Island arc tectonics of New Zealand manifested in helium isotope ratios

Journal Article · Wed Jul 01 04:00:00 EDT 1987 · Geochim. Cosmochim. Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(87)90175-X· OSTI ID:7222728

Sano, Y; Wakita, H; Giggenbach, W F

Thirty gas samples of various types - volcanic gas, geothermal gas, CH/sub 4/-rich natural gas, and petroleum gas - were collected in and around the North Island, New Zealand. /sup 3/He//sup 4/He and /sup 4/He//sup 20/Ne ratios were measured using a mass spectrometer. The observed /sup 3/He//sup 4/He and /sup 4/He//sup 20/Ne ratios of the samples varied from 0.08 x 10/sup -6/ to 8.75 x 10/sup -6/ and from 4.8 to 2100, respectively. Based on a /sup 3/He//sup 4/He-/sup 4/He//sup 20/Ne diagram, He in the samples can be explained by mixing of a subduction-type magmatic, a radiogenic, and an air component. The geographical distribution of /sup 3/He//sup 4/He ratios over the island indicates a clear contrast between forearc and volcanic arc regions: high in the former and low in the latter. A He boundary can be drawn from the Taupo Volcanic Zone to Egmont Volcano in terms of the /sup 3/He//sup 4/He profile. This boundary agrees well with that of high Q/low Q in the upper mantle as well as with the geographical distribution of terrestrial heat flow values. The high /sup 3/He//sup 4/He ratios in the volcanic arc region are attributed to subduction-type He associated with an uprising magma from the upper mantle and the lower ratios in the forearc region to radiogenic He derived from U and Th in basement and sedimentary rocks. This tendency is very similar to that found in northeast Japan and is understood to be a general signature of the He isotope ratio in an island arc system.

• Research Organization: Univ. of Tokyo (Japan)
• OSTI ID: 7222728
• Journal Information: Geochim. Cosmochim. Acta; (United States), Journal Name: Geochim. Cosmochim. Acta; (United States) Vol. 51:7; ISSN GCACA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
ACTINIDES
AUSTRALASIA
CHEMICAL COMPOSITION
CHEMISTRY
ELEMENTS
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GASES
GEOCHEMISTRY
HELIUM ISOTOPES
ISOTOPE RATIO
ISOTOPES
MAGMA
MAGMATISM
MASS SPECTROSCOPY
METALS
NATURAL GAS
NEON ISOTOPES
NEW ZEALAND
SPECTROSCOPY
SUBDUCTION ZONES
TECTONICS
THORIUM
URANIUM
VOLCANIC GASES
VOLCANIC REGIONS
VOLCANISM
VOLCANOES