• Universal stage measurements in petrofabric analysis revisited

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    • Keywords


      Calcite e-twin; c-axis; mica (001); planar deformation features; petrofabric; universal stage.

    • Abstract


      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.

    • Author Affiliations



      1. Geological Studies Unit, Indian Statistical Institute, 203 B T Road, Kolkata 700 108, India.
    • Dates

  • Journal of Earth System Science | News

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      Posted on July 25, 2019

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