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Roden, M.F., Frey, F.A. and Clague, D.A. (1984). Geochemistry of tholeiitic and alkalic lavas from the Koolau Range, Oahu, Hawaii; implications for Hawaiian volcanism. Earth and Planetary Science Letters 69(1): 141-158. |
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Lavas of the post-erosional, alkalic Honolulu Volcanics have significantly lower (super 87) Sr/ (super 86) Sr and higher (super 143) Nd/ (super 144) Nd than the older and underlying Koolau tholeiites. Despite significant compositional variation within lavas forming the Honolulu Volcanics, these lavas are isotopically (Sr, Nd, Pb) very similar which contrasts with the isotopic heterogeneity of the Koolau tholeiites. Among Hawaiian tholeiitic suites, the Koolau lavas are geochemically distinct because of their lower iron contents and Sr and Nd isotopic ratios which range to bulk earth values. These geochemical data preclude simple models such as derivation of the Honolulu Volcanics and Koolau tholeiites from a common source by different degrees of melting or by mixing of two geochemically distinct sources. There may be no genetic relationship between the origin and evolution of these two lava suites; however, the trend shown by Koolau Range lavas of increasing (super 143) Nd/ (sub 144) Nd and decreasing (super 87) Sr/ (super 86) Sr with decreasing eruption age and increasing alkalinity also occurs at Haleakala, East Molokai and Kauai volcanoes. A complex mixing model proposed for Haleakala lavas can account for the variations in Sr and Nd isotopic ratios and incompatible element abundances found in lavas from the Koolau Range. This model may reflect mixing and melting processes occurring during ascent of relatively enriched mantle through relatively depleted MORB-related lithosphere. Although two isotopically distinct components may be sufficient to explain Sr and Nd isotopic variations at individual Hawaiian volcanoes, more than two isotopically distinct materials are required to explain variations of Sr, Nd and Pb isotopic ratios in all Hawaiian lavas. |
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Keywords
alkaline earth metals; basaltic composition; basalts; East Pacific, Ocean Islands; geochemistry; Haleakala; Hawaii; Honolulu County, Hawaii; Honolulu Volcanics; igneous rocks; isotopes; Kauai; Koolau, Range; lava; lead; lithosphere; major elements; mantle; Maui, County Hawaii; melting; metals; mixing; Molokai; Nd-144/Nd-143;, neodymium; Oahu; Oceania; petrology; Polynesia; rare earths;, ratios; Sr-87/Sr-86; stable isotopes; strontium; tholeiite;, tholeiitic composition; United States; volcanic rocks; volcanism;, volcanoes; volcanology, 05A Igneous and metamorphic petrology; 02C Geochemistry of rocks,, soils, and sediments |
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Publisher
Elsevier Science
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