CONTENT and DESCRIPTIONS OF ORE DEPOSITS
Image: The Oktyabr'sky and Taimyr'sky headframes at Talnakh.
Porter GeoConsultancy continued its International Study Tour series of professional development courses by visiting a representative selection of the most significant magmatic nickel sulphide deposits in the northern hemisphere, supported by expert workshops and field workshops outlining their occurrence and setting.
Cu-Ni-PGE deposit, Minnesota, USA,
North American Workshop in Sudbury, Ontario, Canada,
Sudbury Ni-Cu-PGE deposits, Ontario, Canada,
Voiseys Bay Ni-Cu-Co deposits, Canada - presentation,
Eurasian Workshop in Moscow, Russia,
Pechenga District Ni-Cu-Co deposits, Russia - presentation,
Noril'sk & Talnakh Ni-Cu-PGE deposits, northern Siberia, Russia,
Jinchuan Ni-Cu-Co-PGE deposit, Gansu, northern China.
NOTE: Visits (or where specified, detailed presentations and workshops) were successfully completed for all of the deposits listed above.
The tour started in Duluth, Minnesota, USA on the evening of Sunday 9 July and ended in Beijing, China on the evening of Thursday 27 July 2006. Participants were able to take any 4 or more days, up to the full tour, as suited their interests or availability.
The main components of the planned itinerary were:
Duluth Complex - NorthMet Project ...................... Monday 10 July, 2006.
The Duluth Complex in Minnesota, USA, lies within Precambrian shield rocks of the Superior Province which include Archaean mafic to felsic volcanic rocks, greywackes, granitic intrusives and older ortho- and paragneisses; Palaeoproterozoic (2300 to 1800 Ma) clastic and carbonate sedimentary rocks and iron formations of the Animikie Group; and late Mesoproterozoic clastic sedimentary rocks and broadly comagmatic mafic lava flows, pyroclastics and interbedded sedimentary rocks of the Keweenawan Suite.
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A major NE-SW trending, >1500 km long rift zone known as the Midcontinent Rift was developed across the North America continent during crustal scale tectonic extension within the older cratonic mass during the late Mesoproterozoic. Associated gabbroic intrusion resulted in the composite, arcuate, NE-SW elongated, 450 x 100 km Duluth Complex, which formed from up to 40 separate sheet like and cone shaped sub-intrusions and covers an area of approximately 6500 square kilometres.
The Duluth Complex comprises the Anorthositic-, the Troctolitic- and the late stage Felsic-Series. Field relations indicate that the Anorthositic Series, which is in the upper part of the Duluth Complex, is older than the Troctolitic Series that forms the lower two thirds of the Complex, although identical age dates of 1099 Ma for both series suggests rapid intrusion. The Felsic Series and late stage basalts and aplite dykes, cut the Anorthosite and Troctolite Series.
The NorthMet deposit is hosted by the Partridge River Troctolite Series (predominantly troctolite with lesser anorthositic troctolite, gabbro, olivine gabbro, norite and picrite), adjacent to the South Kawishiwi Intrusion (which also contains Cu-Ni-PGE ores) in the Hoyt Lake-Kawishiwi section of the Duluth Mafic Complex. The Partridge River Troctolite Series rocks, which contain inclusions of assimilated footwall rocks, immediately overlie a wedge of sulphide bearing metamorphosed slates, argillites and greywackes of the Proterozoic Virginia Formation separating the Duluth Complex from the underlying Biwabik Iron Formation. The argillaceous horizons of the Virginia Formation are commonly graphitic and sulphide bearing near the base of the formation and locally contain up to 15% thinly laminated pyrrhotite.
