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doi:10.2204/iodp.proc.334.201.2014

Data report: minor element concentrations in pore fluids from the CRISP-A transect drilled during Expedition 334¹

Marta E. Torres,² Jesse M. Muratli,² and Evan A. Solomon³

Abstract

We report on the minor element composition of pore fluids recovered during Integrated Ocean Drilling Program (IODP) Costa Rica Seismogenesis Project (CRISP) Expedition 334 from two sites (U1378 and U1379) drilled in the slope sediments of the overriding Caribbean plate and one site (U1381) that sampled sediments in the incoming Cocos plate. Sr, Ba, Li, B, and Mn were measured using a Leeman Labs Prodigy inductively coupled plasma–optical emission spectrometry, on acidified dilutions of pore water samples at Oregon State University. H₄SiO₄ concentrations were determined colorimetrically in unacidified samples using a Thermo Scientific Genesys 10s Vis spectrophotometer at the University of Washington.

In the slope sediment, alteration of reactive ash layers exerts a control on H₄SiO₄ concentrations and leads to increases in Ba and to some degree Mn. Sr is also released from this reaction, but the pore water profiles also reflect carbonate diagenesis, which is also known to occur in these sediments. Li increases with depth and has a discrete maximum at a shear zone that marks the unconformity between the slope apron sediments and the underlying margin wedge. B shows an increase over seawater values in the shallowmost sediments, possibly due to release of this element from organic matter alteration. A decrease below the near-surface maxima suggests incorporation of this element on clay minerals.

At the incoming site, the concentration-depth profile of H₄SiO₄ reflects lithology with lower concentrations in Unit I and elevated concentrations in Unit II resulting from biogenic silica dissolution. Sr reflects ash alteration within the sediments, and a reversal close to the sediment basement contact indicates diffusional communication with altered seawater in the oceanic basement. Li and Mn profiles are also indicative of diffusional communication with the basement aquifer.

¹ Torres, M.E., Muratli, J.M., and Solomon, E.A., 2014. Data report: minor element concentrations in pore fluids from the CRISP-A transect drilled during Expedition 334. In Vannucchi, P., Ujiie, K., Stroncik, N., Malinverno, A., and the Expedition 334 Scientists, Proc. IODP, 334: Tokyo (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/iodp.proc.334.201.2014

² College of Earth, Ocean, and Atmospheric Science, 104 CEOAS Administration Building, Oregon State University, Corvallis OR 97331, USA. Correspondence author. mtorres@coas.oregonstate.edu

³ School of Oceanography, University of Washington, Seattle WA 98195, USA.

Initial receipt: 14 April 2014
Acceptance: 23 July 2014
Publication: 10 October 2014
MS 334-201

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