Insights into the Galápagos plume from uranium-series isotopes of recently erupted basalts

Handley HK, Turner S, Berlo K, Beier C, Saal AE (2011)

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2011

Journal

Geochemistry Geophysics Geosystems American Geophysical Union (AGU)

Publisher: American Geophysical Union (AGU)

Book Volume: 12

Article Number: Q0AC14

Journal Issue: 9

DOI: 10.1029/2011GC003676

Abstract

Uranium-series isotopes (U-Th- Ra-Pb), major element, trace element, and Sr-Nd isotopic data are presented for recent (<60 years old) Galpagos archipelago basalts. Volcanic rocks from all centers studied (Fernandina, Cerro Azul, Sierra Negra, and Wolf Volcano) display Th excesses (4%-15%) and steep rare earth element (REE) patterns indicative of residual garnet during partial melting of their mantle source. Rare earth element modeling suggests that only a few percent of garnet is involved. Correlations between (U/ Th), radiogenic isotopes and Nb/Zr ratio suggest that the U/Th ratio of these Galpagos volcanic rocks is primarily controlled by geochemical source variations and not fractionation during partial melting. The lowest (Th/U) ratio is not observed at Fernandina (the supposed center of the plume) but at the more geochemically "depleted" Wolf Volcano, further to the north. Small radium excesses are observed for all samples with (Ra/Th) ranging from 1.107 to 1.614. The Ra-Th disequilibria do not correlate with other uranium-series parent-daughter nuclide pairs or geochemical data, suggesting modification at shallow levels on timescales relevant to the half-life of Ra (1600 years). The combination of Ra and Pb excesses is inconsistent with interaction of magma with cumulate material unless decoupling of Pb (or an intermediate daughter, such as Rn) occurs prior to modification of Ra-Th disequilibria. An intriguing correlation of (Pb/ Ra) with Nb/Zr and radiogenic isotopes requires further investigation but suggests possible control via magmatic degassing and accumulation that may somehow be related to source heterogeneities. Copyright 2011 by the American Geophysical Union.

Authors with CRIS profile

Christoph Beier Lehrstuhl für Endogene Geodynamik (LEG)

Involved external institutions

Macquarie University AU Australia (AU) University of Oxford GB United Kingdom (GB) Brown University US United States (USA) (US)

How to cite

APA:

Handley, H.K., Turner, S., Berlo, K., Beier, C., & Saal, A.E. (2011). Insights into the Galápagos plume from uranium-series isotopes of recently erupted basalts. Geochemistry Geophysics Geosystems, 12(9). https://doi.org/10.1029/2011GC003676

MLA:

Handley, Heather K., et al. "Insights into the Galápagos plume from uranium-series isotopes of recently erupted basalts." Geochemistry Geophysics Geosystems 12.9 (2011).

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