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Tatsumoto, M. (1978). Isotopic composition of lead in oceanic basalt and its implication to mantle evolution. Earth and Planetary Science Letters 38(1): 63-87. |
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New data are given in this report for (1) Pb isotopic compositions and U, Th, and Pb concentrations of basalts from the island of Hawaii; (2) redetermined Pb isotopic compositions of some abyssal tholeiites; and (3) U, Th, and Pb concentrations of altered and fresh abyssal basalts, and basalt genesis and mantle evolution are discussed. The Th/U ratios of abyssal and Japanese tholeiites are distinctly lower than those of tholeiites and alkali basalts from other areas. It is thought that these low values reflect a part of the mantle depleted in large ionic lithophile elements. Thus a mantle evolution model is presented, in which Th/U ratios of the depleted zone in the mantle have decreased to 2, and U/Pb ratios have increased, showing an apparent 1.5-b.y. isochron trend in the (super 207) Pb/ (super 204) Pb vs. (super 206) Pb/ (super 204) Pb plot. The Pb isotopic compositions of basalts from the island of Hawaii are distinct for each of the five volcanoes, and within each volcano, Pb's of tholeiites and alkali basalts are similar. An interaction between partially melted material (hot plume?) of the asthenosphere and the lithosphere is suggested to explain the trend in the Pb isotopic compositions of Hawaiian basalts. |
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Keywords
actinides; basalts; crust; data; differentiation; East Pacific, Ocean Islands; evolution; genesis; geochemistry; Hawaii; igneous, rocks; isotopes; lead; magmas; mantle; mathematical models;, metals; mid-ocean ridges; Oceania; oceanic crust; Polynesia;, ratios; tholeiite; thorium; trace elements; United States; upper, mantle; uranium; volcanic rocks, 02, Geochemistry |
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Publisher
Elsevier Science
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1000 AE Amsterdam
The Netherlands
(+31) 20 485 3757
(+31) 20 485 3432
nlinfo-f@elsevier.com |
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