Inherited structural controls on fault geometry, architecture and hydrothermal activity: an example from Grimsel Pass, Switzerland

Belgrano, Thomas M.; Herwegh, Marco; Berger, Alfons

doi:10.1007/s00015-016-0212-9

Cited by 47 publications

(83 citation statements)

References 86 publications

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“…This type of fluid flow in shear zones has been inferred [94] as being enhanced by a postdeformation sericite alteration of feldspars, which can also weaken the rock. The role of exhumed shear zones on active hydrothermal systems has only been discussed before by Belgrano et al [14]. Their conclusions about the sealant effect of mylonites strongly differ from our observations; however their hydrothermal system and geological context are different than the Têt fault system and do not involve metasediment juxtaposition.…”

Section: Brittle Versus Ductile Faultscontrasting

confidence: 86%

“…This has often been demonstrated at a map scale [1,8], but more rarely at the outcrop or microscopic scale [14,15]. Fault damage zones in gneiss appear important for localizing hydrothermal fluid upflow.…”

Section: Brittle Versus Ductile Faultsmentioning

confidence: 99%

“…Subsidiary NW-SE brittle faults ( Figure 2) concentrate similarly oriented fractures in their damage zones. Intersections of the Têt fault and the NW-SE faults damage zones enhance fracture connections and favor the formation of efficient drains for fluids rising [1,14,41] (Figure 10). The temperature-dependence of fluid density induces a buoyancy force allowing hydrothermal fluids to upflow using the highly fractured Têt fault damage zone and subsequently causing isotherm uplift ( Figure 10).…”

Section: Brittle Versus Ductile Faultsmentioning

confidence: 99%

“…Nonmagmatic hydrothermal systems in continental contexts involving high relief and hot springs [7] are rarely studied [8]. Further, processes acting in this kind of hydrothermal systems are essentially explored by numerical models [9,10] (e.g., the Dixie Valley geothermal field in Nevada [11][12][13]), and integrative geological studies as proposed in this paper are few in number [7,[14][15][16].…”

Section: Introductionmentioning

confidence: 99%

“…An interplay of these geometrical/petrophysical factors leads to an upward hydrothermal flow within fault zones [1,14,40]. However, there is no clear evidence of which of these factors, if any, exerts a primary influence.…”

Section: Introductionmentioning

confidence: 99%

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Fault-Related Controls on Upward Hydrothermal Flow: An Integrated Geological Study of the Têt Fault System, Eastern Pyrénées (France)

et al. 2017

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The way faults control upward fluid flow in nonmagmatic hydrothermal systems in extensional context is still unclear. In the Eastern Pyrénées, an alignment of twenty-nine hot springs (29 ∘ C to 73 ∘ C), along the normal Têt fault, offers the opportunity to study this process. Using an integrated multiscale geological approach including mapping, remote sensing, and macro-and microscopic analyses of fault zones, we show that emergence is always located in crystalline rocks at gneiss-metasediments contacts, mostly in the Têt fault footwall. The hot springs distribution is related to high topographic reliefs, which are associated with fault throw and segmentation. In more detail, emergence localizes either (1) in brittle fault damage zones at the intersection between the Têt fault and subsidiary faults or (2) in ductile faults where dissolution cavities are observed along foliations, allowing juxtaposition of metasediments. Using these observations and 2D simple numerical simulation, we propose a hydrogeological model of upward hydrothermal flow. Meteoric fluids, infiltrated at high elevation in the fault footwall relief, get warmer at depth because of the geothermal gradient. Topography-related hydraulic gradient and buoyancy forces cause hot fluid rise along permeability anisotropies associated with lithological juxtapositions, fracture, and fault zone compositions.

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Section: Brittle Versus Ductile Faultscontrasting

confidence: 86%