| Titre | Olivine xenocrysts reveal carbonated mid-lithosphere in the northern Slave craton |
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| Auteur | Veglio, C; Lawley, C J M ; Pearson, D G; Kjarsgaard, B A; Petts, D C; Jackson, S E |
| Source | Lithos vol. 414-415, 106633, 2022 p. 1-14, https://doi.org/10.1016/j.lithos.2022.106633  Accès ouvert |
| Image |  |
| Année | 2022 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20210670 |
| Éditeur | Elsevier |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.lithos.2022.106633 |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Province | Territoires du Nord-Ouest; Nunavut |
| SNRC | 65M; 66C; 66D; 66E; 66F; 66L; 75O; 75P; 76A; 76B; 76F; 76G; 76H; 76I; 76J; 76K |
| Lat/Long OENS | -109.4456 -100.8803 66.9264 63.5639 |
| Sujets | manteau terrestre; xénolites; olivine; lithosphère; croûte continentale; carbonate; thermobarométrie; géochimie des éléments en trace; géochimie des éléments majeurs; géochimie des éléments en trace;
dynamique des fluides; altération; métasomatose; potentiel minier; diamant; kimberlites; Archéen; Craton de Slave ; Kimberlite de Jericho ; géologie générale; minéralogie; géochimie; Sciences et technologie; Nature et environnement;
Précambrien |
| Illustrations | cartes de localisation; cartes géologiques généralisées; tableaux; diagrammes ternaires; graphiques; diagrammes de distribution |
| Programme | Initiative géoscientifique ciblée (IGC-5) Systèmes minéralisés aurifères - Commandes du système - Temps et espace |
| Diffusé | 2022 03 04 |
| Résumé | (disponible en anglais seulement)
The cold, rigid, and melt-depleted mantle underlying Archean cratons plays an important role in the preservation of the overlying continental crust and is one
of the main sources of diamonds. However, with the possible exception of rare earth elements (REE) and platinum group-elements (PGE), the concentrations and host mineral phases for many other critical trace elements within lithospheric mantle remain
very poorly understood. Here we address that knowledge gap, presenting new electron microprobe and laser-ablation inductively-coupled-plasma mass-spectrometry results for a suite of mantle xenoliths (n = 12) and olivine xenocrysts (n = 376) from the
Jericho, Muskox, and Voyageur kimberlites (northern Slave craton, Canada). Low-temperature (<1000?°C) harzburgite xenoliths and olivine xenocrysts suggest that the shallowest portions of the garnet-bearing mantle (less than or equal to 160 km)
underlying the northern Slave craton is chemically depleted and becomes increasing re-fertilized from 160 to 200 km. High-temperature (>1000 °C) garnet and clinopyroxene crystals with Ti/Eu ratios > > 1000, and olivine xenocrysts suggest that
interaction with ultramafic silicate melts is the most likely mechanism to re-fertilize melt-depleted peridotite with incompatible elements toward the base of the lithosphere (~200 km). In contrast, lower temperature garnet and clinopyroxene with
Ti/Eu ratios <1000 are more likely related to metasomatism by carbonatitic melts and/or fluids. Carbonatitic metasomatism is also interpreted as the preferred explanation for the trend of Nb (4?ppm)- and Ta (185 ppb)-rich concentrations of olivine
xenocrysts sampled from mid-lithosphere depths (~140 km). With the exception of a few elements that substitute into the olivine crystal structure during sub-solidus re-equilibration (e.g., Ca, Cr, Cu, Na, Sc, V, Zn), most other olivine-hosted trace
elements do not systematically vary with depth. Instead, we interpret olivine-hosted trace element concentrations that are significantly above the analytical detection and/or quantification limits to reflect trapped fluid (e.g., As, Mo, Sb, Sn),
base-metal sulphide (e.g., Ag, Au, Bi, Pd, Pt, Se, Te), and other mineral inclusions (e.g., U, Th) rather than enrichments of these elements due to substitution reactions or analytical artefacts. We interpret that these inclusions occur in olivine
throughout the garnet stability field, but are relatively rare. As a result, these trapped carbonatitic, proto-kimberlite, and/or other ultramafic silicate melts do not represent a significant source for the suite of trace elements that become
enriched to economic levels in the crust. |
| Sommaire | (Résumé en langage clair et simple, non publié)
L'analyse chimique de l'olivine est utilisée pour créer une carte de la distribution des éléments rares dans le manteau sous-jacent à la mine de
diamant Jericho au Nunavut. |
| GEOSCAN ID | 329648 |
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