A Micro-Volumetric Determination of Sulfate in Pore Waters

Interstitial water studies were done at 9 of the 11 sites visited in the Mississippi Fan and Orca and Pigmy Basins during DSDP Leg 96. High concentrations of sulfate were observed at Mississippi Fan Sites 616, 617, 620, and 623. The maximum sulfate value of 38.8 mM, recorded at Site 617, is the highest ever found in DSDP sediments. Hypersaline interstitial water was observed at Site 618 in Orca Basin. Concentration ratios of salinity to chlorinity and to sodium in interstitial waters are similar to those of Orca Basin bottom water, suggesting that the chemistry of interstitial water is affected by the dissolution of buried salt.

Section: °87°86°85°fmentioning

confidence: 99%

Interstitial Water Geochemistry and Clay Mineralogy of the Mississippi Fan and Orca and Pigmy Basins, Deep Sea Drilling Project Leg 96

Ishizuka¹,

Kawahata²,

Aoki³

1986

“…The titration method of Cescon and Macchi (1973) was used. IAPSO standard seawater was used as a standard.…”

Section: Sulfatementioning

confidence: 99%

Interstitial Water Studies, Leg 25

Gieskes¹

1974

Interstitial water analyses from sediments collected during Leg 25 of the Deep Sea Drilling Project have revealed that in the southwest Indian Ocean, great chemical activity exists in sediments in various depositional environments. Variable sedimentation rates allow us to set some interesting boundary conditions on chemical and transport processes in these interstitial waters, particularly with regard to the distribution of dissolved sulfate. In terrigenous rapidly deposited sediments, large depletions are observed in magnesium and potassium, whereas relatively small decreases in dissolved calcium occur. In slowly deposited detrital sediments, also, large decreases in potassium and magnesium coincide with very large calcium increases. In truly pelagic sediments, a one to one replacement of magnesium by calcium is observed in the interstitial waters, presumably due to reactions in the basal sediment layers. Biogenous deposits have great influence on dissolved silica (sponge spicules and radiolarians) and on dissolved strontium (carbonate recrystallization). Otherwise, dissolved silica reflects the clay mineralogy and shows variations which seem particularly dependent on the presence or absence of kaoUnite. Variable dissolved manganese values reflect reducing conditions and/or availability of manganese in the solid phases for mobilization in reducing sediments.

“…Accordingly, the Fritz-Yamamura method of Cescon and Macchi (1973) was employed with minor modifications. In principle, diluted samples are passed through a cation exchanger to remove cations, then titrated with BaCh using Thorin as an indicator.…”

Section: Sulfatementioning

confidence: 99%

Interstitial Waters of Black Sea Cores

Schug¹

1978

Black Sea interstitial waters show three major features: (1) at Sites 379 and 380 a clear reflection of fresh-water lake stages is obtained. Data from Site 379 indicate that waters in the "Riss" fresh-water or regressive stage, as indicated by Zhuze and Mukhina (this volume), were even fresher than in the latest "Würm" regression and glacial maximum. In the former, chlorinitis of less than 2 °/oo were found, contrasting to about 3 °/oo for the "Würm." No fresh-water stage was found at Site 381, indicating truncation or nondeposition of sediments. (2) Beneath the fresh-water zones (Mindel zone, according to Zhuze and Mukhina, this volume) hypersaline episodes occur, reaching more than 100 °/oo salinity, but there are no permanent evaporitic sediments, such as gypsum. These zones exhibited high calcium and magnesium concentrations. The Black Sea in late Miocene time had waters of more standard marine character in the vicinity of Site 381, and no evaporites occur within middle to late Miocene sediments at this site or, by inference, the remainder of the Black Sea. (3) Many strong diagenetic features occur, including NH4 concentrations considerably exceeding those of K in pore fluids, absence of SO4, and reaction of both Mg and Na with calcium-bearing phases to form diagenetic minerals and liberate CaCh. Silica concentrations are high in diatom-rich zones and lower in clayey sediments, which lack amorphous silica in large quantity.