EL 8434 is located about 28km east of Broken Hill whilst EL 8435 is 16km east of Broken Hill.  Both tenures are approximately 900km northwest of Sydney in far western New South Wales (Figures C2-1 and C2-2 in Appendix A, above). 

EL 8434 and EL 8435 were both granted on the 2^{nd of} June 2016 to Squadron Resources for a term of five (5) years for Group One Minerals.  On the 25^{th of} May 2020, Squadron Resources changed its name to Wyloo Metals Pty Ltd (Wyloo).  In December 2020 the tenure was transferred from Wyloo Metals to Broken Hill Alliance Pty Ltd a 100% subsidiary company of Castillo Copper Limited.  Both tenures were renewed on the 12^{th of} August 2021 for a further six (6) years and are due to expire on the 2^{nd of} June 2027.

EL 8434 lies across two (2) 1:100,000 geology map sheets Redan 7233 and Taltingan 7234, and two (2) 1:250,000 geology map sheets, SI54-3 Menindee, and SH54-15 Broken Hill in the county of Yancowinna.  EL 8434 consists of one hundred and eighty-six (186) units) in the Adelaide and Broken Hill 1:1,000,000 Blocks covering an area of approximately 580km².

EL 8435 is located on the 1:100,000 geology map sheet Taltingan 7234, and the 1:250,000 geology map sheet SH/54-15 Broken Hill in the county of Yancowinna.  EL 8435 consists of twenty-two (22) units (Table 1) in the Broken Hill 1:1,000,000 Blocks covering an area of approximately 68km².

Access to the tenures from Broken Hill is via the sealed Barrier Highway.  This road runs north-east to south-west through the northern portion of EL 8434, passes the southern tip of EL 8435 eastern section and through the middle of the western section of EL 8435.  Access is also available via the Menindee Road which runs north-west to south-east through the southern section of the EL 8434.  The Orange to Broken Hill Rail line also dissects EL 8435 western section the middle and then travels north-west to south-east slicing through the eastern arm of EL 8434 (Figure C2-1).

Figure C2-1:  EL 8434 and EL 8435 General Location Map

Explorers who were actively involved over longer historical periods in various parts of EL8434 were: - North Broken Hill Ltd, CRAE Exploration, Major Mining Ltd and Broken Hill Metals NL, Pasminco Exploration Ltd, Normandy Exploration Ltd, PlatSearch NL/Inco Ltd/ EGC Pty Ltd JV and the Western Plains Gold Ltd/PlatSearch/EGC Pty Ltd JV.

A comprehensive summary of work by previous explorers was presented in Leyh (2009). However, more recently, follow-up field reconnaissance of areas of geological interest, including most of the prospective zones, was carried out by EGC Pty Ltd over the various licenses. This work, in conjunction with a detailed interpretation of aeromagnetic, gravity plus RAB / RC drill hole logging originally led to the identification of at least sixteen higher priority prospect areas. All these prospects were summarized in considerable detail in Leyh (2008).  Future work programs were then also proposed for each area.  Since then, further compilation work plus detailed geological reconnaissance mapping and sampling of gossans and lode rocks has been carried out.

A total of 22 prospects were then recognised on the exploration licence with at least 12 occurring in and around the tenure.

With less than 45% outcropping Proterozoic terrain within the licence, this makes it very difficult to explore and is in the main very effectively screened from the easy application of more conventional exploration methodologies due to a predominance of extensive Cainozoic cover sequences.  These include recent to young Quaternary soils, sands, clays and older more resistant, only partially dissected, Tertiary duricrust regolith covered areas.  The depth of the cover ranges from a few metres in the north to over 60 metres in some areas on the southern and central license.

Exploration by EGC Pty Ltd carried out in the field in the first instance has therefore been heavily reliant upon time consuming systematic geological reconnaissance mapping and relatable geochemical sampling.  These involve a slow systematic search over low outcropping areas, poorly exposed subcrop and float areas as well as the progressive development of effective regolith mapping and sampling tools.  This work has been combined with a vast amount of intermittently acquired past exploration data.  The recent data compilation includes an insufficiently detailed NSWGS regional mapping scale given the problems involved, plus some regionally extensive, highly variable, low-level stream and soil BLEG geochemical data sets over much of the area. 

