2. Platinum-Group Element mineral deposits: exploration, evaluation and beneficiation
Submitting Institution
Cardiff UniversityUnit of Assessment
Earth Systems and Environmental SciencesSummary Impact Type
EnvironmentalResearch Subject Area(s)
Earth Sciences: Geochemistry, Geology
Engineering: Resources Engineering and Extractive Metallurgy
Summary of the impact
Platinum Group Elements (PGE) are critical strategic metals because of
their unrivalled applications in catalysts, fuel cells and electronics and
cancer therapies. Research and analytical methods developed at Cardiff
have impacted on exploration for new PGE deposits, and more efficient
processing of PGE ores by international mining companies. A key milestone
between 2009 and 2012 was the discovery of a 3 billion year old giant
impact crater in West Greenland. This discovery is of major economic
significance because all craters previously found in this size class are
associated with multi-billion dollar mineral and/or hydrocarbon resources.
It led to an intellectual property transaction worth CDN$ 2.1 million and
discovery of nickel and PGE deposits in Greenland by North American Nickel
Incorporated.
Underpinning research
PGEs are among the rarest elements in the Earth's crust. All current
major world minable PGE resources, and likely future potential resources,
occur in mafic igneous rocks. Almost all exploitable PGE ore deposits form
when an immiscible sulphide liquid scavenges PGE from a silicate melt,
then separates and concentrates them. Depending on the extent of sulphide
melt fractionation, its trace element chemistry and any post-magmatic
alteration, the PGE may be distributed between different base metal
sulphide (BMS) minerals or form their own platinum-group minerals (PGM) in
the final ore. Since 2000, research on the distribution of PGE in ores has
changed focus from PGM studies using electron microscopy to include laser
ablation ICP-MS analysis that measures trace PGE concentrations in
sulphide minerals. Drs Prichard and McDonald have been based at Cardiff
from 1996 and 2001 respectively. They are recognized as experts with
established track records in PGE studies using electron microscopy3.1,
3.2 and laser ablation mass spectrometry techniques3.4.
This work is crucial in evaluating the economic potential of PGE mineral
deposits, since the distribution of PGE between BMS and PGM in the ore
strongly influences the type of ore processing and its cost (e.g., at
Aguablanca mine in Spain). Research by Prichard and McDonald in 20103.2
on the redistribution of PGE during low temperature alteration at
Aguablanca has provided significant insights into the potential for
processing oxidized supergene ores that are a presently under-exploited
PGE resource.
In addition to characterizing ore and improving extraction efficiency at
known deposits, research at Cardiff has revealed new targets for PGE
exploration. In 2009-2010, as the Cardiff lead, McDonald's work on the
World's third largest PGE deposit, the Platreef, resulted in a
fundamentally new exploration model involving highly efficient
concentration of PGE in staging chambers3.3, 3.4. The points
where these chambers feed into the Platreef are prime targets for high
grade mineralization3.3 and in 2011 this research won the
Wardell Armstrong prize from the Institution of Materials, Minerals and
Mining. Major extra-terrestrial impact structures are potential hosts for
PGE deposits and the Sudbury Basin, long known to host a range of magmatic
sulphide deposits that are the subject of Prichard's research3.1,
is such an impact structure. Prichard's research at Sudbury since 2009 has
been described as part of a number of "landmark contributions to the
science of nickel deposits" by Peter Lightfoot, chief geologist of the
mining company Vale5.2. Research by McDonald in collaboration
with the Geological Survey of Denmark and Greenland and Lund University,
led to the discovery of a 3 billion year old giant impact crater at
Maniitsoq in West Greenland3.5, 3.6. McDonald led the
geochemical and economic geology aspects of the project. Prior to this
study the oldest known crater was the 2.02 billion year old Vredefort
crater in South Africa. Giant (>150 km diameter) craters have major
exploration significance because all of the craters previously known in
this size class are associated with multi- billion dollar mineral and
hydrocarbon resources (gold and uranium at Vredefort; nickel and copper at
Sudbury; and hydrocarbons at Chixculub). Identifying old eroded craters
such as Maniitsoq is extremely difficult, and it took from 2009 until 2012
to compile enough evidence to validate the discovery3.5. The
earliest version of the impact model was exploited in an intellectual
property transaction in 2011 is now being used by North American Nickel
Incorporated, to guide exploration for nickel and PGE at Maniitsoq3.6.
References to the research
[3.1] Dare, S. A. S., Barnes, S.-J., Prichard H. M. and Fisher
P.C. (2010) The timing and formation of platinum-group minerals from
the Creighton Ni-Cu-PGE sulfide deposit, Sudbury, Canada: early
crystallization of PGE-rich sulfarsenides. Economic Geology 105,
1071-1096.
