Physical Controls Associated with the Distribution of Sulfides in the Voisey's Bay Ni-Cu-Co Deposit, Labrador

Evans-Lamswood, Dawn

doi:10.2113/95.4.749

Cited by 24 publications

(44 citation statements)

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“…Its geology and petrography have been reported by Ryan et al (1995), Naldrett et al (1996), and Li and Naldrett (1999). From east to west, different sulfide ore zones in the intrusion are the Eastern Deeps, Ovoid, Mini Ovoid, Discovery Hill, and the Reid Brook (Evans-Lamswood et al, 2000;Fig. 2).…”

Section: Regional and Local Geologymentioning

confidence: 74%

Oxygen isotopic studies of the interaction between xenoliths and mafic magma, Voisey’s Bay Intrusion, Labrador, Canada

Mariga

Ripley

2006

Geochimica et Cosmochimica Acta

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Section: Regional and Local Geologymentioning

confidence: 74%

Oxygen isotopic studies of the interaction between xenoliths and mafic magma, Voisey’s Bay Intrusion, Labrador, Canada

Mariga

Ripley

2006

Geochimica et Cosmochimica Acta

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“…The Nain batholith was emplaced across the intersection between crustal-scale structures related to the east-west trending Gardar-Voisey's Bay Fault Zone and the north-south trending Paleoproterozoic Torngat Orogen (Myers et al 2008). Together, these structures likely controlled the ascent and emplacement of magmas (Myers et al 2008) and formation of the world-class Voisey's Bay Ni-Cu deposit (Evans-Lamswood et al 2000).…”

Section: Geological Settingmentioning

confidence: 97%

Igneous structure and texture of the ~1.3 Ga Hosenbein anorthosite pluton (Nain, Labrador) and implications for the crystallization of massif-type anorthosite

Voordouw

2010

atgeol

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The ca. 1315 Ma Hosenbein massif-type anorthosite pluton (Nain, Labrador) shows complete exposure of a vertical section, described here for the first time, comprising a ~2000 m-thick Main Zone bound by a ~200 m-thick Marginal Zone. The pluton as a whole consists mostly of monocumulate leucogabbronorite, leuconorite, and anortho-site (~94 vol% of all rocks) with elevated abundances of gabbronorite–ferrodiorite (~27 vol%) in the Marginal Zone. Parental magma likely comprised a plagioclase-phyric basaltic melt, containing ~15–45 vol% plagioclase phenocrysts. Crystallization of this magma produced predominantly massive adcumulate–mesocumulate with less abundant, but regular, occurrences of (in order of relative abundance) gabbronorite–ferrodiorite segregations, mottled texture, foliation, pyroxenite aggregates, and modal layering. Additional key petrographic and compositional features include high-T deformation microstructures in plagioclase, vertically consistent mineral compositions, and enrichment of Fe-Ti-P-HFSE-REE in ferrodiorite. Parts of the Marginal Zone show gneissic–mylonitic fabrics that developed parallel to magma conduits. Collectively these features suggest that the textural and structural evolution of the pluton was controlled by: (a) emplacement of plagioclase-phyric magma, (b) establishment of vast cumulus crystal frameworks, (c) porous flow of intercumulus melt, (d) compaction, and (e) synplutonic deformation. These interpretations contrast with previous work emphasizing the importance of magmatic flow and crystal settling/flotation. RÉSUMÉ Un pan vertical des roches d’anorthosite plutonique de Hoseinbein de massif dont la formation remonterait à environ 1 315 Ma (de Nain, au Labrador) semble entièrement exposé et il est décrit ici pour la première fois. Il s’agit en l’occurrence d’une zone principale de plus ou moins 2 000 m d’épaisseur, ceinturée par une zone marginale de plus ou moins 200 m d’épaisseur. Dans son ensemble, la roche plutonique observée se compose principalement de monocumulat de leucogabbronorite, de leuconorite et d’anorthosite (~94% vol. de toutes les roches), dont notamment des quantités élevées de gabbronorite–jotunite (~27% vol.) dans la zone marginale. Le magma parent se composerait vraisemblablement d’un magma de basalte à phénocristaux de plagioclase, contenant approximativement entre 15 et 45% vol. de phénocristaux de plagioclase. La cristallisation de ce magma a produit surtout de l’adcumulat et du mésocumulat massifs, ainsi que des minéralisations régulières mais moins abondantes issues (dans leur ordre d’abondance) de ségrégations de gabbronorite–jotunite, d’une texture marbrée, d’une foliation, d’agrégats pyroxénitiques et de rubanements modaux. Parmi les autres caractéristiques pétrographiques et de composition importantes, il y a des microstructures de déformation de plagioclase survenue à température élevée, des formations minérales uniformes au plan vertical ainsi qu’un enrichissement de Fe-Ti-P-HFS-REE dans la jotunite. Des sections de la zone marginale présentent des traces d’une texture gneissique-mylonitique qui s’est formée parallèlement aux canalisations magmatiques. Dans l’ensemble, ces caractéristiques portent à croire que l’évolution de la texture et de la structure des roches plutoniques a été déterminée par les phénomènes suivants: (a) l’emplacement du magma de phénocristaux de plagioclase; (b) l’établissement de vastes complexes de cristaux de cumulus; (c) l’écoulement poreux de magma intercumulus; (d) le compactage; et (e) une déformation synplutonique. Ces interprétations diffèrent quelque peu des travaux précédents, où l’accent avait été mis sur l’importance de l’écoulement magmatique, et la décantation et la flottation de cristaux. [Traduit par la redaction]