A string of Ni-Cu and/or PGE deposits are distributed over a 35 km interval along the footwall margin of the Duluth Mafic Complex. Together these are quoted as containing 3.6 Gt @ 0.66% Cu, 0.2% Ni ± locally up to 2 g/t PGE. The NorthMet Project has an open-pit resource of 810 Mt @ 0.43% Cu, 0.11% Ni, 0.12 g/t Pt, 0.44 g/t Pd, 0.06 g/t Au, and 1.5 g/t Ag at a 4:1 stripping ratio. The Mesaba Project, immediately to the northeast, contains >1 Gt @ 0.57% Cu, 0.14% Ni, including 4.5 Mt @ 1.9% Cu, 0.6% Ni as a massive sulphide body predominantly within the footwall sediments. The Birch Lake underground mining resource further to the northeast in the South Kawishiwi Intrusion, has an average thickness of 24 m, and a resource of 29 Mt @ 3.9 g/t Pt eq. (0.7% Cu, 0.2% Ni, 0.25 g/t Au 1.13 g/t Pd, 0.57 g/t Pt, 0.011% Co, 2.90 g/t Ag).
Three types of PGE, Cu-Ni magmatic mineralisation occur within the Duluth Complex, at or near its footwall, as follows:
i). Large, low grade disseminated Cu-Ni sulphide deposits that are locally enriched in PGEs;
ii). Localised high grade zones of massive Ni-Cu sulphides, some of which are moderately enriched in PGEs;
iii). Disseminated, PGE enriched, Cu-Ni sulphides associated with specific types of phase-layer transitions, and in this sense are stratabound deposits.
At NorthMet, 1 to 2% disseminated/interstitial sulphides (pyrrhotite, chalcopyrite, cubanite and minor pentlandite) occur throughout the troctolitic sequence, but are generally more prevalent near the basal contact with the underlying meta-sedimentary rocks.
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Travelling from Duluth, Minnesota, USA to Sudbury, Ontario, Canada .................... Tuesday 11 July 2006.
North American Workshop - Laurentian University, Sudbury .......... Wednesday 12 July, 2006.
A one day workshop was led by Prof. Mike Lesher of the Mineral Exploration Research Centre, Department of Earth Sciences, Laurentian University, Sudbury.
This workshop provided:
as a context to the North American segment of the tour and the Sudbury vists.
- Background information on the principles of the formation of magmatic Ni-Cu-PGE deposits,
- The geological, metallogenic and tectonic setting and descriptions of key magmatic Ni-Cu-PGE in Canada, particularly Raglan and Thompson and
- An overview and context setting of the Sudbury Igneous Complex and ore deposits,
Further detail of the presenters and titles of presentations are to be posted here soon.
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Sudbury ...................... Thursday 13 & Friday 14 July, 2006.
Mine visits, drill core displays and field workshops will demonstrate the different ore styles at Sudbury and the different parts of the Sudbury Igneous Complex.
The Sudbury sulphide nickel deposits are located within the basal layer of the roughly oval shaped 65x25 km, 1.85 Ga Sudbury Igneous Complex (SIC) in south-western Ontario, Canada.
This complex cuts both Archaean rocks on the southern margin of the Superior Province, and the Lower Proterozoic of the Huronian Supergroup. It is also less than 10 km to the north of the 1.2 to 1.0 Ga Grenville Front, and lies on a regional, 350 km long zone of linear gravity and magnetic anomalies. It is overlain by the Lower Proterozoic Whitewater Group, an older sequence consisting of an upward progression of conformable heterolithic breccias, a carbonaceous and pyritic argillite and a proximal turbidite unit which occupies a basin shaped structure and is only found with the oval shaped outcrop zone of the SIC.
The complex dips inward throughout at around 30 degrees and is composed of a sequence of norite, gabbros and granophyres. It comprises two main zones, a lower 500 to 2500m thick Lower Zone of norite and gabbro-norite, grading upwards into quartz- and oxide rich gabbro. The Upper Zone is 1 to 2500 m thick and is mainly a granophyre, with an abruptly transitional margin with the underlying quartz-rich gabbro. The granophyre intrudes the basal Whitewater Group. There is no obvious small scale layering within the complex. A third discontinuous layer is found at the base of the SIC, particularly in embayments into the footwall rocks. This is called the "Sublayer" and contains all of the major Ni-Cu sulphide deposits. The contact with the base of the Lower zone varies from sharp to gradational. It has two facies, namely: i). the Contact Sublayer that is usually <200m thick and composed of discontinuous lenses of gabbro-norite along the basal contact of the SIC, and ii). the Offset Sublayer that constitutes apophyses or dykes of predominantly quartz-diorite that project outwards into the intruded footwall rocks.
