Shear zone vs folding origin for spiral inclusion trails in the Canton Schist

Regression Models for Cyclic Data

“…The data that motivated this paper were collected from garnet porphyroblasts of the Canton Schist, Georgia, USA (Stallard and Hickey, 2001a,b). The process leading to the data that are analysed in this paper is as follows.…”

“…For the rocks in question, there is a second interesting feature. Most display three distinct textural zones that display different inclusion trail texture and mineralogy (Stallard and Hickey, 2001a). These are arranged like the layers of an onion and, for reference, have been labelled core, middle and rim.…”

“…All the samples in this study have been taken from the same small region in a single body of rock (Stallard and Hickey, 2001a,b) and are thought to have formed under similar conditions. Given the strong similarity in textural zoning in porphyroblasts from most of the samples, there is an expectation that the mean FIA orientation in the core, middle and rim of one rock sample may be similar to those in the core, middle and rim of the other samples.…”

The Significance and Application of Foliation Intersection/Inflection Axes (FIA( within Porphyroblasts: A review

“…In multi-FIA samples (samples that contain more than one FIA trend each), errors between relative trends of FIAs are only a function of the last two stages of sample preparation (cutting of slabs and thin section blocks from slabs) as they are obtained from one sample, and they should have a relative precision of ± 4° (Bell and Hickey 1997). Stallard (1999) and Stallard and Hickey (2001) estimated the variation in a FIA set ranges from± 15° to 20° (minimum) to 50°-60° (maximum) from the effects of anastomosing foliations. Consequently, determination of FIAs requires interpreting 2-D sections of usually complex inclusion trails, it is common to find both anticlockwise and clockwise asymmetries within sections oriented close to the FIA.…”

“…Although these inclusion trails (S) l commonly have complex geometries, they attract broad interest as the microstructures preserve unique structural markers, and can be utilized to evaluate deformation and metamorphic processes, quantifying a wide variety of orogenic parameters such as: syn-orogenic bulk short ening directions Rosenfeld 1968;Yeh 2002), fold mechanisms (Bell and Hickey 1997;Hickey and Bell 1999;Yeh 2002), and tracking foliation development during progressively changing metamorphic conditions (Williams 1994;Bell et al 2003). Furthermore, their relationships with the surrounding matrix have been used extensively to reconstruct the deformation history and infer the timing of metamorphic mineral growth relative to deforma tion (e.g., Johnson 1990;Bell et al 1992a, b, c;Passchier et al 1992;Forde and Bell 1993;Johnson 1993a, b;Johnson and Williams 1998;Williams and Jiang 1999;Stallard and Hickey 2001).…”