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“…The Voisey's Bay deposit, located on the East Coast of Canada in Labrador, contains significant economic quantities of sulphidehosted nickel, copper and cobalt ores (Evans-Lamswood et al 2000). The mineralized deposits are part of the Voisey's Bay Intrusive Suite, which consists primarily of layered troctolite-gabbros intruding into Archean quartz-feldspar-biotite gneisses of the Nain province, and Proterozoic sulfidic garnetiferous paragneisses of the Churchill province (Ryan et al 1995).…”

Section: Geological and Geophysical Settingmentioning

confidence: 99%

“…This project deals solely with the Eastern Deeps magmatic system, consisting of a feeder tube (the Eastern Deeps Feeder), which leads into the large Easter Deeps Chamber. The main control on the location of mineralization is structural, which implies that deposition is controlled by morphological changes in the conduit geometry, and not by gravitational settling within the chamber itself (Evans-Lamswood et al 2000). Apart from these areas of massive mineralization, the chamber is dominated by troctolite-gabbros, containing a variable amount of sulphide fragments, and granite-syenite.…”

Section: Geological and Geophysical Settingmentioning

confidence: 99%

Waveform-based simulated annealing of crosshole transmission data: a semi-global method for estimating seismic anisotropy

Afanasiev¹,

Pratt²,

Kamei³

et al. 2014

Geophysical Journal International

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S U M M A R YWe successfully apply the semi-global inverse method of simulated annealing to determine the best-fitting 1-D anisotropy model for use in acoustic frequency domain waveform tomography. Our forward problem is based on a numerical solution of the frequency domain acoustic wave equation, and we minimize wavefield phase residuals through random perturbations to a 1-D vertically varying anisotropy profile. Both real and synthetic examples are presented in order to demonstrate and validate the approach.For the real data example, we processed and inverted a cross-borehole data set acquired by Vale Technology Development (Canada) Ltd. in the Eastern Deeps deposit, located in Voisey's Bay, Labrador, Canada. The inversion workflow comprises the full suite of acquisition, data processing, starting model building through traveltime tomography, simulated annealing and finally waveform tomography.Waveform tomography is a high resolution method that requires an accurate starting model. A cycle-skipping issue observed in our initial starting model was hypothesized to be due to an erroneous anisotropy model from traveltime tomography. This motivated the use of simulated annealing as a semi-global method for anisotropy estimation. We initially tested the simulated annealing approach on a synthetic data set based on the Voisey's Bay environment; these tests were successful and led to the application of the simulated annealing approach to the real data set. Similar behaviour was observed in the anisotropy models obtained through traveltime tomography in both the real and synthetic data sets, where simulated annealing produced an anisotropy model which solved the cycle-skipping issue. In the real data example, simulated annealing led to a final model that compares well with the velocities independently estimated from borehole logs. By comparing the calculated ray paths and wave paths, we attributed the failure of anisotropic traveltime tomography to the breakdown of the raytheoretical approximation in the vicinity of strong velocity discontinuities.

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Physical Controls Associated with the Distribution of Sulfides in the Voisey's Bay Ni-Cu-Co Deposit, Labrador

Cited by 24 publications

References 0 publications

Oxygen isotopic studies of the interaction between xenoliths and mafic magma, Voisey’s Bay Intrusion, Labrador, Canada

Oxygen isotopic studies of the interaction between xenoliths and mafic magma, Voisey’s Bay Intrusion, Labrador, Canada

Igneous structure and texture of the ~1.3 Ga Hosenbein anorthosite pluton (Nain, Labrador) and implications for the crystallization of massif-type anorthosite

Waveform-based simulated annealing of crosshole transmission data: a semi-global method for estimating seismic anisotropy

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