| Titre | Element and isotopic signature of re-fertilized mantle peridotite as determined by nanopowder and olivine LA-ICPMS analyses |
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| Auteur | Lawley, C J M ;
Pearson, D G; Waterton, P; Zagorevski, A; Bédard, J H; Jackson,
S E; Petts, D C; Kjarsgaard, B A; Zhang, S; Wright, D |
| Source | Chemical Geology vol. 536, 119464, 2020 p. 1-17, https://doi.org/10.1016/j.chemgeo.2020.119464 |
| Image |  |
| Année | 2020 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20190600 |
| Éditeur | Elsevier |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.chemgeo.2020.119464 |
| Media | papier; en ligne; numérique |
| Formats | pdf; html |
| Province | Colombie-Britannique |
| SNRC | 94K/12; 94K/13; 94L/09; 94L/10; 94L/11; 94L/12; 94L/13; 94L/14; 94L/15; 94L/16; 94M; 94N/04; 94N/05; 94N/12; 94N/13 |
| Lat/Long OENS | -127.7525 -125.7214 59.8019 58.6883 |
| Sujets | gisements minéraux; métaux de base; métaux précieux; genèse des minerais; minéralisation; enrichissement des minéraux; fusion partielle; lithosphère; manteau terrestre; géologie du substratum rocheux;
lithologie; roches ultramafiques; roches ignées; roches intrusives; péridotites; pyroxénites; dunites; harzburgites; lithogéochimie; géochimie des roches totales; olivine; analyses géochimiques; géochimie des éléments en trace; géochimie des éléments
majeurs; etudes isotopiques; radioisotopes; rapports des isotopes de plomb; osmium; analyse par spectromètre de masse; analyses pétrographiques; analyses par microsonde électronique; antécédents tectoniques; intrusions; filons rocheux; déformation;
métasomatose; ophiolites; rapports sur le terrain; inclusions; modèles; Trias moyen; Trias inférieur; Permien supérieur; Terrane de Cache Creek ; géologie économique; pétrologie ignée et métamorphique; géochimie; géochronologie; Sciences et
technologie; Nature et environnement; Phanérozoïque; Mésozoïque; Trias; Paléozoïque; Permien |
| Illustrations | cartes de localisation; cartes géolscientiques généralisées; photographies; photomicrographies; graphiques; modèles; graphique à barres |
| Programme | Initiative géoscientifique ciblée (IGC-5) Systèmes minéralisés aurifères |
| Programme | GEM : La géocartographie de l'énergie et des minéraux |
| Diffusé | 2020 01 09 |
| Résumé | (disponible en anglais seulement)
The lithospheric mantle should be depleted in base- and precious-metals as these elements are transferred to the crust during partial melting. However, some
melt-depleted mantle peridotites are enriched in these ore-forming elements. This may reflect re-fertilization of the mantle lithosphere and/or sequestering of these elements by residual mantle phase(s). Both processes remain poorly understood
because of the low abundances of incompatible elements in peridotite and the nugget-like distribution of digestion-resistant mantle phases that pose analytical challenges for conventional geochemical methods. Herein we report new major and trace
element concentrations for a suite of mantle peridotite and pyroxenite samples from the Late Permian to Middle Triassic Nahlin ophiolite (Cache Creek terrane, British Columbia, Canada) using Laser Ablation Inductively Coupled Plasma Mass Spectrometry
(LA-ICPMS) analysis of nanoparticulate powders and olivine. Compatible to moderately incompatible element concentrations suggest that Nahlin ophiolite peridotites represent residues after greater than or equal to 20% melt extraction. Pyroxenite dykes
and replacive dunite bands are folded and closely intercalated with residual harzburgite. These field relationships, coupled with the presence of intergranular base metal sulphide, clinopyroxene and Cr-spinel at the microscale, point to percolating
melts that variably re-fertilized melt-depleted mantle peridotite. Radiogenic Pb (206Pb/204Pb = 15.402-19.050; 207Pb/204Pb = 15.127-15.633; 208Pb/204Pb=34.980-38.434; n=45) and Os (187Os/188Os 0.1143-0.5745; n=58) isotope compositions for a subset of
melt-depleted peridotite samples further support metasomatic re-fertilization of these elements. Other ore-forming elements are also implicated in these metasomatic reactions because some melt-depleted peridotite samples are enriched relative to the
primitive mantle, opposite to their expected behaviour during partial melting. New LA-ICPMS analysis of fresh olivine further demonstrates that a significant proportion of the highly incompatible element budget for the most melt-depleted rocks is
either hosted by, and/or occurs as trapped inclusions within, the olivine-rich residues. Trapped phases from past melting and/or re-fertilization events are the preferred explanation for unradiogenic Pb isotope compositions and Paleozoic to
Paleoproterozoic Re-depletion model ages, which predate the Nahlin ophiolite by over one billion years. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Une nouvelle méthode est décrite pour la détermination de très faibles concentrations d'éléments dans les roches. La méthode est appliquée pour
mieux comprendre la valorisation des éléments minéralisateurs à partir de très faibles concentrations. |
| GEOSCAN ID | 321929 |
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