Helium isotopic evolution of Mauna Kea Volcano: first results from the 1-km drill core

Author:

Kurz, Mark D., Kenna, Timothy C., Lassiter, J.C., DePaolo, D.J.

Title:

Helium isotopic evolution of Mauna Kea Volcano: first results from the 1-km drill core

Periodical:

Journal of Geophysical Research

Year:

1996

Volume:

101

Pages:

11,781-11,791

Subject:

Helium Olivine Isotope ratios Hawaii Scientific Drilling Project Mauna Kea volcano

Summary:

To study the temporal helium isotopic evolution of Mauna Kea volcano, helium concentrations and isotopic ratios have been measured in a suite of basaltic olivines from the Hawaii Scientific Drilling Project (HSDP). Lavas from the base of the Mauna Loa section of the core (240-270 m depth) have (super 3)He/(super 4)He ratios between 13.9 and 15.8 times atmospheric (Ra). These values place a minimum age of 30 ka for the top of the Mauna Kea section, and are consistent with radiocarbon chronology. The upper part of the Mauna Kea lava section (290-620 m) has (super 3)He/(super 4)He ratios of 7.0 to 6.8 Ra. Between 620 and 670 m depth there is a transition to higher values, with (super 3) He/(super 4) He ratios between 10.2 and 12.5 Ra at depths greater than 670 m, suggesting a greater contribution of undegassed plume material to the older Mauna Kea tholeiites. The correlations between He, Nd, and Pb isotope ratios demonstrate that the helium isotopic variations are related to mixing of source materials rather than shallow contamination effects.

Label:

Geology

Collection:

Periodicals