Collaborative Research: Petrologic and Geochemical Investigations of Low Temperature, Fluid-Rock Interactions within a Hot Spot, Oceanic Island Volcano from Study of the HSDP Core

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0125495WaltonThe project will focus on combined petrographic and geochemical analyses of altered rock core recovered from a deep drill hole near Hilo, on the Big Island of Hawaii. Some of this material comes from a 3 km-deep drill hole completed by the Hawaii Scientific Drilling Project (HSDP) in September, 1999. The reminder will come from new samples that will be recovered when the existing hole is deepened, beginning in early 2003. The primary objective of this project will be to develop and test models for rock alteration using an integrated analytical approach for studying the recovered core materials. Major questions to be addressed are: (1) What is the alteration history of the basaltic material which underlies Mauna Kea volcano, how has it been influenced by various types of alteration processes, and are these distinct from other forms of seafloor alteration? (2) How has this alteration affected the mineral composition and physical properties of these materials? (3) How significantly has alteration affected the chemical composition of the submarine portions of the Mauna Kea? and (4) What is the evidence regarding (proposed models invoking) deep circulation of ground waters within the interior of this volcano? Questions # 1 and 2 will be addressed through the systematic study of the alteration mineralogy. Question #3 and 4 will be addressed by detailed geochemical investigations of elemental and isotopic signatures associated with the conversion of basaltic minerals and glass to palagonitized glass, layer silicates, and zeolites. Trace element and isotopic analyses will provide the means of evaluating the exchange of basaltic, seawater, meteoric components during alteration. Stable isotopic analyses of alteration minerals should allow us to test a hydrologic model suggesting that meteoric fluids have circulated deep within the interior of Mauna Kea.