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A 4D Model of Neogene Exhumation in the Central Helvetic Alps

Applicant Mancktelow Neil S.
Number 121578
Funding scheme Project funding
Research institution Geologisches Institut ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geology
Start/End 01.10.2008 - 30.09.2011
Approved amount 195'325.00
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Keywords (9)

exhumation; deformation; fluid-rock interaction; Helvetic nappes; European Alps; Helvetic Alps; folding; faulting; extension

Lay Summary (English)

Lead
Lay summary
The Helvetic Alps exposed north of the Rhone valley have been the subject of many studies and are now taken as a classic example of a fold-and-thrust belt developed as the result of shortening perpendicular to the Alpine chain. However, there is increasing evidence that over the last ca. 30 million years the Alps have also undergone significant extension parallel to the chain (i.e. SW-NE), during continued convergence perpendicular the chain (i.e. SE-NW). Although the absolute timing, kinematics and regional extent is not yet determined, this extension parallel to the chain and the associated exhumation of rocks from depth appears to have been most active during two periods, concentrated around ca. 32 million years and ca. 19-17 million years. However, related movements have continued until the present time, with a zone of strongly enhanced seismicity broadly localized along the Rhone Valley. The Simplon Fault Zone is the major young tectonic structure controlling exhumation in the Central Alps. This project is the continuation of a study that until now has focused on the Simplon Fault Zone in the region where it is best defined, from the Val d’Ossola over Simplon Pass and into the Rhone Valley. The continuation project will extend these field and laboratory studies to the west along and to the north of the Rhone Valley. The geometry and kinematics of the study region is fully 3-D, involving interacting folding and thrusting related to convergence and shearing, together with coeval and subsequent faulting and vein formation related to extension and exhumation. Radiometric dating of mineral growth can provide the important 4th dimension of absolute time. The overall aim is to develop a 4D model of the progressive transition from folding, thrusting and crustal thickening to extension, faulting and exhumation in the Helvetic Alps within the footwall of the Simplon Fault Zone.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Two- and three-dimensional thermal modeling of a low-angle detachment: Exhumation history of the Simplon Fault Zone, central Alps
Campani M, Herman F, Mancktelow N (2010), Two- and three-dimensional thermal modeling of a low-angle detachment: Exhumation history of the Simplon Fault Zone, central Alps, in JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 115.
Geochronological evidence for continuous exhumation through the ductile-brittle transition along a crustal-scale low-angle normal fault: Simplon Fault Zone, central Alps
Campani M, Mancktelow N, Seward D, Rolland Y, Muller W, Guerra I (2010), Geochronological evidence for continuous exhumation through the ductile-brittle transition along a crustal-scale low-angle normal fault: Simplon Fault Zone, central Alps, in TECTONICS, 29.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
10th Alpine workshop "CorseAlp2011" 10.04.2011 St Florent, Corsica, France
8th Swiss Geoscience Meeting 19.11.2010 Fribourg
7th Swiss Geoscience Meeting 20.11.2009 Neuchâtel
Gruppo Nazionale di Geofisica della Terra Solida (GNTGS) 16.11.2009 Trieste, Italy


Associated projects

Number Title Start Funding scheme
169055 Structure and evolution of an antiformal nappe stack (Aar massif, Central Alps): Formation of mechanical anisotropies and their bearing on natural risks 01.10.2016 Project funding
120502 TOPOALPS - 4D kinematics of the Neogene western Alps (IP2) 01.06.2008 Project funding (special)
149385 Structure and evolution of an antiformal nappe stack (Aar massif, Central Alps): Formation of mechanical anisotropies and their bearing on natural risks 01.10.2013 Project funding
126408 Glacial Carving versus Tectonic Forcing. Documenting their Relative Contribution to Relief Formation 01.10.2009 Ambizione
137510 A 4D Model of Neogene Exhumation in the Central Helvetic Alps 01.10.2011 Project funding
143165 Glacial Carving versus Tectonic Forcing. Documenting their Relative Contribution to Relief Formation 01.10.2012 Ambizione
109187 A 4D Model of Neogene Exhumation in the Central Alps 01.10.2005 Project funding
109519 Faults and Fluids: deep penetration of meteoric waters into the Alps during their exhumation 01.10.2005 Project funding
132196 Structure and evolution of an antiformal nappe stack (Aar massif, Central Alps): Formation of mechanical anisotropies and their bearing on natural risks 01.10.2010 Project funding

Abstract

The Simplon Fault Zone is the major Neogene tectonic structure controlling exhumation in the Central Alps. This project is the continuation of a study that until now has focused on the Simplon Fault Zone in the region where it is best defined, from the Val d’Ossola over Simplon Pass and into the Rhone Valley. The proposed continuation project will extend these field and laboratory studies to the west along the Rhone Valley and consider the deformation structures associated with Neogene orogen-parallel extension in the Helvetic nappes and underlying Aar massif (i.e. within the footwall of the Rhone-Simplon Fault Zone). Because of the smaller amount of exhumation, metamorphic conditions in this footwall segment did not exceed lower to middle greenschist facies and much deformation occurs around the brittle-ductile transition, continuing with increased exhumation into fully brittle conditions. Brittle fracture is strongly influenced by pore-fluid pressure and is now marked in the field by fibrous pressure shadows, veins and cataclasites sealed by newly precipitated quartz and calcite. These structures provide a chance to study fluid-rock interaction during deformation and exhumation and allow an assessment of the source of these fluids (e.g. metamorphic fluids from below or meteoric water from above). Fluids in small-scale structures, such as pressure shadows and veins, are likely to be effectively rock-buffered, but an isotopic signature of the infiltrating fluids may still be preserved in major faults and particularly within the immediate footwall of the Rhone-Simplon Fault Zone itself. The geometry and kinematics of the study region is fully 3-D, involving interacting folding and thrusting related to convergence, together with coeval and subsequent faulting and vein formation related to extension and exhumation. Ar-Ar and Rb-Sr dating of synkinematic mineral growth (especially white mica) can provide the important 4th dimension of absolute time, determined for specific points on the relative history, obtained from overprinting relationships in the field. The overall aim is to develop a 4D model of the progressive transition from folding, thrusting and crustal thickening to extension, faulting and exhumation in the Helvetic nappes and external massifs within the footwall of the Rhone-Simplon Fault Zone.
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