Structural controls on the primary distribution of mafic–ultramafic intrusions containing Ni–Cu–Co–(PGE) sulfide mineralization in the roots of large igneous provinces

Lightfoot, Peter C.; Evans-Lamswood, Dawn

doi:10.1016/j.oregeorev.2014.07.010

Cited by 99 publications

(36 citation statements)

References 56 publications

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“…This may account for an otherwise paradoxical observation made by Lightfoot and Evans-Lamswood (2015) that Noril'sk-style ores must have equilibrated with many hundreds or thousands of times their own volume of magma, but appear to have been emplaced late during the emplacement history of the host intrusion. In this interpretation, they may have been recycled many times, allowing them to be upgraded by continuous magma flow as originally proposed by Naldrett (1999b), but the final late stage of gravitational re-injection is the one that is preserved.…”

Section: Accepted Manuscriptmentioning

confidence: 97%

The mineral system approach applied to magmatic Ni–Cu–PGE sulphide deposits

Barnes

Cruden

Arndt

et al. 2016

Ore Geology Reviews

232

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Most magmatic Ni-Cu-PGE sulphide deposits occur within long-lived magma pathways fed by high degree partial melts of the mantle. Holistic mineral-system analysis for such deposits has some parallels with dominantly hydrothermal systems, but also some important differences.Major provinces are associated with large volumes of magma erupted at margins of ancient Archaean cratons, and are associated with small intrusions through which large volumes of magmas have passed. There is no demonstrable association with any particular magma type, although in most provinces the ores are found associated with the most primitive available magmas, whatever these may be. Or-bearing intrusions tend to form early in the evolution of the host province, although exceptions exist to this rule, and these intrusions typically account for very small proportions of the volumes of the province as a whole.Ore deposition is favoured by prolonged high-volume flow over a horizontal floor. This floor may take the form of the base of a channelized sill, tube or blade-shaped dyke, which account for most of the known host igneous bodies to significant ore deposits. Deposition mechanisms may be chemical or physical, but large high-grade deposits require a major component of transported sulphide liquid, initially carried as droplets. Late stage migration of sulphide liquid as gravity currents within intrusion networks, coupled with infiltration and melting of floor rocks, accounts for the common observation in mafic intrusion hosted deposits of cross cutting relationships between massive sulphides, host intrusions and country rocks.The following set of criteria is proposed in targeting and evaluating Ni-Cu-PGE sulphide systems: 1) nature of magmatism and relationship to pre-existing cratonic architecture; 2) magmatic and structural controls on the development of protracted-flow magma conduits; 3) access to crustal S A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTNi-Cu-PGE mineral systems Barnes May 2015 2 sources at some point along the pathway; 4) favorable intrusion geometry and emplacement style for deposition, reworking and upgrading of sulphide magmas, and 5) favorable structural history and erosional level for preservation and detectability.These components can be translated into mappable geological criteria. At the predictive targeting scale, the key features are proximity to ancient cratonic boundaries and long-lived, trans-crustal structures, and relationship to voluminous mafic or ultramafic magmatism typically with high Mg and low Ti contents, but otherwise lacking distinctive characteristics. At the detection scale, there are two distinct approaches: recognition of high volume magma pathways with prolonged flow-through operating at length scales of km based on morphological, petrological, geophysical and structural observations; and identification of the petrographic and geochemical signals of accumulation or extraction of sulphide liquid.

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Section: Accepted Manuscriptmentioning

confidence: 97%

The mineral system approach applied to magmatic Ni–Cu–PGE sulphide deposits

Barnes

Cruden

Arndt

et al. 2016

Ore Geology Reviews

232

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“…Sulfide-rich accumulations in small mafic or mafic-ultramafic intrusions, (Fig. 1A,B) usually identifiable as magma conduits (Lightfoot and Evans-Lamswood 2015). Important examples include Voisey's Bay (Canada), Jinchuan (China) and the Norilsk-Talnakh deposits, Siberia.…”

Section: Magmatic Sulfide Deposit Settingsmentioning

confidence: 99%

“…2A), or feeders to large igneous province magmatism in the form of sill-dike combinations (Fig. 2C) or tube-like "chonoliths" (Fig. 2D,E) Lightfoot and Evans-Lamswood 2015). Almost all examples show much higher proportions of sulfide and cumulus silicate minerals (typically olivine) within the flow or intrusion than could have been dissolved in a volume of magma equal to that of the host body, indicating that much larger volumes of magma flowed through the conduit leaving crystals and sulfide liquid behind.…”

Section: The Form Of Ore-hosting Magma Bodiesmentioning

confidence: 99%

Magmatic Sulfide Ore Deposits

Barnes¹,

Holwell

2017

ELEMENTS

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Magmatic sulfide ore deposits are products of natural smelting: concentration of elements from silicate magmas (slags) by immiscible sulfide liquid (matte). Deposits occupy a spectrum from accumulated pools of matte within small igneous intrusions or lava flows, forming orebodies mined primarily for Ni and Cu, to stratiform layers of weakly disseminated sulfides, mined for platinum group elements, within large maficultramafic intrusions. One of the world's most valuable deposits, the Platreef in the Bushveld Complex in South Africa, has aspects of both of these end members. Natural matte compositions vary widely between and within deposits, controlled largely by the relative volumes of matte and slag that interact with one another.

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“…The Rh and Pd proportions at Musongati are very similar to e.g. ~20-50% proportions of Pd in pentlandite in the Bushveld Complex (Osbahr et al, 2014) or PGE proportions in other PGE deposits worldwide (Lightfoot & Evans-Lamswood, 2015). These results demonstrate that a significant amount of PGE are hosted by sulfides.…”

Section: Pge Distributionmentioning

confidence: 56%

Platinum group element mineralization at Musongati (Burundi): concentration and Pd-Rh distribution in pentlandite

Paredis¹,

Muchez²,

Dewaele³

2017

Geol. Belg.

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ABSTRACT. The mafic-ultramafic intrusions of the Karagwe-Ankole belt in Burundi are considered as a new potential source for platinum group elements (PGE). The intrusions have mainly been studied for their PGE potential with regard to PGE concentration, but the mineralogical distribution of PGE has not been examined to the same level. This study focuses on the Pd and Rh distribution in pentlandite of ultramafic rocks of the Musongati layered intrusion. The results are based on whole rock and pentlandite analyses which were incorporated into a mass balance. Palladium proportions in pentlandite vary between 4 and 69%. Rhodium is present in proportions ranging from 1-39% in pentlandite. Other PGE distributions could not be determined in pentlandite due to concentrations below detection limits. The results from this study demonstrate that Pd and Rh are hosted by sulfides since sulfur saturation of the magma occurred early on, perhaps before or simultaneously with the precipitation of silicate minerals. Based on these findings, a preliminary model for the mineralization of PGE in the Musongati intrusion is proposed.KEYWORDS: mafic-ultramafic, layered intrusion, Karagwe-Ankole belt, LA-ICP-MS, NiS FA, pentlandite, mass balance, sulfur saturation.(see further; e.g. Robb, 2005;Kennedy et al., 2013;Kennedy, 2014). A second model is the sulfide fractionation model, which is based on physical and chemical processes where an immiscible sulfide liquid incorporates the major part of PGE (see further; e.g. Dare et al., 2010;Chen et al., 2015). A third, relatively newer model, proposed by e.g. Mungall et al. (2015) is that of flotation of sulfide melt on vapor bubbles, in which the PGE are incorporated during their way up. Knowledge about where and in which phase(s) the PGE occur is, therefore, essential to obtain an insight in the ore-forming processes and hence to assess their recovery from raw materials.In this paper, the results of the investigations for the concentration of PGE in mafic-ultramafic rocks and the Pd and Rh distribution in pentlandite from the Musongati intrusion in Burundi will be discussed. The results are based on whole rock and sulfide phase analyses that were incorporated into a mass balance to calculate the Pd and Rh distribution. Based on these data a preliminary model for the PGE mineralization of the Musongati intrusion is proposed.

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Structural controls on the primary distribution of mafic–ultramafic intrusions containing Ni–Cu–Co–(PGE) sulfide mineralization in the roots of large igneous provinces

Cited by 99 publications

References 56 publications

The mineral system approach applied to magmatic Ni–Cu–PGE sulphide deposits

The mineral system approach applied to magmatic Ni–Cu–PGE sulphide deposits

Magmatic Sulfide Ore Deposits

Platinum group element mineralization at Musongati (Burundi): concentration and Pd-Rh distribution in pentlandite

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