alluvial and bedrock platinum, east asia platinum...yulia nazimova & greg ryan alluvial and...
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Yulia Nazimova & Greg Ryan
Alluvial and bedrock platinum, East Asia
NZ Exploration Ltd
Yulia: [email protected]
Greg: [email protected]
General issues of the presentation
Ural-Alaskan (UA) type zoned complexes and Pt production
Geology of the UA intrusions
Pt bed-rock mineralisation and exploration techniques.
Alluvial platinum exploration and mine.
The presentation focusses only on one specific type of complexes – the UA intrusions
because only this type can produce both bed-rock and alluvial Pt deposits.
What are they - zoned Ural-Alaskan type complexes?
UA-type complexes are concentrically zoned ultramafic-mafic
intrusions typically ranging in size from 12 to 80 sq km, which
exhibit a zonal structure with a dunite core, surrounded
successively by clinopyroxenite and gabbro rims. The dunite
core - mainly its coarse-grained part - contains chromite
mineralisation as well as metallic platinum.
dunite
clino-pyroxenite
Pt placer
The most productive economic deposits of alluvial platinum in the world are
associated with ultramafic zoned complexes of Ural-Alaskan (UA) type.
Location and production of UA Pt deposits
Ural Pt Belt – 380 t Pt,
Kamchatka Pt Belt-Galmoenan – 55 t Pt,
Alaska belt-Good News Bay – 25 t Pt,
BC, Canada, Tulameen complex – 680 kg
Kondyor, Russia – 90 t Pt
Fifield, Australia – 630 kg
50 km2 70km2
50 km2
Urals Kamchatka
They occur in two distinct geological settings:
Within mobile belts (majority) close to
continental margins; intrusions are more or
less deformed, and may also be partly
tectonically dismembered
Within the stable continental platform (more
rarely); the zonal structure and the pipe-like
shape are normally perfectly preserved
Both intrusions exhibit a zonal structure with a well-developed dunite core (about
75-80% of the volume), surrounded by a clinopyroxenite rim 50-500m wide and
some gabbroid occurrences. In Kondyor, a later phase of alkaline rocks has
developed, forming a network of veins in the dunite and clinopyroxenite.
Kamchatka Peninsular, Far East
Siberia, Aldan Shield, Far East
Pt-bearing intrusions of UA type in East Asia
Galmoenan intrusion
There are about 50 UA intrusions within the Kamchatka peninsular. They are associated with
a 500 km long deep-seated fault and regional trust. Only one of them, Galmoenan intrusion, is
Pt-bearing. It is located in a southern part of the tectonic outlier and represents an allochthon,
which has been disclocated by 8-15 km from the line of the main thrust. Galmoenan intrusion
is of the Late Cretaceous age. It is elongate in a NE direction for 14 km long, 2–3 km wide.
Melkomukov, 1998;
Nazimova, 2003
Kondyor Intrusion
The Kondyor intrusion is located in the Russian Far East, about 1100 km north of the
city Khabarovsk. Forming a circular, chimney-like structure about 8 km in diameter
and at least 10 km deep, the massif has a dunite core 5.5 km in diameter. Age
determinations are inconclusive, ranging from Mesozoic to Archean–Early
Proterozoic (about 2.5 Ga)
Photo: Galmoenan massif
2 main types of dunite are distinguished:
- Fine-grained;
- Coarse-grained
The presence of a well-developed dunite core is a
crucial for Pt mineralisation in any UA intrusion.
Fine-grained dunite
Coarse-grained dunite
Fine-grained dunite Coarse and very coarse-grained dunite
Texture,
features
hypidiomorphic-to-allotriomorphic,
At the contact with pyroxenites the structure of
the dunites resembles cumulus.
The presence of rare grains of clinopyroxene.
porphyroclastic crystalloblastic
the presence, in olivine,
of regularly oriented
micro-inclusions of
chrome-magnetite, which
predetermines its
characteristic black
colour
wide variations in grain-size of
olivine, uneven, winding
boundaries of its grains,
carrying traces of strong, inner
plastic deformations, a partial
or full disappearance of micro-
inclusions of chrome-magnetite.
