Skiff Bank is a bathymetric and gravimetric high located ~350 km southwest of the Kerguelen Islands in the northern portion of the Kerguelen Igneous Province (KIP). Ocean Drilling Program Site 1139 was drilled at a water depth of 1415 m on Skiff Bank’s western edge. Hole 1139A penetrated to a depth of 695 meters below seafloor (mbsf) with sediment recovered from the upper 462 m and igneous basement recovered from the lower 233 m. A total of 19 basement units were identified, including variably welded trachytic to rhyolitic volcanic and volcaniclastic rocks (Units 1–5) and 14 lava flows with intermediate to mafic compositions (Units 6–19) (Shipboard Scientific Party, 2000). Core observations indicate that the basement units recovered from Hole 1139A display unique alteration patterns, in terms of both the intensity of alteration and secondary mineralogy, when compared to other drill holes from the Kerguelen Plateau. Basement Units 6–17 contain highly altered breccias, commonly corresponding to flow tops, and more massive and somewhat less altered flow interiors. The breccias are highly oxidized and cemented by calcite and clay minerals. Calcite veins and stringers are common throughout, and the groundmass has a bleached appearance due to the replacement of primary igneous minerals by secondary calcite. The lowermost basement Units 18 and 19 are highly to completely altered by intense oxidation to hematite or by nearly complete bleaching to produce a final mineral assemblage that 1Saccocia, P.J., Teagle, D.A.H., Telford, R.H., Eastley, N., and Brewer, T.S., 2004. Data report: Downhole major and trace element chemistry of volcanic rocks from Skiff Bank, Kerguelen Plateau (ODP Site 1139). In Frey, F.A., Coffin, M.F., Wallace, P.J., and Quilty, P.G. (Eds.), Proc. ODP, Sci. Results, 183, 1–12 [Online]. Available from World Wide Web: . [Cited YYYY-MM-DD] 2Department of Earth Sciences and Geography, Bridgewater State College, Bridgewater MA 02325, USA. psaccocia@bridgew.edu 3Southampton Oceanography Centre, School of Ocean and Earth Science, University of Southampton, Southampton SO14-3ZH, UK. 4Department of Geology, University of Leicester, Leicester LE1 7RH, UK.
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