Lithium and boron isotope systematics in lavas from the Azores islands reveal crustal assimilation
Genske F, Turner SP, Beier C, Haase K, Chu MF, Tonarini S, Pearson NJ (2014)
Publication Language: English
Publication Status: Published
Publication Type: Journal article, Original article
Publication year: 2014
Journal
Publisher: Elsevier
Book Volume: 373
Pages Range: 27-36
DOI: 10.1016/j.chemgeo.2014.02.024
Abstract
The stable isotope systems of Li and B are useful tools for the understanding of ocean island basalt genesis. We have applied both systems to a comprehensive set of well-characterised samples across the Azores islands in order to further evaluate the nature of the mantle source. These ocean islands represent the surface expression of a low-buoyancy mantle plume. The variability of Li and B concentrations and their isotopic compositions across the archipelago builds on recent radiogenic isotope studies from the islands to the west of the Mid-Atlantic Ridge (Flores and Corvo). The results for both systems yield some values that are typical for ocean island basalts; however, the variability of both δLi and δB observed in primitive lavas is most extreme on the western islands of Flores and Corvo (δLi=+3.5 to +8.2‰ and δB=-3.5 to +11.8‰). The large spread in isotopic composition is most likely due to contamination of the magmas during ascent through hydrothermally altered oceanic crust. Models of assimilation fractional crystallisation best explain the variability observed on each island and allow for robust estimates of the mantle source. The implication of these observations is that the interpretation of the radiogenic isotopes and trace elements may have to be treated with care if the stable isotopes record contamination by assimilation of hydrothermally altered material and that the use of Li and B as mantle source tracers may be obscured by shallow level processes. Further, it seems unlikely that the large range observed in Sr and Nd isotopes can reflect variable contributions from recycled low-T materials such as sediment or altered MORB, since there is no correlation between the radiogenic and stable isotope data. © 2014 Elsevier B.V.
Authors with CRIS profile
Felix Genske
Lehrstuhl für Endogene Geodynamik
Christoph Beier
Lehrstuhl für Endogene Geodynamik
Karsten Haase
Lehrstuhl für Endogene Geodynamik
Involved external institutions
Taiwan (TW)
Australia (AU)How to cite
APA:
Genske, F., Turner, S.P., Beier, C., Haase, K., Chu, M.-F., Tonarini, S., & Pearson, N.J. (2014). Lithium and boron isotope systematics in lavas from the Azores islands reveal crustal assimilation. Chemical Geology, 373, 27-36. https://dx.doi.org/10.1016/j.chemgeo.2014.02.024
MLA:
Genske, Felix, et al. "Lithium and boron isotope systematics in lavas from the Azores islands reveal crustal assimilation." Chemical Geology 373 (2014): 27-36.
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