Universal stage measurements in petrofabric analysis revisited
Once an important accessory for petrographic microscope and a valuable tool in mineralogical and petrofabric work, the Universal Stage (U-stage) has been dubbed obsolete with the advent of electron microprobe and XRD, and subsequent phasing out of the production of the optical equipment. Modern-day fabric analysis also relies more on far more expensive texture goniometers, neutron activation analysis and electron back-scattered diffraction analysis (EBSD) equipment. However, routine measurements of crystallographic fabric elements of uniaxial mineral aggregates (quartz- and calcite c-axis), principal axes of important biaxial minerals like olivine, strength of mica (001) fabric, paleostress estimate from mechanical twins (e-twin) in calcite, and evaluation of meteorite impact texture in quartz as well as impact history of asteroids, can still be done by U-stage knowledgeably and in a cost effective manner, subject to adequate training by efficient instructors. In the cases of (e-twin in individual calcite grains and planar deformation features in natural shocked quartz, U-stage measurement cannot still be replaced by EBSD. An abridged review of the science behind U-stage procedure with examples of actual application has been presented to rekindle the interest.
Volume 131, 2022
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