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Article: Geochemistry and U-Pb and 40Ar- 39Ar geochronology of The Man of War Gneiss, Lizard complex, SW England: Pre-Hercynian arc-type crust with a Sudeten-Iberian connection

TitleGeochemistry and U-Pb and 40Ar- 39Ar geochronology of The Man of War Gneiss, Lizard complex, SW England: Pre-Hercynian arc-type crust with a Sudeten-Iberian connection
Authors
KeywordsCornwall England
Geochemistry
Geochronology
Island Arcs
Meta-Igneous Rocks
Ophiolite Complexes
Issue Date1997
PublisherGeological Society Publishing House. The Journal's web site is located at http://www.geolsoc.org.uk/gsl/publications/journals/jgs
Citation
Journal Of The Geological Society, 1997, v. 154 n. 3, p. 403-417 How to Cite?
AbstractThe Man of War Gneiss is a variably deformed meta-igneous body that ranges in composition from gabbro to tonalite and comprises part of the basal structural slice of the Lizard ophiolite complex, SW England. U-Pb dating of zircon demonstrates that the parental magmas crystallized in the earliest Ordovician (499 +8 -3 Ma), but 40Ar- 39Ar step-heating analysis of amphiboles suggests that at least the northernmost zone of the gneiss was subjected to an amphibolite-grade metamorphic event at c. 374 Ma, probably associated with thrust emplacement of the ophiolite. The gneiss exhibits major, trace and rare earth element variations in conformity with an origin through partial melting of an amphibolitic source containing hornblende and plagioclase, probably with minor garnet and zircon. The elemental abundances and variations are characteristic of granitoids formed in supra-subduction zone environments. A granitoid sill within the adjacent Old Lizard Head Series schists, previously inferred to be related to the Man of War Gneiss, is trondhjemitic and exhibits higher SiO 2, TiO 2 and MgO, but lower Zr, V, Ba, and Sr contents, and therefore is probably not genetically related to the latter. The sill may record local melting during ophiolite emplacement. The Man of War Gneiss probably represents a structural inlier of pre-Hercynian basement incorporated in the Hercynian nappes of SW England during NNW-directed thrusting. We emphasize the geological and geochronological similarities between variably deformed granitoid units of the Lizard complex, the Sudeten Massif of southern Poland, and the allochthonous complexes of northern Portugal and NW Spain. These granitoid rocks may represent dispersed remnants of Tremadoc arcs that formed oceanward from the northern margin of Gondwana. This is further convincing evidence that at this time Eastern Avalonia was separated from northern Gondwana by an ocean basin that may have been connected with the Tornquist Sea.
Persistent Identifierhttp://hdl.handle.net/10722/178210
ISSN
2015 Impact Factor: 2.473
2015 SCImago Journal Rankings: 1.449
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorSandeman, HAen_US
dc.contributor.authorClark, AHen_US
dc.contributor.authorStyles, MTen_US
dc.contributor.authorScott, DJen_US
dc.contributor.authorMalpas, JGen_US
dc.contributor.authorFarrar, Een_US
dc.date.accessioned2012-12-19T09:43:27Z-
dc.date.available2012-12-19T09:43:27Z-
dc.date.issued1997en_US
dc.identifier.citationJournal Of The Geological Society, 1997, v. 154 n. 3, p. 403-417en_US
dc.identifier.issn0016-7649en_US
dc.identifier.urihttp://hdl.handle.net/10722/178210-
dc.description.abstractThe Man of War Gneiss is a variably deformed meta-igneous body that ranges in composition from gabbro to tonalite and comprises part of the basal structural slice of the Lizard ophiolite complex, SW England. U-Pb dating of zircon demonstrates that the parental magmas crystallized in the earliest Ordovician (499 +8 -3 Ma), but 40Ar- 39Ar step-heating analysis of amphiboles suggests that at least the northernmost zone of the gneiss was subjected to an amphibolite-grade metamorphic event at c. 374 Ma, probably associated with thrust emplacement of the ophiolite. The gneiss exhibits major, trace and rare earth element variations in conformity with an origin through partial melting of an amphibolitic source containing hornblende and plagioclase, probably with minor garnet and zircon. The elemental abundances and variations are characteristic of granitoids formed in supra-subduction zone environments. A granitoid sill within the adjacent Old Lizard Head Series schists, previously inferred to be related to the Man of War Gneiss, is trondhjemitic and exhibits higher SiO 2, TiO 2 and MgO, but lower Zr, V, Ba, and Sr contents, and therefore is probably not genetically related to the latter. The sill may record local melting during ophiolite emplacement. The Man of War Gneiss probably represents a structural inlier of pre-Hercynian basement incorporated in the Hercynian nappes of SW England during NNW-directed thrusting. We emphasize the geological and geochronological similarities between variably deformed granitoid units of the Lizard complex, the Sudeten Massif of southern Poland, and the allochthonous complexes of northern Portugal and NW Spain. These granitoid rocks may represent dispersed remnants of Tremadoc arcs that formed oceanward from the northern margin of Gondwana. This is further convincing evidence that at this time Eastern Avalonia was separated from northern Gondwana by an ocean basin that may have been connected with the Tornquist Sea.en_US
dc.languageengen_US
dc.publisherGeological Society Publishing House. The Journal's web site is located at http://www.geolsoc.org.uk/gsl/publications/journals/jgsen_US
dc.relation.ispartofJournal of the Geological Societyen_US
dc.subjectCornwall Englanden_US
dc.subjectGeochemistryen_US
dc.subjectGeochronologyen_US
dc.subjectIsland Arcsen_US
dc.subjectMeta-Igneous Rocksen_US
dc.subjectOphiolite Complexesen_US
dc.titleGeochemistry and U-Pb and 40Ar- 39Ar geochronology of The Man of War Gneiss, Lizard complex, SW England: Pre-Hercynian arc-type crust with a Sudeten-Iberian connectionen_US
dc.typeArticleen_US
dc.identifier.emailMalpas, JG: jgmalpas@hku.hken_US
dc.identifier.authorityMalpas, JG=rp00059en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1144/gsjgs.154.3.0403en_US
dc.identifier.scopuseid_2-s2.0-0030761324en_US
dc.identifier.hkuros23037-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0030761324&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume154en_US
dc.identifier.issue3en_US
dc.identifier.spage403en_US
dc.identifier.epage417en_US
dc.identifier.isiWOS:A1997XB28500002-
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridSandeman, HA=6701319997en_US
dc.identifier.scopusauthoridClark, AH=13302632500en_US
dc.identifier.scopusauthoridStyles, MT=7006019893en_US
dc.identifier.scopusauthoridScott, DJ=13308395600en_US
dc.identifier.scopusauthoridMalpas, JG=7006136845en_US
dc.identifier.scopusauthoridFarrar, E=7006838368en_US

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