Yulia Nazimova & Greg Ryan

Alluvial and bedrock platinum, East Asia

NZ Exploration Ltd

Yulia: jul_nz@yahoo.com

Greg: pacificgeological@hotmail.com

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

Washing procedure

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).

There is a big potential to find similar stile of alluvial platinum deposit in many placers in the world including the East Asia.