REG - Empire Metals Ltd - AEM Survey at Pitfield Copper-Gold Project

Empire MetalsAnnouncement

21/09/2022 07:00

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RNS Number : 1141A  Empire Metals Limited  21 September 2022

 

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

 

21 September 2022

Empire Metals Limited

 

Airborne Electro-Magnetic Survey at Pitfield Copper-Gold Project

 

 

Empire Metals Limited (LON: EEE), the AIM-quoted resource exploration and
development company, is pleased to announce the results of the airborne
electro-magnetic ('AEM') survey covering a total of 1,664 line-km over the
majority of the 615 km(2) Pitfield Copper-Gold Project ('Pitfield'), located
in Western Australia.

 

Highlights

·    The AEM survey has identified a suite of anomalous conductive
features, many of which are located in unexplored areas or areas not explored
with modern techniques.

·    30km long regional alteration feature, considered highly prospective
for sediment hosted copper, defined from interpretation of AEM survey and
aeromagnetic data.

·    Successfully mapped variations in the bedrock conductivity response,
providing very useful new basement geological information, particularly over
large areas of the project area of low magnetic intensity.

·    Of particular interest is that some previously defined copper
anomalies based on historical regional stream sediment sampling and/or the
proximity to old copper workings lie along distinct boundaries in conductivity
response.

·    The survey confirms that the Yandanooka Basin contains geological
features that make this an attractive sediment-hosted copper exploration
target.

 

Shaun Bunn, Managing Director, said: "Combined with the highly successful
airborne magnetic survey, Empire now has a clear sense of the significant
mineralised potential of Pitfield. We set out to map the geology of the
Yandanooka basin and in particular to highlight potentially preferred host
rocks for copper. When matched with the aeromagnetic data, a coincidence of
elevated magnetic signature and more resistive rocks in the EM occurs within
the upper Mt Scratch siltstone sequence and defines a 30km long regional
alteration feature. The large area contained within and around the margins of
this feature is considered highly prospective for sediment hosted copper. In
addition, the survey has highlighted specific anomalous conductive areas that
may relate to sulphide accumulations or native copper associated with
mineralised systems.

 

"The new data clearly provides important new geological insights that will be
used in formulating an exploration strategy and work programme for Pitfield."

 

 

Airborne Electro-Magnetic Survey at Pitfield

AEM data is used in minerals, energy, and groundwater resource exploration.
The AEM technique takes advantage of natural variations in electrical
conductivity beneath the surface which results from variation in rock and pore
fluid properties. The presence of electrically conductive minerals such as
graphite, clays, and sulfide minerals, or electrically conductive fluid such
as saline groundwater, results in greater conductivity relative to
non-conductive mineral assemblages or non-conductive fluid (typically fresh
ground water). Due to the influence of both rock and pore water properties on
the AEM response, AEM datasets are normally interpreted in conjunction with
other spatial and airborne datasets including surface geology, soil
geochemistry and magnetics and gravity.

 

AEM data is collected by transmitting an electromagnetic signal from a system
attached to a plane or helicopter. The signal induces eddy currents in the
ground which are detected by receiver coils towed below and behind the
aircraft. AEM techniques can detect variations in the conductivity of the
ground to a depth of several hundred metres, depending on the acquisition
system and geological and hydrogeological stratigraphy. AEM surveys require
complex processing to allow interpretation and therefore are usually designed
to detect particular subsurface targets which are based on a perceived
conductivity contrast, for example:

 

·      the spatial extent of geological features, such as a clay-rich
unit in a sedimentary sequence or a graphite-bearing unit in a metamorphic
complex

·      the depth of an unconformity between sedimentary cover and the
underlying basement rock

·      the location of groundwater resources, such as fresh or saline
aquifers.

 

The AEM survey was flown by New Resolution Geophysics Australia Pty Ltd
('NRG') using the well-known, very capable heliborne 'Xcite' electro-magnetic
acquisition system (Figure 1). NRG's Xcite™ systems are towed arrays, using
high performance AS350 B-series helicopters (or similar). The AS350 is ideal
for the close terrain following required for geophysical surveys.

Figure 1:  NRG's Xcite™ system

The AEM survey covered the entire project area on a 400m line spacing.  A
survey altitude of 30 to 40m (Transmitter-Receiver array) and 60 to 70m
(helicopter) was employed. The magnetometer sensor was located mid-way between
the bird and the helicopter.

A total of 147 lines was flown for an overall 1,664 line km (Figure 2).

Figure 2:  Project Location with extent of recent AEM survey shown.

 

AEM Survey Results

The AEM data mostly concerns the off-time when the transmitter current is off,
leaving only the secondary eddy currents in the receiver. Because the EM
responses exponentially decay after the turn-off, the off-time is usually
divided into  intervals (called time gates, which exponentially expand as
moving from early to late time), and the samples within each time gate are
averaged to produce time channel data. The averaging over time further smooths
out outliers and other noise, making the data more robust for interpretation.

A time domain EM data map is produced by contouring data at a particular time
channel as a function of the horizontal location.  Early time channels are
most sensitive to the near-surface features, while the late time channels
average over a larger volume.  By way of example, in Figure 3, the airborne
EM results for gridded Channel 15 (mid-time) response was selected with warm
colours showing areas of higher conductivity, annotated with historic stream
sediment sampling results and salt lake domain in the south east of the
project.

Figure 3: AEM results showing gridded Channel 15 (mid-time) response.