DOI:
http://dx.doi.org/10.2113/econgeo.105.6.1071
[3.2] Suárez S., Prichard H.M., Velasco F., Fisher P.C.,
and McDonald I. (2010) Alteration of platinum-group minerals and
dispersion of platinum-group elements during progressive weathering of the
Aguablanca Ni-Cu deposit, SW Spain. Mineralium Deposita, 45, 331-350.
DOI: http://dx.doi.org/10.1007/s00126-009-0275-x
[3.3] McDonald I., Holwell D.A., and Wesley B. (2009) Assessing
the Potential Involvement of an Early Magma Staging Chamber in the
Generation of the Platreef Ni-Cu-PGE Deposit in the Northern Limb ofthe
Bushveld Complex: A Pilot Study of the Lower Zone Complex at Zwartfontein.
Applied Earth Science (Trans. IMM section B) 118, 5-20
DOI:
http://dx.doi.org/10.1179/174327509X434902
[3.4] Holwell D.A., McDonald I., and Butler I.B. (2011) Precious
metal enrichment in the Platreef, Bushveld Complex, South Africa: evidence
from homogenized magmatic sulphide melt inclusions. Contributions to
Mineralogy & Petrology, 161, 1011-1026.
DOI: http://dx.doi.org/10.1007/s00410-010-0577-0
[3.5] Garde A.A., McDonald I., Dyck B., and Keulen N. (2012)
Searching for giant, ancient impact structures on Earth: the Mesoarchaean
Maniitsoq structure, West Greenland. Earth & Planetary Science
Letters, 337-338, p.197-210.
DOI:
http://dx.doi.org/10.1016/j.epsl.2012.04.026
[3.6] Garde A.A., Pattison J., Kokfeld T.F., McDonald I., and
Secher K. (2013) The norite belt in the Mesoarchaean Maniitsoq structure,
southern West Greenland: conduit-type Ni-Cu mineralisation in
impact-triggered, mantle-derived intrusions? Geological Survey of
Denmark and Greenland Bulletin 28, 45-48.
http://www.geus.dk/publications/bull/nr28/nr28_p45-48.pdf
Additional Information
Institution of Materials, Minerals and Mining - Award Winners 2011
(Wardell Armstrog Prize for [3.3] to McDonald and co-authors). http://www.iom3.org/content/award-winners-2011
(accessed on 9th July 2013, archived as PDF)
Details of the impact
Understanding the fundamental controls on mineralization and locating the
host phases that control the distribution of the PGE in ores provide key
insights for companies carrying out exploration and/or mineral processing
of PGE. The combination of specialist knowledge and analytical facilities
at Cardiff allows the total distribution of PGE within ores, metallurgical
products or other samples to be mapped and quantified; impacting both on
exploration efficiency and reducing costs at deposits such as Aguablanca
and Sudbury5.1,5.2. The evolution of these research- led
technologies has led to collaborations with major PGE producers and junior
exploration companies. Examples of these industrial impacts include:
Collaboration with Anglo Platinum Ltd (McDonald) resulted in the
identification of staging chambers below the world's third largest PGE
deposit (the Platreef) where highly PGE-rich sulphide liquids were
concentrated3.3. Evidence for this sulphide liquid is preserved
as inclusions trapped in the earliest Platreef minerals3.4.
This new understanding has been used by Anglo Platinum to understand the
development of the Platreef orebody and the underlying factors that affect
the distribution of mineralisation in areas being mined and explored by
the company5.3.
Periodically, certain PGE deposits have been revisited to apply new
analytical methods to solve long-standing problems. Prichard's research on
PGM at the Aguablanca Ni-PGE deposit in Spain began in 2000 and since 2009
this work has been extended through a study of PGE behaviour in the
gossans (siliceous iron oxide caps developed from weathering) in
collaboration with the mine operators, Rio Narcea Recursos S.A3.2.
This research has helped Rio Narcea Recursos S.A understand the ore
mineralogy in a way they would not have been able to do themselves and has
helped the company "add value to the base metal product through the
processing of precious metals within our ores and helped us deal with
smelter credits for precious metals in the ores" 5.1.
In recent years there has been strong activity in the mining sector for
exploration at craters, formed via the impact of asteroids or comets with
the Earth. This is due to the high probability that medium-giant sized
craters will host significant mineral or hydrocarbon resources. For
example, in 2005 it was estimated that in North America alone over US$ 18
billion worth of natural resources were extracted from crater sites each
year. The research carried out by Prichard on the behaviour of PGE in the
sulphide ores at the Sudbury impact crater3.1 has been used by
nickel company Vale to improve extraction efficiency of PGE in their ore5,2.
