = 12.5 and Os = 0.06 ng/g. The total Os flux to North Pacific pelagic clay is 7 to 10 ng Os/cm{sup 2}/10{sup 6} y. Lake Hitchcock sediment provides an integrated value for the local crustal {sup 187}Os/{sup 186}Os ratio. The oxalic acid leaches are assumed to attack hydrogenous phases selectively. A simple model in which the only sources of Os to the ocean are continental crust with the isotopic composition of Lake Hitchcock and extraterrestrial particles with {sup 187}Os/{sup 186}Os = 1.1 results in a cosmic flux of osmium to the sediment of 4.9 ng Os/cm{sup 2}/10{sub 6} y of which 20% is hydrogenous. A model in which the sources of Os to the ocean are continental crust with an {sup 187}Os/{sup 186}Os ratio of 30, oceanic mantle or crust with {sup 187}Os/{sup 186}Os = 1.04 and extraterrestrial particles with {sup 187}Os/{sup 186}Os = 1.1 results in a cosmic flux of Os to the sediment of 5.7 ng Os/cm{sup 2}/10{sup 6} y of which none is hydrogenous. These extraterrestrial Os fluxes correspond to maximum C-1 chondrite accretion rates of between 4.9 {times} 10{sub 4} and 5.6 {times}10{sub 4} tonnes/y.

• OSTI ID: 5557526
• Report Number(s): CONF-8703325-; CODEN: GCACA
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Vol. 52:6; Conference: Isotope tracers in geochemistry and geophysics, Pasadena, CA (USA), 23-25 Mar 1987; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CLAYS
GEOCHEMISTRY
ISOTOPE RATIO
MANGANESE ORES
PACIFIC OCEAN
GEOLOGIC DEPOSITS
CHEMICAL ANALYSIS
CHONDRITES
CONTINENTAL CRUST
GEOLOGIC MODELS
LEACHING
OCEANIC CRUST
ORIGIN
OSMIUM ISOTOPES
PRECIPITATION
SEDIMENTS
CHEMISTRY
DISSOLUTION
EARTH CRUST
ISOTOPES
METEORITES
ORES
SEAS
SEPARATION PROCESSES
STONE METEORITES
SURFACE WATERS
580400* - Geochemistry- (-1989)
580500 - Oceanography- (1980-1989)