A contact metamorphic halo around 1200 m thick occurs in the footwall rocks which have been brecciated for up to 80 km from the complex - the Sudbury Breccia. The composition of the SIC is strongly influenced by the crustal rocks, with a differing succession through the complex to the north where it cuts the Archaean of the Superior Province - the North Range, and the southern side - the South Range where it intrudes the Lower Proterozoic of the Huronian Supergroup. Differences are also noted in the ores in the two ranges.
There are three main ore types, namely: i). Contact type massive sulphides in the noritic Sublayer, with a lower layer of massive sulphide enclosing angular wall rock fragments and stringers extending into the footwall, while upwards the massive sulphides grade into a sulphide-matrix breccia and finally to disseminated sulphides; ii). stockworks of more Cu rich ore in the Sudbury Breccia of the footwall, comprising massive stringers and lenses oriented parallel to the dip of the SIC; iii). deposits associated with Offset Dykes of quartz-diorite that are sub-radial to sub-parallel to the margins of the SIC, with sulphides present as either lenticular zones of sulphide blebs, or as sheaths of sulphide bleb bearing quartz-diorite or Sudbury Breccia on the margin of the dykes.
The main ores are composed of pyrrhotite, pentlandite, chalcopyrite, pyrite and magnetite. Bornite is locally present in higher grade zones, while higher arsenic as arsenides characterises the South Range. The copper rich veins deep in the footwall are dominated by chalcopyrite and cubanite with lesser pentlandite, magnetite and pyrrhotite.
The Sudbury Complex contained around 1650 Mt @ 1.2% Ni, 1.03% Cu.
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Voiseys Bay Presentation ...................... Friday 14 July, 2006.
For operational reasons, it was not possible to secure a visit to the newly commissioned Voieys Bay deposit in Labrador. However, the group received a detailed, illustrated presentation on the geology and mineralisation at Voiseys Bay while in Sudbury, led by Dave Burrows of Inco, and the opportunity to study representative drill core samples through the deposit.
The Voisey's Bay nickel deposit is located on the Labrador coast of the Canadian Province of Labrador and Newfoundland, some 1500 km to the north-east of Montreal.
It is hosted by a 1334 Ma troctolite sheet belonging to the extensive 1350 to 1290 Ma Nain Plutonic Suite (NPS) emplaced at the boundary between the Nain Archaean Province to the east
and the NNW trending 1850 to 1730 Ma Torngat Orogen to the west. The Torngat
Orogen is a zone of deformation separating the Nain Province from the Rae
Archaean Province further to the west. Archaean granitic, quartzo-feldspathic
and mafic orthogneisses of the Nain Province are found to the east at Voisey's
Bay. In the west garnet-sillimanite, and sulphide and graphite bearing
quartzo-feldspathic paragneisses represent both reworked Archaean gneisses,
and Lower Proterozoic intrusives and shelf sediments of the Torngat Orogen.
The NPS is batholithic and covers some 20 000 sq. km in the district. It comprises
a broad spectrum of compositions including anorthosite, granite, troctolite
and ferro-diorite representing the episodic coalescence of multiple plutons
in an extensional environment, tapping the mantle.
The troctolite host to the Voisey's Bay mineralisation comprises two east plunging intrusions,
the lower Reid Brook and the upper Eastern Deeps intrusions. These originally had a 2 km vertical separation. They are linked by a steeply dipping dyke, the Feeder Sheet, that varies from 10 to 100 m in thickness. There are a number of different rock types within these three intrusive bodies, as follows:
i). The higher Eastern Deeps intrusive has an upper olivine-gabbro (OG), grading downwards progressively into a medium grained, even textured troctolite (NT), to a varied texture troctolite (VTT) containing wall rock clasts, to a basal breccia (BBS) at the base, composed of abundant clasts of wall rock and mafics in a troctolite gangue. Various of these lithologies are cut by syenite and granite dykes.
