| Titre | Geochemical constraints on the origin of the Annieopsquotch ophiolite belt, Newfoundland Appalachians |
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| Auteur | Lissenberg, C J; van Staal, C R; Bédard, J H; Zagorevski, A |
| Source | Geological Society of America Bulletin vol. 117, no. 11-12, 2005 p. 1413-1426, https://doi.org/10.1130/B25731.1 |
| Liens | Supplementary Data - Données supplémentaires
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| Image |  |
| Année | 2005 |
| Séries alt. | Commission géologique du Canada, Contributions aux publications extérieures 2004277 |
| Éditeur | Geological Society of America |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1130/B25731.1 |
| Media | papier; en ligne; numérique |
| Formats | html; pdf |
| Province | Terre-Neuve-et-Labrador |
| SNRC | 12A/04; 12A/05; 12A/06; 12A/10; 12A/11 |
| Région | Lloyds Lake; Red Indian Lake |
| Lat/Long OENS | -58.1667 -56.7500 48.8333 48.0000 |
| Sujets | ophiolites; sutures; tectonique de plaques; gabbros; filons rocheux; basaltes; troctolites; tholéiites; magmas; zones de subduction; arcs magmatiques; géochimie des roches totales; orogénies; évolution
tectonique; Géochimie; géologie générale; pétrologie ignée et métamorphique; minéralogie; géologie structurale; tectonique |
| Illustrations | cartes de localisation; photographies; graphiques; cartes géologiques généralisées; graphiques géochimiques |
| Programme | L'Initiative géoscientifique ciblée (IGC-1), 2000-2003 |
| Programme | CRSNG Conseil de recherches en sciences
naturelles et en génie du Canada |
| Programme | Université d'Ottawa, Faculté
des études supérieures et postdoctorales |
| Diffusé | 2005 01 01 |
| Résumé | (disponible en anglais seulement)
The Early Ordovician Annieopsquotch ophiolite belt occurs immediately west of the main Iapetus suture zone, and imposes important constraints on the tectonic
processes associated with closure of the peri-Laurentian portion of Iapetus. The Annieopsquotch ophiolite, the most prominent ophiolite within the Annieopsquotch ophiolite belt, exposes a 5.5-km-thick section of gabbros, sheeted dikes, and pillow
basalts, in which three magmatic episodes have been recognized based on fi eld and geochemical data. The fi rst phase is composed of layered troctolites, which are preserved as enclaves within the gabbro zone. Trace element modeling suggests the
troctolites crystallized from boninitic melts. The troctolite substrate was intruded by the dominant, second, tholeiitic magmatic phase, which formed a gabbro-sheeted dike-basalt sequence. All tholeiites have suprasubduction zone chemical
characteristics, but the suprasubduction zone signature decreases toward the top of the basalt sequence. The third magmatic episode is composed of primitive dikes, which are interpreted as off-axis intrusions. Other ophiolites within the
Annieopsquotch ophiolite belt have comparable geochemical signatures, suggesting they may have constituted a single piece of oceanic lithosphere. Based on geochemical and regional tectonic constraints, the Annieopsquotch ophiolite belt is interpreted
to have formed during initiation of west-directed subduction. Fast rollback of the subducting slab would have induced volatile-fl uxed decompression melting of previously depleted mantle, yielding boninitic melts. The uprasubduction zone tholeiite
sequence would have formed from ascending fertile mantle fl uxed with subduction- related fl uids as ollback continued. This suggests that the Annieopsquotch ophiolite belt does not represent the remnants of normal oceanic crust or ackarc basin
crust, as previously thought. Our model constrains the initiation and early evolution of a westdipping peri-Laurentian ubduction zone that was responsible for formation of several arc-backarc complexes currently preserved in the Annieopsquotch
ccretionary Tract. |
| GEOSCAN ID | 216679 |
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