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Friday, 25 April 2014

Fractures at Rhosyfelin



This photo shows the planar foliation and rather tightly spaced fractures (coinciding with narrow quartz bands?) on a projecting slab of bedrock, in the middle part of the Rhosyfelin rock face.

I'm a bit confused by this photo, because Myris said in a post the other day that the foliations at Rhosyfelin run at 90 degrees from the orientation of the vertical crack which  I featured in an earlier post.  The foliations in this photo run parallel with that crack.  We can't actually see the foliations in this pic, but surely they do not run horizontally here-- ie across the alignment of the fractures or pseudo-bedding? (These are not beds because this is not a sedimentary rock but a metamorphosed igneous one.....)

Can we please get some enlightenment here from Myris, or Richard, or any other geologist?

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