ii). The Feeder Sheet generally comprises the following across its thickness in the upper sections, from the hangingwall - an upper chill zone to an un-mineralised feeder olivine gabbro (FOG), to the leopard troctolite (LT) which has 30 to 50% interstitial sulphides with a sharp contact to a basal breccia (BBS) on the footwall. Lower, towards the Reid Brook intrusive, the BBS may occur anywhere in the feeder and grades into the feeder breccia (FB) which is similar, but much more packed, while the FOG and LT are concentric to massive sulphides, where developed.
iii). The Reid Brook intrusive - the confluence of the Feeder Sheet in the roof of the Reid Brook intrusive is commonly choked by feeder breccia (FB), which also extends for a distance along the roof of the intrusive. This is underlain by a varied texture troctolite (VTT), which grades into the LT of the feeder sheet. The main mass of the intrusive is a leuco troctolite (LUT) similar in some respects to the olivine gabbro of the Eastern Deeps intrusive. Again the intrusive is cut by granite dykes.
Economic mineralisation, mainly massive sulphides occurs both within the Feeder Sheet and at the base of the Eastern Deeps intrusive, adjacent to the entry point of the Feeder Sheet. Within the Feeder Sheet, massive sulphides are restricted to the wider sections and occur as a series of elongate lenses in the plane of the linking sheet, all raking to the east. These include the Mini-Ovoid orebody and the Discovery Hill zone which are within the leopard troctolite (LT), above the basal breccia (BBS). Further to the west and deeper in the Feeder Sheet, the Western Extensions comprise disseminated mineralisation grading towards the footwall into massive sulphides.
The richest body, the Ovoid occupies a 350x600 m basin shaped body that is up to 110 m deep at the thickest point, tapering upwards towards the margins. It overlies a thin band of leopard troctolite (LT) and basal breccia (BBS). This is interpreted to be a depression at the base of the Eastern Deeps intrusive, above the confluence with the Feeder Sheet. Other mineralisation, the Eastern Deeps, is also known from similar positions in the Eastern Deeps intrusive.
The massive sulphides of the Ovoid are 75% pyrrhotite (2 to 5 cm crystals), 12% pentlandite (1 to 2 cm eyes), with irregular chalcopyrite and cubanite. Magnetite is scattered through the pyrrhotite. Disseminated ores of the Western Extension are in a similar proportion, but finer.
The reserve at the Ovoid body is: 32 Mt @ 2.83% Ni, 1.68% Cu, 0.12% Co,
The indicated resource at Eastern Deeps is: 50 Mt @ 1.36% Ni, 0.67% Cu, 0.09% Co,:
The resource at Western Deeps is in excess of 15 to 20 Mt.
The total reserve + inferred and indicated resource was stated as 124.4 Mt @ 1.66% Ni at the end of 1998 and 77.6 Mt @ 2.28% Ni, 1.19% Cu, 0.13% Co in 2005.
The deposit is now in production (2005) and is owned by Inco Limited.
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Travelling from Sudbury, Ontario, Canada to Moscow, Russia .................... Saturday 15 to Sunday 16 July, 2006.
Eurasian Workshop - Moscow ............. Monday 17 July, 2006.
A one day workshop was held in Moscow, led by Prof. Tony Naldrett who provided insights into the setting and styles of magmatic Ni-Cu-PGE mineralisation in Eurasia. It covered:
- The general principles of the setting, formation, geology, geochemistry and mineralogy of magmatic Ni-Cu-PGE deposits;
- The application of the concepts and characteristics outlined above to exploration;
- An overview of the geology, mineralogy and geometry of the key magmatic Ni-Cu-PGE deposits of Eurasia, particularly Noril'sk-Talnakh and Jinchuan;
- A detailed description of the Pechenga Ni-Cu deposits by Dr Valery Smolkin, an expert who has worked on the deposits for many years (see below).
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Pechenga Presentation ............. Monday 17 July, 2006.
For organisational reasons, it was not practical to secure a visit to the Pechenga district. However, a detailed, illustrated presentation on the Pechenga District and its deposits was delivered in Moscow as part of the Eurasian Workshop by an expert geologist, Dr. Valery F. Smolkin, who worked on the deposit for many years.
