Slip systems and critical resolved shear stress in pyrite: an electron backscatter diffraction (EBSD) investigation

Abstract

A suite of experimentally deformed single-crystal pyrite samples has been investigated using electron backscatter diffraction (EBSD). Single crystals were loaded parallel to <100> or <110> and deformed at a strain rate of 10-5s-1, confining pressure of 300 MPa and temperatures of 600°C and 700°C. Although geometrically (Schmid factor) the {001}<100> slip system should not be activated in <100> loaded samples, lattice rotation and boundary trace analyses of the distorted crystals indicate this slip system is easier to justify. Determination of 75 MPa as the critical resolved shear stress (CRSS) for {001}<100> activation, in the <110> loaded crystals, suggests a crystal misalignment of ~5—15° in the <100> loaded crystals would be sufficient to activate the {001}<100> slip system. Therefore, {001}<100> is considered the dominant slip system in all of the single-crystal pyrite samples studied. Slip-system analysis of the experimentally deformed polycrystalline pyrite aggregates is consistent with the single-crystal findings, with the exception that {001}<11̄> also appears to be important, although less common than the {001}<100> slip system. The lack of crystal preferred orientation (CPO) development in the polycrystalline pyrite aggregates can be accounted for by the presence of two independent symmetrically equivalent slip systems more than satisfying the von Mises criterion.

Fluid-present deformation aids chemical modification of chromite: Insights from chromites from Golyamo Kamenyane, SE Bulgaria

“…Lloyd et al, 1997;Menegon et al, 2011), halite (Borthwick and Piazolo, 2010), calcite (Bestmann and Prior, 2003), garnet (Prior et al, 2002), kyanite (Beane and Field, 2007), sillimanite (Piazolo and Jaconelli, 2013), zircon (e.g. Piazolo et al, 2012;Reddy et al, 2007), pyrite (Barrie et al, 2008) and water ice (Piazolo et al, 2008).…”

Advances and Opportunities in Ore Mineralogy

“…Among the ore minerals, pyrite has been a major focus. Many studies used EBSD to target mechanisms of sulphide deformation at different conditions in metamorphic environments [53][54][55][56][57][58][59][60]. Other studies [61][62][63] used EBSD to address the growth of colloform and framboidal pyrite.…”

The effect of Dauphiné twinning on plastic strain in quartz

“…11). Barrie et al (2008) documented a similar switch in the active slip system in pyrite single crystals, due to crystal misalignment resulting from progressive lattice rotation. Furthermore, in regions of confined deformation between discrete twin boundaries, the activation of additional sets of slip systems (like {p} \a[ and {p 0 } \a[) conceivably allows compatibility problems to be overcome.…”

“…11) (e.g. Barrie et al 2008). In porphyroclast A, the basal, the p and the p 0 planes are all subparallel to planes of ideal orientation for shear activation (see Fig.…”

“…Prior et al 2002;Barrie et al 2008;Piazolo et al 2008) is a method for determining the geometry of low-angle boundary and the active slip system(s) from EBSD data. When the 3D orientation of a boundary is unknown, the boundary trace analysis provides a crystallographically consistent solution for the boundary geometry, if ideal tilt and twist boundary models are assumed.…”