title: High-3He Plume Origin and Temporal-Spatial Evolution of the Siberian Flood Basalts.
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 (40)Ar/(39)Ar 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 (3)He/(4)He 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-chondritic, primitive plume. Geochemical data from the 250-million-year-old volcanic rocks higher up in the sequence indicate interaction of this high-(3)He SFBP plume with a suboceanic-type upper mantle beneath Siberia.
authors.forename: A R
authors.initials: AR
authors.lastname: Basu
authors.forename: R J
authors.initials: RJ
authors.lastname: Poreda
authors.forename: P R
authors.initials: PR
authors.lastname: Renne
authors.forename: F
authors.initials: F
authors.lastname: Teichmann
authors.forename: Y R
authors.initials: YR
authors.lastname: Vasiliev
authors.forename: N V
authors.initials: NV
authors.lastname: Sobolev
authors.forename: B D
authors.initials: BD
authors.lastname: Turrin