It first announced the option in November and has since done confirmatory work as part of its technical due diligence.
Rockfire said Copper Dome was a vastly under-explored, potentially large-scale mineralised system only 50km from its Copperhead project, with recent soil sampling identifying "coherent, strong gold and copper anomalism", and rock samples returning copper values up to 23.4% and gold to 3.2g/t.
Previous diamond drilling in 1972 intersected 15.24m at 0.88% copper, including 4.58m at 2.28%, from 161m downhole depth; 12.2m at 0.61%, including 3.05m at 1.24%, from 54m downhole depth; and 24.38m at 0.27%, including 7.4m at 0.43%, from 225m downhole depth.
The company said mineralisation outcropped at surface, providing low-cost, near-surface exploration, which should result in lower exploration costs.
CEO David Price said the geological setting showed "excellent signs for gold and copper mineralisation", with coherent copper occurring around the rim of a mapped porphyry, as well as gold occupying the boundaries of two close-spaced porphyries.
"The company's intention is to expand our exploration into geophysics, including ground magnetics and gradient array IP. These two geophysical techniques are expected to identify clear targets in and around the geochemical anomalies, which will lead towards drilling," he said
He said Rockfire aimed to grow and expand the mineralisation at Copper Dome in conjunction with Copperhead and advance both porphyry projects simultaneously, with the aim of outlining large tonnage copper resources.