Complete fabric analysis of some commonly observed quartz C-axis patterns

The evolution of high-temperature mylonitic microfabrics: evidence from simple shearing of a quartz analogue (norcamphor)

“…Such studies document an increase in microfabric asymmetry into shear zones, supporting the notion that one or more slip systems rotate into an orientation that is subparallel to the bulk shearing plane (e.g. Lister & Hobbs 1980, Schmid & Casey 1986). However, strain paths inferred from strain gradients across shear zones can differ significantly from the actual strain paths of different parts of the sheared rock, especially if localization involved some hardening and broadening of the shear zone.…”

“…By analogy with complete textural analyses of naturally deformed quartz (Schmid & Casey 1986), the strong Y-maximum for quartz in Fig. 12f can be related to a strong activity of prism {m} in the (a) direction.…”

Development of quartz c-axis crossed/single girdles under simple-pure shear deformation: Results of visco-plastic self-consistent modeling

“…Fabric patterns observed in natural quartzites are variable and somewhat complicated, and what controls or affects most of their transitions is not well understood (Wenk, 1985;Wenk and Christie, 1991;Schmid, 1994;Karato, 2008). However, the influence of deformation on the fabric pattern has been recgonized and has found a range of applications in structural geology (Schmid and Casey, 1986). For example, in the presence of basal <a> slip as the dominant slip system, quartz c-axes appear in a cleft girdle under axial extension, in a small circle girdle under axial shortening, and in a crossed girdle with symmetrical or asymmetrical legs under plane coaxial or non-coaxial strain (Tullis, 1977;Tullis et al, 1973;Lister and Hobbs, 1980;Dell'Angelo and Tullis, 1989;Gleason et al, 1993).…”

“…For example, in the presence of basal <a> slip as the dominant slip system, quartz c-axes appear in a cleft girdle under axial extension, in a small circle girdle under axial shortening, and in a crossed girdle with symmetrical or asymmetrical legs under plane coaxial or non-coaxial strain (Tullis, 1977;Tullis et al, 1973;Lister and Hobbs, 1980;Dell'Angelo and Tullis, 1989;Gleason et al, 1993). Crossed girdles may form initially and then switch into a single girdle or even a single c-axis maximum, when dynamic recrystallization sets in and gradually increases with increasing strain (Schmid and Casey, 1986;Law, 1990;Schmid, 1994;Stipp et al, 2002;Mancktelow and Pennacchioni, 2004;Heilbronner and Tullis, 2006). Despite these approaches, there remain two unresolved issues regarding the development of quartz c-axis fabric in non-coaxial deformation.…”

“…Schmid and Casey (1986) proposed that the single girdle developed in simple shear is perpendicular to the shear plane. This perpendicularity seems to be reproduced by some numerical simulations (Etchecopar and Vasseur, 1987;Jessell and Lister, 1990).…”