5.4: Unicoi 2 Greenstone

Introduction to Petrology · LibreTexts

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    From LibreTexts, under CC BY-NC-SA 4.0, as the source states it; its equations are written in TeX, which the PDF shows typeset. This page at LibreTexts.

    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?

    Unicoi-2-Greenstone-and-sandstone-300x225.jpg

    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.

    Unicoi2-ppl-4x-300x225.jpg
    Unicoi2-xpl-4x-300x225.jpg

    Entire thin section scan. 1st = ppl; 2nd = xpl. 

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

    Unicoi-2-ppl-scaled-1.jpg
    Unicoi-2-xpl-scaled-1.jpg

    This page titled 5.4: Unicoi 2 Greenstone was last modified on Fri, 06 May 2022 21:06:27 GMT and 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.