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Lead isotopes in volcanic rocks and possible ocean-floor thrusting beneath island arcs

Earth and Planetary Science Letters

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Abstract

The isotopic composition of lead in the Japanese primary basalts gradually decreases in radiogenic character in a transverse from the Pacific Ocean side to the Japan Sea side, whereas the observed 238U 204Pb and 232Th 204Pb ratios in the basalts increase in the same direction. The isotopic composition of lead suggests that tholeiite (Pacific side) is generated at a shallower depth than alkali basalt (Japan Sea side) as postulated by Kuno. The inverse correlation of the 238U 204Pb with the 206Pb 204Pb ratios could be due to preferential Pb extraction with respect to uranium at shallow depths. Alternatively, these geochemical results can be interpreted in terms of the Pacific oceanic rigid plate being underthurst beneath the island arc. The isotopic variation in basalts across the Japanese island arc would result from different proportions of the plate material and the upper mantle of continental side in the partial melt. ?? 1969.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Lead isotopes in volcanic rocks and possible ocean-floor thrusting beneath island arcs
Series title:
Earth and Planetary Science Letters
Volume
6
Issue:
5
Year Published:
1969
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Earth and Planetary Science Letters
First page:
369
Last page:
376
Number of Pages:
8