I gotta say it makes more sense for RIO to be looking at integrating a manganese miner into its stable than that ongoing BS rumour about it buying Freeport McMoRan. And the plain, boring facts that RIO recently raised U$12Bn in stock sales and that they want to continue growth either organically or via smaller acquisitions (CEO dixit) haven't suddenly gone away. It makes no sense for RIO to sit on a pile of cash like this.
According to the jungle drums, Autlan are doing the blanket "no comment no comment!" to anyone that asks. That fuels the rumours, too. Here's the Autlan company website (English version) FWIW.