Elemental and isotopic compositions of some metalliferous and pelagic sediments from the Galapagos mounds area, DSDP Leg 70

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doi: 10.1016/0009-2541(82)90052-3
Author(s): Barrett, T. J.; Friedrichsen, H.
Author Affiliation(s): Primary:
Oxford Univ., Dep. Geol. and Mineral., Oxford OX1 3PR, United Kingdom
Volume Title: Chemical Geology
Source: Chemical Geology, 36(3-4), p.275-298. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0009-2541 CODEN: CHGEAD
Note: In English. 4 p. refs.; illus. incl. anal., table
Summary: Nontronite, the main metalliferous phase of the Galapagos mounds, occurs at a subsurface depth of approx 2-20 m; Mn-oxide material is limited to the upper 2 m of these mounds. The nontronite forms intervals of up to a few m in thickness, consisting of 100% nontronite granules, which alternate with intervals of normal pelagic sediment. The metalliferous phases represent authigenic precipitates, apparently formed in the presence of upwelling basement-derived hydrothermal solutions. Microprobe analyses (13) indicate that there is little difference in major-element composition between nontronitic material from varying locations within the mounds, and that adjacent granules have very similar compositions and are internally homogeneous. The Pb-isotopic composition of the nontronite and Mn-oxide sediments indicates that they were formed from solutions containing variable proportions of basaltic Pb, introduced into pore waters by basement-derived solutions, and of normal sea-water Pb. The Sr-isotopic composition of these sediments is indistinguishable from that of modern sea-water. Formation T of 20-30°C have been estimated for the nontronites. By comparison, T = or < 11.5°C at 9 m depth have been measured within the mounds and heat-flow data suggest present basement-sediment interface T of 15°-25°C.
Year of Publication: 1982
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 02 Geochemistry; 07 Marine Geology and Oceanography; Alkaline earth metals; Authigenesis; Clay minerals; D/H; DSDP Site 506; DSDP Site 507; DSDP Site 509; Deep Sea Drilling Project; Deuterium; East Pacific; Geochemistry; Hydrogen; Hydrothermal conditions; Hydrothermal mounds; IPOD; Isotopes; Lead; Leg 70; Manganese; Marine environment; Marine sediments; Metals; Nodules; Nontronite; North American Pacific; North Pacific; Northeast Pacific; O-18/O-16; Oceanography; Oxygen; Pacific Ocean; Pb-206/Pb-204; Pb-207/Pb-204; Pb-208/Pb-204; Pelagic environment; Radioactive isotopes; Ratios; Sediments; Sheet silicates; Silicates; Sr-87/Sr-86; Stable isotopes; Strontium
Coordinates: N050000 N050000 W0860000 W0860000
Record ID: 1984002889
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique