Hostname: page-component-76fb5796d-x4r87 Total loading time: 0 Render date: 2024-04-26T12:44:20.229Z Has data issue: false hasContentIssue false
  • English
  • Français

Magnetic anisotropy and X- ray diffraction study of clay minerals in the decollement horizons of the western Helvetic nappes, SW Switzerland

Published online by Cambridge University Press:  09 July 2018

P. Dick  and
M. Burkhard
P. Dick*
Affiliation:
Institut de Géologie, rue E. Argand 11, CH-2007 Neuchâtel, Switzerland
M. Burkhard
Affiliation:
Institut de Géologie, rue E. Argand 11, CH-2007 Neuchâtel, Switzerland
*
*E-mail: pierre.dick@geol.unine.ch
Get access Rights & Permissions [Opens in a new window]

Abstract

Anisotropy of magnetic susceptibility (AMS) and X-ray diffraction studies on shale decollement horizons in the Western Helvetic nappes were conducted to delineate the interactions between clay particles and deformation during a non-coaxial thrusting deformation. The reorientation of magnetic lineations in the decollement horizons, from a NW—SW thrusting direction to a NE—SW oriented lateral escape, provides the opportunity to study the evolution of magnetic fabrics and clay mineralogy during a two-step deformation history. The AMS of these shales originates from paramagnetic phyllosilicate minerals: illite, phengite and chlorite. Clay mineral studies indicate that magnetic lineations parallel to the thrust directions correspond to the spatial organization of the basal planes of phengites, whereas those parallel to the lateral escape movement are caused by illites. This work indicates that the change in direction of magnetic lineations from orogenic contraction to lateral escape not only records the strain history but also the dissolution and neoformation of paramagnetic minerals.

Keywords

magnetic anisotropyX-ray diffractionHelvetic nappesSwitzerland
Type
Research Article
Information
Clay Minerals , Volume 36 , Issue 2 , June 2001 , pp. 181 - 196
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2001

