Temporal helium isotopic variations within Hawaiian volcanoes: Basalts from Mauna Loa and Haleakala

Journal Article · Sun Nov 01 04:00:00 EST 1987 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(87)90366-8· OSTI ID:5152433

Kurz, M D; O'Brien, P A ^[1]; Garcia, M O ^[2]; Frey, F A ^[3]

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1. Woods Hole Oceanographic Institution, MA (USA)
2. Univ. of Hawaii, Honolulu (USA)
3. Massachusetts Institute of Technology, Cambridge (USA)

Helium isotope ratios in basalts spanning the subaerial eruptive history of Mauna Loa and Haleakala vary systematically with eruption age. In both volcanoes, olivine mineral separates from the oldest samples have the highest {sup 3}He/{sup 4}he ratios. The Haleakala samples studied range in age from roughly one million years to historic time, while the Mauna Loa samples are radiocarbon dated flows younger than 30,000 years old. The Honomanu tholeiites are the oldest samples from Haleakala and have {sup 3}He/{sup 4}he ratios that range from 13 to 16.8X atmospheric, while the younger Kula and Hana series alkali basalts all have {sup 3}He/{sup 4}He close to 8X atmospheric. A similar range is observed on Manua Loa; the oldest samples have {sup 3}He/{sup 4}He ratios of 15 to 20X atmospheric, with a relatively smooth decrease to 8X atmospheric with decreasing age. The consistent trend of decreasing {sup 3}He/{sup 4}he ratio with time in both volcanoes, coherence between the helium and Sr and Nd isotopes (for Haleakala), and the similarity of {sup 3}He/{sup 4}He in the late stage basalts to depleted mid-ocean ridge basalt (MORB) helium, argue against the decrease being the result of radiogenic ingrowth of {sup 4}He. The data strongly suggest an undegassed mantle source for the early shield building stages of Hawaiian volcanism, and are consistent with the hotspot/mantle plume model. The data are difficult to reconcile with models for Hawaiian volcanism that require recycled oceanic crust or derivation from a MORB-related upper mantle source. The authors interpret the decrease in {sup 3}He/{sup 4}He with volcano evolution to result from an increasing involvement of depleted mantle and/or lithosphere during the late stages of Hawaiian volcanism.

• OSTI ID: 5152433
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 51:11; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
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CHEMICAL COMPOSITION
CHEMISTRY
EARTH CRUST
ERUPTION
FEDERAL REGION IX
GEOCHEMISTRY
GEOLOGIC HISTORY
GEOLOGIC MODELS
HAWAII
HELIUM ISOTOPES
IGNEOUS ROCKS
IRON COMPOUNDS
IRON SILICATES
ISOTOPE RATIO
ISOTOPES
MAGNESIUM COMPOUNDS
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MINERALS
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NORTH AMERICA
OCEANIC CRUST
OLIVINE
OXYGEN COMPOUNDS
PETROGENESIS
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
STRONTIUM ISOTOPES
TRANSITION ELEMENT COMPOUNDS
USA
VOLCANIC ROCKS
VOLCANOES