Variations in143Nd/144Nd and87Sr/86Sr ratios in oceanic basalts

O’Nions, R.K.; Hamilton, P. J.; Evensen, N. M.

doi:10.1016/0012-821x(77)90100-5

Cited by 683 publications

(134 citation statements)

References 27 publications

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“…The measured Nd isotopic ratios were normalized to 146 Nd/ 144 Nd = 0.7219. During the Nd isotopic measurements, the isotopic ratios measured for the standards, i.e., La Jolla and JNdi-1 (supplied by the Geological Survey of Japan), were 0.511856 ± 0.000007 (2s, n = 9) and 0.512112 ± 0.000006 (2s, n = 29), respectively, and were in good agreement with those reported by O'Nions et al (1977) and Tanaka et al (2000). As the contribution of blank to each sample was less than 1%, no blank correction was performed.…”

Section: Methodssupporting

confidence: 84%

Nd concentration and isotopic composition distributions in surface waters of Northwest Pacific Ocean and its adjacent seas

2004

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Nd isotopic composition and concentration distributions were determined in surface waters of the Northwest Pacific Ocean and its adjacent seas, i.e., the Okhotsk and Japan Seas. The Okhotsk and Japan Seas samples showed higher Nd concentrations (19~31 pmol/kg) than the Northwest Pacific Ocean samples, suggesting a large amount of Nd input from the land areas surrounding the Okhotsk and Japan Seas. Although the Nd isotopic composition data were limited for those regions, each oceanic area showed a distinctive value. The lone sample from the Okhotsk Sea had radiogenic Nd (e Nd = -3.6) that was comparable to samples from the Pacific Ocean, indicating a large amount of radiogenic Nd supply from the Kuril Islands. On the other hand, the Japan Sea samples had the most highly unradiogenic Nd (e Nd = -8.9~-7.2). The southernmost sample had the most negative value, due to the influence of the Tsushima Warm Current (TWC) having a low e Nd value. The latitudinal distributions of Nd isotopic composition and concentration in the surface waters of the Northwest Pacific Ocean showed marked variations. Nd concentration was low at low latitudes (3~8 pmol/kg) and was increased with increasing latitude (16~20 pmol/kg). On the other hand, Nd isotopic composition showed a mid-latitude minimum (e Nd = ~-6) and high e Nd values at low and high latitudes (e Nd = -2~-1). The distribution of the e Nd values seemed to be controlled by three currents: Kuroshio Extension, Oyashio Current and North Equatorial Current (NEC). The Kuroshio Extension, which showed a low e Nd value, seemed to play an important role in transporting continentally derived Nd to the central Pacific. The Oyashio Current and NEC are supplied with large amounts of radiogenic Nd from the Kuril and Aleutian Islands, and the Hawaiian Islands, respectively.Based on the Nd isotopic composition and concentration distributions, we calculated the radiogenic Nd flux to the Pacific Ocean surface waters and estimated the Nd residence time. Our calculation suggested that the radiogenic Nd flux required to account for the Nd isotopic composition is higher than 70% of the unradiogenic Nd flux including Nd remobilization from coastal and shelf sediments and atmospheric input. It was also revealed that a large Nd remobilization flux is necessary to attain a global Nd residence time of ~400 y as estimated in previous studies.

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Section: Methodssupporting

confidence: 84%

Nd concentration and isotopic composition distributions in surface waters of Northwest Pacific Ocean and its adjacent seas

2004

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“…The analytical procedures used have been described (1,25) which cannot be attributed to contamination, then it may be necessary to revise estimates (10,27) for the values of Sm/Nd and Rb/Sr in the bulk earth.…”

Section: Resultsmentioning

confidence: 99%

Neodymium isotopes in flood basalts from the Siberian Platform and inferences about their mantle sources

DePaolo

Wasserburg²

1979

Proc. Natl. Acad. Sci. U.S.A.

