Hafnium isotope variations in oceanic basalts
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Abstract
Routine low-blank chemistry and 0.01-0.04% precision on the ratio 176Hf/177Hf allows study of Hf isotopic variations, generated by β−-decay of 176Lu, in volcanic rocks derived from the suboceanic mantle. Normalized to 176Hf/177Hf = 0.7325, 176Hf/177Hf ranges from 0.2828 to 0.2835, based on 24 basalt samples. 176Hf/177Hf is positively correlated with 143Nd/144Nd, and negatively correlated with 87Sr/86Sr and 206Pb/204Pb. Along the Iceland-Reykjanes ridge traverse, 176Hf/177Hf increases southwards. The coherence of Hf, Nd and Sr isotopes in the oceanic mantle allows an approximate bulk Earth 176Hf/177Hf of 0.28295 to be inferred from the bulk Earth 143Nd/144. This requires the bulk Earth Lu/Hf to be 0.25, similar to that of the Juvinas eucrite. 60% of the Hf isotopic variation in oceanic basalts occurs among mid-ocean ridge samples. Lu-Hf fractionation probably decouples from Sm-Nd and Rb-Sr fractionation in very depleted source regions, with high Lu/Hf, and consequent high 176Hf/177Hf ratios developing in mantle residual from partial melting.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Hafnium isotope variations in oceanic basalts |
| Series title | Geophysical Research Letters |
| DOI | 10.1029/GL007i012p01077 |
| Volume | 7 |
| Issue | 12 |
| Year Published | 1980 |
| Language | English |
| Publisher | American Geophysical Union |
| Description | 4 p. |
| First page | 1077 |
| Last page | 1080 |
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