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Stretching lineations record primarily the vector of greatest stretch, which is perpendicular to the principle plane of shortening. A stretching lineation may be visualised as a ball of treacle (molasses) which, when pulled, forms a cigar-shaped rod parallel to the direction in which it is pulled.
At this point shear foliations begin to break down into a rodding lineation or a stretch lineation. Such rocks are known as L-tectonites. Stretched pebble conglomerate L-tectonite illustrating a stretch lineation within a shear zone, Glengarry Basin, Australia.
Slender prismatic crystals such as amphibole produce a lineation in which these prisms or columnar crystals become aligned. [1] Tectonites are rocks with minerals that have been affected by natural forces of the earth, which allowed their orientations to change. This usually includes recrystallization of minerals, and the foliation formation.
L-fabric — a linear fabric such as mineral stretching lineation where aggregates of recrystallised grains are stretched out into the long axis of the finite strain ellipsoid, where it forms the dominant fabric in a rock, it may be called an L-tectonite.
Because of the constraints imposed by simple shear, displacement is assumed to occur in the foliation plane in a direction parallel to the mineral stretching lineation. Therefore, a plane parallel to the lineation and perpendicular to the foliation is viewed to determine the shear sense.
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[5]: 409 A stretching lineation (line of tectonic transport) in the mylonite foliation plunges 42° in a S43°E direction. [ 5 ] : 409 In the Sims-and-Day model, this last collision in the assembly of the Superior province resulted from northwest-directed tectonic transport of the Minnesota River Valley subprovince terrane against the terrane ...
This stress may be imposed from outside; for example, by the stretching of layers, the rise of pore fluid pressure, or shrinkage caused by the cooling or desiccation of a rock body or layer whose outside boundaries remained fixed. [1] [2] When tensional stresses stretch a body or layer of rock such that its tensile strength is exceeded, it ...