The Pechanga nickel-copper deposits, (with associated cobalt, platinum and palladium) are located on the Kola Peninsula of north-western Russia.
The Pechanga district (or Pechenga Greenstone Belt) lies within the larger, 1000 km long Palaeoproterozoic North Transfennoscandian greenstone belt dated at 2.0 to 1.97 Ma located between blocks of Archaean crust. It contains numerous massive and disseminated Ni-Cu sulphide ore deposits hosted within differentiated sills with composition grading upwards from wehrilte through pyroxenite to gabbro (i.e., gabbro-wehrlite association), with less common non-differentiated ultramafic or gabbro intrusions. Ni-bearing gabbro-wehrlite intrusions are hosted by shales, sandstones and tuffs of the Pilgujarvi formation, with the immediate enclosing rocks to the mineralised intrusives beling peridotites, serpentinite and black schist (meta-tuffs). Sedimentary rocks of the Pilgujarvi formation contain abundant authigenic sulphides, found as disseminated pyrite grains, less commonly concretions and massive or laminated sulphide beds. Ferropicritic volcanics, which are also present within the Pilgujarvi formation and in parts of the overlying mafic volcanic suite, are co-magmatic with the Ni-bearing intrusions.
The ores are principally magmatic sulphide accumulations of pentlandite, pyrrhotite and chalcopyrite occurring as discordant disseminated to net-vein to stringer mineralisation and stratabound massive sulphide lenses in the basal sections of mafic to ultramafic intrusions and flows which have been serpentinised.
Five styles of sulphide occurrence have been recognised, namely i) disseminated sulphides, occurring as both interstitial and globular forms toward the base of the host ultramafic to mafic bodies, within olivine cumulate portions of a ferropicrites phase; ii) massive sulphides found at the lower contact between the ferropicrites of the ultramafic to mafic hosts and the underlying sedimentary rocks; iii) breccia-matrix sulphides, extending for up to a kilometre along strike at the basal contact of the ultramafic to mafic hosts and extending into the sediments - this style comprises a matrix of sulphides exhibiting a tectonic flow fabric, containing fragments of ultramafic and sedimentary rocks; iv) vein or stringer sulphides that are chalcopyrite rich and are predominantly found in the underlying sediments (graphitic pyrite-rich sedimentary rocks, locally known as "black schists"); iv) ore-bearing flows, within the black schists, occurring as pyrite-rich layers, concretions and lenses.
The overall size of the deposits has been estimated at 150 Mt @1% Ni
Reserves in 2000 were approximately: 30 Mt @ 2% Ni, 1% Cu, 0.04% Co
Production + Resources in 2000: 4.7 Mt of contained Ni, 3.5 Mt of contained Cu at grades of 1.2% Ni, 0.9% Cu.
Annual production in the early 1990's was around 35 000 tonnes of Ni per annum.
According to Abzalov (2009), total reserves of the district are estimated as 339 Mt @ an average grade of 1.18% Ni and 0.63% Cu
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Noril'sk & Talnakh ...................... Tuesday 18 to Thursday 20 July, 2006.
The Permo-Triassic Noril'sk and Talnakh clusters of deposits of Siberia, northern Russia are 35 km apart and are developed near the north-western margin of the Siberian Platform. The deposits are found within and adjacent to gabbro-dolerite sills that represent part of the feeder zone of the up to 3500 m thick, vast Permo-Triassic Siberian trap basalts.
The Talnakh cluster of interconnected deposits, Oktyabrsky, Komsomolsky, Taimyrsky, Kharayelakh, Skalisty, Severnijy, Mayak and Mokulaevskoe are operated as the Polar Division, while those at Noril'sk, which include Norilsk-1, Maslovskoye and Chernogorskoye belong to the Bear Creek Division of Nornickel.
The basement to the Siberian Platform is composed of crystalline Proterozoic rocks overlain by late Proterozoic sediments, lower Palaeozoic marine dolomites, argillites and sandstones, and by Devonian marls and evaporites. These are followed by Carboniferous shallow water limestones, continental sediments and coal measures. The Palaeozoic sequence is around 6000 m thick.
