TY - JOUR
T1 - Composition of back-arc basin volcanics, Valu Fa Ridge, Lau Basin
T2 - Evidence for a slab-derived component in their mantle source
AU - Jenner, G. A.
AU - Cawood, P. A.
AU - Rautenschlein, M.
AU - White, W. M.
PY - 1987/1/1
Y1 - 1987/1/1
N2 - Samples dredged from 2 localities near the crest of the Valu Fa ridge, an active back-arc basin spreading centre in the Lau Basin, consist of highly vesicular lava fragments of andesitic composition. The samples are characterized by rare, euhedral An85 plagioclase phenocrysts in a hypocrystalline groundmass of An60 plagioclase laths, brown glass and rare subhedral clinopyroxene. Samples from within and, to a lesser extent, between the dredge hauls show remarkable isotopic and chemical homogeneity, with: 87Sr/86Sr - 0.70330 ± 2; 143Nd/144Nd - 0.51303 ± 2; 206Pb/204Pb - 18.65 ± 2; 207Pb/204Pb - 15.55 ± 1; 208Pb/204Pb - 38.34 ± 4; Sr - 165 ppm; Rb - 7 ppm; Cs - 0.17 ppm; K - 3300 to 4200 ppm; Ba - 96 ppm; and REE - LREE depleted with 12-18 × chondritic abundances. On Sr-Nd, Pb-Pb and Sr-Pb plots the volcanics lie just within or on the edge of the MORB fields, overlapping with island-arc volcanics from the Marianas and Tonga. Compared with MORB and ocean-island basalts, the samples show alkali-element enrichment relative to REE and higher Cs relative to Rb. The isotopic and geochemical characteristics of the Valu Fa Ridge volcanics clearly indicate a minor, but significant, slab-derived component in the back-arc basin mantle source.
AB - Samples dredged from 2 localities near the crest of the Valu Fa ridge, an active back-arc basin spreading centre in the Lau Basin, consist of highly vesicular lava fragments of andesitic composition. The samples are characterized by rare, euhedral An85 plagioclase phenocrysts in a hypocrystalline groundmass of An60 plagioclase laths, brown glass and rare subhedral clinopyroxene. Samples from within and, to a lesser extent, between the dredge hauls show remarkable isotopic and chemical homogeneity, with: 87Sr/86Sr - 0.70330 ± 2; 143Nd/144Nd - 0.51303 ± 2; 206Pb/204Pb - 18.65 ± 2; 207Pb/204Pb - 15.55 ± 1; 208Pb/204Pb - 38.34 ± 4; Sr - 165 ppm; Rb - 7 ppm; Cs - 0.17 ppm; K - 3300 to 4200 ppm; Ba - 96 ppm; and REE - LREE depleted with 12-18 × chondritic abundances. On Sr-Nd, Pb-Pb and Sr-Pb plots the volcanics lie just within or on the edge of the MORB fields, overlapping with island-arc volcanics from the Marianas and Tonga. Compared with MORB and ocean-island basalts, the samples show alkali-element enrichment relative to REE and higher Cs relative to Rb. The isotopic and geochemical characteristics of the Valu Fa Ridge volcanics clearly indicate a minor, but significant, slab-derived component in the back-arc basin mantle source.
UR - http://www.scopus.com/inward/record.url?scp=0023523770&partnerID=8YFLogxK
U2 - 10.1016/0377-0273(87)90045-X
DO - 10.1016/0377-0273(87)90045-X
M3 - Article
AN - SCOPUS:0023523770
SN - 0377-0273
VL - 32
SP - 209
EP - 222
JO - Journal of Volcanology and Geothermal Research
JF - Journal of Volcanology and Geothermal Research
IS - 1-3
ER -