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The initial isotopic compositions of Nd and Sr in basalts from the Central Siberian Plateau and other major continental flood basalts are reported. The continental flood basalts appear to be the product of partial melting of mantle sources that consist of relatively primitive undifferentiated material and are clearly distinct from midocean ridge basalts, which sample mantle reservoirs that have been modified by extraction of continental crust earlier in earth history. These observations provide fundamental constraints on models of mantle structure and dynamics. Isotopic effects of crustal contamination are clearly recognizable in some continental flood basalts, but these effects can be distinguished from isotopic patterns inherited from the mantle magma sources.The purpose of this work is to exhibit data on the isotopic composition of Nd in continental flood basalts (CFBs) that appear to confirm the isotopic contrasts between these magmas and oceanic ridge basalts inferred by DePaolo and Wasserburg (1,2). In addition, we discuss some of the consequences of this distinction for the structure and history of the earth's mantle. Studies of basalts have been a matter of continued geologic interest because the lavas are presumed to represent the underlying mantle. An extensive discussion of basalt genesis and its relation to earth structure, emphasizing petrologic arguments, is given in ref. 3. In the present study, isotopic and trace element variations are emphasized.The largest CFB provinces have ages less than t0.25 aeon (1 aeon = 109 years), which is similar to the maximum age of the ocean basins (t0.2 aeon). Thus, the lavas considered here provide a comparison of continental and oceanic volcanism over a time span that is short compared to the age of the earth. In general, the major element chemical compositions of continental and oceanic basalts are similar. Trace element abundances show midocean ridge basalts (MORBs) are depleted in so-called "large ion lithophile" or "incompatible" elements relative to CFBs (4). MORBs were inferred to come from relatively primitive sources (5), until Tatsumoto et al. (6) and Gast (7) called attention to the depleted trace element patterns and suggested that these reflected the differentiated character of the mantle magma sources. Trace-element and isotopic distinctions between MORBs and intraplate oceanic island basalts (e.g., Hawaii) have been amply documented (6,8). However, the distinction between MORBs and CFBs has received relatively little attention. The possibility of crustal contamination in continental volcanics has to some extent limited the interest in theseocks as samples of mantle sources (9).Distinctions in the modes of emplacement of these two basalt types may relate to differences in their mantle sources. CFBs are erupted from extensive fissure systems. High rates of eruption and low viscosity allow the lavas to flow long distances and result in the "flooding" of large areas. In contrast, MORBs tend to be erupted more passively onto the ocean floor, a...

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“…6). The mean 143 Nd/ 144 Nd (with 2s analytical reproducibility) from 12 and 7 runs of unspiked and spiked BCR-1 were 0.512620ῌ0.000013 (n῍12) and 29) 0.512647ῌ0.000022 MIT 30) 0.51263 ῌ0.00003 Lamont 31) 0.51264 ῌ0.00002 Univ. Minnesota 32) 0.512641ῌ0.000015 Cambridge 33) 0.512648ῌ0.000015 Open.…”

Section: ῃ1mentioning

confidence: 99%

Precise Isotope Determination of Trace Amounts of Nd in Magnesium-rich Samples

Shibata

Yoshikawa

2004

J. Mass Spectrom. Soc. Jpn.

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We developed a technique combining mass spectrometry with chemical separation to analyze Sm῎Nd isotopic compositions of ultramafic rock samples, which have extremely high Mg and low Nd concentrations and are always di$cult to analyze. In the case of ultramafic rocks, abundant Mg forms fluorides during decomposition by HF, and minor amounts of Sm and Nd are strongly partitioned into fluorides, which would be a significant reason of low recovery yields of these elements and obstructed to determine a reliable isotopic ratio of Nd and Sm. We introduced pre-decomposition by HCl prior to the conventional method by HF and HClO 4 that made it possible to elevate recovery yield to 85ῑ. On the other hand, replicate measurements of Nd standard solution (La Jolla) by changing the ion current of Nd ῌ and the amount of Nd indicate that reliable isotopic ratios are measured under the condition of ῐ0.04῎10῍11 A of 144 Nd ῌ ion current and ῐ2 ng of Nd. By applying our method, we analyzed 143 Nd/ 144 Nd ratio and Sm and Nd concentrations of PCC-1, which is an ultramafic standard rock sample of United States Geological Survey. The results of our analysis were 0.512226῍0.000026, 0.00551 ῍0.00041, and 0.0278῍0.0011 ppm, respectively. These results are the first report of 143 Nd/ 144 Nd ratio for PCC-1.

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Variations in143Nd/144Nd and87Sr/86Sr ratios in oceanic basalts

Cited by 683 publications

References 27 publications

Nd concentration and isotopic composition distributions in surface waters of Northwest Pacific Ocean and its adjacent seas

Nd concentration and isotopic composition distributions in surface waters of Northwest Pacific Ocean and its adjacent seas

Neodymium isotopes in flood basalts from the Siberian Platform and inferences about their mantle sources

Precise Isotope Determination of Trace Amounts of Nd in Magnesium-rich Samples

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