| Autor: |
Friedrich Teichmann, Brent D. Turrin, Yurii R. Vasiliev, Paul R. Renne, Nikolai V. Sobolev, Robert J. Poreda, Asish R. Basu |
| Rok vydání: |
1995 |
| Předmět: |
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| Zdroj: |
Science (New York, N.Y.). 269(5225) |
| ISSN: |
0036-8075 |
| Popis: |
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 40Ar/39Ar 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-chondritic, 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. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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