210Pb-226Ra disequilibria in volcanic rocks

Kim Berlo, Simon Turner

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Isotopes of the U-decay series, such as 238U-230Th-226Ra, have been used successfully to study timescales of magmatic processes. This study provides an overview of a shorter lived isotope pair, 210Pb-226Ra, which allows study of processes occuring during a crucial time window for magma ascent and eruption. 210Pb is fractionated from its great-grandparent 226Ra by both Pb-Ra fractionation between crystal and melt and via its intermediate parent 222Rn during degassing. 210Pb-226Ra activity ratios have been measured in volcanic rocks of various settings for the last 40years. Here we review published data and their implications for magmatic processes. In particular it is observed that 210Pb-226Ra fractionation is larger at subduction zone volcanoes than in Mid Ocean Ridge Basalts and Ocean Island Basalts. The larger fractionations, which include both 210Pb deficits and excesses, are the result of recent fractionation of 210Pb-226Ra during magma degassing and gas streaming. MORB and OIB suffer less from overprinting of prior 210Pb-226Ra signals by degassing. These magmas preserve 210Pb-226Ra fractionation induced by partial melting of the mantle placing tight constraints upon magma ascent rates.

LanguageEnglish
Pages155-164
Number of pages10
JournalEarth and Planetary Science Letters
Volume296
Issue number3-4
DOIs
Publication statusPublished - Aug 2010

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Volcanic rocks
Fractionation
fractionation
disequilibrium
volcanology
volcanic rock
rocks
degassing
Degassing
magma
ocean island basalt
ascent
mid-ocean ridge basalt
Isotopes
basalt
isotopes
isotope
Volcanoes
mid-ocean ridges
overprinting

Cite this

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210Pb-226Ra disequilibria in volcanic rocks. / Berlo, Kim; Turner, Simon.

In: Earth and Planetary Science Letters, Vol. 296, No. 3-4, 08.2010, p. 155-164.

Research output: Contribution to journalArticleResearchpeer-review

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