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Tectonic control on the formation of some fibrous quartz veins, Mid-Wales

Published online by Cambridge University Press:  01 May 2009

J. Garth Raybould
J. Garth Raybould
Affiliation:
Nchanga Consolidated Copper Mines Limited(Geology Department)P.O. Box 1ChililabombweZambia
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Summary

Protoquartzites outcropping in a small anticline in the Plynlimon area of mid-Wales contain numerous flat-lying and low-angle, fibrous quartz veins, which are subparallel to the ab plane of the fold. The quartz crystals are elongated at a high angle to the vein walls, and in some cases exhibit a curvature which is thought to have been adopted as the crystals grew. The orientation and internal structure of the veins suggest that they formed on fractures initiated during compression and extended by hydraulic fracture, the crystal curvature being a result of shearing during syntectonic crystal growth. Pore water was important both in bringing about the critical effective stresses required for fracturing and as a carrier of locally remobilized free silica.

Type
Articles
Information
Geological Magazine , Volume 112 , Issue 1 , January 1975 , pp. 81 - 90
Copyright
Copyright © Cambridge University Press 1975

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References

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