Hydrogeologic evidence for a continuous basal shear zone within a deep-seated gravitational slope deformation (Eastern Alps, Tyrol, Austria)

Madritsch, Herfried; Millen, Bernard

doi:10.1007/s10346-006-0072-x

Cited by 17 publications

(23 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These two samples contain respectively 75 and 88 % 2M 1 illite/muscovite, whereas the usual Innsbruck Quartz Phyllite typically contains 25-30 % muscovite (see photomicrograph in Fig. 4b of Madritsch and Millen 2007). If the 2M 1 component in the clay gouge samples is entirely metamorphic muscovite, it must have been concentrated by a factor two or more relative to the protolith Innsbruck Quartz Phyllite, presumably by dissolution of original quartz and plagioclase.…”

Section: Discussionmentioning

confidence: 99%

Timing and conditions of brittle faulting on the Silltal-Brenner Fault Zone, Eastern Alps (Austria)

et al. 2015

View full text Add to dashboard Cite

The Silltal Fault is the northern brittle continuation of the Brenner Fault Zone, marked by a narrow zone of cataclasis and, in three locations, clay-rich fault gouges. The clay mineral composition of these gouges is dominated by higher temperature 2M 1 polytype illite/muscovite, with no 1M/1M d illite or mixed layer illite/ smectite detected. Smectite is limited to the northern samples from the Stephansbrücke location, whereas chlorite is present in all samples. The K-Ar ages from the different sample size fractions (\0.1, \0.4, \2, 2-6, 6-10 lm, ''whole rock gouge'') show a wide spread, from ca. 115 to 12 Ma, with ages consistently decreasing with grain size. Although the ranges overlap, ages from the northern Stephansbrücke samples are generally older (115-36 Ma) than those from the south near Matrei (55-12 Ma), possibly reflecting increasing regional metamorphic temperatures to the south. The well-defined linear relationship between apparent age and hydrogen stable isotope (dD) values establishes a direct correlation between rejuvenation of the K-Ar system and increased interaction with meteoric water introduced and focussed within the fault zone. The dependence of both apparent age and dD on grain size also indicates that radiogenic and stable isotope exchange was controlled by grain size, reflecting new 2M 1 illite growth, mechanical grinding of protolith muscovite during cataclastic faulting, or both. The results demonstrate the advantages of combining radiogenic and stable isotope analysis in interpretation of K-Ar ages from clay fault gouges. The combined approach was necessary to establish the crucial influence on apparent K-Ar ages of meteoric water influx focussed on the fault zone and its interaction with clay-size-fraction grains.

show abstract

Section: Discussionmentioning

confidence: 99%

Timing and conditions of brittle faulting on the Silltal-Brenner Fault Zone, Eastern Alps (Austria)

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Millen, 2003;Kilchmann et al, 2004;Sacchi et al, 2004;Madritsch and Millen, 2007). These processes are strongly controlled by microbial activity and are favoured at low pH-values.…”

Section: Possible Water-rock Interactionsmentioning

confidence: 99%

Aquifer geochemistry of crystalline rocks and Quaternary deposits in a high altitude alpine environment (Kauner Valley, Austria)

Strauhal¹,

Prager²,

Millen³

et al. 2016

AJES

View full text Add to dashboard Cite

In the Upper Kauner Valley of the Tyrolean Central Alps in Austria, some of the slopes, consisting of crystalline bedrock covered by Quaternary deposits, host groundwater of remarkable chemical composition. The bedrock consists mainly of a thick paragneiss series with intercalations of orthogneiss and amphibolite belonging to the Ötztal-Stubai Basement Complex. These metamorphic rocks are ubiquitously fractured and the fracture surfaces are coated with Fe-(hydr-)oxides and chlorite but also carbonates. Sul phides occur as dispersed accessory crystals and locally as small ore deposits. During the Quaternary, the valley floor, slopes, and cirques were covered by clastic sediments of differing thicknesses. A striking feature of the valley is that the slopes have been affected by different types of mass movements (rockfalls, debris flows and deep-seated rockslides). Data from extensive (hydro)geological field surveys, tunnels (exploration drift and water conduction galleries) and exploration drillings indicate that the groundwater preferentially flows within zones of highly weathered bedrock (i.e. the saprolite), brittle fault and fracture zones, deep-seated rockslides, and in the conductive Quaternary deposits, i.e. the talus, colluvium, debris flow and alluvial deposits. Interestingly, unusually high amounts of total dissolved solids (>1000 mg / l) were measured in some spring waters. Tritium and δ18 O values indicate short residence times (<5 years) and the analysis of δ 18 O and δ 2 H data shows that the groundwater is of meteoric origin and that no fractionation or evaporation processes, leading to increased mineralisation, have taken place. Ca and Mg are the dominant cations and SO 4 and HCO 3 are the major anions present. Data correlation shows that the electric conductivity (EC) of the waters increases with increasing Ca, Mg and SO 4 concentration, but not with HCO 3 . Low δ 34 S values indicate that the dissolved sulphate can be attributed to the oxidation of sulphides. Accordingly, the dissolution of carbonate fracture fillings and the oxidation of pyrite and other sulphides are regarded as the main processes responsible for the mineralised groundwater in the study area. Aquifer geochemistry of crystalline rocks and Quaternary deposits in a high altitude alpine environment (Kauner Valley, Austria) 30

