Geology topics
K.M. Chan
Publications and source records attributed to K.M. Chan.
Interstitial water studies on small core samples, Deep Sea Drilling Project, Leg 3
Eleven samples of fluids which had been squeezed on board ship, and four, packaged sediment samples were received in our laboratories. As in Leg 2, the volumes of fluid available were scanty and did not permit multiple determinations of constituents in many of the samples; in Hole 21 the fluid available sufficed only for refractometer readings (a few tenths of a milliliter). Therefore, analytical scatter is again responsible for partially obscuring variations (and constancy) in the conservative constituents such as sodium. However, on the whole the results confirm the features which appeared in Legs 1 and 2. Central oceanic sediments display a remarkable constancy in total salinity, chlorinity and sodium concentration to the greatest depths and ages yet penetrated in the project drillings. Variations attributable to postburial reactions do occur in the remaining major ions, but they usually show little systematic trend with depth--with the exception of potassium, which will be discussed later. Methods remain similar to those employed for Leg 2; the detailed techniques are now being prepared for submission, but a brief description may be obtained from the previous Leg reports (Manheim and Sayles, 1969; Chan and Manheim, 1970). Results from four unsqueezed samples are not complete and, therefore, do not appear here.
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.
Interstitial water studies on small core samples, Deep Sea Drilling Project, Leg 5
Leg 5 samples fall into two categories with respect to interstitial water composition: 1) rapidly deposited terrigenous or appreciably terrigenous deposits, such as in Hole 35 (western Escanaba trough, off Cape Mendocino, California); and, 2) slowly deposited pelagic clays and biogenic muds and oozes. Interstitial waters in the former show modest to slight variations in chloride and sodium, but drastic changes in non-conservative ions such as magnesium and sulfate. The pelagic deposits show only relatively minor changes in both conservative and non-conservative pore fluid constituents. As was pointed out in earlier Leg Reports, it is believed that much of the variation in chloride in pore fluids within individual holes is attributable to the manipulation of samples on board ship and in the laboratory. On the other hand, the scatter in sodium is due in part to analytical error (on the order of 2 to 3 per cent, in terms of a standard deviation), and it probably accounts for most of the discrepancies in total anion and cation balance. All constituents reported here, with the exception of bulk water content, were analyzed on water samples which were sealed in plastic tubes aboard ship and were subsequently opened and divided into weighed aliquots in the laboratory. Analytical methods follow the atomic absorption, wet chemical and emission spectrochemical techniques briefly summarized in previous reports, e.g. Manheim et al., 1969, and Chan and Manheim, 1970. The authors acknowledge assistance from W. Sunda, D. Kerr, C. Lawson and H. Richards, and thank D. Spencer, P. Brewer and E. Degens for allowing the use of equipment and laboratory facilities.