Case studies on the origin of basalt; III, Petrogenesis of the Mauna Ulu eruption, Kilauea, 1969-1971

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Authors:Hofmann, A. W.; Feigenson, Mark D.; Raczek, I.
Author Affiliations:Primary:
Carnegie Inst. Wash., Dep. Terr. Magnetism, Washington, DC, United States
Volume Title:Contributions to Mineralogy and Petrology
Source:Contributions to Mineralogy and Petrology, 88(1-2), p.24-35. Publisher: Springer International, Heidelberg-New York, International. ISSN: 0010-7999
Publication Date:1984
Note:In English. 40 refs.; illus.
Summary:During the Mauna Ulu flank eruption on Kilauea, Hawaii, the concentrations in the lavas of the minor elements K, P, Na and Ti, and the incompatible trace elements (analyzed by isotope dilution) K, Rb, Cs, Ba, Sr, and the REE (except Yb) decreased monotonically and linearly with the time (or date) of the eruption. At the same time, the concentrations of the major elements and of Yb, and the ratios of K/Rb, K/Cs, Ba/Rb, 87Sr/86Sr and 143Nd/144Nd remained constant. Most of the scatter in the raw concentration data is removed by a simple correction for olivine (plus chromite) fractionation previously established by Wright et al. (1975). These results are explained by simple equilibrium partial melting of a uniform source. The degree of melting increased by about 20% of the initial value during the course of the eruption. The trace element data are inverted by the method originated by Minster and Allegre (1978) and simplified by Hofmann and Feigenson (1983). The source has the following element (or isotope) ratios: K/Rb=501 ±7, Ba/Rb=14.0±0.5, Rb/Cs=95±7, Rb/Sr=0.0193 ( +0.0045, -0.0090), (Ce/Ba)CN= 1.1 ±0.1, (Sr/ Ba)CN= 1.l9 (+0.30, -0.19), 87Sr/86Sr=0.703521 ± 0.000016, and 143Nd/l44Nd=0.512966±0.000008. The REE pattern of the source has a nearly flat or slightly negative slope (relative LREE enrichment) between Ce and Dy and a strongly positive slope between Dy and Yb. However, this relative HREE enrichment is poorly constrained by the analytical data, is highly model dependent and may not be a true source feature. The Yb concentration in the source is particularly poorly constrained because it is essentially constant in the melts. On the other hand, this special feature demonstrates that Yb must be buffered by a mineral phase with a high partition coefficient for Yb, namely garnet. The calculated clinopyroxene/garnet ratio in the source is roughly equal to one. In contrast, the source of Kohala volcano had previously been found to contain little or no garnet. [P.Br.]
Subjects:Alkali metals; Alkaline earth metals; Basalts; Case studies; Chain silicates; Clinopyroxene; Composition; Depth; Genesis; Geochemistry; Igneous rocks; Isotopes; Lava; Magmas; Metals; Nd-144/Nd-143; Neodymium; Petrology; Phosphorus; Potassium; Pyroxene group; Rare earths; Silicates; Sodium; Sr-87/Sr-86; Stable isotopes; Strontium; Titanium; Trace elements; Volcanic rocks; Volcanoes; East Pacific Ocean Islands; Hawaii; Hawaii County Hawaii; Hawaii Island; Kilauea; Mauna Ulu; Oceania; Polynesia; United States; Garnet; Ratios
Coordinates:N191500 N192500 W1550500 W1552000
Abstract Numbers:85M/4285
Record ID:1985038024
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from U. S. Geological Survey, Hawaiian Volcano Observatory, United States
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