Osmium isotope

The sources for the even osmium isotopes have been the same since... 

Mossbauer measurements with determination of the electric quadrupole moments have been reported in [253, 254,259]. Wagner et al. [254] measured the quadrupole hyperfine interaction in OSO2 and OSP2 of the Mossbauer isotopes The ratios of the quadrupole moments of the 4 = 72 states in the even osmium isotopes and of the 4 = 5/2 (69.6 keV) and 4 = 3/2 states in Os were deduced very accurately. In Table 7.8, the experimental results [254] are given, from which the following ratios can be calculated ... 

Alves S, Schiano P, Capmas F, Allegre CJ (2002) Osmium isotope binary mixing arrays in arc volcanism. Earth Planet Sci Lett 198 355-369... 

Allegre, C. J. and Luck, J. M., Osmium isotopes as petro-genetic and geological tracers, Earth Planet. Sci. Lett. 48. 148-154 (1980). 

Ravizza G, Norris RN, Blusztajn J, Aubry MP (2001) An osmium isotope excursion associated with the late Paleocene thermal maximum Evidence of intensified chemical weathering. Paleoceanogr 16 155-163 Raymo ME (1991) Geochemical evidence supporting Chamberlain, T. C., theory of glaciation. Geology 19 ... 

Figure 11.28 shows the rhenium and osmium isotopic compositions of black shales and sulfide ores from the Yukon Territory (Horan et al., 1994). The black shale and sulfide layers are approximately isochronous. The superimposed reference isochrons bracket the depositional age of the enclosing shales. One reference line represents the minimum age (367 Ma) with an initial ( Os/ Os)q ratio of one, consistent with the mantle isotopic composition at that age (see later). The other reference isochron is drawn for a maximum age of 380 Ma, with ( 870s/ 860s)o = 12 (the maximum value measured in terrigenous sediments). Further examples of application of Re-Os dating of sediments can be found in Ravizza and Turekian (1989). 

Horan M. E, Morgan J. W, Grauch R. I., Coveney R. M. Jr., Murowchick J. B., and Hulbert L. J. (1994). Rhenium and osmium isotopes in black shales and Ni-Mo-PGE-rich sulfide layers, Yukon Territory, Canada, and Hunan and Guizhou provinces, China. Geochim. Cosmochim. Acta, 58 257-265. 

The Re- Os method was first applied to extraterrestrial samples in the early 1960s when Hirt et al. (1963) reported a whole-rock isochron for 14 iron meteorites that gave an age of 4 Ga. Further development of this system was hindered by several technical difficulties. Rhenium and osmium each exist in multiple oxidation states and can form a variety of chemical species, so complete digestion of the samples, which is required to chemically separate rhenium and osmium for mass spectrometry, is difficult. In addition, accurate determination of rhenium abundance and osmium isotopic composition requires spiking the samples with isotopically labeled rhenium and osmium, and equilibration of spikes and samples is challenging. A third problem is that osmium and, particularly, rhenium are very difficult to ionize as positive ions for mass spectrometry. These problems were only gradually overcome. 

Meisel, T., Walker, R. J. and Morgan, J. W. (1996) The osmium isotopic composition of the Earth s primitive upper mantle. Nature, 383, 517-520. 

Osmium isotopic ratio of the bulk silicate Earth overlaps measurements of ordinary chondrites but is distinct from other chondrite groups. Adapted from Righter et al. (2006). 

Horan, M.F., et al. Rhenium-Osmium Isotope Constraints on the Age of Iron Meteorites, Science, 1118 (February 28, 1992). 

Walker, R.J. and J.W, Morgan Rhenium-Osmium Isotope Systematics of Carbonaceous Chondrites, Science, 519 (January 27, 1989). 

Esser and Turekian (1988) estimated an accretion rate of extraterrestrial particles in ocean bottom and in varved glacial lake deposit on the basis of osmium isotope systematics and concluded a maximum accretion rate of between 4.9 x 104 and 5.6 x 104 tons/a. The discrepancy between this estimate and those derived from helium can easily be attributed to the difference in the size of the cosmic dust particles under consideration. Cosmic dusts of greater than a few ten micrometers may not be important in the helium inventory of sediments because the larger grains are likely to lose helium due to atmospheric impact heating (e.g., Brownlee, 1985). Stuart et al. (1999) concluded from studies on Antarctic micrometeorites that 50- to 1 OO-qm micrometeorites may contribute about 5% of the total flux of extraterrestrial 3He to terrestrial sediments. Therefore, the helium-based estimate deals only with these smaller particles. 

Esser, B. K., Turekian, K. K. (1988) Accretion rate of extraterrestrial particles determined from osmium isotope systematics of Pacific pelagic clay and manganese nodules. Geochim. Cosmochim. Acta, 52, 1383-8. 

