Origin of smectite and illite-smectite in the Barbados accretionary complex: Oxygen isotopic evidence

Tribble, Jane S.; Yeh, Hsueh-Wen

doi:10.1130/0091-7613(1994)022<0219:oosais>2.3.co;2

Cited by 5 publications

(10 citation statements)

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“…The results of TEM and oxygen isotope analyses of bulk clays (Buatier et al, 1992;Tribble and Yeh, 1994) are consistent with four sources or types of smectite-rich clay: (1) subaerial weathering of volcanic protoliths and glass shards; (2) alteration of ash layers and dispersed ash on or near the seafloor; (3) erosion from continental rocks exposed to intermediate and/or advanced levels of diagenesis; and (4) in situ illitization. The challenge now is to determine which of these mechanisms might be most influential within specific lithostratigraphic intervals or structural domains.…”

Section: Discussionsupporting

confidence: 48%

“…Knowledge of thermal structure, as well as the velocities of sed-iment movement within zones of frontal offscraping and underplating, present challenges of their own (Bekins and Dreiss, 1992;Ferguson et al, 1993). To complicate matters further, smectite-to-illite diagenesis may be occurring in situ near the Barbados décollement, but at unusually low temperatures Buatier et al, 1992;Tribble and Yeh, 1994). Acceleration of this important reaction may have occurred in response to the advection of pore water, but other workers have concluded that the I/S mixed-layer clays in question are detrital (Capet et al, 1990).…”

Section: Thematic Backgroundmentioning

confidence: 99%

“…Data from the remaining samples below the décollement are similarly ambiguous. Tribble and Yeh (1994) favored an interpretation in which I/S clays in the underthrust domain (and stratigraphic equivalents at the oceanic reference site) formed by in situ diagenesis, but they also stated that erosion from a terrigenous source that had been exposed to deep burial dia-genesis "cannot be ruled out for the illite-rich illite-smectite on the basis of oxygen isotopic data alone. "…”

Section: Clay Mineralogymentioning

confidence: 99%

“…Consequently, the quantitative connection between their TEM image interpretations and XRD counts attributable to the "neoformed" illite remains somewhat unclear. Tribble and Yeh (1994) completed analyses of oxygen isotope compositions for nine representative samples that had been collected from above, within, and below the décollement zone, as well as two Oligocene samples from the oceanic reference site. The smectite and/or I/S phases were isolated by centrifugation from the bulk clay fraction, but the mineralogic purities and particle sizes of these extracts were not reported.…”

Section: Clay Mineralogymentioning

confidence: 99%

“…The smectite and/or I/S phases were isolated by centrifugation from the bulk clay fraction, but the mineralogic purities and particle sizes of these extracts were not reported. All of the "pure-smectite" samples were obtained from intervals within or immediately above the décollement, and according to Tribble and Yeh (1994), those clays probably formed authigenically, either near the seafloor or during early burial. The two shallowest samples (with intermediate I/S proportions) are either products of weathering on volcanic islands of the Lesser Antilles or mixtures of authigenic and detrital phases.…”

Section: Clay Mineralogymentioning

confidence: 99%

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Clay mineralogy and clay geochemistry in the vicinity of the décollement zone, northern Barbados Ridge

