Platinum potential of the Pacific Rim of Ural-Alaskan type intrusions Yulia Nazimova & Greg Ryan. NZ Exploration Ltd

Transcription

1 Platinum potential of the Pacific Rim of Ural-Alaskan type intrusions Yulia Nazimova & Greg Ryan NZ Exploration Ltd

2 Topics to be covered by the presentation Ural-Alaskan (UA) type zoned complexes and Pt production Russian examples: Pt bed-rock deposits and Alluvial platinum deposits. Pacific Rim potential (with emphasis on New Zealand and Eastern Australia)

3 What are they - zoned Ural-Alaskan type complexes? clinopyroxenite dunite Pt placer Ural-Alaskan-type (UA) complexes are concentrically zoned ultramafic-mafic intrusions with a dunite core, surrounded successively by clinopyroxenite and gabbro rims. The dunite core - mainly its coarse-grained part - contains chromite as well as metallic platinum. UA complexes are sources for large placer platinum deposits. Because the platinum exists in free metallic form (Pt 3 Fe), the placers can be processed by simple gravity separation techniques.

4 Location of UA Intrusions

5 Location and historical production of UA Pt deposits Within mobile belts (majority) close to continental margins; intrusions are more or less deformed, and may also be partly tectonically dismembered UA intrusions occur in two distinct geological settings: Within rift systems in the stable continental platform (more rarely); the zonal structure and the pipe-like shape are normally perfectly preserved Urals Kamchatka 70km 2 50 km 2 Placer Pt production: Ural Pt Belt, Russia 380 t, Columbia Pt Belt (Choco) 150 t, Galmoenan, Kamchatka Russia 55 t, Good News Bay, Alaska - 25 t, Tulameen, BC Canada 680 kg 50 km 2 Kondyor, Russia 100 t Fifield, Australia 630 kg

6 Bedrock platinum potential intrusions Kamchatka Peninsular, Far East Siberia, Aldan Shield, Far East Both intrusions exhibit a zonal structure with a well-developed dunite core (about 75-80% of the volume), surrounded by a clinopyroxenite rim m 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.

7 Galmoenan intrusion Melkomukov, 1998; Nazimova, 2003 There are about 50 UA intrusions within the Kamchatka peninsular. They are associated with a 500 km long deep-seated fault system. Some of them are Pt-bearing, but only Galmoenan intrusion is known to have produced large alluvial deposits. It is located in the southern part of a tectonic outlier and represents an allochthon, which has been dislocated by 8-15 km from the line of the main thrust. Galmoenan intrusion is of Late Cretaceous age. It is elongate in a NE direction, 14 km long and 2 3 km wide.

8 Necessary criteria for bedrock platinum The presence of a well-developed dunite core is crucial for Pt mineralisation in any UA intrusion. 2 main types of dunite are distinguished: - Fine-grained; - Coarse-grained Fine-grained dunite Photo: Galmoenan massif Coarse-grained dunite

9 Platinum mineralisation associated with chromite Galmoenan Kondyor Urals Chromite Veined-disseminated, schlieren, and veined morphological types of Chromite are located in interstices between olivine porphyroclasts and in deformation fractures Pt Chr

10 Platinum 99% of platinum is represented by FePt alloys. Especially Isoferroplatinum (Pt 3 Fe). Chondrite-normalised PGE concentrations for UA complexes. PGE are all characterised by a serrated pattern with positive Ir and Pt, and negative Os, Ru, and Pd anomalies Platinum- Irridium geochemical type.

11 The only historical bed-rock Pt production from a UA intrusion was from the Ural s (Nishniy Tagil) 100 ya, where up to 1200 kg of Pt was mined from chromite stocks. Several mineralised zones have also been delineated recently at both Galmoenan and Kondyor. These zones are characterised by cm to metre-scale chromite segregations occurring sporadically within the dunite. Ore zones: Volumetric, linear, and tabular bodies represented by aggregates of many mineralised clusters Resources Galmoenan Kondyor x 200 m m x m Inferred 30 t Indicated x t Average Grade g/t 1-3 g/t Economic Cut off 0.6 g/t 0.8 g/t Indicated x t Ore Recovery % % Using appropriate exploration techniques in such settings would be critical to success. A very positive feature of such intrusions is that the platinum can be recovered by simple gravity separation

12 Zoned intrusions produce big Pt placer deposits Galmoenan -55 tonnes Pt Kondyor 100 tonnes Pt mining since 1993 from 7 creeks mining since km downstream 12 km Ledyanoy Placer: 2-3 km long, m wide, 0.4-5m thick, average grade g/m 3 Levtyrinvayam Placer: Length of 9 km, width of m thickness m, average grade g/m 3 70 km long, average width 300m. Typical thickness 2.4 m Average grade g/m 3 up to g/m 3 (in some parts inside the ring).

