Australian Critical Minerals Drilling Points to Hidden Copper-Gold System at Flint
Key Takeaways
- Phase 1 diamond drilling at ACM's Flint Project comprised four holes totalling 1,773.3 metres, with FL_DDH002 extended to 656.7 metres after geologists observed encouraging alteration vectors during drilling.
- Two distinct mineral system targets have been confirmed: a high-sulphidation epithermal system in the top 54 metres and geochemical vectors pointing toward a concealed porphyry copper-gold system below 190 metres depth.
- Integrated analysis of drilling and AMT 3D geophysical data has identified two large conductive Lithocap targets in the underexplored southern area — approximately 1,100m x 500m and 800m x 300m respectively.
- No economic grade intercepts have been reported; the significance lies in alteration patterns and geophysical targets that define a framework for systematic follow-up work.
- ACM has designed a five-stage follow-up programme including WorldView-3 satellite mapping, drone magnetics, soil geochemistry, and deep-penetrating IP geophysics before committing to additional drilling across the 4.8 sq km alteration system.
Drilling confirms dual-target potential at ACM’s Flint project in Peru
Phase 1 diamond drilling at the Flint Project in Peru has returned assay and hyperspectral data confirming two distinct mineral system targets: a high-sulphidation epithermal system near surface and a conceptual porphyry copper-gold system at depth. The programme comprised four holes totalling 1,773.3 metres, with drill hole FL_DDH002 extended below its original target depth to a total depth of 656.7 metres after company geologists observed encouraging alteration vectors during drilling.
Australian Critical Minerals Ltd (ASX:ACM) is focused on gold, silver, copper and critical minerals exploration, with its core operations in Peru. This release should be read as early-stage exploration — no economic grade intercepts have been reported. The significance lies in the alteration patterns and geophysical targets identified, which together define a framework for systematic follow-up work.
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What FL_DDH002 found — from the surface to 657 metres
The drill hole tells a two-zone story, with distinctly different geochemical signatures above and below 190 metres depth.
The Flint Project drilling permits for gold-silver targets were secured ahead of the Phase 1 programme, establishing the regulatory foundation that allowed ACM to mobilise and complete the 1,773.3 metre campaign now delivering these alteration and geochemical results.
Zone 1 (0–54m): High-sulphidation epithermal target confirmed
- Advanced Argillic Alteration (AA) confirmed across this interval
- Strongly anomalous epithermal pathfinder elements: arsenic (As), antimony (Sb), tellurium (Te) and thallium (Tl)
- Silver (Ag) detected at ppb level
- Consistent with the high-sulphidation epithermal (HSE) exploration model being evaluated at Flint
Zone 2 (190–656m): Geochemical vectors toward a concealed porphyry system
- Transition from propylitic to phyllic alteration with sulphide content exceeding 10% pyrite
- Molybdenum (Mo) peaking at 23 ppm
- Copper (Cu) typically in the range of 75–131 ppm
- Localised gold (Au) at ppb level
These are pathfinder element anomalies only, not economic grade intervals. Their significance is directional: the alteration sequence and geochemical signature are vectors that point toward proximity to the outer margin of a concealed porphyry system.
Two large conductive targets identified in the underexplored southern area
Integrated analysis of the drilling results alongside the AMT 3D geophysical model (previously reported 4 February 2026) has highlighted two large conductive targets in the southern part of the project:
- Lithocap Target 1: approximately 1,100m x 500m conductive anomaly
- Lithocap Target 2: approximately 800m x 300m conductive anomaly
These targets potentially represent the upper level of “Lithocap” style alteration centres. A Lithocap is typically barren in copper, molybdenum and gold at surface but can conceal significant porphyry mineralisation at depth — making it a meaningful structural signpost rather than a direct ore indicator.
Application of Porphyry Copper Deposit (PCD) trace element metal ratio analysis, specifically the Porphyry Index (MPIxL), to historic rock chip data shows anomalism coincident with both targets. Importantly, FLDDH002 may have been drilled in the outer halo of the porphyry system underlying Lithocap Target 1, with the down-hole geochemical vector pointing east toward the interpreted concealed centre.
