AERIS Resources - The Grade That's Still Open: Forensic Reinterpretation of the EL8810 Open-File Record

Some exploration licences are interesting because of what has been found on them. EL8810, in the Coolabah–Girilambone district about 45 km west-north-west of Nyngan, is interesting because of what was sampled but never finished on it — and that makes it one of the cleaner case studies we've worked through in this series.

The licence forms the northern part of Aeris Resources' Tritton Operations package, held through Tritton Resources Pty Ltd. It was pegged deliberately: to cover the interpreted northern strike extension of the Budgery sandstone marker horizon out of EL6126, the same stratigraphic control that sits in the footwall of the known copper deposits across the Aeris ground. That is a sound, deposit-scale reason to hold this block, and it is worth saying plainly at the outset — the thesis that put this licence into the Aeris portfolio is exactly the kind of thinking that has since turned Tritton into a genuine multi-mine copper hub. This is validation of ground Aeris already holds, not a suggestion of ground it should.

What our forensic pass adds is a second, independent read of the legacy record sitting inside that footprint — the drill collars and surface samples digitised into the NSW GSNSW MinView layer from earlier operators and programs. When you rebuild that record from the authoritative open-file exports (269 in-licence drill collars and 93 surface rock-chip/gossan samples) and cross-reference it era by era, a coherent, low-cost opportunity emerges that is complementary to — and never in competition with — the holder's published Budgery-sandstone copper thesis.

The scale of the system is real. This is the Girilambone Group, the same prolific copper province in which more than 750,000 tonnes of contained copper has been discovered across the broader Aeris holdings since the 1980s. Within EL8810 specifically, the open-file record already contains a tight, coincident geochemical-and-geophysical anomaly — a Cu–Zn–Pb gossan cluster returning up to 1,400 ppm Cu, 5,700 ppm Zn and 780 ppm Pb over roughly 300 m — that, on the evidence in the public file, has never been drill-tested and was never assayed for gold. The most defensible near-term opportunity here isn't a new geological idea; it's a data-and-assay gap left by the constraints of earlier eras, and it can be closed largely from a desk.

Exploration history

The ground has been looked at repeatedly across five decades. Each operator was competent, each was looking for a specific thing, and each left for reasons entirely of their time — commodity cycles, corporate events, and the analytical priorities of the day. Listed oldest-first:

• 1970–71 — Burdett Explorations. Model: ironstone-hosted base metals. Objective: rank ironstone rock-chip anomalies for Cu–Pb–Zn. Work: ironstone rock chips assayed for Cu, Pb, Zn and Ni only. Departure: a first-pass reconnaissance program in an era before gold was a routine multi-element inclusion; the ground moved on with the exploration cycle.

• 1975–79 — North Broken Hill Ltd (NBH), geologist C. Plumridge. Model: Elura-style (Endeavor) leached base-metal gossan. Objective: find a buried Zn–Pb–Ag body under a subtle, leached surface expression via regional gossan sampling. Work: a major regional program — 4,354 rock samples across the Bourke 1:250,000 sheet, of which 60 (the "NY-series") sit inside the present EL8810 footprint; assayed for Cu, Pb, Zn, Ni, Ag and Sn on selected samples. This is the program that first sampled the gossan cluster, and did so because it coincided with an unfollowed 1960s-era aeromagnetic feature. Departure: the NBH regional gossan model of the late 1970s was base-metal-specific; gold was not the target commodity and was not routinely analysed. The program wound down as a regional reconnaissance effort of its era.

• 1981–82 — Preussag. Model: district base metals. Objective: follow up base-metal geochemistry. Work: assayed base metals only. Departure: early-1980s base-metal focus; program concluded with the commodity cycle of the day.

• 1981–82 — Shell Company of Australia (EL1253, "North Compton Downs – Bogan River – Girilambone"). Model: shallow base-metal reconnaissance. Objective: first-pass RAB coverage. Work: 24 RAB collars (6–26 m) in a tight ~5 km strip in the north-east of the present licence; the open-file record carries no assay flags for this strip. Departure: a major carrying out shallow reconnaissance in a period of soft base-metal prices; corporate exploration priorities shifted.

• 1990s — Nord Resources (Pacific) Pty Ltd (EL3138, "Girilambone"; Nord–Straits joint venture). Model: leachable/heap-leach copper. Objective: define leachable oxide copper across the district. Work: the dominant in-licence drill dataset — 244 collars digitised into MinView. Departure: the Nord–Straits leach-copper play was very much a 1990s Girilambone theme; the JV ran its course as corporate ownership and copper economics changed. Critically for us, the results of this drilling reside in the parent report, not the open-file point layer (more below).

• 2003 — GSNSW Cobar Project (Fleming & Hicks). Model: government pre-competitive basement study. Objective: map basement under cover via shallow aircore. Work: one 60 m aircore hole in the south of the licence (CBAC248), with cuttings preserved at the Londonderry Drill Core Library. Departure: a government traverse, not a targeted commercial program — it did its job and moved on.

