REG - Empire Metals Ltd - “Giant” Copper Province Potential at Pitfield

Empire MetalsAnnouncement

25/10/2022 07:00

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RNS Number : 9420D  Empire Metals Limited  25 October 2022

Empire Metals Limited / LON: EEE / Sector: Natural Resources

 

25 October 2022

Empire Metals Limited

("Empire" or "the Company")

 

"Giant" Copper Province Potential at Pitfield Confirmed by Expert Review

 

Empire Metals Limited (LON: EEE), the AIM-quoted resource exploration and
development company, is pleased to announce the results of an expert review on
the Pitfield Copper Project ('Pitfield'), located in Western Australia.
Results from the review which evaluated recent geophysical surveys and the
historical exploration database at Pitfield, confirmed that Pitfield has all
the hallmarks of a "Giant" copper mineralised system.

 

Highlights

·    Pitfield confirmed as having all the hallmarks of a "Giant" copper
mineralised system, potentially containing multiple sediment-hosted
stratabound copper (SSC) deposits.

·    An exceptionally large, magnetic anomaly, extending over 40km N-S has
been identified at Pitfield.

·    SSC deposits are globally significant geological systems which
deliver ~20% of copper production globally and are often very large and
high-grade deposits.

·    The Pitfield geological setting compares favourably with the
sandstone sub-type of SSC, exemplified by the massive Udokan Ore Region in
Russia.

·    Empire to accelerate exploration activities at Pitfield in Q1 2023
including surface mapping, Induced Polarisation (IP) surveying and geochemical
sampling with multiple exploration targets already identified

·    Expert Review undertaken by the Company's exploration team under the
supervision of Ed Baltis (Exploration Consultant) who has more than 30 years'
experience with Western Mining Corporation, Gold Fields and as a consultant in
gold, copper and nickel exploration with a strong focus in Western Australia,
and Dr Neil O'Brien, a PhD economic geologist and former mining executive with
35 years of international experience including with Giant copper deposits
worldwide.

 

Shaun Bunn, Managing Director, said: "We previously held a strong belief that
Pitfield had the potential to contain a major copper deposit with world-wide
significance.  The results of this expert review, which drew on the findings
of the recently completed geophysical surveys, confirm the accuracy of the
historical data we inherited and have identified the regional geological
features consistent with a Giant copper mineralised system.  This makes
Pitfield an exciting exploration target for a SSC deposit and an exceptional
project for us to focus our exploration efforts on.

 

"SCC type deposits are often very large and high-grade deposits and account
for approximately 20% of the world's copper production.   We are looking
forward to increasing our understanding of Pitfield as we embark on our next
phase of exploration which will include surface mapping, Induced Polarisation
(IP) surveying and geochemical sampling. Work is expected to commence in Q1
2023."

 

Technical Highlights

·    Pitfield lies within the Neoproterozoic Yandanooka intracratonic
sedimentary basin which has all the hallmarks of a "Giant" copper mineralised
system, potentially containing multiple SSC deposits.

·    The Neoproterozoic is one of the major SSC mineralisation epochs,
temporally associated with the break-up of the Rodinia supercontinent and is
associated with several of the largest copper SSC deposits discovered to date,
the most important deposits being located in the Central African Copperbelt of
Zambia and the DRC.

·    Widespread copper, silver, nickel and zinc anomalism has already been
identified over large parts of the Yandanooka basin by previous explorers,
particularly in association with magnetite-altered rocks.

·    An exceptionally large, oxidised fluid event has occurred, extending
over 40km N-S, as evidenced by magnetite-altered stratigraphy and
corresponding reduced conductance - likely due to removal of graphite in the
siltstone.

·    This basin-scale alteration extends beyond the magnetite altered
domain as seen in sporadic diamond drilling (which also indicated widespread
Cu depletion in the basement rock) and the formation of the Three Springs
(Imerys) talc deposit to the immediate east of Pitfield.

·    Our Pitfield geological model is based on a basin scale alteration
event, involving hot oxidising, fluids carrying copper leached from the "red
beds" and basement mafic rock, which upon contact with reductants within the
upper siltstones/sandstones resulted in the copper precipitating and
depositing along the reduced stratigraphic layers.

 

Future Work Planned

Pitfield remains an early phase exploration project and as such requires
further surface exploration work to effectively define geochemical (soils,
auger and AC drilling) and geophysical anomalies (electrical surveys such as
IP) prior to evaluating their economic significance through drilling.

