Evolution of gas and aqueous fluid in low-permeability argillaceous rocks during uplift and exhumation of the central Swiss Alps

Mazurek, Martin

doi:10.1016/s0883-2927(99)00062-1

Cited by 16 publications

(15 citation statements)

References 39 publications

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“…Due to harmonic averaging, relatively small, but contiguous, layers of reduced hydraulic conductivity can significantly lower effective vertical hydraulic conductivities and dominate the behaviour of vertical pore fluid migration. It should be noted that low vertical hydraulic conductivities (<10 −12 per Neuzil [20]) are necessary in order to generate and preserve underpressures [3,36]. Exhumation analyses were conducted whereby a helium tracer was simulated for each of the 20 calibrated paleohydrogeologic models over a period of 260 Ma.…”

Section: Discussionmentioning

confidence: 99%

“…They include, among other osmosis, the presence of a nonwetting gas phase, hydromechanical effects due to exhumation, cyclic glacial loading, and crustal flexure [22][23][24][25][26][27][28][29][30]. Abnormal underpressures in geologic formations have been reported in many regions of the globe [2], including China [31,32], Canada [33][34][35], and Switzerland [36]. Such abnormal pressures cannot exist without low permeability formations [3,31,36].…”

Section: Introductionmentioning

confidence: 99%

“…Abnormal underpressures in geologic formations have been reported in many regions of the globe [2], including China [31,32], Canada [33][34][35], and Switzerland [36]. Such abnormal pressures cannot exist without low permeability formations [3,31,36].…”

Section: Introductionmentioning

confidence: 99%

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Assessing Alternative Scenarios for the Cause of Underpressures in the Ordovician Sediments along the Eastern Flank of the Michigan Basin

et al. 2017

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Geoscientific investigations for a proposed deep geologic repository at the Bruce Site, located on the eastern flank of the Michigan Basin, have identified unique and significant underpressured conditions. Along with the measurement of environmental tracer profiles (e.g., helium), this study aims to explore, through a series of numerical simulations, the nature of long-term phenomena responsible for the generation and preservation of formation underpressures. Three families of inverse numerical experiments for underpressure formation were examined by means of one-dimensional hydromechanically coupled models through the vertical hydrostratigraphic column: (i) uncertainty in glaciation scenarios; (ii) uncertainty in initial heads prior to glaciation; and (iii) uncertainty in the degree of hydraulic connectivity between the more permeable Guelph Formation at the Bruce Site and the applied glacial loading, for a total of 20 scenarios, assuming fully saturated conditions. Underpressured initial heads for the paleohydrogeologic simulations lead to lower calibrated vertical hydraulic conductivities. The robustness and resilience of the groundwater system to external perturbations are greater for the state where underpressured conditions predate the onset of glaciation and are better able to preserve the present day helium tracer profile in 260 Ma exhumation analyses.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Assessing Alternative Scenarios for the Cause of Underpressures in the Ordovician Sediments along the Eastern Flank of the Michigan Basin

et al. 2017

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“…Poty et al (1974) and Mullis et al (1994) showed a systematic compositional distribution of fluid populations in veins of the Central Alps, based on careful establishment of fluid inclusion and quartz growth chronology. The composition of the earliest fluid inclusion populations changes systematically with increasing metamorphic grade of the local host rocks, from the diagenetic zone to amphibolites-facies conditions, whereby accompanying vein minerals closely reflect the composition of the local host rock (Mazurek 1999;Mullis et al 1994Mullis et al , 2002Tarantola et al 2007Tarantola et al , 2009). …”

Section: Introductionmentioning

confidence: 99%

Major and trace-element composition and pressure–temperature evolution of rock-buffered fluids in low-grade accretionary-wedge metasediments, Central Alps

