Chemical composition of interstitial solutions from sediments of DSDP Legs 6-8, 11, 12, 14, 15, and 22

• Main Authors: Sayles, Frederick L, Manheim, Frank T
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 1975
• Subjects: 11-102; 12-116; 12-119; 14-137; 15-147; 15-149; 22-214; 22-216; 22-217; 6-50; 6-51; 6-55; 7-66; 8-70; 8-71; Caribbean Sea/BASIN; Caribbean Sea/RIDGE; Deep Sea Drilling Project; DRILL; Drilling/drill rig; DSDP; Glomar Challenger; Indian Ocean//RIDGE; Leg11; Leg12; Leg14; Leg15; Leg22; Leg6; Leg7; Leg8; North Atlantic/BASIN; North Atlantic/HILL; North Atlantic/RIDGE; North Atlantic/SEAMOUNT; North Pacific/BASIN; North Pacific/CONT RISE; North Pacific/PLAIN; North Pacific/RIDGE; Indian; Pacific; North Atlantic
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.706822; https://doi.org/10.1594/PANGAEA.706822

Through the Deep Sea Drilling Project samples of interstitial solutions of deeply buried marine sediments throughout the World Ocean have been obtained and analyzed. The studies have shown that in all but the most slowly deposited sediments pore fluids exhibit changes in composition upon burial. These changes can be grouped into a few consistent patterns that facilitate identification of the diagenetic reactions occurring in the sediments. Pelagic clays and slowly deposited (<1 cm/1000 yr) biogenic sediments are the only types that exhibit little evidence of reaction in the pore waters. In most biogenic sediments sea water undergoes considerable alteration. In sediments deposited at rates up to a few cm/1000 yr the changes chiefly involve gains of Ca(2+) and Sr(2+) and losses of Mg(2+) which balance the Ca(2+) enrichment. The Ca-Mg substitution may often reach 30 mM/kg while Sr(2+) may be enriched 15-fold over sea water. These changes reflect recrystallization of biogenic calcite and the substitution of Mg(2+) for Ca(2+) during this reaction. The Ca-Mg-carbonate formed is most likely a dolomitic phase. A related but more complex pattern is found in carbonate sediments deposited at somewhat greater rates. Ca(2+) and Sr(2+) enrichment is again characteristic, but Mg(2+) losses exceed Ca(2+) gains with the excess being balanced by SO4(post staggered 2-) losses. The data indicate that the reactions are similar to those noted above, except that the Ca(2+) released is not kept in solution but is precipitated by the HCO3(post staggered -) produced in SO4(post staggered 2-) reduction. In both these types of pore waters Na(+) is usually conservative, but K(+) depletions are frequent. In several partly consolidated sediment sections approaching igneous basement contact, very marked interstitial calcium enrichment has been found (to 5.5 g/kg). These phenomena are marked by pronounced depletion in Na(+), Si and CO2, and slight enhancement in Cl(-). The changes are attributed to exchange of Na(+) for Ca(2+) in silicate ...