Project Overview

  • Location
  • Region
  • Project Size
  • Resource
Queensland
Central
245km2
JORC Compliant 415Mt @ 0.25% copper and 31ppm Mo at a 0.2%

Briggs Copper Project

Queensland

The Briggs, Mannersley and Fig Tree Hill Porphyry Copper Project comprises three Exploration Permits for Minerals (EPM) and one application for an EPM covering a total area of approximately 245 km2. It contains a JORC compliant Inferred Mineral Resource estimate of 415Mt @ 0.25% copper and 31ppm Mo at a 0.2% copper cut-off grade at the Briggs Copper deposit (Table 1). The deposit remains open in all directions. The Inferred Resource contains ~1 million tonnes of copper metal and over 28.6 million lbs of molybdenum. The Project is located close to key infrastructure, including sealed roads, rail, grid power, gas pipelines and a deep-water port at Gladstone approximately 50km to the east.

Table 1: Overall MRE (Inferred Resource) for the Briggs Copper Deposit

Tonnes
Mt		 Cu Grade
%		 Mo Grade
ppm		 Cut-off Grade
Cu %		 Cu Metal
Mt		 Mo Metal
Mlb
982.3
0.19
34
0.00
1.85
74.39
905.5
0.20
34
0.10
1.84
67.75
694.1
0.22
33
0.15
1.52
50.38
415.0
0.25
31
0.20
1.03
28.60
153.0
0.29
30
0.25
0.45
10.02
47.8
0.34
28
0.30
0.16
2.91

Geological Setting

The Project lies within the Yarrol Province of the northern New England Orogen containing Silurian to Permian volcanic, volcanoclastic and sedimentary rocks of island arc origin. These are intruded by the late Permian to Triassic Galloway Plains Intrusive Complex (Figure 2). Porphyry copper mineralisation at Briggs and at Mannersley is associated with multi-phase phyllic and potassic altered granodiorite to tonalitic stocks which form part of the Galloway Plains Intrusive Complex, intruded into Silurian to Devonian aged sediments and volcanic rocks.

Alma Metals ALM Briggs Copper Project Location Map
Figure 1: Briggs–Mannersley–Fig Tree Hill Copper Project, Central Queensland, Australia
Alma Metals ALM Briggs Copper Project Geology
Figure 2: Regional Geology: Briggs–Mannersley–Fig Tree Hill Copper Project, Central Queensland, Australia

Briggs Porphyry Copper Mineralisation

The Inferred Mineral Resource of 415Mt @ 0.25% Cu and 31ppm Mo occurs in and around several porphyry intrusions at Briggs. These are porphyritic granodiorite stocks with dimensions up to 500m x 200m which occur at surface and have been drilled to a depth of ~500m. Mineralisation occurs in stockworks of quartz veins containing quartz, chalcopyrite, minor molybdenite, potassium feldspars and locally anhydrite in both the porphyritic granodiorite and in the surrounding volcanic sediments (Figures 3, 4, 5). Biotite alteration is also present in the immediately adjacent host rocks.

Because the deposit outcrops, geochemical soil sampling is a very effective exploration tool (Figure 6). The overall mineral system appears to be at least 2,000m long, is elongated along a prominent WNW to NW trending structural corridor and extends into untested ground held in the Fig Tree Hill EPM to the northwest, providing significant potential to increase the overall size of the resource.

Observation of drill core provides clear evidence that multiple intrusive phases and multiple mineralising events have occurred. Further drilling is required to better define these phases and to determine vectors towards higher grades and additional resource volume.

Drilling to date indicates that the highest copper grades are associated with sub-vertical banded silica bodies at the contacts between different intrusive phases, or in the volcanic sediments immediately adjacent to the granodiorite intrusions. A significant opportunity to increase average grades at Briggs is present once these positions are drilled to a higher density.

Alma Metals ALM Briggs Copper Project Quartz Veins
Figure 3. Outcropping stockwork of quartz-chalcopyrite veins in porphyritic granodiorite at the Central Porphyry.
Alma Metals ALM Briggs Copper Project Sulphides
Figure 4. Copper sulphides in mineralised porphyritic granodiorite, Briggs Central. Hole 23BRD0016 at 123.5m. Within a 2m interval of 61mm diameter core which assayed 0.31% Cu.
Alma Metals ALM Briggs Copper Project Sulphides Volcanic
Figure 5. Copper sulphides in mineralised volcanic sediments surrounding the porphyritic granodiorite, Briggs Central. Hole BD019-003 at 392.1m. Within a 1m interval of 61mm diameter core which assayed 0.44% Cu.
Alma Metals ALM Briggs Copper Project Geochemistry
Figure 6. Gridded soil geochemistry for copper shows the large extent of copper anomalism at surface. The Briggs Inferred Mineral Resource is within a >2km long x 1km wide copper anomaly and remains open in all directions.

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Briggs Copper Project

QUEENSLAND: The Briggs, Mannersley and Fig Tree Hill Porphyry Copper Project comprises three Exploration Permits for Minerals (EPM) and one application for an EPM covering a total area of approximately 245 square kilometres.