Variations in the δD and δ18O compositions of illite-smectites in a partly overpressured Tertiary sequence from an offshore well, Texas Gulf Coast, USA

Primmer, T. J.; Shaw, H. F.

doi:10.1016/0264-8172(91)90009-p

Cited by 8 publications

(12 citation statements)

References 17 publications

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“…Overall, in the Shikoku Basin sediments, the oxygen isotopic ratios of the pore fluids become enriched in 18 O and depleted in D with depth, particularly below the décollement, which is typical for diagenetic systems with extensive fluid-rock interactions, especially of the S -> I transformation reaction (i.e., Mourn and Rosenqvist, 1958;Savin and Epstein, 1970;Suchecki and Land, 1983;Savin and Lee, 1988;Primmer and Shaw, 1991, and references therein). The O and H isotope profiles are not coupled throughout, because the oxygen is also involved, independently of hydrogen, in anhydrous phase reactions, and the hydrogen is strongly influenced by organic matter decomposition reactions.…”

Section: Oxygen and Hydrogen Isotopesmentioning

confidence: 99%

“…There, pore-space reduction and clay transformation reactions are intense. Smectite dehydration alone would not be able to produce these strong inverse isotopic signals because the interlayer water in smectite exchanges continuously with the pore fluids, thus reflecting them (Mourn and Rosenqvist, 1958;Savin and Epstein, 1970;Primmer and Shaw, 1991). The residual diagenetically evolved fluid from the S -> I reaction, which is enriched in 18 O and depleted in D, upon advection and transport into shallower levels of the system may become involved in smectite reactions.…”

Section: Ti I I I I I I I Ii I I I I I I I I I I I 'mentioning

confidence: 99%

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Geochemical and Isotopic Evidence for Fluid Flow in the Western Nankai Subduction Zone, Japan

Kastner¹,

Elderfield²,

Jenkins³

et al. 1993

Proceedings of the Ocean Drilling Program

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At the Western Nankai Trough subduction zone at ODP Site 808, chemical concentration and isotopic ratio depth profiles of D, O, Sr, and He do not support fluid flow along the décollement nor at the frontal thrust. They do, however, support continuous or periodic lateral fluid flow: (1) at the base of the Shikoku Basin volcanic-rich sediment member, situated -140 m above the décollement, and particularly (2) below the décollement. The latter must have been rather vigorous, as it was capable of transporting clay minerals over great distances. The fluid at ~ 140 m above the décollement is characterized by lower than seawater concentrations of Cl-(>18% seawater dilution). It is 18 O-rich and D-poor and has a non-radiogenic, oceanic, or volcanic arc Sr isotopic signature. It originates from "volcanic" clay diagenesis. The fluid below the décollement has also less Cl~ than seawater (>20% dilution), is more enriched in 18 O and depleted in D than fluid, but its Sr isotopic signature is radiogenic, continentalterrigenous. The source of this fluid is located arcward, is deep-seated, where illitization of the subducted clay minerals, a mixture of terrigenous and volcanic clays, occurs. The 3 He/ 4 He ratio below the décollement points to an -25% mantle contribution. The nature of the physical and chemical discontinuities across the décollement suggests it is overpressured and is forming a leaky "dynamic seal" for fluid flow. In contrast with the situation at Barbados and Peru, where the major tectonic features are mineralized, here, although the complex is extremely fractured and faulted, mineralized macroscopic veins, fractures, and faults are absent. Instead, mineralized microstructures are widespread, indicating a diffuse mode of dewatering.

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Section: Oxygen and Hydrogen Isotopesmentioning

confidence: 99%

Section: Ti I I I I I I I Ii I I I I I I I I I I I 'mentioning

confidence: 99%

Geochemical and Isotopic Evidence for Fluid Flow in the Western Nankai Subduction Zone, Japan

Kastner¹,

Elderfield²,

Jenkins³

et al. 1993

Proceedings of the Ocean Drilling Program

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“…During this transition, the δD value and Cl concentration of the connate water become lower due to dilution by dehydrated water from smectite which has lower δD values (D/H isotopic fractionation between smectite and water is about -40‰ at 25°C; Savin and Epstein, 1970;Lawrence and Taylor, 1971;Yeh and Epstein, 1978). Primmer and Shaw (1991) analyzed the oxygen and hydrogen isotopic compositions of argillaceous rocks from a partly overpressured Tertiary sequence in an offshore well from the Texas Gulf Coast. They showed increasing illitization of illite-smectite rich formations with depth of burial and a general trend towards enrichment of D and depletion of 18 O with increasing illitization.…”

Section: Occurrence Of Geopressured Fluidmentioning

confidence: 99%

“…This effect would also deplete the 18 O content of the migrating fluid (Coplen and Hanshaw, 1973;Demir, 1988). Primmer and Shaw (1991) examined the membrane filtration for hydrogen isotope compositions of interlayer water and showed that the water giving rise to the overpressure is more enriched in 18 O than normally pressured pore water. They indicated that membrane filtration cannot satisfactorily explain the trends in the calculated isotopic composition of the water in the overpressured zones.…”

