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Creator |
b75227dc49245aab76a534b836099ab7 |
| 48184 |
Creator |
d8b3b90e24f10b122cfbd5afecaaa40e |
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Creator |
84764f824834b90b789fef94138093b1 |
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Creator |
ext-58463297642c45b2b60ba82853d491a0 |
| 48184 |
Creator |
ext-eb50c84348019134384106c01779f221 |
| 48184 |
Creator |
ext-3e45fae43885b6cde00c20d81d439fe7 |
| 48184 |
Creator |
ext-5ebd227ac5a55506933cc7a12ab9c07d |
| 48184 |
Creator |
ext-7ef22eea7dd1e92e18b6004cfacfb09f |
| 48184 |
Creator |
ext-d213d8f955d239720fd6237d1127fa58 |
| 48184 |
Creator |
ext-d46b2eef1d1b37a476029ba4cb338d7b |
| 48184 |
Date |
2016-03-01 |
| 48184 |
Is Part Of |
p00167037 |
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Is Part Of |
repository |
| 48184 |
abstract |
Measurements of Xe isotope ratios in ocean island basalts (OIB) suggest that Earth’s
mantle accreted heterogeneously, and that compositional remnants of accretion are
sampled by modern, high-<sup>3</sup>He/<sup>4</sup>He OIB associated with the Icelandic
and Samoan plumes. If so, the high-<sup>3</sup>He/<sup>4</sup>He source may also have
a distinct oxygen isotopic composition from the rest of the mantle. Here, we test
if the major elements of the high-<sup>3</sup>He/<sup>4</sup>He source preserve any
evidence of heterogeneous accretion using measurements of three oxygen isotopes on
olivine from a variety of high-<sup>3</sup>He/<sup>4</sup>He OIB locations. To high
precision, the Δ<sup>17</sup>O value of high-<sup>3</sup>He/<sup>4</sup>He olivines
from Hawaii, Pitcairn, Baffin Island and Samoa, are indistinguishable from bulk mantle
olivine (Δ<sup>17</sup>O<sup>Bulk Mantle</sup> − Δ<sup>17</sup>O<sup>High 3He/4He
olivine</sup> = −0.002 ± 0.004 (2 × SEM)‰). Thus, there is no resolvable oxygen isotope
evidence for heterogeneous accretion in the high-<sup>3</sup>He/<sup>4</sup>He source.
Modelling of mixing processes indicates that if an early-forming, oxygen-isotope distinct
mantle did exist, either the anomaly was extremely small, or the anomaly was homogenised
away by later mantle convection.
The δ<sup>18</sup>O values of olivine with the highest <sup>3</sup>He/<sup>4</sup>He
ratios from a variety of OIB locations have a relatively uniform composition (∼5‰).
This composition is intermediate to values associated with the depleted MORB mantle
and the average mantle. Similarly, δ<sup>18</sup>O values of olivine from high-<sup>3</sup>He/<sup>4</sup>He
OIB correlate with radiogenic isotope ratios of He, Sr, and Nd. Combined, this suggests
that magmatic oxygen is sourced from the same mantle as other, more incompatible elements
and that the intermediate δ<sup>18</sup>O value is a feature of the high-<sup>3</sup>He/<sup>4</sup>He
mantle source. The processes responsible for the δ<sup>18</sup>O signature of high-<sup>3</sup>He/<sup>4</sup>He
mantle are not certain, but δ<sup>18</sup>O–<sup>87</sup>Sr/<sup>86</sup>Sr correlations
indicate that it may be connected to a predominance of a HIMU-like (high U/Pb) component
or other moderate δ<sup>18</sup>O components recycled into the high-<sup>3</sup>He/<sup>4</sup>He
source. |
| 48184 |
authorList |
authors |
| 48184 |
status |
peerReviewed |
| 48184 |
uri |
http://data.open.ac.uk/oro/document/554428 |
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uri |
http://data.open.ac.uk/oro/document/554429 |
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uri |
http://data.open.ac.uk/oro/document/554430 |
| 48184 |
uri |
http://data.open.ac.uk/oro/document/554431 |
| 48184 |
uri |
http://data.open.ac.uk/oro/document/554432 |
| 48184 |
uri |
http://data.open.ac.uk/oro/document/554433 |
| 48184 |
uri |
http://data.open.ac.uk/oro/document/554654 |
| 48184 |
volume |
176 |
| 48184 |
type |
AcademicArticle |
| 48184 |
type |
Article |
| 48184 |
label |
Starkey, N.A. ; Jackson, C.R.M.; Greenwood, R.C. ; Parman, S.; Franchi, I.A. ;
Jackson, M.; Fitton, J.G.; Stuart, F.M.; Kurz, M. and Larsen, L.M. (2016). Triple
oxygen isotopic composition of the high-3He/4He mantle. Geochimica et Cosmochimica
Acta, 176 pp. 227–238. |
| 48184 |
label |
Starkey, N.A. ; Jackson, C.R.M.; Greenwood, R.C. ; Parman, S.; Franchi, I.A. ; Jackson,
M.; Fitton, J.G.; Stuart, F.M.; Kurz, M. and Larsen, L.M. (2016). Triple oxygen isotopic
composition of the high-3He/4He mantle. Geochimica et Cosmochimica Acta, 176 pp.
227–238. |
| 48184 |
Title |
Triple oxygen isotopic composition of the high-<sup>3</sup>He/<sup>4</sup>He mantle |
| 48184 |
in dataset |
oro |