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Article: A comparison of chrome-spinels in ophiolites and mantle diapirs of Newfoundland

TitleA comparison of chrome-spinels in ophiolites and mantle diapirs of Newfoundland
Authors
Issue Date1975
PublisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/gca
Citation
Geochimica Et Cosmochimica Acta, 1975, v. 39 n. 6-7, p. 1045-1060 How to Cite?
AbstractUltramafic bodies of Newfoundland occur as two recognizable types, obducted ophiolites in the west and intrusive "mantle diapirs" in the east. The Bay of Islands bodies in the west form a classic ophiolite assemblage comprising, generally from base to top, Iherzolite (primitive mantle), harzburgite (residuum of partial melting), cumulus dunite, gabbro, trondhjemite, sheeted diabase dikes, pillow lava (all representing the magma produced by partial melting), and deep-water sediments. Chromite occurs mainly in cumulus layers and lenses in the cumulus dunite horizon, and as disseminated grains in the harzburgite. The Gander River bodies in the east occur as a discontinuous belt in sedimentary rocks as young as Silurian and show a range of contact relations from faulted to cold intrusive and hot intrusive. They consist predominantly of clinopyroxenite, with variable proportions of dunite, gabbro, diabase and diorite. These features, in conjunction with independent tectonic models, lead to an interpretation of these bodies as mantle diapirs arising from an eastward-dipping subduction zone beneath a lower Paleozoic marginal ocean basin, although further data may show that some of them represent marginal basin crust, in which case they could display similarities to the Bay of Islands ophiolites. The chrome-spinels in these bodies always occur in a dunite fraction and range from disseminated to podiform to banded. The major chemical difference between the spinels in the two types of occurrence is that those of the diapirs have substantially higher Cr:Al ratios than the cumulus spinels of the Bay of Islands. Magnesium is slightly lower in the diapir spinels, but Fe and Ti show no significant differences. The harzburgite (residual mantle) spinels of the Bay of Islands are chemically similar to those of the diapirs, enhancing the interpretation of the latter as residual mantle material. © 1975.
Persistent Identifierhttp://hdl.handle.net/10722/178234
ISSN
2015 Impact Factor: 4.315
2015 SCImago Journal Rankings: 3.016

 

DC FieldValueLanguage
dc.contributor.authorMalpas, Jen_US
dc.contributor.authorStrong, DFen_US
dc.date.accessioned2012-12-19T09:43:34Z-
dc.date.available2012-12-19T09:43:34Z-
dc.date.issued1975en_US
dc.identifier.citationGeochimica Et Cosmochimica Acta, 1975, v. 39 n. 6-7, p. 1045-1060en_US
dc.identifier.issn0016-7037en_US
dc.identifier.urihttp://hdl.handle.net/10722/178234-
dc.description.abstractUltramafic bodies of Newfoundland occur as two recognizable types, obducted ophiolites in the west and intrusive "mantle diapirs" in the east. The Bay of Islands bodies in the west form a classic ophiolite assemblage comprising, generally from base to top, Iherzolite (primitive mantle), harzburgite (residuum of partial melting), cumulus dunite, gabbro, trondhjemite, sheeted diabase dikes, pillow lava (all representing the magma produced by partial melting), and deep-water sediments. Chromite occurs mainly in cumulus layers and lenses in the cumulus dunite horizon, and as disseminated grains in the harzburgite. The Gander River bodies in the east occur as a discontinuous belt in sedimentary rocks as young as Silurian and show a range of contact relations from faulted to cold intrusive and hot intrusive. They consist predominantly of clinopyroxenite, with variable proportions of dunite, gabbro, diabase and diorite. These features, in conjunction with independent tectonic models, lead to an interpretation of these bodies as mantle diapirs arising from an eastward-dipping subduction zone beneath a lower Paleozoic marginal ocean basin, although further data may show that some of them represent marginal basin crust, in which case they could display similarities to the Bay of Islands ophiolites. The chrome-spinels in these bodies always occur in a dunite fraction and range from disseminated to podiform to banded. The major chemical difference between the spinels in the two types of occurrence is that those of the diapirs have substantially higher Cr:Al ratios than the cumulus spinels of the Bay of Islands. Magnesium is slightly lower in the diapir spinels, but Fe and Ti show no significant differences. The harzburgite (residual mantle) spinels of the Bay of Islands are chemically similar to those of the diapirs, enhancing the interpretation of the latter as residual mantle material. © 1975.en_US
dc.languageengen_US
dc.publisherPergamon. The Journal's web site is located at http://www.elsevier.com/locate/gcaen_US
dc.relation.ispartofGeochimica et Cosmochimica Actaen_US
dc.titleA comparison of chrome-spinels in ophiolites and mantle diapirs of Newfoundlanden_US
dc.typeArticleen_US
dc.identifier.emailMalpas, J: jgmalpas@hku.hken_US
dc.identifier.authorityMalpas, J=rp00059en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.scopuseid_2-s2.0-5344269842en_US
dc.identifier.volume39en_US
dc.identifier.issue6-7en_US
dc.identifier.spage1045en_US
dc.identifier.epage1060en_US
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridMalpas, J=7006136845en_US
dc.identifier.scopusauthoridStrong, DF=7201547645en_US

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