There are also a few useful local detailed mapping grids at the higher priority prospects, and many more numerous widespread regional augers, RAB, and percussion grid drilling data sets. Geophysical data sets including ground magnetics, IP and EM over some prospect areas have also been integrated into the exploration models.  These are located mainly in former areas of moderate interest and most of the electrical survey methods to date in this type of terrain continue to be of limited application due to the high degree of weathering and the often prevailing and complex regolith cover constraints.

Between 2007 and 2014 Eaglehawk Geological Consulting has carried out detailed research, plus compilation and interpretation of a very large volume of historic exploration data sourced from numerous previous explorers and dating back to the early 1970's. Most of this data is in non-digital scanned form.  Many hard copy exploration reports (see references) plus several hundred plans have been acquired from various sources, hard copy printed as well as downloaded as scans from the Geological Survey of NSW DIGS system. They also conducted field mapping, costean mapping and sampling, and rock chip sampling and analysis.

Work Carried out by Squadron Resources and Whyloo Metals 2016-2020

Research during Year 1 by Squadron Resources revealed that the PGE-rich, sulphide-bearing ultramafic rocks in the Broken Hill region have a demonstrably alkaline affinity.  This indicates a poor prospectivity for economic accumulations of sulphide on an empirical basis (e.g., in comparison to all known economic magmatic nickel sulphide deposits, which have a dominant tholeiitic affinity).  Squadron instead directed efforts toward detecting new Broken Hill-Type (BHT) deposits that are synchronous with basin formation.  Supporting this modified exploration rationale are the EL's stratigraphic position, proximity to the Broken Hill line of lode, abundant mapped alteration (e.g., gahnite and/or garnet bearing exhalative units) and known occurrences such as the "Sisters" and "Iron Blow" prospects.

The area overlies a potential magmatic Ni-Cu-PGE source region of metasomatised sub-continental lithospheric mantle (SCLM) identified from a regional targeting geophysical database.  The exploration model at the time proposed involved remobilization of Ni-Cu-PGE in SCLM and incorporation into low degree mafic-ultramafic partial melts during a post-Paleoproterozoic plume event and emplacement higher in the crust as chonoliths/small intrusives - Voisey's Bay type model.  Programs were devised to use geophysics and geological mapping to locate secondary structures likely to control and localise emplacement of Ni-Cu-PGE bearing chonoliths. Since EL8434 was granted, the following has been completed:

•           Airborne EM survey.

•           Soil and chip sampling.

•           Data compilation.

•           Geological and logistical reconnaissance.

•           Community consultations; and

•           Execution of land access agreements

.

Airborne EM Survey

Geotech Airborne Limited was engaged to conduct an airborne EM survey using their proprietary VTEM system in 2017.  A total of 648.92-line kilometres were flown on a nominal 200m line spacing over a portion of the project area. Several areas were infilled to 100m line spacing.

The VTEM data was interpreted by Southern Geoscience Consultants Pty Ltd, who identified a series of anomalies, which were classified as high or low priority based on anomaly strength (i.e., does the anomaly persist into the latest channels).  Additionally, a cluster of VTEM anomalies at the "Sisters" prospect have been classified separate due to strong IP effects observed in the data.  Geotech Airborne have provided an IP corrected data and interpretation of the data has since been undertaken.

Soil and Chip sampling

The VTEM anomalies were followed up by a reconnaissance soil sampling programme. Spatially clustered VTEM anomalies were grouped, and follow-up soil lines were designed.  Two (2) VTEM anomalies were found to be related to culture and consequently no soils were collected.  Two (2) other anomalies were sampled which were located above thick alluvium of Stephens Creek and were therefore not sampled.  A line of soil samples was collected over a relatively undisturbed section at Iron Blow workings and the Sisters Prospect.