A major research milestone during the REF period has been the discovery
of the giant Maniitsoq impact crater in West Greenland3.5. Due
to the highly eroded nature of the crater it took three years from
2009-2012 to establish the validity of the Maniitsoq crater among the
scientific community3.5. However the mineral exploration
industry was quicker to grasp the significance of the discovery and
exploit it before the research was formally published. The opportunity was
taken up in late 2010 by two mining consultants, John Ferguson and John
Rowntree, who recognized the potential of the impact model and used it to
prepare an outline programme for a mining company to acquire a licence and
carry out exploration for nickel and PGE at Maniitsoq5.4. They
recognised that the key targets were supercooled magmas (termed norites)
carrying nickel and copper sulphides (with by-product PGE) that were
produced shortly after the impact and which invaded the fractured target
rocks. Modelling carried out by McDonald and his colleagues in 2011
identified the likely size of the crater and the limits of shock
metamorphism, which could be used to optimise the size and geographical
spread of the likely licence area. The size of the crater predicted by the
impact model indicated that there should be many more of these mineralized
norites than had been discovered by ground surveys in the 1970s and by
fixed wing aeroplane geophysical surveys in the 1990s. In August 2011
North American Nickel Incorporated (NAN) acquired the intellectual
property rights for the Ferguson-Rowntree exploration plan5.6
for cash and share warrants worth CDN$ 2.1 million plus a 1.25% net
smelter royalty each - reducible to 0.5% upon payment of CDN$ 1 million
each to Ferguson and Rowntree5.8. NAN committed $CDN 7.7
million in 2011-12 to prospecting the site and in late 2011 a
helicopter-supported electromagnetic survey discovered 17 new norite
targets for test drilling, consistent with the model. This had risen to
102 targets by June 20135.9. NAN management have fully
incorporated the impact model5.7,5.9, been involved in
follow-up research3.6 and have expressed the view that now the
science is confirmed3.5, 3.6, they stand the best chance of
success if they explore "from an impact point of view"5.5.
Sources to corroborate the impact
[5.1] Confirmation by Chief Geologist for Aguablanca mine, Rio Narcea
Recursos SA, of the impact of research by Prichard and McDonald (reference
[3.2]) at the Aguablanca nickel-PGE deposit.
[5.2] Confirmation by Chief Geologist (Nickel) for Vale on the impact of
Prichard's research at Sudbury , including reference [3.1].
[5.3] Confirmation by Former Head of Platinum Geology, Anglo Platinum Ltd
on the impact of improved understanding of the Platreef through research
by McDonald, including references [3.3] and [3.4].
[5.4] Confirmation by Director of Spar Resources Pty Ltd and advisor to
North American Nickel Incorporated on the impact of the discovery of a
giant impact crater at Maniitsoq by Garde, McDonald and others and its
exploration potential (references [3.5] and [3.6]).
[5.5] Confirmation by Chief Geologist for North American Nickel on the
usefulness of the impact model for Maniitsoq on the company's exploration
strategy (reference [3.5])
[5.6] Confirmation of acquisition of exploration licence by North
American Nickel
http://www.northamericannickel.com/news/news-details/2011/North-American-Nickel-Acquires-
Large-Mineral-Exploration-Licence-in-Greenland1126311/default.aspx
(accessed 24th September 2013, archived as PDF)
[5.7] Confirmation that North American Nickel has recognised and
appreciated the exploration significance of impact model developed by
McDonald and his colleagues
http://www.northamericannickel.com/news/news-details/2012/Earths-Oldest-Meteor-Impact-Site-
Discovered-at-North-American-Nickels-Maniitsoq-Ni-Cu-PGE-Project-Southwest-
Greenland1130135/default.aspx (accessed 24th September 2013,
archived as PDF)
[5.8] North American Nickel's Full Financial Statement (12 months ended
December 2012). Confirmation of expenditure (p.16 and section10d), share
warrant agreements and intellectual property rights (p.22) for Maniitsoq.
http://www.northamericannickel.com/files/doc_financials/Q4%202012%20Dec%2031%2012%20Fi
nancial%20Reports%20Complete_v001_p11272.pdf(accessed 24th
September 2013, archived as PDF)
[5.9] North American Nickel investor presentation with geology based on
the impact model (slides 10, 11, 16 and 30), including 102 conductive
targets recognised for follow-up work (slide 18).
http://www.northamericannickel.com/files/doc_presentations/NAN%20Maniitsoq%20Sept%205%2
02013.pdf (accessed 24th September 2013, archived as PDF)