Yakushev, A.B., Vakatov, V.I., Vasko, V., Lebedev, V.Ya., Timokhin, S.N., Tsyganov, Yu.S., Zvara, I. "On-line Experiments with Short-lived Osmium Isotopes as a Test of the Chemical Identification of the Element 108 - Hassium" In Extended Abstracts of "1st International Conference on Chemistry and Physics of the Transactinide Elements", Seeheim, Germany, 26-30 September 1999, P-M-17. 

Rauch, S., Hemond, H.F., Peucker-Ehrenbrink, B. Recent changes in platinum group element concentrations and osmium isotopic composition in sediments from an urban lake. Environ. Sci. Technol. 38, 396-402 (2004)... 

Meisel T., Walker R. J., Irving A. J., and Lorand J.-P. (2001) Osmium isotopic compositions of mantle xenoliths a global perspective. Geochim. Cosmochim. Acta 6S, 1311-1323. 

The late veneer hypothesis has gained additional support from the analyses of the osmium isotopic composition of mantle rocks. Meisel et al. (1996) determined the Os/ Os ratios of a suite of mantle xenoliths. Since rhenium is more incompatible during mantle partial melting than osmium, the Re/Os ratio in the mantle residue is lower and in the melt higher than the PM ratio. By extrapolating observed trends of Os/ Os versus AI2O3 and lutetium, two proxies for rhenium, Meisel et al. (1996) determined a Os/ Os ratio of 0.1296 0.0008 for the primitive mantle. This ratio is 2.7% above that of carbonaceous... 

Osmium isotopes currently provide the strongest case for mineral-to-mineral disequilibrium, and for mineral-melt disequilibrium available from observations on natural rocks. Thus, both osmium alloys and sulfides from ophiolites and mantle xenoliths have yielded strongly heterogeneous osmium isotope ratios (Alard et al., 2002 Meibom et al., 2002). The most remarkable aspect of these results is that these ophiolites were emplaced in Phanerozoic times, yet they contain osmiumbearing phases that have retained model ages in excess of 2 Ga in some cases. The melts that were extracted from these ophiolitic peridotites contained almost certainly much more radiogenic osmium and could, in any case, not have been in osmium-isotopic equilibrium with all of these isotopically diverse residual phases. 

U and U, and this is in part responsible for the more complex isotopic relationships displayed by lead isotopes in comparison with the systematics of strontium, neodymium, hafnium, and osmium isotopes. The mantle geochemistry of noble gases, although of course an integral part of mantle geochemistry, is treated in Chapter 2.06. 

The Re-Os decay system is discussed separately, in part because there are far fewer osmium isotope data than Sr-Nd-Pb data. This is true because, until —10 years ago, osmium isotopes in silicate rocks were extraordinarily difficult to measure. The advent of negative-ion thermal ionization mass spectrometry has decisively changed this (Greaser et al., 1991 Vblkening et al., 1991), and subsequently the number of publications providing osmium isotope data has increased dramatically. 

Figure 9 Osmium isotope ratios in MORE and abyssal peridotites. This diagram shows that osmium is generally compatible in peridotites during MORE melting. The systematic differences in Os/ Os ratios between MORE and peridotites suggest that the melts may not be in isotopic equilibrium with their residual peridotite (sources Martin, 1991 Roy-Earman and Allegre, 1994 Snow and Reisberg, 1995 Schiano et al., 1997 Erandon et al., 2000).

Lassiter J. C. and Hauri E. H. (1998) Osmium-isotope variations in Hawaiian lavas evidence for recycled oceanic lithosphere in the Hawaiian plume. Earth Planet. Sci. Lett. 164, 483-496. 

Martin C. E. (1991) Osmium isotopic characteristics of mantle-derived rocks. Geochim. Cosmochim. Acta 55, 1421-1434. 

Meibom A. and Frei R. (2002b) Evidence for an ancient osmium isotopic reservoir in Earth. Science 296(5567), 516-518. 

Vdikening J., Walczyk T., and Heumann K. G. (1991) Osmium isotope ratio determinations by negative thermal ionization mass spectrometry. Int. J. Mass Spectrom. Ion Process. 105, 147-159. 

Kumar N., Reisberg L., and Zindler A. (1996) A major and trace element and strontium, neodymium, and osmium isotopic smdy of a thick pyroxenite layer from the Beni Bousera ultramafic complex of northern Morocco. Geochim. Cosmochim. Acta 60, 1429-1444. 

Reisberg L. and Lorand J.-P. (1995) Longevity of sub-continental mantle lithosphere from osmium isotope systematics in erogenic peridotite massifs. Nature 376, 159-162. 

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