Mapping magma sources in the east Sunda-Banda arcs, Indonesia: Constraints from helium isotopes

Journal Article · Sat Feb 01 00:00:00 EST 1992 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(92)90105-R· OSTI ID:5195296

Hilton, D R; Hammerschmidt, K ^[1]; Hoogewerff, J A; van Bergen, M J ^[2]

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1. Freie Univ. Berlin (West Germany)
2. Univ. of Utrecht (Netherlands)

The authors report new helium isotope analyses of olivine and clinopyroxene separates from recent lavas for eleven volcanoes from Flores in the east Sunda arc through the inactive segment between the arcs to Banda Island at the extreme of the contiguous Banda arc. In the east Sunda arc, {sup 3}He/{sup 4}He ratios (R) vary between 4.5 R{sub A} (R{sub A} = air {sup 3}He/{sup 4}He) for the leucitic Batu Tara volcano to a remarkable low of pure radiogenic helium (0.0075 R{sub A}) for Werung at the southern tip of Lomblen Island. Lavas from the inactive zone have a narrower range in R/R{sub A} - from 3.9 for Kisu in the straits of Pantar to 1.0 for Romang Island. The authors' one locality (Banda Island) in the Banda arc gives the highest R/R{sub A} ratio (3.1) observed along this arc to date. They combine these helium isotope results with published and on-going strontium isotope studies, and show that the source of the helium in the crustal component is unlikely to be terrigenous sediments derived from the Australian continent; rather, degassing of Australian continental crust appears to be the dominant process controlling the helium budget. The He-Sr isotope systematics also provide a framework to account for the areal pattern of {sup 3}He/{sup 4}He in this part of the arcs: the radiogenic crustal component is diluted with mantle helium both in a down-dip direction and with increasing lateral distance from the collision zone. These factors result in an excellent first-order relationship between the {sup 3}He/{sup 4}He ratio, degree of He/Sr enrichment and alkalinity of the erupted lavas. Such a relationship has a direct bearing on models of the tectonic evolution of the collision zone, and on the observation that helium isotopes are decoupled from strontium and other geochemical signatures along the Banda arc.

• OSTI ID: 5195296
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Vol. 56:2; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
INDONESIA
MAGMA SYSTEMS
OLIVINE
ISOTOPE RATIO
PYROXENES
VOLCANIC ROCKS
PETROGENESIS
CHEMICAL COMPOSITION
COMPARATIVE EVALUATIONS
CONTINENTAL CRUST
DEGASSING
GEOCHEMISTRY
GEOLOGIC MODELS
HELIUM ISOTOPES
LAVA
MAGMA
PLATE TECTONICS
SUBDUCTION ZONES
ASIA
CHEMISTRY
DEVELOPING COUNTRIES
EARTH CRUST
EVALUATION
GEOTHERMAL SYSTEMS
IGNEOUS ROCKS
ISLANDS
ISOTOPES
MINERALS
OXYGEN COMPOUNDS
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
TECTONICS
580000* - Geosciences