Graphic derivation of the local sense of shear strain components in stretched walls of lithotectonic boundaries

摘要: Abstract Lithotectonic boundaries (LTBs) are deformed interfaces between rock masses such as sheared strata, midcrustal thrust slices or sutured microcontinents. Structural analysis of strained LTB walls have focussed attention on cuts through the foliation normal and mineral lineation direction, but this practice is commonly inappropriate for investigating tangential shear strain ( γ ). A simple graphic technique introduced whereby one may derive sense large components in two sections across an wall segment; section parallel to other foliation. The orientation ellipse used each deduce its component by visual inspection. applicable metamorphic rocks with L – S fabrics, without reliable gauges incremental total longitudinal strain. If factor prolateness/oblateness ellipsoid unknown, then direction cannot be fixed within angle Journal Geology , 20, 969–973). However, accurately determined if cross fortuitously contains well direction. Similarly, can local corresponds oblate prolate spheroid. Where nearly spheroidal, therefore discern which under consideration has larger magnitude. This proves advantageous assessing Alleghanian below Brevard fault zone (Grandfather Mountain area), southern Appalachians. Here a ductile thrust, >1 km into stretched footwall. Close zone, however, sinistral component, unless dip >40°.