• 2006–07 — Reveal Resources / Nimrodel (Buckaroo Project, EL6624). Model: structurally controlled ironstone/base-metal-gold. Objective: ridge-and-spur rock-chip sampling northward into the Tritton ground. Work: 33 in-licence rock chips (the "BK-series"), and — notably for the era — a full multi-element suite including gold. These are the samples that lit up the old Bunyarra workings. Departure: a first-year program; exploration priorities and funding moved before the anomalies were systematically followed up for gold.

• 2018–present — Aeris Resources / Tritton Resources Pty Ltd. EL8810 was granted on 14 December 2018 to cover the northern Budgery-sandstone extension. The holder's first-year work (per the 2019 IMER) was a considered, disciplined desktop step: a high-level historical data review, compilation of prior reports, database and landholder updates, and initial land access — the correct, low-cost first move on newly granted ground, and the foundation for targeted mapping to locate the marker horizon. This is the most informed and best-resourced chapter the ground has ever had: a producing copper company, with the Tritton mill at the centre of a stated long-life multi-mine hub strategy, holding the licence as part of a 2,160 km² package it knows intimately.

Why the grade is still open

Cross-referencing the eras against each other is where the forensic value sits. No single operator missed anything; the record as a whole has a structural blind spot that only becomes visible when you overlay the datasets:

• The drilling was never assayed in the open file. Of the 269 in-licence collars, none carries an open-file assay. The 244-collar Nord population also carries a uniform 1.0 m "placeholder" depth — a digitising artefact of the collar-only export, not evidence of 244 one-metre holes. The real depths and any downhole assays sit in the parent report (DIGS R00020113) and have simply never been propagated into the point layer. That is a data-plumbing gap from the 1990s, not a geological verdict.

• The best surface anomaly was never drilled. The NY-series gossan cluster (NY6921–NY6926) is a coherent ~300 m Cu–Zn–Pb feature that NBH sampled specifically because it coincided with an unfollowed aeromagnetic anomaly. It is a coincident geochemical-geophysical target — and on the open-file evidence it has never had a hole put into it.

• Gold was systematically under-tested — district-wide. Across Burdett, NBH, Preussag and Shell, samples were assayed for base metals but seldom for gold, because in each of their eras gold was not the commodity being sought. The one program that did run a full gold-inclusive suite (Reveal's 2006–07 Buckaroo work) immediately returned 0.14 g/t Au with 436 ppm As at the old Bunyarra workings. Gold here isn't demonstrated — but crucially, it has never been excluded across a large, prospective sample population.

• Preserved material is still sitting on a shelf. CBAC248's cuttings are held, unanalysed, at Londonderry — a modern multi-element-plus-gold re-assay opportunity that requires no field access at all.

• The miss, precisely: Between 1970 and 2007, capable explorers crossed this ground looking for one commodity each — ironstone base metals, an Elura-style lead-zinc lens, leachable copper. Every one of them assayed for base metals; almost none assayed routinely for gold, because in their eras gold was not the target and the analytical budget went to the commodity of the day. A coherent Cu–Zn–Pb gossan cluster was sampled at surface in the 1970s on a coincident magnetic high — then never drilled, and never assayed for gold. That is not a gap in anyone's current program; it's a forty-year-old blind spot in the historical record, sitting inside a modern, well-run copper tenure, that can be closed with desktop data recovery and a re-assay before a single new hole is required.

Significant grades in the open-file record

A transparency note that is itself the point of the article: because the in-licence drilling was never assayed in the open file, the strongest numbers the system has produced are all surface rock-chip and gossan samples. That is the opportunity, not a limitation. All grades in ppm unless noted; 1 g/t = 1 ppm.

Sample / setting	Grade	Operator (source report)	Why it matters
NY6921 — gossan cluster	1,400 Cu · 2,000 Zn · 225 Pb	NBH / Plumridge, 1975–79 (Capnerhurst 2003, R00041449)	Highest copper in the coincident magnetic-anomaly cluster; never drilled
NY6926 — gossan cluster	1,250 Cu · 5,700 Zn · 460 Pb	NBH / Plumridge (R00041449)	Highest zinc in the cluster; "ball-textured laterite" on the target horizon
NY6925 — gossan cluster	430 Cu · 1,300 Zn · 780 Pb	NBH / Plumridge (R00041449)	Lead crosses Plumridge's own unconditional mineralisation threshold (>700 ppm Pb) — his model says "mineralisation, regardless of nickel"
NY6922 — gossan cluster	1,000 Cu · 770 Zn · 125 Pb	NBH / Plumridge (R00041449)	Confirms the cluster's tenor is coherent, not a single spot high
BK15 — Bunyarra old workings	0.14 g/t Au · 436 As · 170 Cu · 280 Zn · 40 Sb	Reveal / Nimrodel, 2006–07 (Ferguson & Luders, R00041908)	The only in-licence sample with meaningful gold and arsenic — a structurally focused, gold-bearing ironstone at a historical working
BK35 — large ironstone W of workings	299 As · 284 Cu · 234 Zn	Reveal / Nimrodel (R00041908)	Extends the As–Cu ironstone signature ~along strike; a mappable body, not a point
BK16 — ~100 m N of workings	0.05 g/t Au · 154 As	Reveal / Nimrodel (R00041908)	Gold-plus-arsenic repeats north of Bunyarra — a trend, not an isolated chip

These are historical open-file results reported from surface samples and are not verified by a Competent Person (see closing statements). No JORC-compliant estimate is stated or implied.