The host sills are developed within and adjacent to the continental scale, NNE trending Noril'sk-Kharayelakh fault. These ore bearing sill like intrusive bodies have known dimensions of as much as 15x0.5 to 2 km and are from 50 to 300 m in thickness, although they only represent 1 to 2% of the total mafic intrusives in the district. A typical sill is said to consist of a lower olivine bearing, melanocratic gabbro-dolerite with a picritic composition, passing upwards into leucocratic gabbro-dolerites near the top. This has been variously interpreted to result from differentiation or from multiple intrusive pulses. On both the upper and lower margins there are zones of taxite containing increased sulphides, platinoids and chromite. A taxite is a mafic igneous rock with a very variable texture (from fine to pegmatitic) - and composition (leucocratic to melanocratic) - with discrete ghost-like remnants of inclusions of other gabbroic and country rocks. The upper zone is more weakly taxitic. A strong hornfels halo extends for 100 m below the sills and up to 250 m above.
There are three main ore types developed at Noril'sk and Talnakh. These are:
i). Disseminated sulphides within the differentiated gabbro-dolerite sills, principally on the lower margins of the mineralised sills in the taxitic and to a lesser degree the picritic zones. They occur as droplets, schleiren and fine sulphide veinlets, forming sheet like conformable bodies up to 40 m thick and comprise combinations of chalcopyrite, cubanite and pyrrhotite with troilite and pentlandite. Grades average 0.5 to 0.6% Ni, 0.6 to 0.7% Cu, and 5 to 6 g/t PGE;
ii). Massive sulphides found principally on the lower contact of the mineralised sills, both within the enclosing rocks and to a lesser degree the sill, and are often separated from the sill by several metres of barren sediment or cupriferous mineralisation. Sometimes they are also found on the upper margin of the sill. In other locations the massive sulphides cut across the sill to its upper margins. The massive sulphides are divided into either pyrrhotite, cubanite or chalcopyrite types, depending on the dominant sulphide, with associated pentlandite moihoekite and talnakhite. Individual massive sulphide bodies may be up to 60 m thick as at Oktyabr'sky where it cover an area of 3.5 sq km. Grades vary drastically with the sulphide assemblage, but are of the order of 2.8% Ni, 5.6% Cu and 15 g/t PGE. There is evidence that the massive sulphides post date the disseminated sulphides; and
iii). Vein disseminations of 'cupriferous' ore which are found below the massive sulphide, between the massive sulphide and the lower margins of the sill, and within sediments on the upper margin of the sill, often associated with zones of 'skarn' altered brecciated dolerite and marl/argillite. They may be 10 to 20m thick. The main metallic minerals are pyrrhotite, pentlandite, chalcopyrite, cubanite, millerite, pyrite, magnetite, bornite, chalcocite, etc.
The total production + resource in the Noril'sk-Talnakh district are quoted by Naldrett (2004) at:
