Canada’s Turquoise Hill Resources (TSX, NYSE: TRQ) is taking Rio Tinto (ASX, LON, NYSE: RIO) to arbitration over the mining giant’s role and obligations to support the company in securing additional funding for the vast Oyu Tolgoi copper-gold-silver mine in Mongolia.

Turquoise Hill said a special committee of its board, which approved the arbitration, concluded that Rio’s approach to the financing of the mine expansion was “incompatible with the company’s announced strategy to maximize debt and/or hybrid financing for the Oyu Tolgoi project so as to minimize the size, and defer the timing, of an equity rights offering (if any)”.