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5.12: Cranberry Gneiss (Orthogneiss)

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

    No outcrop images available. This was collected near Independence, not too far away from the other Cranberry Gneiss sample (next page).

    The classic interpretation of the Cranberry Gneiss is that it is a paragneiss (sedimentary protolith). This is true in many places, including sample S5 (next page). However, the Cranberry Gneiss on this page is pretty clearly an orthogneiss (igneous protolith). Field mappers in the area are now starting to distinguish between these two types of gneisses.

    Thin Section Photos and Videos

    1st = plane polarized light; 2nd = cross-polarized light.

    Spot 1

    Biotite (brown), orthoclase, recrystallized quartz.

    Cranberry-4x-ppl-no1-300x225.jpg
    Cranberry-4x-xpl-no1-300x225.jpg

    Spot 2

    Biotite,quarts, magnetite, plagioclase, dusty orthoclase, a zircon (inside the magnetite at bottom right).

    Cranberry-4x-ppl-no2-300x225.jpg
    Cranberry-4x-xpl-no2-300x225.jpg

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

    Cranberry-ppl-scaled-1.jpg
    Cranberry-xpl-scaled-1.jpg

    This page titled 5.12: Cranberry Gneiss (Orthogneiss) was last modified on Fri, 06 May 2022 21:15:09 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.