1.309 Gt @ 1.77% Ni, 3.57% Cu, 0.061% Co, 9.5 g/t PGE (including 1.84 g/t Pt, 7.31 g/t Pd).
Ore reserve and mineral resources at 31 December, 2011 (Noril'sk Nickel webpage, 2013) were:
Talnakh proved ore reserves
Massive sulphide ore - 46.867 Mt @ 2.71% Ni, 3.36% Cu, 5.81 g/t Pd, 1.33 g/t Pt, 0.15 g/t Au, 7.54 g/t 6PGM
Cuprous ore - 34.468 Mt @ 1.04% Ni, 4.19% Cu, 9.95 g/t Pd, 2.37 g/t Pt, 0.70 g/t Au, 12.44 g/t 6PGM
Disseminated ore - 40.966 Mt @ 0.45% Ni, 0.79% Cu, 3.49 g/t Pd, 1.29 g/t Pt, 0.19 g/t Au, 4.97 g/t 6PGM
TOTAL Talnakh proved ore - 122.301 Mt @ 1.48% Ni, 2.73% Cu, 6.20 g/t Pd, 1.61 g/t Pt, 0.32 g/t Au, 8.06 g/t 6PGM
Talnakh probable ore reserves
Massive sulphide ore - 79.074 Mt @ 2.55% Ni, 2.69% Cu, 4.84 g/t Pd, 0.89 g/t Pt, 0.14 g/t Au, 6.30 g/t 6PGM
Cuprous ore - 49.412 Mt @ 0.79% Ni, 3.53% Cu, 7.52 g/t Pd, 1.93 g/t Pt, 0.56 g/t Au, 9.67 g/t 6PGM
Disseminated ore - 32.996 Mt @ 0.37% Ni, 0.62% Cu, 0.76 g/t Pd, 1.29 g/t Pt, 0.19 g/t Au, 3.47 g/t 6PGM
TOTAL Talnakh probable ore - 161.482 Mt @ 1.56% Ni, 2.53% Cu, 5.17 g/t Pd, 1.18 g/t Pt, 0.28 g/t Au, 6.75 g/t 6PGM
Talnakh measured + indicated mineral resources
Massive sulphide ore - 20.470 Mt @ 4.23% Ni, 5.83% Cu, 12.95 g/t Pd, 2.54 g/t Pt, 0.51 g/t Au, 15.91 g/t 6PGM
Cuprous ore - 1.505 Mt @ 0.80% Ni, 2.26% Cu, 6.64 g/t Pd, 1.91 g/t Pt, 0.41 g/t Au, 8.74 g/t 6PGM
Disseminated ore - 1332.722 Mt @ 0.52% Ni, 1.05% Cu, 2.89 g/t Pd, 0.83 g/t Pt, 0.19 g/t Au, 3.89 g/t 6PGM
TOTAL Talnakh resources - 1354.697 Mt @ 0.57% Ni, 1.12% Cu, 3.04 g/t Pd, 0.86 g/t Pt, 0.19 g/t Au, 4.08 g/t 6PGM
Noril'sk disseminated ore
Proved reserves - 32.897 Mt @ 0.34% Ni, 0.48% Cu, 4.03 g/t Pd, 1.64 g/t Pt, 0.17 g/t Au, 5.98 g/t 6PGM
Probable reserves - 22.306 Mt @ 0.28% Ni, 0.36% Cu, 4.28 g/t Pd, 1.75 g/t Pt, 0.20 g/t Au, 6.37 g/t 6PGM
Measured + indicated resources - 25.802 Mt @ 0.33% Ni, 0.45% Cu, 4.24 g/t Pd, 1.67 g/t Pt, 0.15 g/t Au, 6.30 g/t 6PGM
Combined Talnakh and Noril'sk ores
Proved + probable reserves - 338.986 Mt @ 1.33% Ni, 2.26% Cu, 5.38 g/t Pd, 1.42 g/t Pt, 0.28 g/t Au, 7.12 g/t 6PGM
Probable reserves - 22.306 Mt @ 0.28% Ni, 0.36% Cu, 4.28 g/t Pd, 1.75 g/t Pt, 0.20 g/t Au, 6.37 g/t 6PGM
Measured + indicated resources - 1380.499 Mt @ 0.57% Ni, 1.11% Cu, 3.07 g/t Pd, 0.87 g/t Pt, 0.19 g/t Au, 4.12 g/t 6PGM
Inferred resources - 462.709 Mt @ 0.89% Ni, 1.85% Cu, 4.40 g/t Pd, 1.12 g/t Pt, 0.26 g/t Au, 5.75 g/t 6PGM.
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Travelling from Norilsk to Moscow, Russia .................... Friday 21 July 2006.
Travelling from Moscow, Russia to Beijing, China .................... Saturday 22 & Sunday 23.
Travelling from Beijing to Jinchuan in China by road .................... Monday 24 July 2006.
Jinchuan .................... Tuesday 25 to Wednesday 26 July, 2006.
The Jinchuan Ni-Cu-PGE deposit is located in north-central Gansu Province, China, some 300 km NNW of Lanzhou, and 1200 km to the west of Beijing.
