Chilean mining company Antofagasta Minerals, one of the biggest global copper producers, on Tuesday was facing potential strikes from workers at its Zaldivar mine and by supervisors at Centinela as contract talks continue. Zaldivar workers will vote on whether or not to strike by the end of the week, legal advisor Marcos Lopez, who was also employed by a union at BHP Billiton’s Escondida mine during a historic 43-day strike earlier in the year, said.