Understanding epithermal and porphyry systems — why the alteration story matters
High-sulphidation epithermal systems are gold and silver deposits that form at relatively shallow depths, typically where magmatic fluids interact with near-surface groundwater. They are characterised by intensely altered, acid-leached rocks and specific pathfinder elements — arsenic, antimony, tellurium and thallium — that signal their presence even before ore-grade mineralisation is intersected.
Beneath many of these epithermal systems sits a porphyry copper-gold deposit: a much larger, lower-grade system formed at greater depth around a cooling intrusive body. The Lithocap sits between them — a surface “cap” of altered, generally metal-poor rock that is a natural consequence of the hydrothermal system above the porphyry. It is often barren at surface but acts as a reliable signpost to the more valuable mineralisation below.
The progression of alteration types observed in FL_DDH002, from Advanced Argillic near surface through propylitic and into phyllic alteration at depth, is precisely the sequence exploration geologists look for as a directional vector toward the porphyry source. Each alteration type reflects increasing temperature and proximity to the heat and fluid source.
ACM has drawn comparisons to Andean porphyry-epithermal systems including BHP/Lundin’s Filo del Sol, Atex Resources’ Valeriano, and Mogotes Metals’ Filo Sur. These are offered as analogues for the style of geological system being investigated at Flint — not as comparisons of grade, size or economic potential. Flint is located in a prolific epithermal-porphyry corridor in northern Peru, approximately 60km from the La Arena epithermal Au-Ag and porphyry Cu-Au system.
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What comes next — the follow-up exploration programme
ACM is designing an integrated, multi-stage exploration programme to systematically de-risk the Lithocap targets and the underexplored southern high-sulphidation area before committing to additional drilling. The planned sequence is:
- WorldView-3 (WV3) satellite alteration mapping across the full 4.8 sq km alteration system to define higher-temperature alteration centres
- Drone magnetic survey over the Lithocap and southern high-sulphidation (HSE) area to identify covered intrusive centres that may have acted as heat engines and metal sources
- Low detection limit soil and rock chip geochemistry and TerraSpec alteration analysis across key areas identified by the WV3 and magnetics programme
- Deep-penetrating IP (Induced Polarisation) geophysics over priority coincident anomaly zones to refine drill targets
- Selection of priority drill targets from the integrated dataset
The southern high-sulphidation target area remains largely untested by modern systematic exploration, making it a material area of interest for the next programme.
Executive Chairman Dean de Largie commented on what the Phase 1 results mean for the project’s direction:
Dean de Largie, Executive Chairman
“The Phase 1 drilling programme has materially improved ACM’s understanding of the Flint hydrothermal system. It has strengthened the epithermal model and generated a credible deeper porphyry-related target concept. Assays from FL_DDH002, together with downhole hyperspectral data, confirm advanced argillic alteration and associated elevated epithermal pathfinder elements, including arsenic and antimony, near surface. These results are consistent with the high-sulphidation epithermal exploration model being evaluated at Flint.”
On the deeper porphyry potential, de Largie added: “At depth, FL_DDH002 intersected increasingly intense phyllic alteration with substantial pyrite and low-level copper and molybdenum anomalism. These results provide encouraging geological and geochemical vectors supporting the potential for a concealed porphyry-related system within the broader Flint alteration footprint.”
Key facts at a glance — Flint Project snapshot
| Parameter | Detail | Significance | Status |
|---|---|---|---|
| Phase 1 drilling | 1,773.3m, 4 holes | Systematic target testing | Complete |
| FL_DDH002 depth | 656.7m | Extended for alteration vectors | Assays received |
| Lithocap Target 1 | ~1,100m x 500m | Potential porphyry Lithocap | Follow-up planned |
| Lithocap Target 2 | ~800m x 300m | Potential porphyry Lithocap | Follow-up planned |
| Project footprint | 4.8 sq km alteration system | Porphyry-epithermal scale | Mapping planned |
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