Helium isotopic and chemical composition of gases from volcanic-hydrothermal systems in the Philippines
- Inst. of Geological and Nuclear Sciences, Lower Hutt (New Zealand)
- Univ. of Rochester, NY (United States). Dept. of Geological Sciences
Relative {sup 3}He, {sup 4}He, Ne, Ar, N{sub 2} and CO{sub 2} contents of gases collected from high temperature geothermal systems associated with active subduction zones in the Philippines, (Cagua, Alto Peak, Mahagnao, Mambucal and Mount Apo) correspond to {sup 3}He/{sup 4}He ratios of 6.9 to 7.6 R{sub A}, CO{sub 2}/{sup 3}He ratios of 10 to 50 {times} 10{sup 9} and N{sub 2}/Ar ratios of 200 to 500. The data suggest that He is essentially of upper mantle origin and that CO{sub 2} and N{sub 2} are predominantly derived from subducted sediments. Highest CO{sub 2}/He ratios are observed for systems along the centerline between major zones of active subduction to the E and W of the Philippine islands. The high values may tentatively be explained in terms of derivation from an especially CO{sub 2}-rich magmatic environment created by the supply of volatiles from two subduction systems. The low {sup 3}He/{sup 4}He ratios of 0.4 and 0.6 R{sub A} for two springs on the island of Palawan indicate that the thermal waters there are the result of only residual geothermal activity associated with an, at present, inactive subduction zone.
- OSTI ID:
- 143814
- Journal Information:
- Geothermics, Vol. 22, Issue 5-6; Other Information: PBD: Oct-Dec 1993
- Country of Publication:
- United States
- Language:
- English
Similar Records
He, Ne, Ar, and C isotope systematics of geothermal emanations in the Lesser Antilles Islands Arc
He and Sr isotopic constraints on subduction contributions to Woodlark Basin volcanism, Solomon Islands