Phoenix's previous land position had been 3,880 acres, or 7.43sq.km.
The two new blocks include Windy Devil, which is contiguous with Horseshoe, where 2018 sampling results reported grades as high as 9.19% copper, 580g/t silver, 2.02g/t gold, and 20% lead in surface rock chips.
CEO Dennis Thomas said the new Windy Devil block contained more than 30 unnamed prospects, including multiple previously mined shafts and adits.
"The mineralised extensions along strike from the Empire mine in the Horseshoe block, as well as extensive surface mapping and geological interpretation during the 2018 field season, made the expansion into Windy Devil imperative," he said.
The company said the larger second block, Navarre Creek, could potentially lead to near-surface precious metal discoveries as it contained a volcanic-hosted epithermal ‘hot springs'-type alteration zone and a 2.5-km brecciated jasperoid, which was geologically similar to the Carlin Trend in Nevada.
Thomas said Navarre Creek to the west was "also recognised during the 2018 field season as a highly prospective target area based on the classic hot springs style alteration evident on the surface".
With the enlarged land package, Phoenix said it had decided to focus on Empire and Idaho and had, therefore, let its option to acquire an 80% interest in the Gordon Lake gold property in Canada lapse.
"Now that we control the Horseshoe, Windy Devil, and Navarre blocks, we have secured a substantial district footprint that will [make] future operations and expansion easier to navigate," Thomas said.
"Given the focus on the Empire mine property and the wider district, including the two cobalt properties on the Idaho Cobalt Belt, we felt it was prudent to allow our option on the Gordon Lake gold property in Canada to lapse and focus purely on Idaho."
Phoenix's shares were down 4.7% on the news at 18.10p (US24c), which was also down 37.6% in the past six months.