TIDMEEE
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
-- T he 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.
-- Su ccessfully 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(TM) 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(TM) 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 or
contact:
Empire Metals Ltd Tel: 020 7907 9327
Shaun Bunn / Greg Kuenzel
S. P. Angel Corporate Finance LLP Tel: 020 3470 0470
(Nomad & Broker)
Ewan Leggat / Adam Cowl
-------------------
Shard Capital Partners LLP (Joint Tel: 020 7186 9950
Broker)
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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