Iron ore and gold, Eastern Goldfields, Central Yilgarn
Project
Summary
 Strong
demand from Chinese steel industry
Australia
one of two main suppliers of exported iron ore with high grade
product
Established
production from BIF in the Central Yilgarn near Red Rock’s
tenements by Portman Mining
Good
infrastructure
Takeover
of Portman Mining by Cleveland Cliffs Inc and plans for increased
production
Multiple
BIF horizons at Mt Alfred cover 14km of strike up to 90m above
the surrounding plain level
BIF
units are between 15m and 100m wide and easily accessible
from nearby station tracks
Aeromagnetic
data confirms continuity of BIF within the tenement and also
strike extensions for a further 75km south.
General - Area
The Central Yilgarn Iron project comprises three ELAs being
E29/560 Mt Ida, E29/581 Mt Alfred and E30/296 Mt Hope, collectively
covering approximately 460km2. Banded Iron Formation (“BIF”)
strike-length is significant within each of the tenements.
Results of previous surface sampling at Mt Ida include economic
grades of hematite and goethite iron ore with supporting low
phosphorus. The tenements are located in a region with good
infrastructure and existing iron ore production from the Koolyanobbing
operations of Portman Ltd.
Access to each of the tenements is good with sealed and formed
gravel roads directly linking the regional centre of Kalgoorlie
with each project area. A spur line at nearby Menzies provides
a rail link to deepwater port facilities at Esperance.
Exploration for gold, copper, uranium and nickel has been
carried out in the Central Yilgarn area. However no systematic,
modern efforts for iron ore have been carried out within the
current tenements despite these areas showing demonstrated
prospectivity for this commodity.
Geology
The tenements are in the central parts of the Yilgarn Craton
in Western Australia. The Yilgarn block is a segment of stable
Archaean crust composed of typical greenstone belts of volcanic,
sedimentary, and intrusive sequences interspersed between
large areas of granitic lithologies. The Yilgarn is well endowed
in commodities such as gold, nickel, copper, and iron. Major
gold camps include Kalgoorlie, Southern Cross, Leonora, Meekatharra
and Wiluna. Nickel production is sourced from the Mt Keith,
Kambalda, Lake Johnston, Forrestania and Ravensthorpe areas.
Iron production in the Yilgarn is predominantly from the Koolyanobbing
area in the Central Yilgarn, with smaller operations in the
Northwest Yilgarn that include Tallering Peak.
Tenements of the Central Yilgarn Iron project cover parts
of the generally north- striking Ularring and adjacent Illaara
Greenstone Belts. These belts comprise basalt, intrusive ultramafic
units, acid volcanics, interlayered clastic sediments, and
BIF bounded by granite to the east and west. Significant structural
deformation has resulted in regional scale folding, strong
foliation, medium-high metamorphic grades and thrust-repetition
of stratigraphy. Importantly, metamorphism and deformation
has altered original magnetite mineralisation in the BIF units
to hematite and goethite with a corresponding increase in
grade up to 67% Fe.
Koolyanobbing Iron Operation
Koolyanobbing Iron is owned and operated by Portman Ltd (“Portman”),
which is a subsidiary of US based Cleveland Cliffs Inc. The
operation is located approximately 150km southwest of the
Mt Ida, Mt Alfred and Mt Hope tenements, and 175km west of
Kalgoorlie. It currently produces some 5,000,000 tpa of ore
that is shipped to Asian markets via the port of Esperance.
Ore feed for the primary crushing facilities at Koolyanobbing
has historically been sourced from deposits at Koolyanobbing,
but more recently been supplemented with ore trucked from
resources at Windarling and Mt Jackson, 100km north. An expansion
of infrastructure from 5,000,000 tpa to 8,000,000 tpa is currently
underway.
Deposits at Koolyanobbing were first mined in 1948 by the
Western Australian Government to supply the charcoal iron
industry at Wundowie near Perth. Further deposits were developed
in the mid 1960s by BHP Ltd, who operated the mine until 1983.
Portman resumed mining in 1994 under a Joint Venture agreement
with the Anshan Iron and Steel Complex of China. In 2000 Portman
took 100% ownership and looked toward expanding the Koolyanobbing
operation with increased ore feed from satellite ore-bodies
at Mt Jackson and Windarling.
