Both companies previously reached an earn-in agreement related to the project for a minimum of $8.45m in October last year.
The revised arrangement will see Avanco offer $4m towards the acquisition within two months, and an additional $5m will be made in ten equal payments of $0.5m once the permitting process is completed.
The company will also be entitled to a net smelter royalty of up to 1% on the first 500,000oz of gold production, 2% on production between 500,000-1,500,000oz, and 1% on production exceeding 1,500,000oz.
Avanco managing director Tony Polglase said: “We are very excited about acquiring 100% of CentroGold, which we believe is one of the best undeveloped gold projects in Brazil.
“The project fits well into our business model of developing low-risk-low-capex mines that capitalise on our Brazilian and Aussie 'know how'.
"CentroGold hosts the higher grade and shallow Cipoeiro deposit which also benefits from good access to infrastructure.”
An infill drilling programme aimed at enhancing Joint Ore Reserves Committee (JORC) resources is scheduled to begin in the near future.
A scoping study is set to be finalised by end of the year, and the definitive feasibility study is scheduled for completion in first half of next year.
The permitting process is targeted for completion in the second half of 2018, while first production from the project is slated to be achieved in the second half of 2019.
The project is estimated to be capable of producing up to 100,000oz gold per year.