U.S. Geological Survey Open-File Report 03-221
A Pictorial Survey of the Bedrock Beneath Western Cape
Cod, Massachusetts
![]() K-feldspar porphyroclast in a fine-grained felsic gneiss (69MW1603) showing tartan twinning. Note the relatively straight grain boundaries in matrix K-feldspar, indicating recrystallization. Biotite, aligned in the foliation, wraps the porphyroclast of K-feldspar. Click here for a zip file with full resolution image. bt:
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