Rio Tinto Limited (ASX:RIO) has entered into a joint venture with Antipa Minerals Limited (ASX:AZY) which allows it to earn a 75 per cent interest in the Citadel project which includes the Calibre discovery.
 

Rio Tinto will stump up $3 million of exploration funds in the next 18 months and then progressively farm-in to the gold-copper-silver-tungsten rich deposit in a series of up to four stages for a 75% interest. 
 

Rio cannot withdraw during the initial part of the programme and could spend up to $60 million for its slice of the pie. 
 

Drilling for the programme is expected to commence in the first half of 2016. 
 

Rio Tinto reported a net profit of $1.04 billion for the 2015 financial year.