Concentrations of minor and trace elements (Li, Rb, Sr, Ba, Fe, and Mn) in interstitial water (IW) were found in samples collected during Ocean Drilling Program (ODP) Leg 166 from Sites 1005, 1006, and 1007 on the western flank of the Great Bahama Bank (GBB). Concentrations of Li range from near-seawater values immediately below the sediment/water interface to a maximum of 250 mu M deep in Site 1007. Concentrations determined during shore-based studies are substantially lower than the shipboard data presented in the Leg 166 Initial Reports volume (range of 28-439 mu M) because of broad-band interferences from high dissolved Sr concentrations in the shipboard analyses. Rubidium concentrations of 1.3-1.7 mu M were measured in IW from Site 1006 when salinity was less than 40 psu. A maximum of 2.5 mu M is reached downhole at a salinity of 50 psu. Shipboard and shore-based concentrations of Sr (super 2+) are in excellent agreement and vary from 0.15 mM near the sediment water interface to 6.8 mM at depth. The latter represent the highest dissolved Sr (super 2+) concentrations observed to date in sediments cored during the Deep Sea Drilling Project (DSDP) or ODP. Concentrations of Ba (super 2+) span three orders of magnitude (0.1-227 mu M). Concentrations of Fe (<0.1-14 mu M) and Mn (0.1-2 mu M) exhibit substantially greater fluctuations than other constituents. The concentrations of minor and trace metals in pore fluids from the GBB transect sites are mediated principally by changes in pore-water properties resulting from early diagenesis of carbonates associated with microbial degradation of organic matter, and by the abundance of detrital materials that serve as a source of these elements. Downcore variations in the abundance of detrital matter reflect differences in carbonate production during various sea-level stands and are more evident at the more proximal Site 1005 than at the more pelagic Site 1006. The more continuous delivery of detrital matter deep in Site 1007 and throughout all of Site 1006 is reflected in a greater propensity to provide trace elements to solution. Concentrations of dissolved Li (super +) derive principally from (1) release during dissolution of biogenic carbonates and subsequent exclusion during recrystallization and (2) release from partial dissolution of Li-bearing detrital phases, especially ion-exchange reactions with clay minerals. A third but potentially less important source of Li (super +) is a high-salinity brine hypothesized to exist in Jurassic age (unsampled) sediments underlying those sampled during Leg 166. The source of dissolved Sr (super 2+) is almost exclusively biogenic carbonate, particularly aragonite. Concentrations of dissolved Sr (super 2+) and Ba (super 2+) are mediated by the solubility of their sulfates. Barite and detrital minerals appear to be the more important source of dissolved Ba (super 2+) . Concentrations of Fe and Mn (super 2+) in anoxic pore fluids are mediated by the relative insolubility of pyrite and incorporation into diagenetic carbonates. The principal sources of these elements are easily reduced Fe-Mn-rich phases including Fe-rich clays found in lateritic soils and aeolian dust.

West: -79.4500 East: -79.0000 North: 25.0000 South: 24.0000

Expedition: 166

Site: 166-1005

Site: 166-1006

Site: 166-1007

Provider: SEDIS Publication Catalogue

Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=10.2973/odp.proc.sr.166.118.2000 (c.f. for more detailed metadata)

Data download: application/pdf

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