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You are browsing the archive for 2021 January 20.

20 January 2021

Peering through

When hiking recently in my neighborhood, I saw this gleaming apparition appear in an eroded gully in a dirt road: Those multicolored stripes are varying compositions in a zone of ultramylonite: ductilely-sheared-out rock that formed in the deep equivalent of a “fault” in the Blue Ridge basement complex. We call it a “shear zone” most of the time, but a better descriptor would be “high strain zone.” These rocks are …

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