Underwood¹,

Deng²

1997

Proceedings of the Ocean Drilling Program, 156 Scientific Results

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Fine-grained sediments recovered during Leg 156 of the Ocean Drilling Program contain assemblages of clay minerals that change considerably with depth. Key structural and stratigraphic features within the toe of the northern Barbados accretionary prism include the basal décollement and a sharp boundary between lithologic Units II and III; this lithologic boundary occurs within the décollement zone. We analyzed three size fractions (4−8 µm, 1−4 µm, and <1 µm) by X-ray diffraction and obtained chemical data from the <1-µm size fractions by scanning electron microscopy coupled with energy dispersive spectroscopy. Relative proportions of expandable clay minerals increase significantly, but erratically, near the top of the décollement zone. Proportions of discrete smectite and smectite-rich illite/smectite (I/S) mixed-layer clays decrease steadily down the décolle-ment zone. The base of the décollement zone is characterized by unusually high concentrations of illite. These changes in clay mineralogy influence the shear strength of claystones at the deformation front and help control the position of the décollement.Relative abundances of illite within all lithofacies units increase in coarser size fractions, and this trend is consistent with a detrital source. Kaolinite does not display any systematic partitioning within Unit II, but its proportions increase in the finer size fractions within Unit III. The smectite content of Unit II increases with decreasing grain size; Unit III shows the opposite trend between particle size and % smectite. Bentonite-like samples probably originated through in situ alteration of disseminated volcanic ash, but we believe that the pyroclastic material was mixed into a background sediment that already contained abundant detrital smectite. Illitic mixed-layer clays within the underthrust domain (Unit III) also appear to be detrital in origin. Correlations among both % smectite and % kaolinite and most major-element oxides are statistically significant, but correlations for illite are not. Expandable clays vary considerably in their chemical make-up; the most common type appears to be a Mg-poor, K-rich, Fe-Al-beidellite. We rely upon actualistic provenance connections for late Quaternary clays to guide our interpretations of Miocene and Oligocene sediment dispersal. If these analogues are valid, then the proto-Orinoco and protoAmazon Rivers were the most important detrital sources for the older hemipelagic and turbidite deposits of Barbados Ridge.

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Section: Discussionsupporting

confidence: 48%

Section: Thematic Backgroundmentioning

confidence: 99%

Section: Clay Mineralogymentioning

confidence: 99%

Section: Clay Mineralogymentioning

confidence: 99%

Section: Clay Mineralogymentioning

confidence: 99%

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Clay mineralogy and clay geochemistry in the vicinity of the décollement zone, northern Barbados Ridge

Underwood¹,

Deng²

1997

Proceedings of the Ocean Drilling Program, 156 Scientific Results

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Potassium and boron co-depletion in Canadian Shield brines: evidence for diagenetic interactions between marine brines and basin sediments

Bottomley

Clark

2004

Chemical Geology

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Negative‐polarity seismic reflections along faults of the Oregon accretionary prism: Indicators of overpressuring

Moore¹,

Moore²,

Cochrane³

et al. 1995

J. Geophys. Res.

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Either thrusting of higher over lower impedance sediment or reduction of impedance locally in the fault zone can produce negative-polarity reflections along the protothrusts and the frontal thrust of the Oregon accretionary prism. The vertical displacement of protothrusts averages only 27 m, is uncorrelated to the occurrence of polarity reversals, and is insufficient to generate the impedance contrasts associated with the negative-polarity reflections. The negative-polarity reflections from the protothrusts are probably due to localized impedance reduction in the fault zone. Waveform modeling of these negative-polarity reflections indicates they develop due to a single interface with negative impedance contrast. This seismic signal could be produced by a fault zone with a sharp upper boundary with low impedance fault material and a transition down section to sediment of higher impedance. An impedance inversion due to the 1-km throw on the frontal thrust could create the observed negative-polarity reflections. Interval velocities do not decrease across the frontal thrust, but core-scale velocity measurements indicate a velocity decrease in the frontal thrust. Therefore the negative-polarity reflections are apparently produced by a localized decrease in impedance. Waveform modeling of frontal thrust reflections suggests the low impedance interval is about 20 m thick with discrete upper and lower boundaries. Moderately dipping faults are an efficient path for fluid expulsion across the turbidites with low equivalent vertical permeability. Fluid migration from the overpressured section up the faults can locally reduce the velocity sufficiently to cause the negativepolarity reflections.

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Origin of smectite and illite-smectite in the Barbados accretionary complex: Oxygen isotopic evidence

Cited by 5 publications

References 0 publications

Clay mineralogy and clay geochemistry in the vicinity of the décollement zone, northern Barbados Ridge

Clay mineralogy and clay geochemistry in the vicinity of the décollement zone, northern Barbados Ridge

Potassium and boron co-depletion in Canadian Shield brines: evidence for diagenetic interactions between marine brines and basin sediments

Negative‐polarity seismic reflections along faults of the Oregon accretionary prism: Indicators of overpressuring

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