Section: Occurrence Of Geopressured Fluidmentioning

confidence: 99%

Stable and noble gas isotopic study of thermal and groundwaters in northwestern Hokkaido, Japan and the occurrence of geopressured fluids

et al. 2010

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owing to interaction with the surrounding rocks. In several areas, fossil sea water was found to have δ 18 O values of +5 to +8‰ due to the oxygen isotopic shift caused by the interaction, but to retain almost the same Cl concentration as fresh sea water (e.g., Sakai and Matsubaya, 1974;Mizukami et al., 1977;Shibata et al., 2005).At depths below ca. 2 km in sedimentary regions associated with oil and/or natural gas, formation waters tend to be geopressured fluid with pressures between hydrostatic and lithostatic values (e.g., Myers, 1968;Jones, 1970;Oki et al., 1999;Xu et al., 2006). The δD and δ 18 O data show that most geopressured fluid can be explained as a mixture of fossil sea water and local meteoric water, with an oxygen isotope shift due to rock-water interaction. Recently, fluids that have oilfield-like characteristic, with unusually high δD (-20‰) and low Cl concentrations (ca. 6,000 mg/L) have been observed along faults in the Horonobe area (Ishii et al., 2006). These fluids might have originated as a mixture between sea water and Stable and noble gas isotopic study of thermal and groundwaters in northwestern Hokkaido, Japan and the occurrence of geopressured fluids (Received July 14, 2009; Accepted June 7, 2010) Thermal and groundwaters are distributed along the west coast and in the inland region of Northwestern Hokkaido, Japan. The waters in the latter group have relatively high temperatures. Stable (D, O) and noble gas isotopic compositions of 23 thermal and groundwaters were analyzed to investigate their origins. The Cl concentrations vary from 45 to 19,300 mg/L and the δD values are in the range of -90 to -8‰. The δD-δ 18 O plots show a linear relationship which can be explained by a simple mixing of local meteoric waters and altered sea water, with oxygen isotopic shift of 5‰. However, a δD-Cl plot shows that there is also a contribution of an additional water component of different origin. This 3rd component has a δD value of -20‰ and Cl concentration of 6,000 mg/L. Multivariate statistical analysis of the observed chemical and isotopic compositions using the code M3 (M; multivariate mixing and mass balance) also supports the view that the Toyotomi thermal water has the composition closest to that of the 3rd groundwater component. This component is regarded as a geopressured fluid.The 3 He/ 4 He ratios in these waters are in the range of (0.1-5) × 10 -6 , which indicate contributions of both mantle and crustal He to the thermal and groundwaters in the studied area. The Toyotomi thermal water has a 3 He/ 4 He ratio of 5.5 × 10 -7 , and a high 3 He/ 20 Ne ratio (~700). These results indicate a crustal He input with a small amount of mantle-derived He and imply that the 3rd groundwater component is of deep origin. On the basis of isotopic and chemical compositions, 5 of 23 samples studied groundwater and thermal waters are contributed by a geopressured fluid component. The results show that geopressured fluids with a δD value of -20‰ and Cl concentration of 6,000 mg/L are widely distributed ...

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“…Previous studies of the isotopic evolution of clay minerals during burial metamorphism and illitization of detrital-rich mudrocks show a general trend of ~sO-depletion and D-enrichment with increasing burial metamorphism (Yeh and Savin 1977;Eslinger et al 1979;Yeh 1980;Primmer and Shaw 1991). The isotopic composition of clay minerals from the Monterey Formation is of particular interest because diagenetically altered siliceous mudstones are interbedded with bentonite and metabentonite layers (Compton 1991) which allows a comparison of clay minerals derived from detrital and volcanic glass precursors.…”

Section: Introductionmentioning

confidence: 99%

Stable Isotope Evolution of Volcanic Ash Layers During Diagenesis of the Miocene Monterey Formation, California

Compton

Conrad

Vennemann

1999

Clays and clay miner.

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Abstract--The oxygen and hydrogen isotope compositions of volcanic ash layers from coastal outcrops of the Miocene Monterey Formation elucidate the progressive burial diagenesis of glass to bentonite and metabentonite. Volcanic glass that texturally appears unaltered is found to have fiJsO and bD values that are significantly higher than fresh volcanic glasses. The positive shift in ~L~O and 3D values is proportional to the amount of hydration and chemical alteration of the glass samples. Initial hydration of the glass results in the exchange of Na for H; later hydration results in the loss of K and Fe in exchange for H and Na. The 8~80 values of the most hydrated glass, and clay minerals from bentonite and metabentonite layers are approximately in equilibrium with slightly modified seawater. The ~D values of the hydrated glass, and clay minerals from bentonite and metabentonite layers, are significantly depleted in D relative to seawater and suggest meteoric exchange associated with tectonic uplift and erosion in the Pliocene and Pleistocene. Smectite from bentonite layers has g~80 and gD values similar to the most hydrated glass samples, suggesting similar glass-water and smectite-water fractionation factors. Kaolinite and mixedlayered illite-smectite (I-S) altered from smectite have lower g~80 and higher SD values than their precursor. The g~80 and gD of nonvolcanic siliceous mudstones from the Pt. Arguello oil field show an unusual decrease in gD with increasing burial depth that probably reflects the presence of organic hydrogen in the analyzed samples as well as possible D-depleted formation waters from detrital illite-water and hydrocarbon-water exchange.

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Variations in the δD and δ18O compositions of illite-smectites in a partly overpressured Tertiary sequence from an offshore well, Texas Gulf Coast, USA

Cited by 8 publications

References 17 publications

Geochemical and Isotopic Evidence for Fluid Flow in the Western Nankai Subduction Zone, Japan

Geochemical and Isotopic Evidence for Fluid Flow in the Western Nankai Subduction Zone, Japan

Stable and noble gas isotopic study of thermal and groundwaters in northwestern Hokkaido, Japan and the occurrence of geopressured fluids

Stable Isotope Evolution of Volcanic Ash Layers During Diagenesis of the Miocene Monterey Formation, California

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