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| Figure 8. Photomicrograph from “Breccia no. 2” (near Stop 3) showing a rounded abraded plagioclase xenocryst with attached biotite. The morphological similarity between single crystals in breccias and those as phenocrysts within xenoliths suggests that many xenocrysts are derived from xenoliths. Other thin sections show various stages of phenocrysts separating out of xenoliths. A mafic xenolith is in the upper left corner. Plain polarized light; length of photo is 2.6 mm. |