Authigenic clay minerals in volcanic ash layers from ODP Site 808 in the Nankai Trough, and their formation condition estimated from those oxygen isotope ratios

Author(s): Nakagawa, Seiko; Masuda, Harue; Okudaira, Takamoto; Chiba, Hitoshi
Author Affiliation(s): Primary:
Osaka City University, Department of Geosciences, Osaka, Japan
Okayama University, Japan
Volume Title: Chikyukagaku (Tokyo. 1967) Geochemistry (Tokyo. 1967)
Source: Chikyukagaku (Tokyo. 1967) = Geochemistry (Tokyo. 1967), 43(1), p.1-13. Publisher: Nihon Chikyukagakukai, Tokyo, Japan. ISSN: 0386-4073 CODEN: CYKGAM
Note: In Japanese with English summary. 47 refs.; illus., incl. sect., 4 tables, sketch map
Summary: Mineralogy and oxygen isotope ratios of <0.1 µm authigenic clay minerals were determined for the nine volcanic ash layers in the sediment column from 580 to 1255 meters below sea floor at ODP Site 808 in the Nankai Trough. Seven of 9 samples comprise of monomineralic smectite, and 2 samples from 922.2 and 998.6 mbsf comprise of R=1 illite-smectite mixed-layered clay minerals. Assuming that oxygen isotope compositions of the clay minerals are equilibrated with those of the coexisting porewater, of which composition is the same as that of sea water, formation temperature of the clay minerals was estimated to be ca 50°C regardless of burial depth. It means that the smectite was formed most actively when the temperature of sediments rose at ca 50°C during burial, and no distinctive change of oxygen isotope composition occurred after its formation. Three samples from 775.6, 812.3 and 1253.8 mbsf gave the high formation temperature of ca 75°C, probably due to the simultaneous formation of clinoptilolite and/or analcime. R=1 illite-smectite mixed-layered clay minerals may be formed at the same temperature as smectite but under different condition(s) of water/rock ratio and/or porewater chemistry.
Year of Publication: 2009
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 06 Petrology, Sedimentary; Accretionary wedges; Analcime; Authigenic minerals; Burial; Clay minerals; Clinoptilolite; Diagenesis; Framework silicates; Igneous rocks; Illite; Isotope ratios; Isotopes; Major elements; Marine sediments; Nankai Trough; North Pacific; Northwest Pacific; O-18/O-16; ODP Site 808; Ocean Drilling Program; Oxygen; Pacific Ocean; Pore water; Pyroclastics; Sea water; Sediments; Sheet silicates; Silicates; Smectite; Stable isotopes; Temperature; Volcanic ash; Volcanic rocks; Water-rock interaction; West Pacific; X-ray diffraction data; Zeolite group
Coordinates: N322105 N322111 E1345646 E1345634
Record ID: 2011015653
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