The Capital Project

The Capital Project is in the Lachlan Fold Belt, near Goulburn, in NSW and comprises three Exploration Licences (ELA5955, ELA5956 and ELA5987) totalling 358km2. The Project was acquired in June 2020 and the ELAs have been granted.

It covers a possible extension of the stratigraphy and structure that hosts Sky Metals’ (ASX: SKY) significant Hume gold discovery at its Cullarin Gold Project in the region (see Figure below. The Capital Project area also displays similar host stratigraphy and structures to Regis Resources’ (ASX: RRL) major McPhillamys Gold Project in the Lachlan Fold Belt, in Central Western NSW.

The Capital Project has not been explored for gold since the early 1900s. The mineralisation styles in the belt exhibit thickness and grade – and is supported by exploration success in the sediments of the Lachlan Fold Belt. This type of gold mineralisation style fits the Aruma sediment-hosted gold model.

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Figure 1: Capital Project Location plan showing leases and gold occurrences.

The Capital Project consists of three granted ELs and cover some 358km2 of Ordovician and Silurian Lachlan Fold Belt prospective geology. The area has been the location of historic gold mining activities in the late 1800s and early 1900s on small scale quartz vein alluvial and bedrock mining that produced over 1.500ozs recorded production.

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Table 1: Lease Details

Geology

The Capital Project is situated in the Palaeozoic marine sediments of the Lachlan Fold Belt which is the host rocks of the McPhillamys and Cowal gold deposits.

A mapping project by Roland M Hill,  “   The Geology of the Geary’s Gap-Sutton-Gundaroo Area, New South Wales”” for the Bureau of Mineral Resources, Geology and Geophysics in 1969 (Record No. 1969/ 148) listed the geology as Sediments.

The sediments fall into three distinct classes:

(i) Quartz greywacke or Bouma name – A(i) – Greywacke
(ii) Shale – C(iii) Shale
(iii) Argillite B(ii) – Siltstone

Or more fully and stratigraphically in chronological order

Bed                 Name

E                      Chert

D                      Shale

C                      Siltstone

B                      Greywacke

A                      Conglomerate.

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Figure 2: GEOLOGY OF THE GEARY’S GAP – SUTTON – GUNDAROO AREA, NEW SOUTH WALES. By Roland M. Hill, BMR 1969 Records 1969/148

The Summary from the report confirms the geology required.

The Geary’s Gap – Sutton – Gundaroo area consists of complexly folded quartz greywackes, shales and argillites interbedded with acid turfs and volcanics, and intruded by bosses of adamellite (Sutton Granite) and dykes of porphyritic micro granodiorite.  Faulting has taken place at different times during the evolution of the area and has produced not only the Cullarin Horst of which the area forms a section but many smaller horsts and grabens within the Cullarin Horst. In one of the smaller grabens cross-cutting the Cullarin Horst orthoquartzite gravels have been deposited and later lateritised.

Although once the site of a gold rush, the present economic potential of the area is confined to the building stone it may provide and the water it can conserve to support its agricultural industries.

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Figure 3: Capital Project plan showing geology, structures and gold occurrences with Figure 3 section as the yellow arrow bar A-B.

The Stratigraphy consists of very wet deep marine sandstone-siltstone-shale, known as a Bouma sequence, derived from ash deposits. These sediments are highly reactive and reduced sulphidic with significant low level base and precious metals with saline pore water (sea water).

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Table 2: Geological section at Bywong Lake George from B at the top to A at the base

The “Mine Sequence” the Abercrombie Sandstone is described as:

Brown and buff to grey, thin- to thick-bedded, fine- to coarse-grained mica-quartz (+/-feldspar) sandstone, interbedded with laminated siltstone and mudstone. Sporadic chert-rich units.

This Sandstone is obviously a Bouma Sequence and will have rhythmic repeated layers of

Chert – Shale – Siltstone- greywacke -conglomerate.

These are classic turbidites and are fining up and often excluding some layers due to cyclic deposition. The makeup will depend on the volcanic sources, basic or felsic, and transport. Glass is usually the major component and will be seen as chlorite-oligoclase with some pyroxene.

When this is intruded by a very hot I type granite (Sutton Granodiorite) it heats the Abercrombie sandstone and Warbisco shale in a skarn style environment, which is a powerful hydrothermal system and is related to the porphyry systems seen in the large mines at Cowal and Cadia. The rocks in contact with the granite are baked to near melting in a hornfelsed rock that is up to 2.75km thick. This is very similar to the Mt Todd deposit in the NT which is associated with shale lodes as seen at Cosmo and Rustlers roost deposits in the Pine Creek Geosyncline.