13 Placer platinum At both Galmoenan and Kondyor, 70-95% of the platinum occurs in the basal wash, with minor quantities on false bottoms. 97% of the PGM - Isoferroplatinum (Pt3Fe) Grain size 0.2-5mm (close to the intrusion) and mm (more distant 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.

14 New Zealand

15 New Zealand platinum potential Green Hills Complex 14 km 2. Map by Mossman, 1973 Dunite core 3 x 1.5 km

16 Green Hills Chromite mineralisation within dunite core Green Hills chromite Galmoenan chromite Platinum mineralisation in chromitites (Isoferroplatinum, Sperrylite) (by Arculus et all, 2000)

17 Green Hills potential, New Zealand The Green Hills prospect has been investigated by several companies including McIntyre Mines NZ Ltd , Sigma Resources NL , Waitiri Capital Ltd and Altan Minerals Ltd The exploration model was based on analogy with the Great Dyke and Stillwater not U/A intrusions. dunite The alluvial Pt potential was not investigated. While the deposit is very close to the coast, there are still several areas where significant Pt placers could have developed.

18 UA intrusions and ophiolite complexes have several similarities UA Intrusions UA Intrusions + Ophiolites Ophiolites Zoned intrusion Located within the same tectonic structure, and have similar age Linear complexes Dunite Wherlite (Ol+CPx) Clinopyroxenite Mafic/ultramafic rocks: dunite (Ol), peridotite, pyroxenite, gabbro Ol > Ni, Co Harzburgite (Ol+OPx), Lherzolite (Ol+CPx+OPx) (Fe, Mg) (Cr, Fe) 2 O 4 chromite Chromite mineralisation (Mg, Fe)(Cr, Al) 2 O 4 Chrom-spinel Pt PGE mineralisation Ir, Os, Ru

19 clinopyroxenite with minor peridotite and dunite unit up to 160g/t Pt in dredge concentrates with Pt:Pd =16:1 Takaka Riwaka Collingwood 1 2 Red Hills/ Livingstone Red Mountain/ Rotoroa Region coarse-grained isoferroplatinum 3 Potential areas for platinum placers Green Hills Waikawa Longwood 4

20 Fifield Platinum Belt, Eastern Australia The Fifield Ural-Alaskan belt extends over an area 500 km long (N-S) and 80 km wide (E-W). UA complexes in the Fifield area are generally pipe-like bodies which are circular or elliptical in plan view. The size of the intrusions varies from a few sq km up to 120sq km. Similar regional setting and geology with Kondyor. 630 kg Pt and 325 kg Au were produced from deep leads near Fifield during the 1890s-1900s (by Elliot et al, 1991)

21 Fifield Area Intensive exploration has been carried out on the intrusions themselves. Pt resources in Laterites: Owendale Intrusion (Du and Py): g/t (16 t Pt) Tout Intrusion (dunite core): g/t Pt (23 t Pt). 630 kg Pt from deep leads Pt leads -30 m wide, up to 3 km long. Grades: g/t Pt PGE = 90% Pt, 8% Os, 1% Ir, 1% Rh There has been very limited exploration that has specifically targeted placer Pt. Placer exploration has concentrated on the mined deep leads, and a small area near Owendale.

22 Fifield Platinum Belt, Eastern Australia Throughout the Belt, extensive exploration has been carried out mainly focused on the intrusion themselves, rather than on alluvial platinum potential. There is still good potential for alluvial Pt within the whole Belt. + laterite potential resources: Owendale Intrusion (Du and Py): g/t (16 t Pt); Tout Intrusion (dunite core): g/t Pt (23 t Pt). Mining production example: 3 t of Pt Yubdo Intrusion, Ethiopia

23 Kamchatka, Galmoenan 55 t Pt Urals, Nizhniy Tagil Fifield, Australia 180 t Pt?

24 Conclusion There is still excellent potential for discovering new Pt deposits throughout the Pacific Rim!!

25 New deposits still are waiting to be discovered! Thank you for your attention! 感謝您的關注! NZ Exploration Ltd