TORONTO, Feb 21 (Reuters) - Copper miner First Quantum Minerals said on Wednesday it was seeking $20 billion through international arbitration after Panama ordered the closure of the company's mine in the central American nation.

"We have provided a minimum value sought in those proceedings of $20 billion, reflecting an estimated fair market value of initial investment," First Quantum CEO Tristan Pascal said on an earnings call. (Reporting by Divya Rajagopal, writing by David Ljunggren)