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Lanphere, M.A. and Frey, F.A. (1987). Geochemical evolution of Kohala Volcano, Hawaii. Contributions to Mineralogy and Petrology 95(1): 100-113. |
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Kohala Volcano, the oldest of five shield volcanoes comprising the island of Hawaii, consists of a basalt shield dominated by tholeiitic basalt, Pololu Volcanics, overlain by alkalic lavas, Hawi Volcanics. In the upper Pololu Volcanics the lavas become more enriched in incompatible elements, and there is a transition from tholeiitic to alkalic basalt. In contrast, the Hawi Volcanics consist of hawaiites, mugearites, and trachytes. 87Sr/86Sr ratios of 14 Pololu basalts and 5 Hawi lavas range from 0.70366 to 0.70392 and 0.70350 to 0.70355, respectively. This small but distinct difference in Sr isotopic composition of different lava types, especially the lower 87Sr/86Sr in the younger lavas with higher Rb/Sr, has been found at other Hawaiian volcanoes. Our data do not confirm previous data indicating Sr isotopic homogeneity among lavas from Kohala Volcano. Also some abundance trends, such as MgO-P2O5, are not consistent with a simple genetic relationship between Pololu and Hawi lavas. We conclude that all Kohala lavas were not produced by equilibrium partial melting of a compositionally homogeneous source. |
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Keywords
alkali basalts; alkaline earth metals; basalts; East Pacific Ocean, Islands; geochemistry; Hawaii; igneous rocks; isotopes; Kohala;, lava; metals; Oceania; petrology; Polynesia; rare earths; shield, volcanoes; Sr-87/Sr-86; stable isotopes; strontium; tholeiitic, basalt; trace elements; United States; volcanic rocks; volcanoes;, volcanology, 02D Isotope geochemistry; 05A Igneous and metamorphic petrology |
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