Sevigny, James H. (1988) Geochemistry of Late Proterozoic amphibolites and ultramafic rocks, southeastern Canadian Cordillera. Canadian Journal of Earth Sciences, 25 (8) 1323-1337 doi:10.1139/e88-127
| Reference Type | Journal (article/letter/editorial) | ||
|---|---|---|---|
| Title | Geochemistry of Late Proterozoic amphibolites and ultramafic rocks, southeastern Canadian Cordillera | ||
| Journal | Canadian Journal of Earth Sciences | ||
| Authors | Sevigny, James H. | Author | |
| Year | 1988 (August 1) | Volume | 25 |
| Issue | 8 | ||
| Publisher | Canadian Science Publishing | ||
| DOI | doi:10.1139/e88-127Search in ResearchGate | ||
| Generate Citation Formats | |||
| Mindat Ref. ID | 480109 | Long-form Identifier | mindat:1:5:480109:6 |
| GUID | 0 | ||
| Full Reference | Sevigny, James H. (1988) Geochemistry of Late Proterozoic amphibolites and ultramafic rocks, southeastern Canadian Cordillera. Canadian Journal of Earth Sciences, 25 (8) 1323-1337 doi:10.1139/e88-127 | ||
| Plain Text | Sevigny, James H. (1988) Geochemistry of Late Proterozoic amphibolites and ultramafic rocks, southeastern Canadian Cordillera. Canadian Journal of Earth Sciences, 25 (8) 1323-1337 doi:10.1139/e88-127 | ||
| In | (1988, August) Canadian Journal of Earth Sciences Vol. 25 (8) Canadian Science Publishing | ||
| Abstract/Notes | Late Proterozoic amphibolites and ultramafic rocks from the southeastern Canadian Cordillera have been analysed for major and trace elements in order to determine the nature and origin of the protoliths. Geologic relations indicate that these rocks were produced during an episode of continental rifting in the Precambrian. Based on rare-earth-element (REE) patterns, immobile-incompatible-element ratios, and characteristic elemental abundances, amphibolites are subdivided into alkaline and tholeiitic metabasalts. Alkaline basalts are recognized by their steep REE patterns, high Zr/Y, high TiO2 and P2O5 abundances, and low Y/Nb and Ti/Zr. Tholeiitic basalts are subdivided into three groups: (I) high-Mg#, high-field-strength-element (HFSE)-depleted, light-REE (LREE)-enriched tholeiites with flat heavy REE (HREE) patterns; (II) LREE-enriched tholeiites depleted in HREE; and (III) low-Mg# tholeiites with flat REE patterns. Ultramafic rocks occur as boudins of partially recrystallized Cr-spinel-bearing harzburgite or therzolite, enriched in LREE (Ce/Sm = 1.7–1.9), HFSE, CaO, Al2O3, and TiO2 relative to depleted mantle.Geochemical data suggest that the basalts were derived from a heterogeneous mantle source that underwent different degrees of partial melting with variable amounts of subsequent crystal fractionation of the melts. High Mg#, high Cr and Ni abundances, low HFSE abundances, and high olivine saturation temperatures suggest that group I tholeiites are primary mantle melts produced by a relatively high degree of partial melting of a LREE-enriched, HFSE-depleted source. Group II and III basalts have undergone moderate olivine and pryoxene and limited plagioclase fractionation. Mass-balance calculations suggest that the ultramafic rocks represent a crustally contaminated primary-mantle-derived melt.Les éléments majeurs et traces des amphibolites et des ultramafites, d'âge protérozoïque tardif, du sud-est de la Cordillère canadienne ont été analysés dans le but de déterminer la nature et l'origine des protolithes. Les relations géologiques indiquent que ces roches se sont formées durant un épisode de rifting continental dans le Précambrien. Les diagrammes des terres rares, les rapports des éléments immobiles et incompatibles et les compositions chimiques caractéristiques ont permis de subdiviser les amphibolites en métabasaltes tholéiitiques et alcalins. Les basaltes alcalins sont reconnus par les courbes abruptes dans les diagrammes des terres rares, les rapports Zr/Y élevés et les fortes teneurs en TiO2 et P2O5 et les rapports Y/Nb et Ti/Zr faibles. Les basaltes tholéiitiques sont subdivisés en trois groupes : (I) avec Mg# élevé, appauvrissement en éléments de force de champ élevée, tholéiites enrichies en terres rares légères avec courbe horizontale des terres rares lourdes; (II) tholéiites enrichies en terres rares légères et appauvries en terres rares lourdes; et (III) tholéiites avec Mg# faible et avec courbe horizontale des variations des terres rares. Les ultramafites se présentent en boudins formés d'harzburgite incluant un spinelle chromifère partiellement recristallisé ou de therzolite qui sont enrichies en terres rares légères (Ce/Sm = 1,7–1,9), en éléments à force de champ élevée, en CaO, Al2O3 et TiO2, comparativement à un manteau appauvri. | ||
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