The signs point to a substantial maiden resource for Sunstone Metals Ltd (ASX:STM) at the El Palmar T1 gold-copper porphyry discovery in Northern Ecuador with new assays from trenching revealing significant mineralisation at surface.
Results from surface trenching include 40.4 metres at 0.86 g/t gold and 524 parts per million (ppm) ppm copper in P6-7d and 21 metres at 0.34 g/t gold and 714ppm copper in P6-7c. Both are open on all sides.
These results demonstrate the extensive near-surface mineralisation of this growing porphyry gold-copper discovery with strong gold and copper porphyry grades in intervals of fresh rock set to underpin new shallow drilling programs.
“Extensive near-surface mineralisation”
Sunstone managing director Patrick Duffy said the results continued to demonstrate the vast extent and shallow nature of the mineralisation at El Palmar. “We have established that there is extensive near-surface mineralisation with strong grades.
“These trenching results lead us to the mineralisation and will therefore underpin the next drilling program at El Palmar, increasing its efficiency and effectiveness.”
The trenching results are from a broader trenching program to enlarge the areas of gold-copper mineralisation at El Palmar in preparation for the next phase of drilling.
About the trenching
In trench 6-7d, two fresh rock samples each over 0.7 metres returned assays of 1.36 g/t gold and 0.22% copper, and 0.97g/t gold and 0.16% copper, which are strong gold and copper grades for a porphyry system.
Where the porphyry is exposed as fresh rock in the trench, copper values are elevated, suggesting overall copper has been leached at surface and that the fresh rock copper values are more indicative of the porphyry target.
The high-grade trench interval is interpreted to correlate with results from drill hole EPDD004, which intersected 97 metres at 0.43 g/t gold and 0.11% copper for 0.61 g/t gold equivalent, about 200 metres below the trench.
Sunstone’s trenching program has been completed in areas only where, for safety reasons, the younger cover is less than 2 metres thick and, for example, means that trench P6-7 comprises four segments.
The new trench results also define a second major locus of higher-grade mineralisation within the broader T1 mineralised system.
Trench 6-3 in the SW part of T1 identified high-grade porphyry gold up to 1.13 g/t gold over a 2-metre interval within a broader open-ended 10-metre mineralised interval.
This area corresponds to a planned drill target within T1 that is expected to identify new parallel mineralised zones.
Resource estimate
These trenching results will be incorporated into a mineral resource estimate once the next phase of drilling is completed.
“Internal studies have commenced in preparation for a maiden resource estimate,” Duffy said.
“The value of a significant outcropping component to the extensive El Palmar porphyry gold-copper system cannot be underestimated as we prepare for a mineral resource estimate, consider reasonable prospects for economic development, and allow for exploration of deeper targets to strongly enhance the overall scale of this cluster of porphyry deposits.”
Sunstone has extended the trenching program to assess the potential for mineralisation outside of the original T1 magnetic anomaly target and to test for the amalgamation of targets T1, T2 and T5.