Sunstone Metals Ltd (ASX:STM) has confirmed the Bramaderos Project’s Alba target is a high-grade gold-copper porphyry discovery thanks to a follow-up drill program at the southern Ecuador asset.
The explorer fielded high-grade gold-copper assays from three follow-up drill holes at Alba, with one hole ending in mineralisation.
Sunstone has long suspected that Alba had discovery potential: a previous drill hole returned a 111-metre gold intersection, grading 2.35 g/t, from 93 metres.
Follow-up drilling continues at Bramaderos, with two more rigs heading to the Alba target to prove up Sunstone’s exploration capacity.
Alba stacking up to world-class porphyries
Speaking to the findings at its gold-copper play, Sunstone managing director Malcolm Norris said the latest results were “extremely exciting”.
“We now have enough drilling and geological data to build a picture of a high-grade gold-copper porphyry system at Alba,” he explained.
“Furthermore, there are signs that grade is increasing with depth in the system given the high-grade results in BMDD021.
“We are generating grades which are consistently in line with or better than those seen in many of the most important porphyries around the world.
“We would encourage investors to compare the Alba grades with some of those world-class gold-copper porphyries.
“We are also confident that the extensive electrical geophysical survey just completed at Alba and Limon will generate additional Alba-style drilling targets,” Norris concluded.
Shares have been as much as 6.42% higher in early trading to A$0.083.
Follow-up program
Sunstone recently drilled three follow-up holes — BMDD021, BMDD022 and BMDD023 — at the Alba gold target.
The best assays include:
- 223.7 metres at 0.58 g/t gold and 0.13% copper from 107.6 metres, including 137.4 metres at 0.75 g/t gold and 0.17% copper from 135 metres, including 60.7 metres at 1.01 g/t gold and 0.19% copper from 136 metres in BMDD021;
- 239.4 metres at 0.42 g/t gold and 0.13% copper from 82.5 metres to end of hole in BMDD022, including an open interval at the end of hole of 7.9 metres at 0.84 g/t gold and 0.21% copper from 314 metres; and
- 222.4 metres at 0.37 g/t gold and 0.13% copper from 76.4 metres, including 84.2 metres at 0.51 g/t gold and 0.16% copper from 183 metres in BMDD023.
Interestingly, hole BMDD022 ended in mineralisation, with 0.9 g/t gold and 0.23% copper reported in the last 1.9-metre sample. This hole has now been extended with assays pending.
What’s more, all holes intersected copper as chalcopyrite, bornite and covellite in variably veined stockwork porphyry.
Overall, Sunstone believes the latest results from Alba show there are big things in store for the Bramaderos asset. This is because:
- The currently known size of the high-grade porphyry is expected to grow as more holes are drilled;
- Alba delivers a high-grade domain that could play a critically important role in a development scenario at Bramaderos, particularly given its potential to provide high-grade feed at the start of an operation;
- The Alba results have significant flow-on effects for the potential value of the directly adjacent Brama system;
- Plans for the maiden mineral resource estimate for Brama will likely be expanded to incorporate Alba; and
- Other Alba-style exploration targets are now being defined within the broader Bramaderos concession, including at Limon, where porphyry targets remain below the gold-bearing lithocap.
With three drill rigs soon to turn the soil at Bramaderos, Sunstone is determined to take a closer look at Alba’s mineralised potential.