Southwestern Virginia Case Study

A4 Mylonite 2

Elizabeth Johnson

Outcrop and Hand Sample Photos and Videos

Click on the image to enlarge.

This mylonite is located in the same outcrop as mylonite 1 (mylonite 2 is farther south than mylonite 1).  It is hard to know what the protolith was, but based upon the porphyroclasts it was likely an ultramafic or mafic rock.

Can you see the mylonite fabric in this photo?

The students are pointing to one metamorphic feature with their pencils.  There is another structure above and to the left of the blue pencil.  Can you identify it also?

It’s huge!  What am I standing next to?

 

Thin Section Photos and Videos

Click on the image to make it larger. 1st = plane polarized light; 2nd = cross-polarized light.

The brown minerals (in ppl) are likely some type of amphibole.  Green in ppl is chlorite. Qtz is also present.  Are the amphiboles prophyroclasts or porphyroblasts?

 

Entire thin section scan. 1st = ppl; 2nd = xpl. Click on the image to make it larger.

S-C fabric is visible in the thin section.

Media Attributions

  • OLYMPUS DIGITAL CAMERA
  • OLYMPUS DIGITAL CAMERA
  • OLYMPUS DIGITAL CAMERA
  • A4 mylonite 2 4x ppl
  • A4 mylonite 2 4x xpl
  • A4 mylonite2 ppl
  • A4 mylonite2 xpl

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Introduction to Petrology by Elizabeth Johnson is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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