CSAMT survey at Los Lirios maps a feeder zone and an open sulphide anomaly. Phase 2 drilling targets a maiden resource. Here's the geophysics explained.
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EV Resources (ASX: EVR) has finished interpreting a 2D inversion model from a controlled source audio-frequency magnetotelluric (CSAMT) survey at the Lirios 1 prospect within its Los Lirios antimony project in Mexico. The survey mapped subsurface conductivity changes across a 500-metre vertical window. It returned two major anomalies: a potential sulphide feeder zone at depth adjacent to existing drilling, and a massive untested anomaly to the southeast that remains open. A broader structural network of sub-parallel vertical features was also delineated, parallel to the known San Elias and San Miguel feeder structures.
Managing director Mike Brown said the survey delivered more than the company had hoped.
“By successfully mapping a robust network of vertical fault structures, we now possess a critical vectoring tool to target high-grade zones within this CRD system,” he said.
The results feed directly into planning for an aggressive Phase 2 drill program aimed at a maiden mineral resource estimate (MRE). Antimony prices are favourable globally, and the company sees a clear path forward.
The CSAMT survey delineated a network of sub-parallel vertical features and lineaments bounding the low-resistivity target zones. Those features run parallel to the known San Elias and San Miguel feeder structures. The company now has high-potential targeting vectors for drilling areas where the structures intersect the receptive limestone unit.
Delineating the fault network allows EV Resources to predict where hydrothermal fluid interaction has been highest, providing a potential roadmap for localised high-grade zones. The two low-resistivity anomalies sit within this network.
One anomaly sits adjacent to existing drilling at depth. It is interpreted as a sulphide feeder zone. The company drilled shallow holes earlier; this anomaly lies below them, suggesting the mineralised system extends deeper than previously thought.
The second anomaly lies to the southeast, outside the current drill pattern. It is described as massive and untested. The anomaly remains open in multiple directions. If it contains sulphides, it could significantly expand the mineralised footprint.
CSAMT measures subsurface conductivity. A transmitter on the ground sends a controlled frequency signal, and receivers measure how the Earth responds. Data is inverted into a 2D resistivity model. In mining exploration, the goal is to find resistivity contrasts that could mark sulphide accumulations or feeder structures.
At Los Lirios, the country rock is limestone and gypsum. Those rocks are very high resistivity (low conductivity). The CSAMT picked up two low-resistivity anomalies. Because of that contrast, the anomalies have been interpreted as sulphide-enriched units or zones. The survey also mapped a network of sub-parallel vertical features and lineaments bounding the low-resistivity zones. Those features are parallel to known structures – San Elias and San Miguel – which are already identified as feeders.
The vertical depth window was 500 metres. That means the model sees down to about 500 m below surface, which is deeper than most early-stage ground geophysics. For a small-cap explorer, that is a meaningful increase in resolution.
The typical mistake is to treat a resistivity anomaly as a direct detection of mineralisation. It is not. A low-resistivity reading can come from graphite, saline groundwater, clay alteration, or even a buried pipe. The only way to confirm a sulphide source is with drilling that returns assay grades.
The better read is to ask what else could produce the same signal. At Los Lirios, the country rock is high-resistivity limestone and gypsum, so any low-resistivity anomaly stands out. Still, the interpreter needs to rule out water-filled fractures or clay-rich fault gouge. The CSAMT data provides a vector, not a verdict.
EV Resources has existing drilling at Lirios 1. The CSAMT anomaly adjacent to that drilling is a feeder zone at depth. If that anomaly is cored and returns antimony or base-metal grades, it will validate the geophysical fingerprint. If it hits barren water or graphite, the CSAMT method loses credibility for this system.
The two anomalies are not equally ranked. The feeder zone adjacent to existing holes carries higher confidence because it aligns with known mineralisation. The southeast anomaly is higher risk but higher reward – it could double the strike length of the system if confirmed.
Brown said the company would target both with the Phase 2 drill program. “Our strategy here is clear and aggressive: test these highly prospective structural corridors, where hydrothermal fluids interaction with the receptive tabular limestone unit is optimised, expand the mineralisation footprint testing the potential sulphide anomalies, and accelerate towards a maiden JORC MRE,” he added.
The CSAMT has given EV Resources a targeting map. The next step is drilling. Here is what a trader or investor should watch for in the Phase 2 results.
Antimony prices are in a favourable cycle, driven by demand from flame retardants, military applications, and the broader critical-minerals narrative. A maiden MRE at Los Lirios could attract strategic interest or joint-venture partners. The company is not waiting for a bull market – it is accelerating exploration now.
A maiden MRE for an early-stage project like Los Lirios usually requires at least two to three drilling campaigns. By identifying the feeder zone and the southeast anomaly, EV Resources can prioritise the holes most likely to add tonnage. The company is not doing a wide-spaced grid; it is targeting specific geophysical features.
For investors following small-cap ASX plays, the key number to track is the number of drillhole intercepts that match the CSAMT model. Each confirmed target upgrades the project’s reliability and reduces the risk of a miss in the next hole. A recent analysis of small-cap ASX explorers noted that the gap between a compelling geophysics release and a de-risked resource often comes down to execution in the field. EV Resources has the map. Now it needs the core.
The Phase 2 drill program will target the structural corridors where hydrothermal fluids interacted with the tabular limestone unit. Brown said the company has a robust network of vertical fault structures – a vectoring tool to target high-grade zones. If the first few holes hit mineralisation that correlates with the resistivity model, the path to a maiden MRE shortens further. Drill results will determine the stock’s next move.
Prepared with AlphaScala research tooling and grounded in primary market data: live prices, fundamentals, SEC filings, hedge-fund holdings, and insider activity. Each story is checked against AlphaScala publishing rules before release. Educational coverage, not personalized advice.