Olivine composition Fo = 83,2 (15 analyses)
SiO2=40.84, MgO=48.73, FeO*=9.83,
CaO=0.11, MnO=0.21, NiO=0.20
Fo = 87,2 (41 analyses)
SiO2=41.42, MgO=50.3, FeO*=7.4,
CaO=0.10, MnO=0.18, NiO=0.21
Chromspinel Mainly accessory and dessiminated
chromspinel. It is distributed quite regularly in
the rock and is observed in two structural
positions: inside olivine grains and in
interstitions. The ore segregations of chromspinel
in this type of dunite are not typical.
Wide development of segregations of chromspinel of
veined- disseminated, schlieren and veined
morphological types (chromite ore), located in
interstitions of olivine porphyroclasts and fractures of
deformation, associated with later generations of
olivine.
Chromspinel
Composition
(% by weight).
From hypidiomorphic-to-allotriomorphic dunite
( 28 an)
---------------------------------------------------
MgO = 7.44
Al2O3 = 8.13
Cr2O3 = 40.39
MnO = 0.62
Fe2O3 = 12.24
FeO = 21.41
TiO2 = 0.44
From porphyroclastic dunite
(26 an)
-------------------------------------
MgO = 8.85
Al2O3 = 7.92
Cr2O3 = 47.11
MnO = 0.55
Fe2O3 = 16.70
FeO = 19.17
TiO2 = 0.29
From crystalloblastic
dunite (44 an)
-------------------------------------
MgO= 9.6
Al2O3 = 7.7
Cr2O3 = 48.4
MnO = 0.74
Fe2O3 = 16.55
FeO = 17.7
TiO2 =0.25
The degree of
serpentinisation
more than 70% 10-20% absent
Two major types of dunite
PGM, extracted from fine-grained dunites
Pt3Fe
Os
Os
Pt3Fe
PtFe
PtFe
Pt3Fe
PtFe
Pt3Fe is observed in a form of independent, fine (3-15 micron) idiomorphic grains.
Platinum in fine-grained and coarse-grained dunite is different in size, mineral and chemical composition
Pt2FeCu
Serp
IrAsS
Pt2FeCu
Pt3Fe
are characterized by xenomorphic grains of the size up to a few cm. It is localized mainly in
interstitions of chromite and olivine and along deformation fractures in them
Fine-graned dunite:
very simple mineral composition
Coarse-grained dunite:
About 56 PGE minerals were distinguished
Platinum 99% platinum is represented by Fe-Cu-Pt alloys. Among them, Isoferroplatinum (Pt3Fe)
is the main.
All of them are characterized by a serrated pattern with positive
Ir and Pt , and negative Os, Ru, and Pd anomalies – Platinum-
Irridium geochemical type.
Chondrite-normalized PGE concentrations
for UA complexes.
Pt
Everywhere, Platinum mineralisation is in association with chromite
Galmoenan Urals
Pt
Chr
Chromite
Kondyor
veined-disseminated, schlieren,
and veined morphological types
of chromite are located in
interstices between olivine
porphyroclasts and in
deformation fractures
Southern part of Galmoenan (Nasimova, 2003)
In the southern part of the Galmoenan intrusion are delineated two mineralized zones that strike for 1300 and 500 m respectively, 200 m wide.
P2 (inferred) resources – 30t Pt
Several mineralised zones have been delineated on both Galmoenan and Kondyor. These
zones are characterised by cm to metre-scale chromite segregations occurring sporadically
within the dunite.
The only historical bed-rock Pt production was in Ural’s (Nishniy Tagil)100 ya, where was
mined 300 kg of Pt from chromite stock.
Platinum distribution within the chromite segregations is very irregular,
with variations up to 340% having been encountered in individual
samples. The “nugget effect” (isolated assays up to 100s of ppm Pt) is
very characteristic of this style of mineralisation.
