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Determination of trace element mineral/liquid partition coefficients in melilite and diopside by ion and electron microprobe techniques

Kuehner, S. M. and Laughlin, J. R. and Grossman, L. and Johnson, M. L. and Burnett, D. S. (1989) Determination of trace element mineral/liquid partition coefficients in melilite and diopside by ion and electron microprobe techniques. Geochimica et Cosmochimica Acta, 53 (12). pp. 3115-3130. ISSN 0016-7037. http://resolver.caltech.edu/CaltechAUTHORS:20150424-150904750

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Abstract

The use of the ion microprobe for quantitative analysis of Sr, Y, Zr, La, Sm, and Yb in melilite and pyroxene is evaluated. Three trace element-doped synthetic glasses of composition Ak_40, Ak_80, and Di_2AbAn were analyzed by ion microprobe (IMP) using ion yields determined from Corning glass standards. IMP-determined oxide concentrations in the Di_2AbAn glass agree well with electron microprobe (EMP) analyses (to within 6%), but IMP analyses of the melilite glasses deviate from EMP averages by up to 19%. The deviations are due to erroneous SiO_2 estimates caused by suppression of Si ion intensities by the enhanced concentrations of Ca and Al in the melilite glasses compared to the standards. Thus, in order to determine compositions of melilite, diopside, and glass from subliquidus experiments on each of the three starting compositions, we adopted a new set of ion yields such that IMP analyses of the three starting glasses reproduce the EMP average compositions. Further IMP and EMP comparisons of the subliquidus assemblages show that quantitative analyses of melilite, diopside, and glass can be obtained by IMP that are within 10% of the concentrations obtained by EMP, when ion yields determined from glass starting compositions are used. EMP-IMP comparison of crystal and glass analyses also suggests that a structural matrix effect may result in overestimation of SrO (10–12%) in melilite by IMP. Comparison of our data for Ak_12 and Ak_90 melilite compositions with literature results shows that melilite/liquid for REE^3+ determined by IMP decrease with increasing X_Ak (Ak_90: D_La = 0.038, D_Sm = 0.032, D_Yb = 0.0086; Ak: 0.67, 0.75, 0.25, respectively) while that for Sr (=Eu^2+) changes only slightly (0.99 to 0.78, respectively). Since X_Ak increases with decreasing temperature for all melilite with X_Ak<0.7, a progressively larger positive Eu anomaly is predicted for melilite as it crystallizes with falling temperature. Our diopside/liquid data are characterized by a large degree of scatter on most interelement correlation plots of apparent partition coefficients. The data cannot be understood in terms of simple models of boundary layer formation but require a complex surface partitioning explanation. Nevertheless, estimates of diopside/liquid are in excellent agreement with literature data.


Item Type:Article
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http://dx.doi.org/10.1016/0016-7037(89)90093-8DOIArticle
http://www.sciencedirect.com/science/article/pii/0016703789900938PublisherArticle
Additional Information:© 1989 Pergamon Press. Received 6 February 1989, Accepted 15 September 1989. We are grateful to I. M. Steele and A. M. Davis for guidance in the operation of the electron and ion microprobes, respectively, and also for their discussions of our results. We thank John Beckett for the melilite starting materials and for helpful discussions, and Astrid Howard for help with synthesis experiments. We profited from discussions with E. Stolper and from reviews by R. Hervig, N. Shim& and D. Lindstrom. This work was supported by funds from the National Aeronautics and Space Administration through grants NAG 9-54 (to L. Grossman), NAG 9-94 (to D. S. Burnett), and NAG 9-5 1 (to R. N. Clayton).
Funders:
Funding AgencyGrant Number
NASANAG 9-54
NASANAG 9-94
NASANAG 9-51
Record Number:CaltechAUTHORS:20150424-150904750
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150424-150904750
Official Citation:Kuehner, S. M., Laughlin, J. R., Grossman, L., Johnson, M. L., & Burnett, D. S. (1989). Determination of trace element mineral/liquid partition coefficients in melilite and diopside by ion and electron microprobe techniques. Geochimica et Cosmochimica Acta, 53(12), 3115-3130. doi: http://dx.doi.org/10.1016/0016-7037(89)90093-8
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:56977
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:27 Apr 2015 21:02
Last Modified:27 Apr 2015 21:02

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