 

The AEM survey has confirmed that the Yandanooka basin contains geological
features that make this an attractive sediment-hosted copper exploration
target.  Some of the key findings include:

 

·    the survey has been successful in mapping significant variations in
rock conductivity within the Yandanooka Formation, and has confirmed
conductive stratigraphy associated with the Mt Scratch siltstone or its
lateral facies equivalent;

·    the large area of magnetite-altered Mt Scratch siltstone is less
conductive overall, and more variable in its conductivity containing both
conductive anomalies due to potential association with sulphides, and more
resistive domains which may reflect rock alteration, both of which are of
exploration interest;

·    in general, the more resistive rocks are associated with the older
Mullingarra gneiss basement and the sandstone mafic conglomerate bearing lower
parts of the Yandanooka Group, the latter having a thickness of at least
1,000m; and

·    the mapped drainage and salt lake domain in the south east sector of
the project corresponds closely with high conductivity in the AEM and is
interpreted to be a mainly surficial response to saline groundwater, thus the
AEM survey has been less effective at mapping basement geology in this area.

 

The outline of the magnetic anomalism closely matches the more resistive
domain within the Mt Scratch siltstone succession, which forms the upper part
(up to 9,000m thick) of the Yandanooka basin. Outside the magnetic anomaly
domain, the Mt Scratch siltstone is more consistently conductive indicating a
component of reduced, possibly graphite-bearing sedimentary units.

 

The lower +1,000m includes substantial thicknesses of sandstone and mafic
clast conglomerate which may provide 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 can be the redox trap for the
copper fluids mobilised from deeper in the basin. This fits the reduced
sediment hosted copper model very nicely.

 

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

 

 

Geophysical consultant Newexco has evaluated and identified a suite of
anomalous conductive features which are annotated on Figure 5 as violet
squares. Many of these features are located in  areas unexplored by modern
techniques, some with empirical support in regional stream sediment sampling
or proximity to old copper workings. The areas of interest are defined by
anomalies lying along distinct boundaries in conductivity response.

Figure 5: Central part of the project area showing Channel 15 of the AEM
survey along with historic stream sediment sampling and historic copper
workings

 

In the central part of the project area, a cluster of conductivity anomalies
were defined from the AEM survey. CRA completed stream sediment sampling over
parts of this area some 30 years ago identifying significant copper anomalism
as shown in Figure 5, along with broadly coincident zinc, silver and nickel,
all elements likely to be elevated in sediment-hosted copper systems. The
stream sediment sampling was completed over relatively subdued topography with
extensive shallow cover, so is likely to have only been partially effective in
evaluating the bedrock potential. Nonetheless, a broad target area of
coincident EM conductivity anomalies and Cu-Zn-Ag metal anomalism can be
defined for further exploration. A conductivity anomaly defined over some
1.5km at the southern end of the Mt Scratch workings is also of interest,
along with several features closely associated with the linear contact between
high conductivity units to the east and variable conductivity units to the
west, and coinciding with the margin of the regional alteration feature.

 

The next step is to integrate all new geophysical data into an interpreted
geological map, prior to planning the Company's first phase of on-ground
exploration. This will include, amongst other things:

 

·    access agreements with local landowners;

·    soils or auger geochemistry over key prospective areas to define
drilling targets; and

·    further definition of the AEM anomalies using on ground Moving Loop
EM to validate and confirm the orientation of conductive features.

 

Location and Regional Geology

Pitfield is comprised of a granted Exploration Licence (E70/5465) and an
Exploration Licence Application (E70/5876) covering a total of 615 sq km.
Pitfield is located near Three Springs, a town  313 kilometres north of
Perth, Western Australia on the Midlands Road, which until the opening of the
Brand Highway in 1975 was the main road route from Perth to the state's north.
(Figure 6).

 

Figure 6- Location Map - Showing Pitfield Tenements and Major Access Roads.

 

Local Geology and Historical Mining Activities

Pitfield lies at 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.

 

Major lithological contacts, either within basins or at the basement contact
(particularly transitions between oxidised and reduced rocks) can focus copper
deposition. Pitfield is located along strike from the historic Baxters copper
mine at Arrino which produced 106 tonnes of copper at a grade between 20-30%
Cu which, along with numerous other prospects, demonstrates that the copper
mineralisation process has occurred in the Pitfield area.

 

Historical geochemical sampling by CRA (which became part of Rio Tinto Group)
and others has confirmed that a previously identified magnetic anomaly
associated with alteration including magnetite/hematite, epidote replacement
and fractures and carbonate-quartz veinlets is host to extensive copper
anomalism, extending south from Baxters and with greater than 150ppm Cu in
soils identified over a strike length of 7km (refer Figure 7.).  The anomaly
remains open to the south and east including over 10km of this high-intensity
magnetic feature within the project which is yet to be explored. Limited
exploration has been undertaken within the project outside a 5km radius from
the Baxters mine.

 

 

Figure 7.  Local Geology showing tenements and location of historic mining activities and 7km copper anomaly south of Baxters.

 

 

Previous governmental regional magnetic surveys were flown at 200m
line-spacing and indicated strongly magnetic stratigraphy/alteration within
the project area. Empire's recently completed airborne magnetic and
radiometric survey was flown on a 50m line spacing at a height of some 30m and
comprising some 3,470 line-km, giving an enhanced magnetic and radiometric
resolution over the main areas of interest. This identified a major magnetic
anomaly extending over 20km along the western boundary of the licence area
that closely aligns with the surface copper anomaly identified by CRA when
conducting surface sampling in the early 1990s (Figure 6).

 

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                                                       Tel: 020 7236 1177
 PR)

 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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