 

The interpretive geological mapping has provided multiple exploration targets
which will be followed up with further field work in the coming months.  Land
access agreements with local farmers are required for some of the areas of
interest.

 

Geological Model for a Sediment-Hosted Stratabound Copper Deposit

SSC deposits are the second most important source of copper in the world
behind porphyry copper deposits. Around 20% of the copper in the world is
produced from this class of often very large and high-grade deposits. These
deposits also typically have potential for large scale, low-cost bulk mining.

 

SSC deposits are bodies of disseminated, cementing, and lesser veinlet-hosted
copper (Cu) minerals that typically follow the same structures within their
sedimentary or metasedimentary host rocks. These SSC deposits are
characterized by strong zoning of the ore minerals laterally along and across
the host rock bedding from pyrite, to chalcopyrite, to bornite, to chalcocite,
and to hematite. Chalcocite and bornite zones are typically the ore zones.

 

SSC deposits occur where there are strong reductants present that can
precipitate sulphur (S) and copper (Cu) from warm (~ 75-220 °C), oxidized
(hematite-stable), metals-transporting, sedimentary brines.

 

They are divided into three sub-types of deposits based on rock varieties:

 

·    reduced facies type deposits (e.g. Kupferschiefer) are hosted in
black to gray to green shales or siltstones;

·    sandstone-type deposits (e.g. Revett) are hosted in gray,
well-sorted, fine to coarse grained sandstones; and

·    redbed-type deposits are hosted in otherwise oxidized sandstones.

 

These host rocks either lie atop or are enclosed within thick (greater than
300m and commonly greater than 1km) sequences of red beds. The association
with red beds is an important distinction from other Cu deposits found in
sedimentary rocks.

 

SSC deposits are an important source of other metals, ranking first among all
deposit types in the world for cobalt (Co) production and fourth among all
deposit types in silver (Ag) production. However, those that contain byproduct
Ag do not contain byproduct Co and vice versa.

 

The important key parameters that, when found in combination can lead to a
world class SSC deposit (as illustrated in Figure 1.) include:

 

·    intracratonic rift basin setting allowing oxidised fluids to evolve
and persist for a significant period - in other words  a "closed" basin;

·    a basal sequence of red bed sediments that provide a source for
oxidized fluids and metals (red beds being hematite-bearing sandstones,
conglomerates, siltstones), the presence of reduced carbonaceous rocks
(containing organic matter, graphite or hydrocarbons) stratigraphically higher
in the sequence that provide a redox trap to allow for the precipitation of
copper;

·    a basin scale oxidised fluid flow system that leaches large areas of
source rocks,ideally over a prolonged period of time.

Figure 1: Conceptual sequence favourable for SSC deposits (Hitzmann et al
Economic Geology 2010)

 

 

Pitfield Copper Project Comparison with the SSC Model

 

Pitfield lies in a unique setting along the boundary of Western Yilgarn
province, where a major craton-scale structure internal to Southwest Gneiss
province intersects and offsets the Yilgarn margin and controls the position
of the Neoproterozoic Yandanooka basin, the only example of this globally
important copper prospective age adjacent to the western Yilgarn craton
(Figure 2).

 

 

Figure 2- Location Map - Showing Yandanooka Basin

 

Surface geological and structural mapping has been combined with the new
geophysical mapping and historical drillhole logging to produce a detailed
geological interpretive map of the basin and surrounding region which clearly
shows the structures most prospective for a SSC deposit, and in particular the
Mt Scratch siltstones (Figure 3).

 

 

Figure 3: Pitfield Interpretative Geology and Structural Map

 

The 9,000m thick Mt Scratch siltstone has been subdivided based on geophysical
character as follows:

·    the conductive sequence is shown in darker blue and likely contains
reduced graphite bearing units;

·    the highly magnetic units (magnetite bearing) are highlighted in
stippled fill; and

·    low magnetic units and low/variable conductivity are in light blue.

