In:
Journal of Geophysical Research: Solid Earth, American Geophysical Union (AGU), Vol. 101, No. B5 ( 1996-05-10), p. 11807-11813
Abstract:
Oxygen isotope ratios of olivine in 23 tholeiites from the Hawaii Scientific Drilling Project (HSDP) core (15 from Mauna Kea, 8 from Mauna Loa) and three samples of outcropping subaerial or dredged submarine Mauna Kea lavas have been measured by laser fluorination. The δ 18 O values are 4.6–5.4‰, confirming previous observations that some Hawaiian lavas are derived from sources with δ 18 O values lower than typical upper mantle (δ 18 O olivine ≈ 5.2 ± 0.2‰). The Mauna Kea‐Mauna Loa transition marks a shift from δ 18 O values lower than the mantle average in Mauna Kea olivines (∼4.8) to more typical mantle values in Mauna Loa olivines. Lavas containing olivines with δ 18 O values similar to the typical upper mantle are associated with more “primitive” or less depleted radiogenic isotope characteristics; i.e., with higher 3 He/ 4 He ( 〉 13 Ra), higher 87 Sr/ 86 Sr ( 〉 0.7036) and lower ϵ Nd ( 〈 6.5), and with 206 Pb/ 204 Pb ratios less than ∼18.3. These relationships indicate that the δ 18 O values of the relatively enriched source components of the Hawaiian plume sampled by Mauna Loa lavas are comparable to (or greater than) the mantle average. This conclusion is supported by δ 18 O values of olivine from other high 3 He/ 4 He islands, which are also comparable to the upper mantle average. The low δ 18 O values in Hawaiian lavas are derived from a source having more MORB‐like, or depleted, He, Nd, and Sr isotope ratios, but more radiogenic Pb than is seen in the Mauna Loa lavas. Assimilation of 18 O‐depleted lower oceanic crust from the underlying Pacific crust by hot, MgO‐rich parental magmas or melting of older, recycled oceanic crust entrained in the Hawaiian plume are both possible sources of this 18 O‐depleted, MORB‐like component in Hawaiian magmas.
Type of Medium:
Online Resource
ISSN:
0148-0227
Language:
English
Publisher:
American Geophysical Union (AGU)
Publication Date:
1996
detail.hit.zdb_id:
161666-3
SSG:
16,13
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