The assets include the Mount Block exploration tenement, an access easement and the Que River mine lease as well as the remaining base metal exploration and development rights on the Hellyer polymetallic mine lease, in Tasmania's west.
NQ Minerals agreed to acquire the package with a view to starting gold production from Hellyer later this year.
Bass first announced the deal in May 2017, with the initial consideration being a 1% net smelter return royalty and A$650,000 in bonds and refunds.
Only three weeks ago, NQ presented at a conference in New York, forecasting an admission to London's AIM in the next few months and production via tailings retreatment by the December quarter.
The company, which had been responsible for all costs since the acquisition was announced, flagged a 10-year mine life that would generate expected revenue of more than US$715 million.
As well as a precious metals concentrate, NQ was also planning to produce a zinc concentrate and a lead-silver-gold concentrate.
Capital costs for the restart were estimated at just $15.1 million and the project generated an internal rate of return of 189%.
Bass said late on Friday that the term sheet had been terminated by mutual consent and Bass was no longer subject to exclusivity terms.
The company will appoint advisors to run a formal sale process and said current zinc and base metals prices could make the projects more attractive to potential buyers.
"The company is encouraged by the interest it has received in these assets becoming available again at a time of such limited supply," Bass CEO Tim McManus said.
"We'll look to maximise the value for our shareholders with this divestment, and expedite the process in that regard."
Bass' current focus is the operating Graphmada large flake graphite mine in Madagascar.
Shares in Bass closed on Friday at A3.2c, valuing the company at A$76 million.