The Jinchuan Ni-Cu-PGE deposit (>500 Mt @ 1.2% Ni, 0.7% Cu, ~0.4 g/t PGE), one of the largest magmatic sulphide deposits in the world, is located within the westernmost terrane of the North China Craton. It is hosted within the 6.5 km long, Neoproterozoic (~0.83 Ga) Jinchuan ultramafic intrusion, emplaced as a sill-like body into a Palaeoproterozoic suite of gneisses, migmatites, marbles and amphibolites, below an active intracratonic rift. The parental magma was high-Mg basalt, generated through melting of sub-crustal lithospheric mantle by a mantle plume during the initiation of Rodinia supercontinent breakup. The Lower Palaeozoic collision of the exotic Qilian Block with the breakup-related southern margin of the craton accreted a subduction complex, and emplaced voluminous granitic intrusions and foreland basin sequences within the craton, to as far north as Jinchuan. During the Cainozoic, allochthonous Lower Palaeozoic rocks were thrust up to 300 km to the northeast over cratonic basement, to within 25 km of the Jinchuan deposit.
The Jinchuan ultramafic intrusion was injected into three interconnected sub-chambers, each containing a separate orebody. In detail it comprises two intrusive phases with different characteristics, the Western Intrusion in the western sub-chamber, and the Eastern Intrusion in the other two. Both essentially comprises an olivine-orthopyroxene-chromite cumulate, with interstitial orthopyroxene, clinopyroxene, plagioclase and phlogopite, and is predominantly composed of lherzolite (~80%), with an outer rim of olivine pyroxenite and cores of mineralised dunite. Mineralisation occurs as disseminated and net-textured sulphides, predominantly within the dunite, with lesser, PGE rich lenses, late massive sulphide accumulations, small copper rich pods and limited mineralised diopside skarn in wall rock marbles. The principal ore minerals are pyrrhotite (the dominant sulphide), pentlandite, chalcopyrite, cubanite, mackinawite and pyrite, with a variety of platinum group minerals and minor gold. The deposit underwent significant post-magmatic tremolite-actinolite, chlorite, serpentine and magnetite alteration.
The volume of the Jinchuan intrusion accounts for <3% of the total parental magma required to generate the contained olivine and sulphide. It is postulated that mafic melt, intruded into the lower crust, hydraulically supported by density contrast buoyancy from below the Moho, ponded in a large staging chamber, where crystallisation and settling formed a lower sulphide rich mush. This mush was subsequently injected into nearby shallow dipping faults to form the Jinchuan intrusion.
The deposit was discovered prior to 1958, when the state owned predecessor of the Jinchuan Group Co., Ltd was founded to undertake its development. Mining commenced in 1960 at the No. 1 mine, including an early open pit, prior to going underground in 1963. The larger No. 2 underground mine commenced production in 1996 (pers.com., Jinchuan Mining, 2006).
Chai and Naldrett (1992) recorded that the deposit contained >500 million tonnes of ore @ 1.2 wt.% Ni, 0.7 wt.% Cu, based on Chinese ore reserve protocols. In addition, they stated that the ore carried PGE + Au totalling ~1 g/t. These tonnages and grades would make it the third largest high-grade sulphide nickel deposit in the world, after Sudbury in Canada and Noril'sk-Talnakh in Russia.
In 2006 the remaining reserve, based on 50 m centre drill intersections, was 432 Mt of ore, after a total historical production of ~90 Mt (pers.com., Jinchuan Mining, 2006). The bulk grade of the whole deposit in 2000 was 1.05% Ni, 0.66% Cu, 0.031% Co, 0.23 g/t Pt, 0.11 g/t Pd, 0.01 g/t Os, 0.01 g/t Ir, 0.01 g/t Ru, 0.005 g/t Rh, 0.001% Se, 0.0003% Te and 4.28% S, (pers.com., Jinchuan Mining staff, 2000), 0.1 to 0.6 g/t Au (Zhou et al., 2002). ..... MORE
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Travelling from Jinchuan to Beijing .................... Thursday 27 July, 2006, arriving before 18:00 pm.
The summaries above were prepared by T M (Mike) Porter from a wide range of sources, both published and un-published. Most of these sources are listed on the "Tour Literature Collection" available soon from the Nickel 2006 Tour options page.
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T M (Mike) Porter, of Porter GeoConsultancy
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