BSE image, EBSD-derived phase and orientation (IPF-X) maps (left to right) from a granite gneiss. Both (b) & (c) correspond to the region enclosed by the yellow rectangle in (a). Mineral abbreviations in (b) are as per Whitney & Evans (2010, Am Min).
I'm mentoring one of the doctoral students (check his work here) in the Exp Rock Def group and a part of the research aims to investigate the cause(s) of shear zone initiation. We also wish to explore the correlation between the thicknesses and mineralogy of the shear zones, and the mechanism(s) that accommodated the deformation within them. Preliminary studies have been conducted and the manuscript is in progress.
Selected EBSD derived phase and orientation maps. Magnetite-Hematite intergrowth textures are shown in (a) and (c). All the figures represent XZ-sections.
My second postdoctoral project aimed at examining the deformation behaviors of the Fe-oxides and quartz of Banded Iron Formation (BIF) samples from Southern India. We (my co-authors & I) established that both quartz and magnetite accommodated deformation via dislocation creep. Prominent subgrain boundaries in a few magnetite grains, rarely reported in naturally deformed samples, were also observed. Furthermore, we employed boundary trace analysis using the SGBta script in MATLAB to determine the nature of the subgrain boundary walls (tilt, twist, or general) in both quartz and magnetite, and dominant slip systems in the latter. Parallelism of basal and octahedral planes of hematite and magnetite grains, respectively, was evident in the pole figures. They testified to the redox nature of the topotaxial replacement of the latter by the former. Please check Dutta et al. (2022) (or the Preprint) for more.
Longitudinal axial section of a deformed sample and the corresponding SEM images. Area fractions and grain equivalent diameters of the phases are shown too. Green bars: root mean square. Mineral abbreviations are as per Whitney & Evans (2010, Am Min).
 pole figures at different strain segments and melt %. Yellow squares: maximum intensity. Color map 'bilbao' after Crameri (2018)
During my first postdoctoral project, I worked with the EBSD data derived from the longitudinal axial section (see top figure) of a deformed metapelite sample. We (my co-authors & I) examined the deformation behaviors of the minerals viz., Qz, Ms, Kfs, Bt, Mul, Crd, & Ilm, under melt-present conditions. We proposed that grain boundary sliding was the dominant deformation mechanism, and melt inhibited intragranular plastic deformation of the major phases viz. Qz & Kfs. Consequently, the crystallographic preferred orientations (see the figure above) were weak, intragranular strain was low, & low-angle misorientation axes did not exhibit crystallographic control. Please check Dutta et al. (2021) (or the Preprint) for more.
Selected results of CPO, low angle (2–10°) misorientation (left panel), and CVA (right panel) analyses of the quartz grains from the granite gneiss of the Tso Morari Crystallines..
My first attempt at working with EBSD data was during my doctoral research. I focused on the crystallographic preferred orientations of quartz grains from samples of granitic gneiss. The EBSD data was post-processed using the MTEX toolbox in Matlab. Low-angle misorientation analysis was also performed to estimate the deformation temperatures. Moreover, the nature of deformation was established using the CVA analysis (Michels et al. 2015, Geology). Finally, the work proposes that extrusion of the Tso Morari Crystallines (Ladakh Himalaya, India) was triggered by the return flow and buoyancy of the subducted continental crust and facilitated by the Indo-Eurasia collision. Continued convergence likely promoted non-planar triclinic transpression. Please check Dutta & Mukherjee (2021) for more.