Pumpellyite-dominated metadomain alteration at Builth Wells, Wales; evidence for a fossil submarine hydrothermal system?

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Authors:Bevins, R. E.
Author Affiliations:Primary:
Natl. Mus. Wales, Dep. Geol., Cardiff, United Kingdom
Volume Title:Diagenesis and low-temperature metamorphism
Volume Authors:Robinson, D., editor
Source:Mineralogical Magazine, 49 Part 3(352), p.451-456; Diagenesis and low-temperature metamorphism, Bristol, United Kingdom, April 12-13, 1984, edited by D. Robinson. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0026-461X
Publication Date:1985
Note:In English. 17 refs.; illus. incl. 2 tables
Summary:Two metamorphic alteration styles have been observed in basic lavas and volcaniclastic rocks of the Builth Volcanic Series of Ordovician age exposed at Llanelwedd Quarry, in the Builth lnlier, Wales. The first alteration style is characterized by the development of a mineral assemblage comprising albite+chlorite+ sphene+ pumpellyite ± prehnite ± calcite ± white mica, although original textures are largely preserved. This alteration pattern corresponds with that developed in volcanic and volcaniclastic rocks elsewhere in Wales, and which is attributed to the effects of burial. The second alteration style is characterized by the development of metadomains dominated by pumpellyite or, more rarely, prehnite. In the metadomains no original textures are seen in hand specimen. This alteration pattern has, so far, not been observed elsewhere in Wales, and it is here suggested that it might result from a submarine hydrothermal circulation system. [R.A.H.]
Subjects:Chain silicates; Chemical composition; Genesis; Grade; Hydrothermal alteration; Low-grade metamorphism; Marine environment; Metamorphic rocks; Metamorphism; Metasomatism; Metavolcanic rocks; Mineral assemblages; Ordovician; Orthosilicates; Paleozoic; Patterns; Petrography; Petrology; Prehnite; Processes; Pumpellyite; Pumpellyite group; Silicates; Sorosilicates; Textures; Europe; Great Britain; Powys Wales; United Kingdom; Wales; Welsh Basin; Western Europe; Builth Volcanic Series; Builth Wells; Llanelwedd Quarry
Coordinates:N520500 N521500 W0032000 W0033000
Abstract Numbers:85M/3535
Record ID:1985075834
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland
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