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Table 3: Geological section showing temperatures and gold deposition zones.

The gold positions as shown above explain the pattern of gold occurrences at Bywong and Aruma will be investigating a very useful pattern emerging in the big gold discoveries in the Pilbara and that is that they are all situated in sediments of varying ages but have uniform alteration styles, being hydrothermal gold-sulphide-carbonate-mica stratabound driven by granitic heat sources.

The small coarse nuggetty gold mines situated in the Bywong Gundaroo Project area (ELA5987) are situated on the Whiskers Fault and were quartz veins with nuggetty gold in coarse sandstones or greywackes.

Two distinct types of mineralized styles are evident in the most mines of hydrothermal origin:

Shale Hosted Lode

1) strata-bound ore where fine sulphides are disseminated within carbonaceous and ferruginous shale (and conglomerate),

and

Greywacke QV

(2) fault-hosted mineralization is associated with pyrite and carbonaceous interbedded shales, or in rare instances is associated with strongly deformed quartz veins and stringers along the fault

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Figure 4: The Aruma “Gold in Sediments” model, showing quartz veins relationship   with lodes, from Schwann, 2018, and the A-B arrow of figure 3.

The use of the Bouma Terms will allow predictive geology and identification of targets for Quartz Vein and Lode style deposits in folded sediments. The use of folded sedimentary structures instead of straight linear “shears” will allow the exploration to define potential large high grade multi style gold deposits.

Previous Exploration

Historical exploration was done from the 1860s by prospectors culminating in the 1890s with some 1,500 ounces produced in the Macs Reef Bywong areas. Previous modern exploration was undertaken the 1970s by various companies, but mainly for base metals with North Broken Hill Limited delineating a 71,000oz Au resource at Wet Lagoon, now called the Hume Discovery.

Gold and copper:

Old shafts, costeans, and pits are the only evidence of past mining in the district. They are located in two distinct areas, the orthoquartzite gravels, and in the areas of most intense quartz veining within the sediments.

Within the orthoquartzite gravels alluvial gold was sought. Generally shafts were sunk, some to over sixty feet, and the gold was extracted by sluicing the excavated material. The quartz veins were also mined from shafts and large open pits. The veins were traced along strike for up to a mile by a series of shafts and pits. Local residents report that a large battery operated within-the area when the mining activity was at its peak. Carne (1895), reported on the workings in the area, and his map has been reproduced (Fig.6) to show more accurately the extent of the diggings.

Exploration Rationale

The basis for this exploration methodology is the Hydrothermal Model used by Aruma Resources and is based on

  • A belt or sequence of reactive (available Ca and Fe++) porous mafic rocks (usually Bouma Sequence rocks) In a structural corridor defined by crustal sutures and or felsic dykes
  • A granite intrusive nearby, normally in the fold axis
  • Sequential CO3 – HS – K – SiO2 alteration evidence
  • Pre-existing gold occurrences may be there depending on outcrop and gold grain-size

Once the lease is obtained, a data base is assembled and any obvious pre-existing anomalies evaluated. This will involve mapping- prospecting- geochemical sampling- geophysics- drilling to pre resources status.

The leases at Capital are in different status positions detailed below

 

Lease

Area

km2

Out

crop

Maps Gold Geochem Geophysics Drill

Rating

%

5955 48 10% minor nil Base metals Mag  Rad Gravity nil 10
5956 156 <10% minor Minor pits Base metals Mag  Rad Gravity nil 20
5987 168 50% old Major pits minor Mag  Rad Gravity nil 50

Table 4: Lease appraisal

The next step being undertaken is to use a local expert to evaluate the methodology and results to date and suggest the way forward. This will probably be the use of High Res magnetics to define stratigraphy and structure, them EM with the HyMap/Aster/AEM to look conductors (black shales) and explore the non-conductors in the same stratigraphy.

Foundation managing director since the company listed, Peter has applied his sediment hosted gold theory to exploring in Western Australia. Having worked in iron ore, nickel sulphides and laterites, copper, gold and manganese Peter’s background is chemical geology.

The prospective Lachlan Fold belt geology fits the requirements of the Sediment Hosted Gold theory for gold and the area now being explored has the requirements of rock type, heat sources and structures with known gold occurrences.