Interstitial water studies on small core samples, leg 4

Reorganization and recodification of shipboard procedures for collecting interstitial waters has resulted in improved and more regular collection and analysis of pore fluids. Comparative studies of waters squeezed and analyzed on shipboard and analyzed in the shore laboratory show generally good agreement, except for some aberrations whose sources are hard to track down. Influences of pressure and temperature during squeezing on composition of effluents were re-examined for clayey samples from Leg 4 cores. Pressure was not found to be significant, whereas the temperature effects are significant, but are less than variations attributable to diagenetic reactions in the sediments. Conservative constituents, such as, chloride, sodium and bromide, remain relatively constant (within about 1.5 per cent) with changing depth in the holes; but, large depletions with respect to normal sea water occur in calcium (to 0.06 g/kg), magnesium (to 0.7), potassium (to 0.20), and sulfate (to 0.11) in most of the cores. On the other hand, large enrichments of calcium (to 1.57 g/kg) and lithium (to 1.7 ppm) occurred in Holes 24 and 24A. The depletion of several constituents in pore waters of Hole 26 (Vema fracture zone) caused a drop in total salt content to as low as 31 o/oo. However, no real dilution effects are involved, since chloride and sodium values remain typical of those in ocean bottom waters.