| Titre | Trace metal and isotopic depth profiles through the Abitibi cratonic mantle |
| Auteur | Lawley, C; Kjarsgaard, B; Jackson, S; Yang, Z; Petts, D; Roots, E |
| Source | Lithos vol. 314-315, 2018 p. 520-533, https://doi.org/10.1016/j.lithos.2018.06.026 |
| Année | 2018 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20170370 |
| Éditeur | Elsevier |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.lithos.2018.06.026 |
| Media | papier; en ligne; numérique |
| Référence reliée | Cette publication est reliée les
publications suivantes |
| Formats | pdf; html; docx |
| Province | Québec; Ontario |
| SNRC | 31M; 31N; 31O/04; 31O/05; 31O/12; 31O/13; 32B/04; 32B/05; 32B/12; 32B/13; 32C; 32D; 32E; 32F; 41P; 42A; 42H |
| Lat/Long OENS | -82.0000 -75.6667 49.6667 47.1667 |
| Sujets | gisements minéraux; métaux; genèse des minerais; contrôles structuraux; études de la croûte; craton; manteau terrestre; lithosphère; analyses par microsonde électronique; analyse par spectromètre de
masse; pyroxene monoclinique; olivine; silicates; sulfures; péridotites; grenat; analyses des éléments en trace; analyses statistiques; conditions de pression-température; altération; mise en place; métasomatose; kimberlites; fluage; volcanisme;
levés géophysiques; levés sismiques; vitesse des ondes sismiques; anomalies; etudes isotopiques; rapports des isotopes de plomb; Archéen; Bouclier Canadien; Ceinture d'Abitibi Greenstone ; Dyke de Buffonta ; géologie économique; géochimie;
géophysique; Précambrien |
| Illustrations | geoscientific sketch maps; profiles; photomicrographs; plots; models |
| |
| Programme | Systèmes aurifères, Initiative géoscientifique ciblée (IGC-5) |
| Diffusé | 2018 06 28 |
| Résumé | (disponible en anglais seulement)
Geophysical imaging of trans-lithospheric structures provide a spatial link between ore deposits in the crust and the underlying cratonic mantle. However, the
deep lithosphere's role in ore deposit genesis remains poorly understood because remotely acquired datasets do not provide any direct constraints on the behaviour of ore elements within these mantle-roots. The abundance and behaviour of ore elements
governs the metallic endowment of the cratonic mantle and the economic potential of mantle-derived magmas. Herein we present in situ electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)
geochemical datasets for clinopyroxene and olivine mantle xenocrysts from the Jurassic Kirkland Lake kimberlite field, Abitibi greenstone belt, Canada. We specifically focus on unconventional trace elements, including ore elements with chalcophile
and/or siderophile affinities (Ag-As-Au-Bi-Cu-Mo-Pb-Pt-Pd-Sb-Se-Sn-Te-W-Zn). Robust principal component analysis suggests that low-T, large-ion lithophile element alteration (Ba-Sr), which likely occurred during kimberlite emplacement, represents the
largest source of variance for the xenocrysts dataset. PT-dependent element partitioning during sub-solidus equilibration represents the second most important control on olivine and clinopyroxene chemistry. We demonstrate that least-altered, high-PT
mantle silicates are, in fact, a significant mineral host for a range of ore elements (Cu-Zn ± Ag ± As ± Se ± Sn ± Mo) within equilibrated, garnet peridotite at depth (70-190 km). Statistical analysis of the raw, individual mass sweeps for each
LA-ICP-MS signal suggest that the most abundant ore elements (Cu-Zn) occur predominantly as PT-dependent substitution reactions with the dominant mineral-forming elements, rather than as inclusions. A subset of high-PT olivine (160-180 km) yields
Fe-Ni-S-poor and Na (Au ± Pt ± Pd)-rich compositions, which may reflect metasomatism, sulphide segregation and trapping of precious metal-bearing fluids at the base of the lithosphere. These anomalous mantle fragments possibly represent the first,
direct sampling of precious metal-modified mantle peridotite beneath the Abitibi. Mid-PT olivine xenocrysts (70-120 km), which yield Mg-rich and high field-strength element-poor compositions, document a highly melt-depleted segment of mantle
peridotite coincident with and below a shallow-dipping, low-seismic-velocity anomaly and conductive feature of the Kirkland Lake mid-lithosphere at 70-100 km. We speculate that the trace element signature of mid-PT xenocrysts documents the
re-distribution of high-charge and incompatible elements from refractory garnet peridotite to phlogopite- and/or amphibole-bearing peridotite with conductive metasomatic up-flow zones. The rapid, sub-solidus diffusion of elements at high-T suggest
that these processes likely occurred during, and/or immediately preceding, kimberlite volcanism. New in situ Pb isotope analyses of clinopyroxene xenocrysts sampled from metasomatized, low-Al garnet peridotite, however, also document ancient
metasomatic events that likely pre-date Jurassic kimberlitic volcanism by at least one billion years. |
| Résumé | (Résumé en langage clair et simple, non publié)
The Targeted Geoscience Initiative (TGI) is a collaborative federal geoscience program that provides industry with the next generation of
geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. Factors that influence the metal endowment within the source regions of ore deposits, however, remain poorly
understood. This study addresses that knowledge gap by documenting the distribution of metals of economic interest within mantle minerals. |
| GEOSCAN ID | 306645 |
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