The "small but high-grade" copper inferred resource was 230,000 tonnes grading 2% copper, containing 4,600t of copper, with traces of tungsten and molybdenum.

The deposit, which is a joint venture with 60% owner Arafura Resources (ASX:ARU), outcropped at surface, remained open at depth and looked to be favourable to openpit extraction.

Thor bought into Bonya with the key aim of discovering tungsten deposits near its 100%-owned Molyhil tungsten-molybdenum project, although executive chairman Mick Billing said the "free" copper resource was "a bonus".

The company said the deposit could potentially add six months of profitable mine life to the adjacent Molyhil project as valuable supplementary mill feed to the process plant.

"The Molyhil processing plant design is amenable to the treatment of copper ores of this nature, without modification, and we expect this material will flow though the plant with no additional investment required, other than mining and haulage," Billing said.

He said that there could also be satellite tungsten and copper deposits within economic trucking distance of Molyhil.

An external review of the vanadium deposits on the project licence is ongoing and Thor was planning drilling at several outcropping tungsten deposits at Bonya in early 2019 once drill site access clearance was completed.

Thor's shares were up 5.68% Monday in London morning trade to 1.96p (US2.52c).