 

Pitfield's favourable geology has attracted major mining companies that have
historically carried out preliminary exploration activities within the area,
including:

 

·    BHP (1984) who identified similarities between the Yandanooka basin
and African copper belt sequences and completed IP geophysics, shallow RAB,
and four stratigraphic diamond holes focussed along the western contact of the
Yandanooka basin within the basement Mullingarra gneiss, which indicated a
significant depletion of base metals (including Cu) in the basement rock;

·    CRA (1993) which completed IP geophysics and auger sampling defining
a significant Cu-in-auger anomaly (plus Ag) over some 7km strike length open
to the east and south and they followed up with two diamond holes, the
southern hole on Pitfield recording copper anomalism with a maximum value of
570ppm (from 4m chip samples of drillcore) associated with fracture-controlled
malachite and minor native copper. CRA also carried out soil sampling in the
Mt Scratch area which shows a strong correlation between more strongly
anomalous copper-in-soils with magnetic units within the stratigraphy. Rock
chip samples taken by CRA from surface exposures returned very encouraging
Cu-Ag values (up to 2.3% Cu and 20.8 g/t Ag) within the magnetic units
highlighting a large, highly prospective SSC target.

 

The 7km Cu anomaly in the south at Pitfield is located higher in the sequence
than the nearby historic Baxters copper mine at Arrino (which produced 106
tonnes of copper at a grade between 20-30% Cu) and thus more proximal to the
contact between the lower red-bed source rocks and the reduced layers in the
Mt Scratch siltstone that provide an effective redox trap for the copper
fluids. This, along with numerous other prospects including the Mt Scratch
workings in the northern section of the project licence demonstrates that the
copper mineralisation process has occurred extensively across the Pitfield
project area.

 

The stratigraphic mapping by BHP in the 1980s provides a very good description
of the lower "red bed" part of the Yandanooka succession, confirming red beds
of 1.0 to 1.5km in thickness, increasing in thickness to the south and
dominantly siltstone and sandstone with local carbonate rocks in the north
(Figure 4).

 

The geophysical surveys have confirmed that the Yandanooka basin contains
geological features that make this an attractive sediment-hosted copper
exploration target, evidenced by:

 

·    the Airborne Electro-Magnetic (AEM) survey which has identified
significant variations in rock conductivity including a suite of anomalous
conductive features within the Mt Scratch siltstone, which indicates the
presence of sulphides and/or importantly reductants such as graphite.

·    the Airborne Magnetic (AM) survey which has distinguished a
widespread, stratabound, over 40km long regional magnetic anomaly
(magnetite-bearing alteration), which coincides with previously defined copper
anomalies based on historical shallow drilling and regional rock, soil and
stream sediment sampling.

Figure 4.  Historic BHP stratigraphic section focussed on the lower
Yandanooka Group, 1984.

 

 

The lower +1,000m of the basin includes substantial thicknesses of sandstone
and mafic clast conglomerate which provides copper-bearing source rocks for
the basin outcropping adjacent to and overlying the Mullingarra gneiss (refer
Figure 4), while the overlying reduced Mt Scratch siltstone acts as a redox
trap for the copper fluids mobilised from deeper in the basin. This fits the
reduced sediment hosted copper model very nicely.

 

The massive magnetic anomaly, extending over 40km north-south, shows that the
project area has been impacted by a large alteration event such as the influx
of warm, oxidized, metals-transporting, sedimentary brines. It is important to
note that the deeper diamond drilling by BHP (1984) confirmed that the
basement rock was depleted in Cu, indicating that the base metals have been
leached and mobilised by the fluids passing through and most likely explains
the Cu anomalies identified within the upper zones of siltstone/sandstone.

 

Further evidence of a regional scale alteration event can be found at the
adjacent Three Springs Talc Mine lying just to the east of Pitfield. This
large talc deposit was formed when hot fluids carrying silica passed through
massive dolomite formations, leaving silica and transporting away calcium to
be replaced by magnesium - creating talc.

 

 

 

Comparison with other World Class Copper Provinces

The geology at Pitfield aligns closely with the SSC Model described above and
given the scale of alteration identified by the geophysical surveys, which
extends well over 40km north to south, the project area could contain a
"Giant" mineralised system which hosts multiple SSC deposits.

 

SSCs have been found on every continent (except Antarctica) however more than
80% of total resources contained in SSCs occur in the Central African Copper
Belt in the Democratic Republic of Congo (DRC) and Zambia, and Kupferschiefer
in Germany and Poland.

 

The most important deposits are located in the Central African Copperbelt of
Zambia and the DRC. These reduced-facies and sandstone-hosted deposits have
large tonnages and unusually high grades (~2.5%). Known resources in the belt
are ~152Mt contained copper across more than 80 deposits, with the USGS
estimating a further 168Mt Cu remaining to be discovered, ~75% of which is in
the DRC. These deposits are the world's main source of Co, which adds
significantly to the value of these deposits.

