Fractionation of Potassium/Rubidium by Amphiboles: Implications Regarding Mantle Composition
- 20 January 1967
- journal article
- other
- Published by American Association for the Advancement of Science (AAAS) in Science
- Vol. 155 (3760), 325-327
- https://doi.org/10.1126/science.155.3760.325
Abstract
We show that the rubidium in amphiboles is generally depleted with respect to potassium. The K:Rb ratios of 50 analyzed amphiboles range from 100 to 5000, averaging 1120. This fractionation effect holds for potassium concentrations ranging from 0.05 to 1.5 percent. The K:Rb ratios of abyssal tholeiites do not place unambiguous limits on the K:Rb ratio of the upper mantle, since partial melting of a mantle material such as amphibole peridotite would produce a liquid with a K:Rb ratio higher than that in the initial material. Large-scale mineralogic control of distributions of trace elements in the mantle could produce trends with depth that are the reverse of trends normally attributed to differentiation processes.Keywords
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