Fabric studies within the Cascade Lake shear zone, Sierra Nevada, California Basil Tikoff a, T , Matthew R. Davis b,1 , Christian Teyssier b,1 , Michel de St. Blanquat c,2 , Guillaume Habert c,2 , Sven Morgan d,3 a Department of Geology and Geophysics, University of Wisconsin, Madison, WI 53706, USA b Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA c CNRS—UMR5563 / LMTG, University Paul-Sabatier, 38 rue des 36-Ponts, 31400 Toulouse, France d Department of Geology, Central Michigan University, Mt. Pleasant, MI 48859, USA Received 8 August 2002; accepted 1 March 2005 Available online 12 April 2005 Abstract The Cascade Lake shear zone occurs on the eastern margin of the Tuolumne Intrusive Suite, Sierra Nevada Batholith, California. Foliation in the zone is NNW trending and subvertical, and lineation is moderately south plunging. Deformation is syn-tectonic with emplacement of the Cathedral Peak granodiorite. A deformation gradient exists toward the NE margin of this pluton, with higher strains and lower temperatures of deformation found near the contact. We compare fabric data collected very densely in this shear zone using several techniques: field fabrics, 3D orientation of K-feldspar megacrysts, and AMS (anisotropy of magnetic susceptibility) analysis. In general, the results from the three different methods are in agreement. Deformation in this shear zone is part of a larger pattern of deformation within the Cathedral Peak granodiorite, as recorded by AMS analysis, and dextral shearing associated within the last stage of plutonism within the Sierra Nevada magmatic arc. D 2005 Elsevier B.V. All rights reserved. Keywords: Shear zone; Sierra Nevada; Fabric analysis 1. Introduction The meaning of particular granitic fabrics and how they can be used to interpret emplacement histories is a subject of continuing interest in the earth sciences. In many cases, structures and fabrics formed purely by the ascent of buoyant magma appear to be overprinted by structures related to regional (or local) tectonics, making interpretations difficult. Paterson et al. (1989) defined magmatic flow as deformation by displace- 0040-1951/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.tecto.2005.03.003 T Corresponding author. Fax: +1 608 262 0693. E-mail addresses: basil@geology.wisc.edu (B. Tikoff), mdavis@hwtc.com (M.R. Davis), teyssier@tc.umn.edu (C. Teyssier), michel@lmtg.ups-tlse.fr (M. de St. Blanquat), habert@lmtg.ups-tlse.fr (G. Habert), sven.morgan@cmich.edu (S. Morgan). 1 Fax: +1 612 625 3819. 2 Fax: +33 5 61 52 05 44. 3 Fax: +1 989 774 2142. Tectonophysics 400 (2005) 209– 226 www.elsevier.com/locate/tecto