HR: 16:35h
AN: GP34A-02 INVITED     [Abstracts]
TI: The Acquisition of a Mineral Fabric During Simple Shear: Implications for the Measurements of Anisotropy of Magnetic Susceptibility of Tectonically Deformed and Igneous Rocks.
AU: * Cañón-Tapia, E
EM: ecanon@cicese.mx
AF: CICESE Geology Dept., P.O. Box 434843, San Diego, CA 92143, United States
AB: Other than their elongation ratio and the initial distribution of orientations of a set of particles, a key element controlling the acquisition of a stable fabric in simple shear is the amount of deformation expected for a rock: Small shear strains favor a stable fabric whereas large shear strain leads to a periodic behavior. Paradoxically, many workers interested in the AMS of tectonically deformed rocks have considered that under simple shear the fabric will behave rotationally whereas those workers interested in the AMS of dykes, lavas or other igneous rocks usually assume that the fabric is essentially stable. In this work I reexamine the conditions controlling the acquisition of a mineral fabric during simple shear, presenting threshold values that can be used as guidelines in the interpretation of AMS results obtained from a variety of rock types. Due to the many factors influencing fabric acquisition, it is also shown that unless some key parameters are determined from an independent technique, most models attempting to map the amount of deformation with a degree of anisotropy are extremely limited.
DE: 1518 Magnetic fabrics and anisotropy
DE: 1540 Rock and mineral magnetism
DE: 8094 Instruments and techniques
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly