Southwestern Virginia Case Study

Unicoi 2 Greenstone

Elizabeth Johnson

Outcrop and Hand Sample Photos and Videos

Click on the image to enlarge.

The greenstone (metamorphosed basalt; greenish) is on the right.  The sandstone unit is on the left.  There is near vertical primary bedding here.  Can you see how the metamorphic foliation of the greenstone is at an angle to the bedding plane of the sandstone?

Can you see the amygdules and vesicles in the greenstone?  These are filled with chlorite and zeolites.

Thin Section Photos and Videos

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

The center of this thin section image is a partially filled vesicle (amigdule).  The white in ppl is a hole in the amygdule  The chlorite (green) shows anomalous interference colors – this is “Berlin blue.”  In xpl, you can see the remnants of plagioclase microphenocrysts in the surrounding metabasalt.

 

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

The amygdules are clearly visible in this image.  Some are clearly stretched by metamorphism.

Media Attributions

  • Unicoi 2 Greenstone and sandstone
  • Unicoi2 ppl 4x
  • Unicoi2 xpl 4x
  • Unicoi 2 ppl
  • Unicoi 2 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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