High-3He plume origin and temporal-spatial evolution of the Siberian flood basalts

Asish R. Basu, Robert J. Poreda, Paul R. Renne, Friedrich Teichmann, Yurii R. Vasiliev, Nikolai V. Sobolev, Brent D. Turrin

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Abstract

An olivine nephelinite from the lower part of a thick alkalic ultrabasic and mafic sequence of volcanic rocks of the northeastern part of the Siberian flood basalt province (SFBP) yielded a 40ArX39Ar plateau age of 253.3 ± 2.6 million years, distinctly older than the main tholeiitic pulse of the SFBP at 250.0 million years. Olivine phenocrysts of this rock showed 3He/4He ratios up to 12.7 times the atmospheric ratio; these values suggest a lower mantle plume origin. The neodymium and strontium isotopes, rare earth element concentration patterns, and cerium/lead ratios of the associated rocks were also consistent with their derivation from a near-cnondritic, primitive plume. Geochemical data from the 250-million-year-old volcanic rocks higher up in the sequence indicate interaction of this high-3He SFBP plume with a suboceanic-type upper mantle beneath Siberia.

Original languageEnglish (US)
Pages (from-to)822-825
Number of pages4
JournalScience
Volume269
Issue number5225
DOIs
StatePublished - Aug 11 1995
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General

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