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

Geochimica et Cosmochimica Acta

By:
, , ,
DOI: 10.1016/0016-7037(96)89674-8

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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

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Osmium and neodymium isotopic constraints on the temporal and spatial evolution of Siberian flood basalt sources
Series title:
Geochimica et Cosmochimica Acta
DOI:
10.1016/0016-7037(96)89674-8
Volume
59
Issue:
24
Year Published:
1995
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
5159
Last page:
5168
Number of Pages:
10