Osmium and neodymium isotopic constraints on the temporal and spatial evolution of Siberian flood basalt sources

Horan, M. F.; Walker, R. J.; Fedorenko, V. A.; Czamanske, G. K.

Abstract:

Picrites from the Gudchikhinsky suite, the oldest rocks examined, have ??Os of +5.3 to +6.1 and ??Nd of +3.7 to +4.0. The osmium and neodymium isotopic compositions of these rocks are similar to some modern ocean-island basalts (OIB), consistent with their derivation from an mantle plume. Picrites from the stratigraphically higher Tuklonsky suite have similar ??Os of +3.4 to +6.5, but ??Nd of -0.9 to -2.6. The similar ??Os, but lower ??Nd , suggest that some magmas from the same OIB-type, mantle source were contaminated by lithospheric components. A differentiated ankaramite flow, associated with the top of the stratigraphically higher Morongovsky suite, has ??Os of +9.8 to +10.2 and ??Nd of +1.3 to +1.4. The higher ??Os may indicate that the plume source was heterogeneous with respect to osmium isotopic composition, consistent with osmium isotopic measurements in rocks from other plume sources. Mg-rich, alkaline rocks (meymechites) from the Guli area that erupted much nearer the end of the flood-basalt event have ??Os of -1.2 to -2.6 and ??Nd of +3.7 to +4.9. These rocks were probably produced by low degrees of partial melting of mantle after the main stages of flood-basalt production. -from Authors

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Article

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70019044

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Horan, M. F.; Walker, R. J.; Fedorenko, V. A.; Czamanske, G. K.

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5168

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English

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Geochimica et Cosmochimica Acta

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Osmium and neodymium isotopic constraints on the temporal and spatial evolution of Siberian flood basalt sources; 1995; Article; Journal; Geochimica et Cosmochimica Acta; Horan, M. F.; Walker, R. J.; Fedorenko, V. A.; Czamanske, G. K.