RIO Tinto's uranium subsidiary, Energy Resources of Australia, suffered its biggest one-day share price plunge in more than two years on Friday.

This came as it unveiled an 83 per cent profit slide and said it wouldn't pay a final dividend.

The stock dived more than 12 per cent as ERA also revealed it would stop plant processing at its Northern Territory Ranger mine for three months and forecast a further sales fall this year.

ERA, in which Rio has a 68 per cent stake, posted a net profit after tax of $47 million for 2010, well below its $272 million result the previous year, as wet weather "severely affected" mining.

The strong Australian dollar, lower uranium sales price and lower grade of ore also hit the bottom line, it said. Sales revenue fell $572 million, down 26 per cent.

ERA said the Ranger processing decision would ensure water in a tailings storage facility remained at the required level after higher-than-average rainfall.

Because of this, production this year is tipped to be similar to last year, though uranium oxide sales are forecast to be 10 per cent lower.

"In view of the uncertainty surrounding ERA's production in the first half of 2011, ERA directors have decided that a final dividend for 2010 will not be paid," the company said.

In better news for Rio, an Indian consortium ruled out a rival bid for takeover target Riversdale Mining, clearing the way for Rio's $3.9 billion friendly move.

Shares in Riversdale, an Africa-focused coking coal explorer, fell below Rio's $16 an offer price, after India's International Coal Ventures Limited declared it would not make an offer.

ERA shares closed down 12.89 per cent, or $1.53 at $10.34. Riversdale was 2.28 per cent lower, or 37 to $15.87 while Rio Tinto lost 22, or 0.26 per cent, to $85.82.