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Oxygen isotopic heterogeneity of Pali Aike basaltic magmas from southern Patagonia as evidenced by oxygen isotope compositions of olivines

Title
Oxygen isotopic heterogeneity of Pali Aike basaltic magmas from southern Patagonia as evidenced by oxygen isotope compositions of olivines
Authors
Choo M.K.Kim K.H.Lee J.I.Lee M.J.Choi S.H.Park K.-H.
Ewha Authors
김규한
SCOPUS Author ID
김규한scopusscopus
Issue Date
2015
Journal Title
Geochemical Journal
ISSN
0016-7002JCR Link
Citation
vol. 49, no. 1, pp. 83 - 101
Keywords
HIMULaser fluorinationOxygen isotopePali Aike olivinePatagonia
Publisher
The Physiological Society of Japan
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
Oxygen isotope ratios were determined using laser fluorination methods on 15 olivines and seven matrix samples separated from the Pali Aike alkali basalt of southern Patagonia. The δ18O values were measured in ranges of 4.23 to 5.23% and 4.64 to 5.26% for olivine and matrix, respectively. The δ18O values of Pali Aike olivines are lower and have a wider range than those of normal upper mantle (5.0-5.4%). We considered that the heterogeneity of the oxygen isotope compositions of Pali Aike olivine provides evidence of assimilation at a shallow level and the presence of recycled material. The differences between olivine and matrix δ18O values indicate that Δ18O<inf>(melt-ol)</inf> (0.14 to 0.50) was within equilibrium fractionation for some and in disequilibrium for most samples at magmatic temperature. Oxygen isotope compositions in disequilibrium indicate that the lower δ18O for the melt is explained by interaction with low δ18O hydrothermally altered rocks. The low δ18O<inf>olivine</inf> values for low forsterite (Fo) contents of Pali Aike lavas can be explained by the effect of shallow-level assimilation. The oxygen isotope values for the olivine of high-MgO (or high-Fo) compositions are thought to represent oxygen isotope variation in the mantle source region. The low and variable δ18O signature of Pali Aike olivine can be explained by crustal recycling, such as a contribution from the hydrothermally altered oceanic crustal melt. These heterogeneous oxygen isotope compositions indicate that Pali Aike olivines require both assimilation at a shallow level and a component of the high-μ end-members (HIMU) mantle derived from recycled mantle lithologies in the form of pyroxenite or eclogite. Copyright © 2015 by The Geochemical Society of Japan.
DOI
10.2343/geochemj.2.0333
Appears in Collections:
사범대학 > 과학교육과 > Journal papers
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