Manganese and gold in the East Pilbara
Project Summary
 90%
manganese used for steelmaking
strong
demand from Chinese and Indian steel industries foreseen
Australia
became largest producer in 2004
East
Pilbara an established producer with growing capacity and
well placed to meet regional demand
Red
Rock has major acreage position in prospective areas
Sampling
of Red Rock tenements has given some high grade results
591
ppb Au in streams indicates unexplored gold potential
General
Manganese is essential to iron and steel production by virtue
of its sulphur-fixing, deoxidizing, and alloying properties.
Steelmaking, including its iron-making component, has accounted
for most of the manganese demand. Among a variety of other
uses, manganese is a key component of widely used aluminium
alloys and is used in oxide form in dry cell batteries.
Red Rock’s Oakover Project comprises four Exploration
Licence applications covering 695 km2 in the Eastern Pilbara
Region of Western Australia, which is fast emerging as a world
class manganese (and gold) province. The tenements are situated
on the eastern margin of the Pilbara Craton, some 250 kilometres
east-southeast of Port Hedland, 1,300 kilometres north-northeast
of Perth, and within 40 km to 80 km of the Woodie Woodie mine.
The manganese production from the Woodie Woodie mine owned
and operated by Consolidated Minerals Ltd (“CML”)
already accounts for 5% of the world’s supply. Furthermore
CML is in the process of upgrading the mining and production
facilities. This aims to achieve a 60% increase in its manganese
production during the first half of 2005 after announcing
in mid-December the completion of its A$6.5 million expansion
project, underpinning a new long-term production level of
1 million tonnes per annum.
The current market for manganese is strong with the Chinese
Steel industry requiring an estimated 3.5 million tonnes of
+45% Mn in 2004. Demand for increased manganese ore from Chinese
steel mills is anticipated to at least remain steady if not
increase over the next three years.
There is a strong possibility that demand from India will
increase over the next few years and thus contribute to further
requirements for manganese ores. This represents probable
sustainability of the manganese price for the mid-term future
(5 to 8 years) and more than likely longer-term as the steel
industry shows no signs of abating.
Current production of manganese concentrate from Woodie Woodie
is approximately 600,000tpa. In the region, manganese mineralisation
has also been identified at areas including Mt Sydney, Ripon
Hills, Bee Hill and Rove Hill. Manganese mineralisation has
been identified at numerous prospects within each of Red Rock’s
tenements but have only had cursory attention.
Also geologically significant is that the Oakover Project
tenements are proximal to the major Telfer gold mine (Measured/Indicated
400Mt at 1.5 g/t Au) and the Nifty copper mine, where the
Measured/Indicated resources total 28 Mt at 3.0% Cu. A number
of strong gold in stream anomalies have been outlined within
the current tenements but no follow-up has been carried out.
Existing infrastructure is already in place from relatively
nearby mining operations (Woodie Woodie manganese and Telfer
gold mines) that will help accelerate the proposed exploration
and possible development of the Oakover Project. This infrastructure
includes a bitumen road all the way through to the deep-water
port at Port Hedland, local pastoral station airstrips and
overnight road transport of supplies for machinery and spare
parts from the regional mining centre of Newman. Port Hedland
is a major iron-ore exporting port providing access to Asian
markets.
Geology and Mineralisation
The regional geology of the project area comprises the eastern
part of the Archaean-Proterozoic Pilbara Craton, and to the
east, portions of the Gregory Range granitic complex and the
Paterson Orogen. These are overlain by Mesoproterozoic-Phanerozoic
rock sequences of the North Carnarvon and Canning Basins.
The basement of the Archaean granite-greenstone is characterised
by linear to curvilinear granitoid sequences that envelop
elongate and avoid granitoid complexes.
The greenstones include metamorphosed mafic to ultramafic
volcanic rocks, felsic to intermediate volcanic rocks, clastic
sedimentary rocks, cherts, banded iron formation (“BIF”)
and sills of mafic to ultramafic intrusives. The granitoid
complexes are large, domal, composite bodies with some complexes
containing enclaves of metamorphosed greenstones in layered
mafic-ultramafic bodies.
The Canning Basin rocks consist of Palaeozoic-Mesozoic sequences
which lie unconformably on Pre-Cambrian basement. The North
Carnarvon Basin comprises post-Permian sediments. All the
above have an extensive surficial cover derived from weathering,
erosion and transport.
The structural setting of the Pilbara Craton is currently
under review. In summary, the most conspicuous structures
are broad, domal granitoid complexes separated by synformal
greenstone belts, having broad lateral continuity. Alternative
models suggest that modern plate-tectonic processes have operated
in the evolution of the granitoid-greenstone-basement and
that the major lineaments represented large-scale crustal
features having a long history of development and reactivation.
