en.Wedoany.com Reported - Cobra Resources (LSE: COBR) has completed its first diamond drilling program at the Mount Manna copper project in South Australia. Located along the national railway and Barrier Highway, between the mining centers of Broken Hill, the Port Pirie base metals smelter, and Adelaide, the project sits in a region containing approximately 70% of Australia's copper reserves. The project combines a calc-silicate skarn, where copper grades track the proximity of porphyry pencil intrusions within a dolomite unit, and a larger porphyry system that had never been directly drilled prior to this program.
The four holes deployed aimed to explore the source of material for the shallow, high-grade skarn at the Blue Rose prospect and verify the presence of an intrusive porphyry source below. Past exploration had identified shallow copper mineralization over a 1.6-kilometer strike length, providing Cobra with surface scale but without confirming the deep driving force. Diamond core has not yet returned assay results, but geological observations point to a porphyry system and provide a method for locating further mineralization.
The 1,465-meter drilling program had a dual objective: to confirm whether shallow skarn grades continue at depth and to test for the presence of an intrusive porphyry below. Cobra drilled four diamond holes totaling 1,465 meters of HQ core, originally planned for 1,800 meters, with the rig operating 24 hours a day. Hole locations were designed to test the extension of shallow copper-gold mineralization at Blue Rose, the depth continuity of the skarn, and the endoskarn model. Diamond core allows direct reading of the structural and geological controls on mineralization, thereby optimizing the design of the next drilling phase.
A bornite zone discovered between 220 and 257 meters depth points to a hotter, potentially higher-grade core than the overlying chalcopyrite-dominated skarn. One hole, designed to test depth continuity below shallow reverse circulation (RC) intercepts—which included 74 meters at 1.02% copper and 0.25 g/t gold from 72 meters depth, and 86 meters at 0.60% copper and 0.14 g/t gold from 18 meters depth—traced chalcopyrite from 169 to 209 meters before entering a bornite zone from 220 to 257 meters. Bornite occurs within mineralized biotite schist enveloping porphyry diorite and monzonite intrusions, forming at higher temperatures within the potassic zone of the porphyry system. Chalcopyrite continued to the hole's end at 321 meters depth. Cobra Resources Managing Director Rupert Verco stated that the discovery of a bornite-rich zone associated with the porphyry intrusive sequence is a positive indicator of a potentially higher-grade porphyry system. Bornite has a higher copper-to-iron ratio than the surrounding chalcopyrite, so a bornite-dominated zone pushes drilling closer to the thermal center of the system.
The bornite zone coincides with an inverted magnetic low anomaly, directly linking a geophysical feature to copper and transforming the magnetic dataset into a target generator. Copper at Mount Manna is associated with a diorite-type porphyry formed during a period of magnetic polarity reversal, causing reverse magnetization to manifest as a deep magnetic low anomaly. Bornite mineralization near the porphyry intrusion spatially coincides with an inverted magnetic anomaly (an east-west trending feature). This coincidence establishes a direct correlation between magnetic signatures and copper mineralization, providing a repeatable method for targeting further high-grade pockets and additional porphyry-style mineralization within the project. Rupert Verco noted that insights from this drilling are improving understanding of the mineralizing system and the relationship between geophysics and mineralization, and as this relationship becomes clear, more scalable targets are emerging. With this correlation, existing magnetic surveys have been transformed into a ranked set of drilling targets rather than individual anomalies, and these findings have already optimized target selection for the next drilling phase.
A large fault-controlled anhydrite breccia between 190 and 220 meters depth is interpreted as a conduit for copper-bearing fluids flowing from the porphyry to the Blue Rose skarn. One hole encountered this large fault-controlled anhydrite breccia from 190 to 220 meters depth, formed from oxidized, sulfate-rich fluids of the porphyry system, interpreted as a structural conduit connecting the parent porphyry to the overlying Blue Rose skarn. The breccia itself is sulfide-free, so the zone is a vector rather than an intercept, but anhydrite breccia of this scale is uncommon, indicating a large porphyry system feeding the conduit.
Another hole shows mineralization strengthening with depth toward the heat source, and shallow oxide copper lies outside the modeled skarn footprint, expanding the target in two directions. One hole encountered shallow oxide copper from 14 to 67.5 meters depth, outside the current modeled skarn footprint, extending the near-surface target beyond its mapped limits. Deeper in this hole, magnetite and chalcopyrite increase with depth, and garnet appears, both indicating a rising temperature gradient as the drill hole approaches the intrusive heat source. Chalcopyrite recurs with pyrite and magnetite across multiple intervals from 74 to 342 meters depth, suggesting mineralization is not confined to the shallow skarn.
Extensive potassic alteration in one hole, along with sulfide mineralization now observed to depths of 300 meters, brings drilling close to a large porphyry body within known high-grade zones. This hole encountered large alteration zones, including potassic alteration from 265 to 320 meters depth, containing abundant pyrite and pyrrhotite with minor chalcopyrite. Potassic alteration of this scale forms near the core of a porphyry system, supporting proximity to a large porphyry body. Across the program, observed sulfide mineralization now extends to 300 meters depth within existing high-grade zones, deepening a system previously defined primarily at surface.
Based on these observations, Cobra exercised its option to fully own Mount Manna and has planned a September program to test the newly ranked magnetic targets. Cobra formally exercised its option to acquire 100% of Hamelin Gully, the holder of the Mount Manna license, converting observations into ownership. Hamelin Gully holds three exploration licenses covering 1,855 square kilometers. This step allows the company to advance two South Australian projects simultaneously: the Mount Manna copper project and the Boland in-situ recovery rare earth project. Rupert Verco stated that with strong shareholder support, they exercised the Mount Manna option and are now advancing two significant South Australian projects concurrently.
Diamond core is being sampled for assay and petrological analysis, and these findings will be used to design a follow-up reverse circulation (RC) program aimed at expanding scale and testing exploration targets. This RC program is scheduled for September 2026 and will test other key magnetic targets now ranked by the correlation.
What this program provides Cobra is an exploration model for the rest of the system, based on a geophysical dataset that now maps to copper and alteration vectors, all pointing to a single large porphyry source. This gives the company a clear path to test the scale of Mount Manna, rather than a single width of copper mineralization. Grade remains an open question, not to be answered until laboratory results are received.
It is emphasized that these geological observations are qualitative visual estimates from diamond core logging, and no laboratory assay results have been reported. Visual estimates of mineral abundance are not a substitute for laboratory analysis and do not provide information on impurities or deleterious attributes relevant to economic value. Regardless of assay results, the targeting methodology is the enduring outcome of this program, but confirmation of grade and the high-grade porphyry theory depends on laboratory results expected in August 2026, ahead of the September 2026 RC program.
