Tracing crustal and slab contributions to arc magmatism in the Lesser Antilles island arc using helium and carbon relationships in geothermal fluids
Journal Article
·
· Geochimica et Cosmochimica Acta
- Vrije Univ., Amsterdan (Netherlands). Dept. of Earth Sciences
- Vrije Univ., Amsterdam (Netherlands). Dept. of Earth Sciences
- ISOLAB, Spijk (Netherlands)
The authors report helium and carbon isotope and CO{sub 2}/{sup 3}He ratios from a regional survey of geothermal fluids from the Lesser Antilles island arc, an arc system where there is compelling geochemical evidence for the superimposition of a crustal component onto mantle-derived magmas. A predominant mantle helium isotope signature is observed throughout the arc. The highest ratios coincide with MORB helium ({approximately}8R{sub A} where R{sub A} = air {sup 3}He/{sup 4}He) and occur towards the center of the arc (the islands of Martinique, Dominica, Guadeloupe, and Montserrat). In the south and north of the arc (Grenada, St. Vincent, St. Lucia in the south and Nevis and Saba in the north) {sup 3}He/{sup 4}He ratios are lower and lie between 4.9 and 6.8R{sub A}. This regional variation is also apparent in the carbon isotope systematics: the central portion of the arc (Martinique to Montserrat) have {delta}{sup 13}C(CO{sub 2}) values between {minus}2{per_thousand} and {minus}4{per_thousand} (vs PDB), heavier than the range observed in MORB ({minus}4 to {minus}9{per_thousand}). The south of the arc (Grenada to St. Lucia) is characterized by MORB-like carbon isotope ratios (centered on {minus}6{per_thousand}). CO{sub 2}/{sup 3}He ratios are significantly higher than the MORB value ({approximately}2 {times} 10{sup 9}) for the entire arc. The values in the central islands fall close to 10{sup 10} whereas the southern volcanoes have higher ratios between 10{sup 10}--10{sup 13}.
- OSTI ID:
- 338614
- Journal Information:
- Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 19-20 Vol. 62; ISSN GCACAK; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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