Permo-Carboniferous mylonite formation in the Walls boundary fault system, Shetland

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doi: 10.1144/pygs.47.4.339
Authors:Roddom, D. S.; Miller, J. A.; Flinn, D.
Author Affiliations:Primary:
Bullard Lab., Dep. Earth Sci., Cambridge, United Kingdom
Other:
Univ. Liverpool, United Kingdom
Volume Title:Proceedings of the Yorkshire Geological Society
Source:Proceedings of the Yorkshire Geological Society, 47(4), p.339-343. Publisher: Yorkshire Geological Society, Leeds, United Kingdom. ISSN: 0044-0604
Publication Date:1989
Note:In English. 11 refs.; illus. incl. 2 tables, sketch map
Summary:The geological setting, petrography and 40 Ar/ 39 Ar step heating analyses are presented for two samples of mylonite from the Walls Boundary fault which is exposed in coastal sections as a vertical, gouge-filled fracture. One sample of mylonite consists of relict K-feldspar and albite porphyroclasts, with kinked muscovite, elongated quartz, in a matrix of quartz, K- feldspar, albite, epidote and white mica. Accessories include apatite, zircon, ilmenite, sphene and hematite. Ultramylonite is of similar composition except in lacking large feldspar porphyroclasts. Secondary cataclasis is exhibited by both specimens, due to movement on the gouge fault. Growth and recrystallization of K-feldspar and white mica occurred during mylonitization and was partly responsible for partial overprinting of the K/Ar age of the host rock. The 40 Ar/ 39 Ar results indicate that the phase of movement associated with the mylonitization occurred during the latest Carboniferous or early Permian. [R.K.H.]
Subjects:Carboniferous; Ductility; Fault zones; Faults; Genesis; Interpretation; Metamorphic rocks; Metasomatism; Mylonites; Mylonitization; Paleozoic; Permian; Petrology; Processes; Systems; Transcurrent faults; Atlantic Ocean Islands; England; Europe; Great Britain; Scotland; Shetland Islands; United Kingdom; Western Europe; Walls boundary fault system
Abstract Numbers:90M/4899
Record ID:1990036982
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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