Iron ore is sourced from BIF hosted ore-bodies in greenstone
sequences; a similar geological setting to that at the Mt
Ida, Mt Alfred, and Mt Hope areas. The primary iron formation,
which has been strongly folded and thickened, is composed
of banded magnetite-talc schist and quartz-magnetite containing
some pyrite, and siderite and massive pyrite containing some
specular hematite, magnetite and graphite.
The original Dowd's Hill deposit at Koolyanobbing had a strike
length of 900 m, varied from 50m to 300m in width, and extended
for 50m to 80m below the current ground level. The ore comprised
hard, massive goethite, coarse grained, friable specular hematite,
some massive fine grained hematite, yellow limonite, and minor
magnetite. Bands of chlorite schist and friable iron-leached
jaspilite also occur within the ore zones. The average grade
of the ore between 1967 to 1972 when 8Mt was mined was 61.4%
Fe, 0.13% P with 6% LOI. In 2004, global resources (Inferred,
Indicated and Measured) of goethite and hematite ore for the
Koolyanobbing, Mt Jackson and Windarling ore-bodies was 149.5Mt
at 62.13% iron, 0.11% phosphorus and 6.71% LOI.
General - Mt
Alfred
The Mt Alfred tenement is located 135km northwest of Menzies
and 260km north of Southern Cross in the Southern Yilgarn,
covering an area of 210km2. Access from Kalgoorlie is via
the sealed Wiluna Road to Menzies then by the formed Menzies-Sandstone
road that traverses the tenement from north to south. Access
within the project area is via pastoral station tracks.
Geology
and Mineralisation
Rocks of the Illaara greenstone belt constitute an interlayered
metamorphosed sequence of greywacke sediments, BIF, basic
and acid volcanic rocks, together with coarse grained basic
and ultramafic intrusive rocks. Granitic lithologies bound
the belt’s eastern and western margins. Folding is ubiquitous
in the BIF throughout the area. These are represented by major
flexures of the whole units about south-plunging axes, and
by small scale folds intraformational to the fine-scale layering.
Eastern parts of the tenement include large areas of BIF accumulation,
while central parts show repetition of this stratigraphy.
In the east, multiple BIF horizons cover 14km of strike and
form a prominent line of north striking hills that are up
to 90m above the surrounding plain level. BIF units are between
15m and 100m wide and are easily accessible from nearby station
tracks. Hematite and goethite mineralisation has been confirmed
by previous workers but no analytical data including iron
is recorded.
Aeromagnetic data interpretation confirms the strike continuity
of the BIF units within the Mt Alfred tenement and extensions
for a further 75km south. A significant portion of the BIF
extensions are held by Portman who intend to evaluate it with
traditional methods of exploration for iron ore.
Mt Alfred also warrants exploration for iron ore with multiple
horizons of hematite and goethite mineralised BIF strike.
BIF stratigraphy forms a prominent line of hills that continue
for some 14km and stand up to 90m above the surrounding plain.
Aeromagnetic data confirms continuity of BIF within the tenement
and also strike extensions for a further 75km south. Much
of the southern BIF extensions are held by Portman who intend
to evaluate the ground with traditional methods of iron ore
exploration.
History
The iron ore prospectivity of the Mt Alfred area was first
recognised by Clough and Sons Pty Ltd in the late 1960s who
acquired licences over the area to evaluate the extensive
strike of BIF. However, all its efforts became focused on
the Mt Caudan disco south of Southern Cross and, as a consequence,
no work was completed at Mt Alfred.
Between the mid 1970s and mid 1990s, Norgold Ltd, the Electrolytic
Zinc Company Ltd and Sipa Resources Ltd carried out exploration
for gold and copper. Work included stream sediment sampling,
rock-chip sampling, and drilling; but even though much BIF
was sampled in the course of exploration, analysis did not
include iron. Drilling immediately north of the Mt Alfred
tenement returned 2m at 0.41g/t gold.
In the mid 1970s Uranerz Australia Pty Ltd briefly evaluated
the eastern shores of Lake Barlee (that impinges on the western
parts of the tenement) for uranium. Anomalous results were
returned but no resource was defined.
In summary, although much exploration has taken place over
the Mt Alfred tenement, none has specifically been for iron
ore. This is despite the confirmation of hematite mineralisation
in the BIF units, and their large strike extent.
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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