The document, which has yet to be approved by Congress, will see First Quantum pay $375 million a year plus a royalty of 12% to 16% of the mine's gross profits.
The bank for decades held more than 300 tonnes equivalent of gold, but between 2015 and 2017 the government began using the precious metal as a collateral for loans with international banks.
Embryonic plans to nationalize mining, the creation of a one-chamber Congress, water rights, and protections for indigenous territories are some of the more edgy motions the assembly will discuss.
The initial capital requirement at Escalones is $438.4 million, followed by a sustaining investment of $192.5 million over the 20-year life of the project.
Las Bambas, which produces 2% of the world's copper supply, has said it will have to suspend production on February 20 if the road is not cleared by then.
"There's a general cooling of the economy in China. Infrastructure and property are both key in terms of driving metals demand and we do not expect a quick reversal in either."