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Aubourg, C., Rochette, P. & Vialon, P. (1990) Direction of transport revealed by the magnetic fabric of the subalpine Terres Noires, French Alps. C.R. Acad. Sci., Paris, 310, 1341–1346.Google Scholar
Aubourg, C., Rochette, P. & Vialon, P. (1991) Subtle stretching lineation revealed by magnetic fabric of Callovian-Oxfordian black shales (French Alps). Tectonophysics, 185, 211–223.CrossRefGoogle Scholar
Bailey, S.W. (1972) Determination of chlorite compositions by X-ray spacings and intensities. Clays Clay Miner. 20, 381–388.CrossRefGoogle Scholar
Borradaile, G.J. (1987) Anisotropy of magnetic susceptibility; rock composition versus strain. Tectonophysics, 138, 327–329.CrossRefGoogle Scholar
Borradaile, G.J. & Henry, B. (1997) Tectonic applications of magnetic susceptibility and its anisotropy. Earth Sci. Rev. 42, 49–93.CrossRefGoogle Scholar
Brindley, G.W. & Gillery, F.H. (1956) X-ray identification of chlorite species. Am. Miner. 41, 169–186.Google Scholar
Brown, G. (1955) The effect of isomorphous substitutions on the intensities of (001) reflections of micaand chlorite- type structures. Mineral. Mag. 30, 657–665.Google Scholar
Brown, G. & Brindley, G.W. (1980) X-ray diffraction procedures for clay mineral identification. Pp. 305–359 in. Crystal Structures of Clay Minerals and their X-ray Identification (Brown, G. & Brindley, G.W., editors). Monograph 5. Mineralogical Society, London.Google Scholar
Burkhard, M. (1988) L’Hélvetique de la bordure occidentale du massif de l’Aar (évolution tectonique et métamorphiqu e). Eclogae Geol. Helv. 81, 63–114.Google Scholar
Chagnon, A. & Desjardins, M. (1991) Determination of the composition of chlorite from X-ray diffraction and microanaly sis data. Canad. Mineral. 29, 245–254.Google Scholar
Dick, P. (2000) Tectonic transport directions in the Helvetic-Subalpine thrust system of the NW-Alpine arc. PhD thesis, Univ. Neuchâtel, Switzerland.Google Scholar
Dick, P. & Burkhard, M. (1999) Comparison between magnetic fabrics and paleostress from major decollement horizons in the Helvetic Nappes (SW Switzerland); implications for the formation of the Helvetic Arc. Eur. Union Geosci. Conf., EUG 10, 4, 626.Google Scholar
Esquevin, J. (1969) Influence de la composition chimique des illites sur leur cristallinité. Centre de Recherches de Pau (Societe Nationale des Petroles d’Aquitaine), Bulletin, 3, 147–153.Google Scholar
Goy-Eggenberger, D. (1998) Faible métamorphisme de la nappe de Morcles: minéralogie et géochimie. PhD thesis, Univ. Neuchâtel, Switzerland.Google Scholar
Hamilton, N. & Rees, A.I. (1970) The use of magnetic fabric in palaeocurrent estimation. Palaeogeophysics, 445–464.Google Scholar
Hirt, A.M., Lowrie, W., Clendenen, W.S. & Kligfield, R. (1988) The correlation of magnetic anisotropy with strain in the Chelmsford Formation of the Sudbury Basin, Ontario. Tectonophysics, 145, 177–189.CrossRefGoogle Scholar
Hounslow, M.W. (1985) Magnetic fabric arising from paramagnetic phyllosilicate minerals in mudrocks. J. Geol. Soc. 142, 995–1006.CrossRefGoogle Scholar
Housen, B.A. & Van der Pluijm, B.A. (1991) Slaty cleavage development and magnetic anisotropy fabrics. J. Geophys. Res. 96, 9937–9946.Google Scholar
Housen, B.A., Tobin, H.J., Labaume, P., Leitch, E.C., Maltman, A.J., Shipley, T., Ogawa, Y., Ashi, J., Blum, P., Brueckmann, W., Felice, F., Fisher, A., Goldberg, D., Henry, P., Jurado, M.J., Kastner, M., Laier, T., Meyer, A., Moore, J.C., Moore, G., Peacock, S., Rabaute, A., Steiger, T., Underwood, M., Xu, Y., Yin, H., Zheng, Y. & Zwart, G. (1996) Strain decoupling across the decollement of the Barbados accretionary prism. Geology, 24, 127–130.2.3.CO;2>CrossRefGoogle Scholar
Kligfield, R., Owens, W.H. & Lowrie, W. (1981) Magnetic susceptibility anisotropy, strain, and progressive deformation in Permian sediments from the Maritime Alps (France). Earth Planet. Sci. Lett. 55, 181–189.CrossRefGoogle Scholar
Mosar, J. (1988) Metamorphisme transporte dans les Prealpes; Transported metamorphism in the Prealps. Schweiz. Mineral. Petrogr. Mitt. 68, 77–94.Google Scholar
Oinuma, K., Shimoda, S. & Sudo, T. (1972) Triangular diagrams in use of a survey of crystal chemistry of chlorites. Proc. Int. Clay Conf., Madrid, 161–171.Google Scholar
Petruk, W. (1964) Determination of the heavy atom content in chlorite by means of the X-ray diffractometer. Am. Miner. 49, 61–71.Google Scholar
Ramsay, J. (1981) Tectonics of the Helvetic Nappes, Pp. 293–309 in. Thrust and Nappe Tectonics (McClay, K.R. & Price, N.J., editors). Spec. Publ. 9, Geological Society, London.Google Scholar
Rey, J.-P. & Kubler, B. (1983) Identification des micas des séries sédimentaires à partir de la série harmonique (001) des préparations orientées. Schweiz. Mineral. Petrogr. Mitt. 63, 13–36.Google Scholar
Rochette, P., Jackson, M. & Aubourg, C. (1992) Rock magnetism and the interpretation of anisotropy of magnetic susceptibility. Rev. Geophys. 30, 209–226.CrossRefGoogle Scholar