Bed-rock Platinum Mineralisation
The average grain-size of the PGM is 380 µm. Despite the
presence of large quantities of small inclusions of PGM (50%,
<0.05 mm), the bulk (70%) of the actual metal content is
composed of grains >0.4 mm
Representative sample should be not les than 250 kg
The general features of PGM in zoned complexes. PGE concentrations associated with very coarse-grained dunites and chromitites is
characterized by a strong predominance of Pt-Fe alloys (Isoferroplatinum –Pt3Fe);
rather small dimensions of the ore bodies ( majority of chromite segregations in dunite are from 10 cm to meter and a half long and few centimeters wide), occurring in groups or as isolated lenses and nests of irregular shape;
a very irregular distribution of platinum within the ore body.
extremely high Pt grade of ores (at the deposit “Gosshakhta”, Nizhny Tagil, the average grade in near surface parts reached 400g/t);
There is potential for economically mineable platinum deposits to exist within UA intrusions, particularly in Kondyor and Galmoenan. But such deposits are likely to comprise aggregates of many mineralised clusters, occurring with sufficient density and grade to be viable.
Using appropriate exploration techniques in such settings would be critical to success.
the trench and drill samples should be no less than 250 kg per 1m interval, in order to give
reliable and repeatable results.
It is also necessary to generate average grades over relatively large blocks. Pilot processing
of bulk (several tonnes) samples should be part of this process.
Preconcentation before sending samples to the analitical labs.
A very positive feature of such intrusions is that the
platinum can be recovered by simple gravity separation
Alluvial platinum. Galmoenan intrusion, Kamchatka,
Since 1993,8 platinum placers have been delineated at Galmoenan. Of the 7 currently being
mined, the biggest, Ledyanoy and Levtyrinvayam, have produced about 25 t of platinum each.
The Ledyanoy placers formed in several creeks close to the intrusion, with productive horizons typically 2-
3 km long, 20-130m wide and 0.4-5m thick, with average grade varying from 0.4-7 g/m3. Overburden
thickness varies from a few metres to 60m.
Interestingly, the Levtyrinvayam placer commences 12km from the intrusion. Various theories have been
proposed to explain this but none has been substantiated. With a length of 9 km, width of 250-400m and
thickness of 2.5-4m, the average grade of the productive horizon varies from 0.8-5.2 g/m3. Overburden
thickness is typically 7-8m.
The Kondyor placers occur both inside the ring structure (Kondyor River and its tributaries)
and beyond the gorge through the ring, where the Kondyor flows into the Uorgalan River.
Platinum placers are known to extend for 70 km downstream, with the average width 300m.
Mining began in 1984 and annual production is still 3-4 tonnes. The average platinum grade
varies from 0.5-5 g/m3 up to 60-80 g/m3 (in some parts inside the ring). Productive horizons
typically 2.4m thick with the overburden thickness up to 5.5m.
Beside the platinum, the heavy concentrate contains also chromite (2.5-8%), titanomagnetite
(nuggets) and gold (first tens of mg/m3)
Kondyor Placer
The alluvial deposit has been subdivided into 5 complexes of different ages (Pliocene-Early
Pleistocene, Middle Pleistocene, Early and the second half of Late Pleistocene, Holocene.
At both Galmoenan and Kondyor, 70-95% of the platinum occurs in the basal
wash, with minor quantities on “false bottoms”. Isoferroplatinum (Pt3Fe)
comprises 97% of the PGM, with grain size varying from 0.2-5mm close to the
intrusion and from to 0.05-0.5mm more distant from the intrusion. Grains also
become more rounded with increasing distance from the intrusion.
Typically 2.5% of the concentrates are composed of nuggets. Kondyor has
produced more than 20 nuggets weighing more than 1 kg, the largest being 3.5kg.
The largest nugget from Galmoenan was 1.2 kg. Chromite and magnetite are also
present in the concentrate and minor gold occurs at Kondyor.
