Intrusive dike complexes, cumulate cores, and the extrusive growth of Hawaiian volcanoes

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2013-07
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Flinders, Ashton F.
Ito, Garrett
Garcia, Michael O.
Sinton, John M.
Kauahikaua, Jim
Taylor, Brian
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American Geophysical Union
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The Hawaiian Islands are the most geologically studied hot-spot islands in the world yet surprisingly, the only large-scale compilation of marine and land gravity data is more than 45 years old. Early surveys served as reconnaissance studies only, and detailed analyses of the crustal-density structure have been limited. Here we present a new chain-wide gravity compilation that incorporates historical island surveys, recently published work on the islands of Hawai‘i, Kaua‘i, and Ni‘ihau, and >122,000 km of newly compiled marine gravity data. Positive residual gravity anomalies reflect dense intrusive bodies, allowing us to locate current and former volcanic centers, major rift zones, and a previously suggested volcano on Ka‘ena Ridge. By inverting the residual gravity data, we generate a 3-D view of the dense, intrusive complexes and olivine-rich cumulate cores within individual volcanoes and rift zones. We find that the Hāna and Ka‘ena ridges are underlain by particularly high-density intrusive material (>2.85 g/cm3) not observed beneath other Hawaiian rift zones. Contrary to previous estimates, volcanoes along the chain are shown to be composed of a small proportion of intrusive material (<30% by volume), implying that the islands are predominately built extrusively.
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Flinders, A. F., G. Ito, M. O. Garcia, J. M. Sinton, J. Kauahikaua, and B. Taylor (2013), Intrusive dike complexes, cumulate cores, and the extrusive growth of Hawaiian volcanoes, Geophys. Res. Lett., 40, 3367–3373.
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©2013. American Geophysical Union. All Rights Reserved.
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