Miron

Wagner

Wälle

et al. 2012

Contrib Mineral Petrol

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The chemical composition of fluid inclusions in quartz crystals from Alpine fissure veins was determined by combination of microthermometry, Raman spectroscopy, and LA-ICPMS analysis. The veins are hosted in carbonatebearing, organic-rich, low-grade metamorphic metapelites of the Bündnerschiefer of the eastern Central Alps (Switzerland). This strongly deformed tectonic unit is interpreted as a partly subducted accretionary wedge, on the basis of widespread carpholite assemblages that were later overprinted by lower greenschist facies metamorphism. Veins and their host rocks from two locations were studied to compare several indicators for the conditions during metamorphism, including illite crystallinity, graphite thermometry, stability of mineral assemblages, chlorite thermometry, fluid inclusion solute thermometry, and fluid inclusion isochores. Fluid inclusions are aqueous two-phase with 3.7-4.0 wt% equivalent NaCl at Thusis and 1.6-1.7 wt% at Schiers. Reproducible concentrations of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, B, Al, Mn, Cu, Zn, Pb, As, Sb, Cl, Br, and S could be determined for 97 fluid inclusion assemblages. Fluid and mineral geothermometry consistently indicate temperatures of 320 ± 20°C for the host rocks at Thusis and of 250 ± 30°C at Schiers. Combining fluid inclusion isochores with independent geothermometers results in pressure estimates of 2.8-3.8 kbar for Thusis, and of 3.3-3.4 kbar for Schiers. Pressure-temperature estimates are confirmed by pseudosection modeling. Fluid compositions and petrological modeling consistently demonstrate that chemical fluid-rock equilibrium was attained during vein formation, indicating that the fluids originated locally by metamorphic dehydration during near-isothermal decompression in a rock-buffered system.

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“…Faulted/fractured mudstones with very low effective permeability and a thickness of >100 m occur at depths shallower than 1 km (e.g., the Palfris Formation at depths of >∼400 m at Wellenberg, Switzerland (Nationale Genossenschaft für die Lagerung Radioaktiver Abfälle [Nagra], 1997), the Opalinus Clay at Mont Terri, Switzerland (Mazurek et al, ), and the Toarcian‐Domerian at Tournemire, France (Patriarche et al, )). The deeper part of the Palfris Formation has long been identified as an aquiclude, and very low effective permeability has been indicated from the occurrence of pressure anomalies and stagnation of ancient fossil water (>1 Ma; Mazurek, ; Mazurek et al, ). The generation and preservation of pressure anomalies depend on the hydraulic conductivity, hydraulic diffusivity, strain rate, and the shortest distance over which a pressure anomaly can be dissipated by flow, which require an effective permeability comparable to that of the rock matrix (Neuzil, ).…”

Section: Introductionmentioning

confidence: 99%

Assessment of Hydraulic Connectivity of Fractures in Mudstones by Single‐Borehole Investigations

Ishii

2018

Water Resources Research

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Assessing the hydraulic connectivity of fractures by single-borehole investigations is crucial to radioactive waste disposal but is still a challenge as such connectivity is difficult to measure directly. This study presents geological, hydrological, hydrochemical, and rock-mechanical data for three faulted/ fractured mudstones (the Koetoi, Wakkanai, and Palfris Formations) and proposes a new methodology for assessing the hydraulic connectivity of fractures. The methodology consists of three steps: (a) dividing the formation into two domains with a ductility index (DI) of >2 and <2 (DI is defined as the effective mean stress normalized to the tensile strength of intact rock), (b) estimating the hydraulic connectivity of fractures by analyzing pressure change obtained by packer tests and geological interpretation, and (c) verifying the estimation using pore pressure and water chemistry/geochemistry. The first step is necessary because the failure mode of damage-zone fractures in fault zones can differ between the DI > 2 and DI < 2 domains, which may lead to significant differences in the hydraulic connectivity of fractures. During the second step, potential domains in which the hydraulic connectivity of fractures is limited are identified where upward trends, characterized by slopes of 0.5-1.0, are observed during the middle to late period of elapsed time on log-log plots of pressure derivatives. Although the third step can be performed in various ways, this study employs the observation of pressure anomalies and the detection of young external water. Analyses of the three formations demonstrate the applicability and reliability of the proposed methodology.

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Evolution of gas and aqueous fluid in low-permeability argillaceous rocks during uplift and exhumation of the central Swiss Alps

Cited by 16 publications

References 39 publications

Assessing Alternative Scenarios for the Cause of Underpressures in the Ordovician Sediments along the Eastern Flank of the Michigan Basin

Assessing Alternative Scenarios for the Cause of Underpressures in the Ordovician Sediments along the Eastern Flank of the Michigan Basin

Major and trace-element composition and pressure–temperature evolution of rock-buffered fluids in low-grade accretionary-wedge metasediments, Central Alps

Assessment of Hydraulic Connectivity of Fractures in Mudstones by Single‐Borehole Investigations

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