Petrology, geochemistry, and ages of lavas from Northwest Hawaiian Ridge volcanoes
Michael O. Garcia, John R. Smith, Jonathan P. Tree, Dominique Weis, Lauren Harrison, Brian R. Jicha, 2015. "Petrology, geochemistry, and ages of lavas from Northwest Hawaiian Ridge volcanoes", The Origin, Evolution, and Environmental Impact of Oceanic Large Igneous Provinces, Clive R. Neal, William W. Sager, Takashi Sano, Elisabetta Erba
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The Northwest Hawaiian Ridge is a classic example of a large igneous province. The morphology and geology of the ridge is poorly characterized, although it constitutes the longest segment (~47%) of the Hawaiian-Emperor Chain. Here we present a new bathymetric compilation, petrographic and X-ray fluorescence (XRF) data for lavas from 12 volcanoes along the Northwest Hawaiian Ridge, and review literature data for the age and isotopic variation of the ridge. The bathymetric compilation revealed that the Northwest Hawaiian Ridge consists of at least 51 volcanoes. The 45 new XRF analyses show that the Northwest Hawaiian Ridge contains tholeiitic and alkalic lavas with compositions typical of lavas from the Hawaiian Islands. The absolute ages and duration of volcanism of individual Northwest Hawaiian Ridge volcanoes are poorly known, with modern 40Ar/39Ar ages for only 10 volcanoes, mostly near the bend in the chain. We infer the initiation age of the Hawaiian-Emperor Bend to be ca. 49–48 Ma, younger than the age for the onset of island arc volcanism in the western Pacific (52–51 Ma). Thus, the kink in the Hawaiian-Emperor Chain and the onset of arc volcanism were not synchronous. Isotopic data are sparse for the Northwest Hawaiian Ridge, especially for Pb and Hf. Two transitional lavas from just south of the bend have Loa trend type Pb and Sr isotopic ratios. Otherwise, the available chemistry for Northwest Hawaiian Ridge lavas indicates Kea-trend source compositions. The dramatic increase in melt flux along the Hawaiian Ridge (~300%) may be related to changes in melting conditions, source fertility, or plate stresses.