Warke founded Arizona Mining, which ASX-listed South32 acquired the remaining 83% of for US$1.3 billion last year.
Warke has become executive chairman and largest shareholder of Tethyan with about 16% after his Augusta Investments subscribed for 11.5 million units of Tethyan's recent 16.6 million unit offering, which raised a total of C$3.3 million (US$2.5 million) at 20c per unit.
Jerrold Annett, who had joined Augusta in 2017 as corporate development senior vice president for Arizona and Titan Mining, becomes Tethyan's CEO.
Donald Taylor, who has been awarded for the discovery of Arizona's Taylor deposit, becomes a non-executive director.
Tethyan's non-executive chairman John Proust and John Carlile have resigned from the board.
"We are excited about bringing Tethyan into the fold and combining our knowledge and expertise to build a strong platform for growth, starting with the highly prospective and under-explored Western Tethyan mineral belt of Eastern Europe," Warke said.
Tethyan plans to use the proceeds to advance its Rudnica copper-gold project and Kizevak zinc-lead-silver project 5km apart in Serbia, where results from the late-2018 drilling programmes are due out soon.
In connection with the placement, Tethyan brought forward issuing the final tranche of 5 million shares to Dr Radomir Vukcevic for the company's 2018 Taor acquisition.
Tethyan said Perth-based Vukcevic now held a 15.74% stake but had "no present intention" to dispose of or acquire further shares in the company.
Tethyan shares hit 45c on Friday, their highest point since November 2017, before closing up more than 28% or 9.5c to 43c to capitalise it over $12 million.