The court said Vale had failed to convince him to dismiss the case in which it is accused of conspiring to steal Rio's rights for part of iron ore reserve potentially worth billions.
The vote of the full plenary was prompted earlier this month when the EU's environment committee rejected a deal worked out after more than two years of lobbying by Canada.
The potential buyer — community-owned firm Baroka Tribal Mining— will also acquire Amplats' 22.5% percent indirect stake in its joint venture partner, Atlatsa Resources.
