The interstitial water (IW) sampling program at Site 1114 was limited because of difficult coring conditions and low core recovery. Five IW samples were obtained: three from the upper 76 mbsf and one each from 210 and 229 mbsf.
The IW was analyzed for salinity, pH, alkalinity, major cations (Na+, K+, Ca2+, and Mg2+) and anions (Cl- and SO42-), Li+, Sr2+, and SiO2. Results of shipboard inorganic chemical analyses are presented in Table T9. The salinity, alkalinity, and dissolved Na+, Cl-, SO42-, and Mg2+ concentrations all remain in a narrow range. Only dissolved K+, Ca2+, Li+, Sr2+, and SiO2 exhibit significant variations. Because of the limited data obtained, observed IW compositional variations can only be interpreted with caution.
The low alkalinity and near-seawater SO42- concentration in all IW samples indicate that either no significant microbially mediated oxidation of organic matter takes place in the sediment column, or that evidence of previous organic matter diagenesis has been erased either by diffusion or by fluid flow through the fractures observed in the sediments (see "Structural Geology"). Because of the existence of concentration gradients of certain nonconservative IW constituents downhole (e.g., K+), extensive present-day fluid flow through the sediment column seems unlikely.
Increasing dissolved Li+ and Ca2+ concentrations downhole suggest an input of these elements at depth, possibly through the alteration of volcanic minerals in the sediments or by upward diffusion of remnant hydrothermally altered fluids. It should be noted, however, that dissolved Li+ is depleted relative to seawater (27M/kg) in all IW samples from this site, albeit less so in the two deeper samples. Dissolved Li+ in IW from Sites 1110 and 1111 was also found to be depleted relative to seawater (see "Inorganic Geochemistry" in the "Sites 1110-1113" chapter).
The variations in dissolved Sr2+ are unusual. A depletion relative to seawater (84 µM) occurs in the four shallower samples, whereas a return to a near-seawater value is observed in the deepest sample. Concentrations of dissolved Sr2+ are decoupled from those of dissolved Ca2+. Thus, dissolution of biogenic calcite seems unlikely to be responsible for the Sr2+ increase deeper downhole, and the source of Sr2+, as that of Ca2+, may be the alteration of basement rocks.
A depletion of K+ downhole is inconsistent with upward diffusion from basement of a remnant hydrothermal fluid as proposed above. Such a fluid should also be enriched in K+. However, it is possible that formation of kaolinite, observed by X-ray diffraction (see "Lithostratigraphy" and Table T3), may deplete any upward diffusing fluid of its dissolved K+.
Dissolved SiO2 concentrations are generally low except in Sample 180-1114A-9R-1, 142-152 cm. The low dissolved SiO2 concentration may reflect typical sedimentary diagenetic reactions that occur deep within sedimentary sequences such as observed at Site 1109 (see "Inorganic Geochemistry" in the "Site 1109" chapter). Low concentrations of this constituent, however, may also be consistent with alteration of basement rocks by hydrothermal fluids, which could promote silicate mineral precipitation in the overlying sediment column.
Although IW is slightly depleted in dissolved Mg2+ relative to seawater, the lack of any gradient suggests either erasure of any evidence of sedimentary reactions through an input of seawater, or a lack of reactions that can remove this element from pore fluids. This contrasts sharply with what is observed at Sites 1109 and 1115 (see "Inorganic Geochemistry" in the "Site 1109" chapter and "Inorganic Geochemistry" in the "Site 1115" chapter), where the alteration of volcanic minerals and subsequent formation of clay minerals such as smectites generally leads to depletion of this constituent downhole.
The composition of IW at this site contrasts substantially with what has been observed at other sites drilled during Leg 180, suggesting that tectonic activity and possibly hydrothermal fluid circulation have influenced sediments and affected the fluid chemistry. However, insufficient data are available to identify unequivocally individual processes.