Diagrammatic sections across the eastern side of the Pilbara
Craton in the vicinity of Red Rock’s Oakover Project
have been derived from both geological mapping and geophysical
(aeromagnetic) interpretation. This work reveals a series
of near-vertical easterly dripping faults and shear zones,
the most important of which are the Bamboo Creek Shear Zone
and the Baramine, Camel Hump and Vines Fault/Thrust.
The geological and structural settings of the four tenements
comprise Archaean aged basalts, tuffaceous sediments, dolomites
and chert breccias which are overlain by the Proterozoic aged
Pinjian Chert Breccia and Manganese Group sediments. Past
sampling records returned manganese grades generally in excess
of 25% Mn and as high as +50% Mn. These manganese-bearing
sediments form part of the manganese-rich region of the Oakover
Basin which was referred to as the ‘Pilbara Manganese
Province’.
There are three main manganiferous sedimentary source rocks
in the East Pilbara area of which two, namely the Carawine
Dolomite and the associated overlying Pinjian Chert Breccia
occur within the Project area.
The current tenements cover strong surface gold anomalies
of up to 591 ppb Au that are ready for follow-up work. The
geological setting is highly favourable for hosting large
gold ore-bodies especially of Telfer and Carlin type.
The project area lies at the east edge of the Archaean Pilbara
Craton in an ancient continental margin setting, similar to
the newly recognised Ashburton gold province, which hosts
Sipas’ Mt Olympus deposits at the south edge of the
Craton. During the Proterozoic the Oakover area was an obliquely
convergent continental collision regime, creating a set of
westwardly directed thrusts, transgressional NW trending faults
and tensional NS faults. This intense structural regime has
created both a deep-tapping system for access of gold bearing
fluids, and structurally prepared sites for gold mineralisation.
The giant Telfer gold deposit lies 140km to the east. It is
significant that the Oakover Project gold anomalies lie in
a corridor that includes Telfer and the major Pilbara gold
deposits, such as Bamboo Creek. Also, there is a clear regional
association with known manganese deposits, such as at Woodie
Woodie and Ripon Hills, hosted in Carawine dolomite.
It is possible that these manganese deposits occur peripheral
to a major undiscovered gold mineralised system, because in
the outermost zone of some porphyry copper systems manganese
is deposited after being leached out of the host rocks in
the inner zones.
History
In 1924, Government Geologist, Blatchford, reported manganese
occurrences in the Barramine-Braeside region east of the Oakover
River. In 1938, Finucane (GSWA geologist) mapped manganese
occurrences west of the Braeside area. In the early 1950s,
following the rise in price for manganese, extensive exploration
of the Oakover River drainage basin was carried out. The main
areas of known manganese mineralisation were assessed at Woodie
Woodie, Mount Sydney, Ripon Hills, Mount Cooke, Syndam Hill,
Skull Springs and Ant Hill, Bee Hill, Yarrie and Nimingarra
(de la Hunty 1963). Production from WA in 1960 was reported
as 434,563 tonnes grading 47.3% Mn.
In 1989 and early 1990s, again following an increase in the
price of manganese, redevelopment of the Woodie Woodie mine
occurred and other companies namely; CML (then Portman Mining
Ltd), Hancock Mining, Pennant Resources, King Mining and Sovereign
Resources carried out regional exploration that identified
additional manganese mineralisation.
Table
1 - Selected results from Valiant’s
sampling within Red Rock’s current tenements.
| Block ID |
Occurrence ID |
Mn % |
Fe % |
Si % |
| 804t |
b301 |
50.64 |
0.96 |
9.58 |
| 804t |
b311 |
53.4 |
2.95 |
4.42 |
| 804z |
b292 |
49.67 |
6.65 |
4.04 |
| 949f |
b026 |
51.66 |
5.44 |
2.85 |
| 949f |
b027 |
53.74 |
3.35 |
3.22 |
| 949f |
b054 |
54.24 |
4.41 |
1.86 |
| 949l |
b031 |
53.77 |
2.74 |
5.54 |
| 949m |
b012 |
51.1 |
8.73 |
4.5 |
| 949m |
b045 |
45.44 |
13.1 |
3.19 |
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Table 1 above shows assays from surface samples taken by Valiant
during its 1992-93 exploration program with one of the current
tenements. The manganese values are comparatively high whilst
the iron and silica values vary from low to high. The block
ID refers to the graticular tenement blocks of one minute
of latitude x one minute of longitude.
In 1993, Valiant Consolidated Limited (“Valiant”)
discovered the Mike deposit near Woodie Woodie and also purchased
the Woodie Woodie deposit from Portman Mining. These operations
closed in 1998, following another downturn in the price of
manganese. In April 1998, Portman changed its name to CML.
Since that time, extensive exploration and development have
led to CML becoming a leading world producer of manganese.
Based
on an independent geological assessment of the Australian
Manganese and Iron Projects located in the States of Western
Australia and Tasmania, Australia by Al Maynard and Associates
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