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5.4: Unicoi 2 Greenstone

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    Outcrop and Hand Sample Photos and Videos

    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

    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. 

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


    This page titled 5.4: Unicoi 2 Greenstone is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Elizabeth Johnson and Juhong Christie Liu (Virtual Library of Virginia) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.