Georgetown
Project

The geophysical anomalies at the Georgetown Project include what may be one of Australia’s largest untested intrusion related gold prospect. Plutonic’s path to discovery is clear:

• Refine the 3D geometry and depth of targets through the use of Induced Polarisation (IP) ground geophysics over high priority areas (completed in 2023), and 
• Test targets with diamond drilling.

Plutonic’s Georgetown Project is located in north-eastern Queensland’s Georgetown Inlier, between the communities of Croydon and Georgetown on the Savanah Way (Figure 1). Access is excellent with the main target abutting the National Highway 1. The project consists of two granted tenements (Figure 2) covering a variety of compelling exploration targets.

The Georgetown Inlier consists of variably deformed and metamorphosed sedimentary and volcanic rocks of Paleo- to Mesoproterozoic age, intruded by Mesoproterozoic granitoids. This Proterozoic basement is extensively intruded by Silurian to Devonian (430 to 380 Ma) granitoid batholiths and dominantly felsic Carboniferous to Permian (ca. 350 top 230 Ma) intrusive and extrusive complexes. Some of these are spatially and genetically associated with the intrusion-related gold systems. Parts of the Georgetown Inlier are covered by Jurassic to Cretaceous clastic sedimentary rocks, Cenozoic sediments and basalt flows. 

The Georgetown Project (Figure 3) straddles the boundary between the Paleoproterozoic, represented by folded and metamorphosed siliciclastic sedimentary successions of the upper Etheridge Group, and the Mesoproterozoic, represented by less deformed, unmetamorphosed siliciclastic sedimentary rocks of the Langlovale Group.

Two reversely magnetised Permo-Carboniferous volcano-plutonic complexes of the Kennedy Igneous Association have been recognised in the central and western parts of the Georgetown Project (Figure 4). The central complex (Falling in Reverse/Langlo) is at least 18 km by 6 km in size and is composed of the Goat Creek Andesite and Bullseye Rhyolite of the early Permian Mount Little Volcanic Group. The Goat Creek Andesite comprises of extrusive amygdaloidal ± porphyritic basaltic andesite whilst the Bullseye Rhyolite consists of a series of extrusive units, including rhyolitic ash tuff, crystal tuff, ignimbrite, minor lava and agglomerate. Dacite, rhyolite porphyry and microgranite have been recorded at the Langlo epithermal gold-silver prospect, which is located at the southern end of the magnetic complex.

A second Permo-Carboniferous volcano-plutonic complex (Hypa Hypa target) is located near the western border of the Georgetown Project. This complex, which is at least 11 km by 3 km in size, is associated with the early Permian (ca. 279 Ma) Awring Granodiorite, a high-level intrusive body with porphyry copper affinities that is composed of hornblende-biotite granodiorite, tonalite and biotite leucogranodiorite. The Awring Granodiorite is accompanied by several additional extrusive and intrusive igneous units that also form part of the Permo-Carboniferous Complex. These include the early Permian Wallys Dolerite (pigeonite-augite dolerite) and stratigraphic members of the early Permian Mount Little Volcanic Group, including McFarlanes Andesite (amygdaloidal two-pyroxene andesite), Little Pocket Dacite (porphyritic biotite-hornblende dacite lava and agglomerate) and Linley Rhyolite (rhyolitic ignimbrite). NW-SE-striking rhyolite dykes are common in the structural zone encompassing the complex.

The Georgetown Project area has been subject to exploration by a wide range of companies since the 1960’s. However, surprisingly little systematic drilling has been completed as historical exploration was commonly cursory and hindered by shallow (centimetres to metres) to moderate (several tens of metres) cover. Plutonic is employing modern exploration techniques to peer through the cover in this highly prospective but under-explored region.

Recent advances in the understanding of Intrusion-Related Gold Systems (IRGS) and a comprehensive review of historical exploration and data from the Georgetown Project area leads Plutonic to conclude that significant potential exists for large, bulk-tonnage, low-moderate grade gold or gold-silver systems. Plutonic is committed to testing these areas with Induced Polarisation geophysics and drilling.