One hundred and sixty-six (166) soil samples were collected at a nominal 20cm depth using a 2mm aluminum sieve.  Two (2) rock chips were also collected during this program.  The samples were collected at either 20m or 40m spacing over selected VTEM anomalies.  The samples were pulverised and analysed by portal XRF at ALS laboratories in Perth.

Each site was annotated with a "Regolith Regime" such that samples from a depositional environment could be distinguished from those on exposed Proterozoic bedrock, which were classified as an erosional environment.  The Regolith Regime groups were used for statistical analysis and levelling of the results.  The levelled data reveals strong relative anomalies in zinc at VTEM anomaly clusters 10, 12 and 14 plus strong anomalous copper at VTEM 17.

As the strata is tightly folded, the intersected cobalt-rich layers are overstated in terms of apparent thickness, however the modelling software calculates a true, vertical thickness.  Cobalt mineralisation is commonly associated with shears, faults, amphibolites, and a quartz-magnetite rock within the shears, or on or adjacent to the boundaries of the Himalaya Formation. In general, most of the cobalt and rare earth element - rich layers have a north-northwest to north strike.

REE enrichment generally occurs as a 5 to 10-metre-thick zone between the completely weathered layer and strongly weathered layer and it is targeted for commercial mining (Figure D2-2).  Compared to other REE deposits, regolith-hosted rare earth element deposits are substantially low-moderate grade (containing 0.05-0.3 wt.% extractable REEs).  Nevertheless, due to its easy extraction method, low processing costs and large abundance, the orebodies are generally economic to be extracted (Duuring, (2020); Kanazawa and Kamitani (2006); and Murakami, H.; Ishihara (2008)).

Figure C2-2: Weathering Profile over REE - Rich Granite

https://en.wikipedia.org/wiki/Regolith-hosted_rare_earth_element_deposits

Weathering profile of regolith hosted REE deposits shown above, the legend is: (A) Humic layer. (B) Completely weathered layer. (C) Strongly weathered layer. (D) Weathering front. (E) Unweathered rock.

Most of the REE found in cerium monazite (Ce (PO₄)) which always contains major to minor amounts of other REE (Nd, La, Pr, Sm etc) replacing Ce.  Also, the mineral often contains trace amounts of U and Th (coupled with Ca).  This will be collaborated with XRD and/or SEM analysis. 

Header information about all drillholes and surface samples completed at Reefs Tank, Tors Tank and Fence Gossan have been tabulated in this release in Appendix B.

No metal equivalents have been reported.  Rare earth element results have been converted to rare earth oxides as per standard industry practice (Castillo Copper 2022c, 2023a).

No compositing of assay results has taken place, but rather menu options within the Datamine GDB module have been used to create fixed length 1m assay intervals from the original sampling lengths.

The rules follow very similarly to those used by the Leapfrog Geo software in creating fixed length samples.

A database of all the historical borehole sampling has been compiled and validated. It is uncertain if there is a strong relationship between the surface sample anomalies to any subsurface anomalous intersections due to the possible masking by variable Quaternary and Tertiary overburden that varies in depth from 0-15m.  The mineralisation appears to be secondary enrichment in the regolith clays and extremely weathered material derived from quartzo-feldspathic pegmatites.  

Current surface anomalies are shown on maps released on the ASX (Castillo Copper 2022a, 2022b, 2022c and 2023a).  All historical surface sampling has had their coordinates converted to MGA94, Zone 54.

All recent laboratory analytical results have been recently reported (see Castillo Copper 2022a, b, c, 2023a) for assay results.

Regarding the surface and sampling, no results other than duplicates, blanks or reference standard assays have been omitted.

Historical explorers have also conducted airborne and ground gravity, magnetic, EM, and IP resistivity surveys over parts of the tenure area but this is yet to be fully georeferenced (especially the ground IP surveys).  Squadron Resources conducted an airborne EM survey in 2017 that covers Iron Blow and The Sisters, but not the southern cobalt and REE prospect areas.