Geological setting

EL8810 lies in the Girilambone Group of the northern Lachlan Orogen, in the Cobar–Girilambone region — a strongly foliated, bedded and laminated succession of quartz to quartzo-feldspathic sandstone, quartzite, shale, phyllite and chert, with minor mafic volcanics and intrusives, regionally metamorphosed to upper greenschist facies. Structure is dominated by a strong north-west-trending foliation with generally reverse, north-easterly dips, overprinted by a later NNE-trending fault set; shear zones carry ankerite–pyrite–arsenopyrite alteration in more ductile settings. This is the same structural-stratigraphic architecture that hosts the district's structurally controlled copper deposits, where the Budgery sandstone is used as a footwall marker horizon — the control that underpins Aeris's targeting across the package.

The overprint that matters most is the regolith. This is a concealed, sparsely outcropping landscape: thin Cainozoic cover, extensive aeolian dust, incised palaeovalleys, and a mid-Tertiary laterite–ferricrete–silcrete peneplain. Iron-oxide-rich palaeosurfaces in this terrain both concentrate and mask bedrock base-metal and arsenic signatures. That single fact governs the whole interpretation: it justifies a surface-geochemistry-led approach, but it also means every ferruginous surface anomaly must be tested against a supergene-scavenging "false anomaly" alternative before it is drilled — which is exactly why the recommended first steps here are data recovery and re-assay, not a drill rig.

Top three targets

T1 — The NY6921–26 Cu–Zn–Pb gossan cluster (highest-ranked, cheapest to advance).What it is: a tight ~300 m cluster of six "ball-textured laterite" gossan samples (to 1,400 ppm Cu / 5,700 ppm Zn / 780 ppm Pb) sitting on a coincident 1960s aeromagnetic feature, in the north of the licence. What testing achieves: ground-truthing, close-spaced re-sampling with a modern multi-element-plus-gold suite (including nickel, to complete Plumridge's own scavenging discrimination test), and reconciliation against current aeromagnetic/AEM coverage would either sustain a coincident geochem-geophysical drill target or retire it — before any drilling spend. Alignment with Aeris: this is a copper-zinc target on the Budgery-sandstone trend at the northern end of the package — directly on-thesis for a company whose stated goal is discovering large Tritton- or Murrawombie-sized systems to feed the central mill, with gold purely as upside.

T2 — The Bunyarra-workings ironstone As–Au–Cu–Sb trend.What it is: the BK15/BK16/BK35 ironstones (0.14 g/t Au, 436 ppm As at an old working; the anomaly repeats ~100 m north and in a large ironstone to the west). What testing achieves: mapping the ironstone's strike and structure, and confirming its position relative to the licence boundary, would establish whether a structurally controlled, oxidised gold-bearing system extends into the tenure. Alignment with Aeris: consistent with the arsenopyrite-bearing shear alteration in the holder's own structural account — a natural, low-cost complement to the copper focus that adds gold optionality without diverting from it.

T3 — Recovery of the 244-collar Nord EL3138 drill dataset.What it is: a licence-spanning legacy drill population with no open-file assay and a placeholder depth. What testing achieves: extracting the true depths, downhole lithology and any assays from DIGS R00020113 into the holder's database is a pure desktop exercise that would, at minimal cost, either materially de-risk or down-rank large parts of the ground and supply the spatial control the surface geochemistry lacks. Alignment with Aeris: this is precisely the kind of low-cost information gain a disciplined operator values — it feeds directly into the same near-mine/greenfields targeting engine driving the Tritton hub, and it converts a 1990s data gap into decisions the current team can actually use.

Closing statements

This is not a JORC-compliant statement. Historical results are reported from open-file sources and have not been verified by a Competent Person.

All data are sourced from publicly available NSW DIGS / GSNSW MinView open-file records and public ASX disclosures. CAADIA Metals has no interest in, and no commercial relationship with, Aeris Resources Ltd; the subject tenure (EL8810) is wholly held by Tritton Resources Pty Ltd, a subsidiary of Aeris Resources Ltd (ASX: AIS).

This article is general information only. It is not investment advice or a recommendation regarding Aeris Resources securities.

The full technical synthesis, intercept overview, indicative drill/work programme and source register are available on request.