Three primary exploration targets (Figure 5) are defined by areas of anomalously low magnetics (indicative of either reversely polarised ‘highs’ or magnetite destruction due to alteration) located at the intersection of several major, crustal-scale structures.

Falling in Reverse

• Defined by major geophysical magnetic low anomalies (Figure 6, Figure 9):
  • Reversely magnetised intrusives emplaced during the polar reversal of the Permo-carboniferous, or
  • Magnetic destruction/alteration zones located along a significant intrusive NW-trending corridor, coincident with a continental scale gravity ridge.
• Occurs at the confluence of two major crustal scale gravity ridges and a major WNW-trending igneous (magmatic-hydrothermal) belt.
• 3D magnetic inversion modelling unveils “fingers” emanating from a deep seated intrusive-hydrothermal complex
• Marked by outcropping intensely altered rhyolitic breccias (common for IRGS systems) and other high level felsic intrusives (ignimbrites, potential tuffs as per Mount Leyshon)
• >16kmx 6km target zone associated with elevated Au-Ag-As-Sb-Bi-W in substation soil geochemical survey (Figure 7).
• Located beneath thin, transported cover
• Possibly one of the largest untested intrusion related gold system in Australia

Hypa Hypa

• A set of major geophysical magnetic low anomalies (Figure 8).
• Located immediately west of the giant Falling in Reverse target
• Best rock chip assay: 23.4ppm Ag, 0.13g/t Au, 137ppm Bi, 5.1%Cu and 2.7ppm Te 
• Potential for multiple intrusion related gold systems

Langlo

• Historically recognised as an outcropping epithermal vein system on the south-eastern flank of Plutonic’s large-scale Falling in Reverse target

• • Surrounded by breccias and altered fault zones.
  • Located on a NW trending mag low connected to the Falling in Reverse system at depth. 
  • Metal anomalism in soils, rock chips and drilling gives confidence in fertility of the under-explored hydrothermal system at Falling in Reverse (below transported cover).

• Hosts up to 6km of highly elevated Au-Ag-Bi-Mo-Sb-W soil anomalism (IRGS pathfinder elements) and rock chips:

• • Assays up to 0.82 g/t Au, 2.5 g/t Ag, 844 ppm As, 12.7 ppm Bi, 18.3 ppm Mo, 34.7 ppm Sb, 80.5 ppm Sn, 0.54 ppm Te, 32.7 ppm W (Figure 10)

• Two historic explorers have drilled shallow RC holes at the prospect:

• • Recognition that the near surface expression of the vein system is at the epithermal ‘boiling zone’ with blade replacement textures and chalcedonic quartz veining, indicating optimal gold deposition most likely to occur deeper in the system.
  • Gold grades up to 2m @ 0.24g/t Au from (LA6, Keela-Wee Exploration), 8m @ 0.18g/t Au and ending (open) in 28m @ 0.11g/t Au at 94m (LA7, Keela-Wee Exploration) and 1m @ 0.73g/t Au from 57m (BCRCC001, Bowen Energy).

• Plutonic does not consider the historic drilling at Langlo systematic or composed within a well-defined targeting strategy, however:

• • The broad anomalism of the area is recognised, along with the potential for a large fertile system both at depth, and at the much larger and connected Falling in Reverse target.
  • The company also considers the possibility that Langlo may be a distal Epizonal IRGS expression of the broader system, rather than a standalone low sulphidation epithermal Au-Ag system.
  • More work will be undertaken to better characterise the relationship between the two adjacent prospects.

Representative rock textures from Falling in Reverse/Langlo and Hypa Hypa are shown in figures 11 and 12 respectively.

The economic mineral potential of the project was strongly enhanced by completion of an induced polarisation ground geophysical survey in 2023 (Figure 13). Carried out by Fender Geophysics on behalf of Plutonic, the program consisted of six east-west lines of standard roll-along pole-dipole (PDIP) configuration, using 100m dipoles. Lines varied in length from 2.6 km to 5.9 km. The survey successfully delineated several large IP chargeability anomalies; one of these is over 1 km wide, with a 7.5 km strike length, and located at the geological contact between the main Permo-Carboniferous intrusive complex and basement rocks (Figure 14).

Drill programs are currently being designed to test these high confidence and compelling targets.