 

The recent opening of the massive Khoemacau mine in the Kalahari Copperbelt in
Botswana is a potentially significant development. The project, which entered
production in June 2021, has total resources of 503Mt at 1.4% Cu and 17 g/t
Ag.

 

The Kupferschiefer deposits of western Poland and eastern Germany have
produced much of Europe's Cu for more than 800 years. The name comes from the
German words for copper (Kupfer) and shale (schiefer). Since 1958 they have
produced ~15 Mt Cu, with another 30 Mt awaiting development. The USGS
estimates ~110 Mt Cu remains undiscovered, with the large majority in
southwestern Poland.

 

The Revett Formation in Montana and Idaho is also known also to host
significant developed and undeveloped Cu-Ag resources in sandstone-style
deposits. However, given the geological setting at Pitfield the most obvious
comparison, on a worldwide, large scale basis, is Udokan.

 

The Udokan mine is a large copper mine located in the south of Russia in
Zabaykalsky Krai, around 30 km south of the town of Novaya Chara on the Baikal
Amur Mainline. The mine is part of the massive Udokan Ore Region that includes
the Udokan, Kalar and Kodar ranges. The Udokan Ore Region represents the
largest copper deposit in Russia and third largest in the world, having
estimated reserves of 1.2 billion tonnes of ore grading 2% Cu.

 

Udokan has several key features which are common to Pitfield, including:

 

·    Udokan is a sandstone sub-type of SSC deposits;

·    Copper mineralisation assemblages are of three types;

o  chalcocite-bornite, always associated with magnetite, and makes up >80%
of the potentially economic primary resource

o  chalcopyrite-bornite or

o  chalcopyrite-pyrite

·    Within higher grade chalcocite-bornite mineralisation, sulphide or
quartz-carbonate-epidote-sulphide veins with magnetite haloes crosscutting or
sub-parallel to bedding are always present in association with the dominant
bedding-parallel disseminated to stringer sulphides;

·    Individual orebodies are 300 - 2,000m in strike, can continue for up
to 2,500m down-dip, and 16-52m in thickness; and

·    Main mineralisation is Cu-Ag-Fe, minor Co, Ni, Zn, Mo, Au

 

 

Figure 5: Udokan deposit geologic map and cross sections, where red denotes a
bornite-chalcocite-chalcopyrite ore body.

 

Market Abuse Regulation (MAR) Disclosure

Certain information contained in this announcement would have been deemed
inside information for the purposes of Article 7 of Regulation (EU) No
596/2014, as incorporated into UK law by the European Union (Withdrawal) Act
2018, until the release of this announcement.

 

**ENDS**

 

 

 

For further information please visit www.empiremetals.co.uk
(http://www.empiremetals.co.uk)   or contact:

 Empire Metals Ltd                                       Tel: 020 7907 9327

 Shaun Bunn / Greg Kuenzel
 S. P. Angel Corporate Finance LLP (Nomad & Broker)      Tel: 020 3470 0470

 Ewan Leggat / Adam Cowl
 Shard Capital Partners LLP (Joint Broker)               Tel: 020 7186 9950

 Damon Heath
 St Brides Partners Ltd (Financial PR)                   Tel: 020 7236 1177

 Susie Geliher / Ana Ribeiro / Max Bennett

 

About Empire Metals Limited
Empire Metals is an AIM-listed (LON: EEE) exploration and resource development company with a project portfolio comprising gold interests in Australia and Austria.

 

The Company's strategy is to develop a pipeline of projects at different stages in the development curve. Its initial focus has been on the high-grade Eclipse and Gindalbie Gold Projects in Western Australia.  The Company expanded its exploration licence area in April 2022 from 9.5km(2) to 1,728km(2) with the acquisition of the Pitfield Copper-Gold Project and the Walton Copper-Gold Project in Western Australia, and the Stavely Copper-Gold Project in the Stavely Arc region of Victoria.

 

Empire also holds a portfolio of three precious metals projects located an historically high-grade gold production region comprising the Rotgulden, Schonberg and Walchen prospects in central-southern Austria.

 

The Board continues to evaluate opportunities through which to realise the
value of its wider portfolio and reviews further assets which meet the
Company's investment criteria.

 

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