show abstract

“…Only in few locations, mainly in less densely foliated gneisses, block toppling is observed. The uneven topography of the valley flanks and the scarps with pronounced along-strike variations in their height resemble the morphologic expressions caused by large-scale sagging processes and the accompanying smaller-scale gravitational processes (Agliardi et al 2001;Dramis & Sorriso-Valvo 1994;Gutiérrez-Santolalla et al 2005 and references therein; Hippolyte et al 2006;Madritsch & Millen 2007). At least some of the scarp-related faults are still active: At the Oberalp Pass, geodetic measurements along a ~170-m-long profile reveal height changes of ~0.7 mm/yr across a fault with an uphill-facing scarp (Eckhardt et al 1983).…”

Section: Geological Setting and Field Observationsmentioning

confidence: 99%

Composite faults in the Swiss Alps formed by the interplay of tectonics, gravitation and postglacial rebound: an integrated field and modelling study

2008

View full text Add to dashboard Cite

Along the flanks of several valleys in the Swiss Alps, well-preserved fault scarps occur between 1900 and 2400 m altitude, which reveal uplift of the valley-side block relative to the mountain-side block. The height of these uphillfacing scarps varies between 0.5 m and more than 10 m along strike of the fault traces, which usually trend parallel to the valley axes. The formation of the scarps is generally attributed either to tectonic movements or gravitational slope instabilities. Here we combine field data and numerical experiments to show that the scarps may be of composite origin, i.e. that tectonic and gravitational processes as well as postglacial differential uplift may have contributed to their formation. Tectonic displacement may occur as the fault scarps run parallel to older tectonic faults. The tectonic component seems, however, to be minor as the studied valleys lack seismic activity. A large gravitational component, which is feasible owing to the steep dip of the schistosity and lithologic boundaries in the studied valleys, is indicated by the uneven morphology of the scarps, which is typical of slope movements. Postglacial differential uplift of the valley floor with respect to the summits provides a third feasible mechanism for scarp formation, as the scarps are postglacial in age and occur on the flanks of valleys that were filled with ice during the last glacial maximum. Finite-element experiments show that postglacial unloading and rebound can initiate slip on steeply dipping pre-existing weak zones and explain part of the observed scarp height. From our field and modelling results we conclude that the formation of uphill-facing scarps is primarily promoted by a steeply dipping schistosity striking parallel to the valley axes and, in addition, by mechanically weaker rocks in the valley with respect to the summits. Our findings imply that the identification of surface expressions related to active faults can be hindered by similar morphologic structures of non-tectonic origin.

show abstract

Hydrogeologic evidence for a continuous basal shear zone within a deep-seated gravitational slope deformation (Eastern Alps, Tyrol, Austria)

Cited by 17 publications

References 17 publications

Timing and conditions of brittle faulting on the Silltal-Brenner Fault Zone, Eastern Alps (Austria)

Timing and conditions of brittle faulting on the Silltal-Brenner Fault Zone, Eastern Alps (Austria)

Aquifer geochemistry of crystalline rocks and Quaternary deposits in a high altitude alpine environment (Kauner Valley, Austria)

Composite faults in the Swiss Alps formed by the interplay of tectonics, gravitation and postglacial rebound: an integrated field and modelling study

Contact Info

Product

Resources

About