Mg, Ca and exchange in the sediment-pore water system, hole 149, DSDP

Perry, Edward A.; Gieskes, Joris M.; Lawrence, J. R.

doi:10.1016/0016-7037(76)90006-5

Cited by 104 publications

(61 citation statements)

References 22 publications

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“…3). It is known that alteration of volcanic materials to clay minerals in oceanic sediments lead to changes in magnesium concentration and oxygen isotopic composition in interstitial water (Lawrence et al, 1975(Lawrence et al, , 1979Perry et al, 1976). Matsuhisa and Matsumoto (1986) also suggested that the decrease of oxygen isotopic compositions with depth was a result of isotopic exchange reactions with the minerals in oceanic sediments during diagenesis.…”

Section: Combination Plot Of CL -Concentrations Vs δ 18 O Values Imentioning

confidence: 99%

Chemical and isotopic compositions of brines from dissolved-in-water type natural gas fields in Chiba, Japan

2006

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Chemical and isotopic compositions of brines collected from the Minami-Kanto natural gas field in Chiba, central Japan, were measured to investigate their origin and relation to microbial methane formed from the coexisting brines. The isotopic compositions of water in the brines are -3.8 to -1.5‰ and -15 to -1‰ in δ 18 O H2O and δD H2O values, respectively, which are correlated with their chloride concentrations, suggesting that the brines are derived from seawater and that some of them have been mixed with meteoric water. The brines have high concentrations of iodine up to 0.14 g/l which are related to those of dissolved bromine and ammonia. These dissolved chemicals are suggested to have been liberated from marine sediments into pore water through the diagenetic decompositions of organic matter. The hydrogen isotopic compositions of methane (δD CH4 ) in the natural gases are -195 to -146‰. The average isotopic difference between δD CH4 and δD H2O for the samples is about 180‰, suggesting that the methane was formed by microbial activity via a CO 2 -reduction pathway. However, because the data obtained in this study were widely scattered on the δD CH4 -δD H2O plot, it is not possible to confirm that the obtained data follow the linear correlation predicted by Schoell (1980) for methane formation by CO 2 -reduction.

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Section: Combination Plot Of CL -Concentrations Vs δ 18 O Values Imentioning

confidence: 99%

Chemical and isotopic compositions of brines from dissolved-in-water type natural gas fields in Chiba, Japan

2006

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“…9)). At most of these localities, pore water δ 18 θ values decrease from about 0 o/ 00 just below the seafloor at rate of about -0.2 o/ oo per 100 m to -1.0 o/oo per 100 m. At the Leg 127 sites, we ascribe the significant decreases in pore water δ 18 θ values down to the top of the opal-CT zone largely to the alteration of volcanic ash layers (e.g., Perry et al, 1976;Gieskes, 1981;Gieskes and Lawrence, 1981). In contrast, the marked change in slope of these profiles at the opal-A/opal-CT transition at Sites 794,795, and 797 reflects exchange with isotopically heavy oxygen made available through the dissolution of abundant biogenic silica as well as contribution of heavy oxygen from basement alteration and possibly advective transport (e.g., Tamaki, Pisciotto, Allan, et al, 1990;Brumsack and Zuelger, this volume;Murray et al, this volume;Murray and Brumsack, this volume).…”

Section: Pore Watersmentioning

confidence: 69%

Thermal History of Japan Sea Sediments from Isotopic Studies of Diagenetic Silica and Associated Pore Waters

Pisciotto¹,

Murray²,

Brumsack³

1992

Proceedings of the Ocean Drilling Program

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Over a broad region of the eastern Japan Sea, Neogene opaline diatomaceous sediments alter with depth to hard porcellanites and cherts composed of opal-CT and quartz. We examined the oxygen isotopic compositions of these diagenetic silica minerals at four widely spaced sites occupied during ODP Leg 127 in order to investigate the thermal history of the region. Formation temperatures computed from these isotopic data range from 22° to 68° C for opal-CT and from 44° to 92° C for diagenetic quartz, quite similar to temperature ranges estimated from the extrapolated modern gradients, 36°-43°C and 49°-64°C, respectively. At each site the isotopic temperature values cluster near the extrapolated ambient sediment temperatures. As a first approximation, the similarities suggest that the positions of the silica transformations in the basin are controlled by the present thermal regime.In detail, isotopic and ambient temperatures differ. If these differences are real, then they reflect variations in the thermal histories at these sites. At Sites 794 and 797 in the Yamato Basin, isotopic temperatures and gradients computed from these data are lower than or comparable to ambient temperatures and gradients. We suggest that the silica zones have roughly equilibrated with the modern gradients at these localities. At Site 795 in the Japan Basin, isotopic temperatures are also lower than ambient sediment temperatures at comparable depths, but the gradient computed from the isotopic temperatures is higher than the present measured gradient. For both scenarios to hold, the silica zones must have formed under initially high gradients during the early post-rift period at this locality. These zones were then rapidly buried and have yet to equilibrate with the modern lower gradient. At Site 796 on Okushiri Ridge, isotopic temperatures exceed present temperatures as expected for an area of recent uplift. The gradient computed from our isotopic data and the thickness of the opal-CT zone indicate a higher gradient than at present at this site, apparently reflecting higher heat fluxes during the early post-rift period or recent frictional heating from nearby reverse fault activity.

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“…These Ca and Mg trends are common in many DSDP cores (Lawrence et al, 1975;Kastner and Gieskes, 1976;Perry et al, 1976b); they have been attributed either to dolomitization of foraminifer-nannofossil oozes, or to release of Ca and uptake of Mg by alteration of volcanic basement rocks. Because little or no dolomite has been detected in the carbonate deposits that make up most of the Leg 62 sections, the Ca and Mg pore-water trends probably reflect alteration of the basaltic basement and ash beds.…”

Section: Diagenesismentioning

confidence: 99%

Mg, Ca and exchange in the sediment-pore water system, hole 149, DSDP

Cited by 104 publications

References 22 publications

Chemical and isotopic compositions of brines from dissolved-in-water type natural gas fields in Chiba, Japan

Chemical and isotopic compositions of brines from dissolved-in-water type natural gas fields in Chiba, Japan

Thermal History of Japan Sea Sediments from Isotopic Studies of Diagenetic Silica and Associated Pore Waters

Origin and Alteration of Volcanic Ash and Pelagic Brown Clay, Deep Sea Drilling Project Leg 62, North-Central Pacific

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