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

Are quartz LPOs predictably oriented with respect to the shear zone boundary?: A test from the Alpine Fault mylonites, New Zealand

“…Experiments by Heilbronner and Tullis [2006] produced quartz single-girdle LPOs that forwardrotated relative to the SZB to reach a final stable orientation forward-inclined by 268 relative to SZB at finite shear strains >8 (Figure 1d). Recent field-based studies have inferred that the final, stable position of a single-girdle quartz LPO may be forward-inclined to the SZB by 20-308 [Keller and Stipp, 2011;Kilian et al, 2011], and such a process has been modeled using self-consistent viscoplastic (VPSC) theory in cases where multiple slip systems are simultaneously active [Keller and Stipp, 2011;Nie and Shan, 2014].…”

A Multiscale Numerical Modeling Investigation on the Significance of Flow Partitioning for the Development of Quartz c‐Axis Fabrics

“…The standard models summarized in Figure 1 are based on deformation of pure quartz aggregates under limited (mostly simple shearing) single‐scale uniform flows (e.g., Keller & Stipp, 2011; Lister et al., 1978; Lister & Hobbs, 1980; Lister & Williams, 1979; Morales et al., 2014; Nie & Shan, 2014; Wenk et al., 1989). The spatial variation of quartz c‐axis fabrics is a manifestation of heterogeneous deformation and, we suspect, is related to flow partitioning (e.g., Jiang, 1994a, 1994b; Lister & Williams, 1983) and strain buildup in rheologically distinct domains.…”

“…These are interpreted as reflecting the slip systems during deformation (e.g., Mainprice et al., 1986; Okudaira et al., 1995; Schmid & Casey, 1986; Simpson & Schmid, 1983). The models summarized in Figure 1 were based on numerical modeling of pure quartz aggregates using the Taylor‐Bishop Hill model (e.g., Lister, 1977; Lister & Hobbs, 1980; Lister & Williams, 1979) and the viscoplastic self‐consistent (VPSC, Lebensohn & Tomé, 1993) model (e.g., Morales et al., 2011; Nie & Shan, 2014; Wenk et al., 1989). Both model methods predicted that the c‐axis girdle is antithetic or normal to the shear zone boundary in the coordinate system used here.…”

“…Little et al (2016) suggested that plane-strain general flows may produce synthetically-inclined c-axis girdles. The VPSC modeling of Takeshita et al (1999) and Nie and Shan (2014) considered such flows but did not obtain any synthetically-inclined c-axis girdles. Their models did not consider cases where prism<a> and rhomb<a> slips are more significant than basal<a> slip.…”