Placer platinum
Placer Mine Alluvial mine
Because the platinum exists in free metallic form (Pt3Fe), the placers can be processed by simple
gravity separation techniques
Cleaning the concentrate
Cradle and crushing (several stage)
Magnetic separation
Concentration Table
Placer exploration Alluvial platinum exploration in Russia, employs similar techniques to those used for
alluvial gold. Once good source rocks have been located, the downstream river systems are
systematically drill-tested. Because the placers are generally several kilometres long,
reconnaissance grids typically have 1km line spacing, with 20-40m hole spacing along the
grids. Once placers are located, the line spacing is progressively reduced. In areas with
coarse gold (suggesting the presence of buried channels), the hole spacing is also reduced.
The main rig used for placer exploration in Russia is the
UKB rig. It is similar to a very large (sludge pump section
is 150mm in diameter) cable tool rig, which also
incorporates a hammer system, that breaks up large rocks
and helps the drill string to work down through the
sediment. Rigs usually operate in pairs, with a mobile lab
between them. Drill rates of 2000-3000m per month can
be achieved, with samples processed as drilling proceeds.
In permafrost, it may be possible to drill to 100m depth
without using casing.
Drilling equipment
Sampling processing procedure
Research shows that the optimum sample interval is
0.4m. Sample processing is carried out on site.
Coarse sample material is reduced in a concrete
mixer-like machine with a 3mm sieve. A centrifuge
produces a heavy mineral concentrate, which is sent
to the lab, where the platinum is separated under
binocular microscope and weighed. Grade polygons
can then be assigned to each drill hole, to facilitate
resource estimation.
Platinum Placer location - Pacific Rim
Alaska
British Columbia,
Kamchatka
Konder, Russia
Fifield,
Australia New Zealand
This presentation is based on Yulia’s 10 years work in the Galmoenan area, consulting work on the Kondyor
deposit, Greg’s extensive experience working on placer deposits, as well as his visit to the Galmoenan placers.
The authors have also reviewed the following publications:
1. Koryaksko–Kamchatsky region – a new platinum province of Russia.// Saint-Petersburg Cartographic Factory,
VSEGEI Press, 2003, pp. 283-315 (in Russian).
2. Bogdanovich A.V., Petrov S.V., Nazimova Yu.V., Vasilyev A.M.,Urnysheva S.A. (2010): Peculiarities of
processing minerals with high non-uniformity of valuable components distribution (example of platinum ores).//
Obogashcheniye rud, 2, pp 3-8 (in Russian).
3. Mochalov, A.G. & Khoroshilova, T.S. (1998): The Kondyor alluvial placer of platinum metals.// Proc. Int.
Platinum Symp. Theophrastus Press, Athens, Greece, pp 206-220.
4. Malitch K. N., Efimov A. A., Badanina I. Yu. (2012): The Age of Kondyor Massif Dunites (Aldan Province,
Russia): First U–Pb Isotopic Data // Doklady Earth Sciences, Vol. 446, Part 1, pp. 1054–1058
5. Malitch, K.N. (1999): Platinum-Group Elements in Clinopyroxenite–Dunite Massifs of Eastern Siberia
(Geochemistry, Mineralogy, and Genesis).// VSEGEI Press, St. Petersburg, Russia (in Russian).
6. Melkomukov V.N., Zaytsev V.P. (1999): Platinum placers of Seynav–Galmoenan knot (Koryak–Kamchatka
province).// Platinum of Russia,III, pp 143-149 (in Russian).
7. Nazimova Yu.V., Zaytsev V.P., Petrov S.V. (2011): The Galmoenan massif, Kamchatka, Russia: geology, PGE
mineralization, applied mineralogy and beneficiation// Canadian Mineralogist, v.49, 6, pp 1433-1453
8. Nekrasov I.YA., Lennikov A.M., Oktyabrsky R.A., Zalishchak B.L.,Sapin B.I. (1994): Petrology and Platinum
Mineralization of the Alkaline-Ultramafic Ring Complexes. Nauka, Moscow, Russia (in Russian).
9. Petrov S.V., Nazimova Yu.V., Bogdanovich A.V. (2010): Applied PGE mineralogy and ore beneficiation of the
Galmoenan deposit, northern Kamchatka.// Proc. 11th Int. Platinum Symp. (Sudbury).