Brioverian volcanism and Cadomian tectonics, Baie de St. Brieuc, Brittany; stages in the evolution of a late Precambrian ensialic basin

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Authors:Roach, R. A.; Lees, G. J.; Shufflebotham, M. M.
Author Affiliations:Primary:
Univ. Keele, Dep. Geol., Keele, United Kingdom
Univ. Coll. Wales, United Kingdom
Volume Title:Cadomian Orogeny
Volume Authors:D'Lemos, R. S., editor; Strachan, R. A.; Topley, C. G.
Source:Geological Society Special Publications, Vol.51, p.41-67; The Cadomian Orogeny, Oxford, United Kingdom, Apr. 1988, edited by R. S. D'Lemos, R. A. Strachan and C. G. Topley. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0305-8719
Publication Date:1990
Note:In English. 91 refs.; illus. incl. cols., sects., geol. sketch maps
Summary:During late Precambrian times, the N Brittany and Lower Normandy region was the site of extensive submarine basaltic volcanism. Two volcanic formations have been identified on the S side of the Baie de St. Brieuc. The Erquy Volcanic Formation (EVF), over 2 km thick, is a sedimentary-volcanic sequence in which the basalts occur mainly as pillowed, massive or composite massive-pillowed flows. Farther west, the Hillion Volcanic Formation (HVF) shows similar thickness, attitude and range of lithologies and is now considered to form part of the same late Precambrian volcanic suite as the EVF. The suite was erupted in a marginal basin environment founded on a a slightly older crust of calc-alkaline plutonic rocks, now represented in part by the adjacent Penthievre massif. Basic sheets (the Dahouet dykes) cutting this basement are considered co-genetic with the volcanic rocks of the EVF and HVF. Chemically, the metabasic lavas, sub-volcanic sills and dyke rocks are sub-alkaline, tholeiitic basalts and basaltic andesites. [R.A.H.]
Subjects:Basins; Cadomian Orogeny; IGCP; Igneous rocks; Interpretation; Orogeny; Precambrian; Sedimentary basins; Structural geology; Tectonics; Upper Precambrian; Volcanic rocks; Brittany; Europe; France; Western Europe; Baie de Saint Brieuc; Evolution
Abstract Numbers:90M/3400
Record ID:1991029944
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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