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Volumn 281, Issue 5378, 1998, Pages 805-807

Diffusion kinetics of samarium and neodymium in garnet, and a method for determining cooling rates of rocks

Author keywords

[No Author keywords available]

Indexed keywords

NEODYMIUM; SAMARIUM;

EID: 0032493902     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.281.5378.805     Document Type: Article
Times cited : (212)

References (26)
  • 8
    • 3542997137 scopus 로고    scopus 로고
    • note
    • 149Sm concentrations varying between ∼100 and 200 ppm in two different stock solutions used in this work.
  • 10
    • 3543037852 scopus 로고    scopus 로고
    • note
    • - accelerated to 10 keV. The samples were held at ∼+4.5 kV, resulting in an impact energy of ∼14.5 keV. Two approaches were used to avoid contribution of secondary ions from the crater walls. For some of the samples, a 50-nA primary beam was focused onto a spot and rastered over a 200 μm by 200 μm area. An aperture inserted into the path of the ions allowed only those originating from a 60-μm-diameter circular area in the center of the crater into the mass spectrometer. For other samples, a 15-to 20-nA primary beam was focused by Kohler illumination to generate a circular, flat-bottomed crater ∼120 μm in diameter (24). Secondary ions from the central 10 or 20 μm of the crater were allowed into the mass spectrometer by selecting either a 100-or 200-μm field aperture. In both cases a 75-V offset was applied to the sample voltage to minimize the contribution of molecular ions to the mass spectrum (25). Crater depths were determined with a Dektak surface profilometer and varied as a function of primary beam current and analysis time (1 to 2 hours) between ∼3000 and 7000 Å.
  • 15
    • 0001063588 scopus 로고
    • Diffusion, Atomic Ordering and Mass Transport, J. Ganguly, Ed. Springer-Verlag, New York
    • S. Chakraborty and J. Ganguly, in Diffusion, Atomic Ordering and Mass Transport, J. Ganguly, Ed. (Advances in Physical Geochemistry 8, Springer-Verlag, New York, 1991), pp. 120-175.
    • (1991) Advances in Physical Geochemistry , vol.8 , pp. 120-175
    • Chakraborty, S.1    Ganguly, J.2
  • 16
    • 3543015246 scopus 로고    scopus 로고
    • M. Morioka H. Nagasawa, in (15), pp. 176-197
    • M. Morioka and H. Nagasawa, in (15), pp. 176-197.
  • 19
    • 3543014622 scopus 로고
    • thesis, Brown University, Providence, RI
    • R. A. N. Coghlan, thesis, Brown University, Providence, RI (1990).
    • (1990)
    • Coghlan, R.A.N.1
  • 22
    • 3543036680 scopus 로고
    • _, Mat. Sci. Forum 7, 145 (1986).
    • (1986) Mat. Sci. Forum , vol.7 , pp. 145
  • 23
    • 3543009862 scopus 로고    scopus 로고
    • in preparation
    • C in Dodson's (21) eqn. 23 equals exp(G), where G is the spatially averaged value of the closure function G(X) of his (22) eqn. 20. In deriving the expression for G(X), Dodson (22) assumed that the dimensionless quantity M ≫ 1, which implies removal of the composition of the crystal from its initial composition in all parts. The closure function has been modified so that it is valid for any arbitrary value of M, numerically evaluated as a function of the normalized radial distance from the center of a grain, and then spatially averaged to yield average closure function versus M; for example, G(M = 0.001) = 0.9018, G(0.01) = 2.7603, G(0.10) = 3.8693, G(0.4) = 4.0041, as compared to Dodson's (22) G = 4.0066.
    • Ganguly, J.1
  • 26
    • 3543004389 scopus 로고    scopus 로고
    • note
    • We thank M. H. Dodson and J. Ruiz for helpful discussions and for providing some of the isotopeenriched solutions, respectively. This research was supported by U.S. National Science Foundation grant EAR 9418941 and EAR 9805232.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.