Experts believe the US firm could achieve $300 million in operating and cost savings from combining its mines in Nevada with those of the Canadian rival.
The Westhaven surge is a reversal of fortune for Gren Thomas, who got his share position by bankrolling the company, keeping it afloat through years of struggle and shoestring budgets.
The Zaldívar copper mine in Chile, a joint venture between Antofagasta and Barrick, will be able to replace greenhouse gas emissions equivalent to 350,000 tonnes per year, or about 87,000 vehicles annually.