* Mines also faced with proposed windfall tax
* "Small amount" of minerals should be sold in S.Africa
* Union boss attacks new ANC leadership figure Ramaphosa (Adds platinum, iron ore plan details, quotes)
By Jon Herskovitz and Peroshni Govender
BLOEMFONTEIN, South Africa, Dec 19 (Reuters) - South Africa wants to impose export curbs on minerals such as platinum and iron ore as part of a drive by the ruling African National Congress to create more jobs in industry in the continent's biggest economy, a top official said on Wednesday.
The policy proposals from the Trade and Industry Ministry are meant to encourage more processing of minerals domestically but are unlikely to go down well with mining companies already being threatened with windfall taxes on their profits.
Speaking on the sidelines of an ANC conference in the central city of Bloemfontein, ministry director-general Lionel October said firms would only be required to set aside "small amounts" for sale locally at an unspecified discount.
"Our competitive advantage is access to the raw materials. That is why we must give access to the raw materials at developmental prices," he told Reuters. He did not elaborate on the definition of "small".
At the conference, which re-elected President Jacob Zuma as party chief, the ANC has tried to strike a pro-business tone to counter a clamour for radical policy shifts from the millions of South African blacks who have seen little improvement in their lives since the end of apartheid in 1994.
The 100-year-old liberation movement rejected wholesale nationalisation of the mines - championed by expelled ANC Youth League leader Julius Malema - but endorsed a "resource rent" tax that amounts to a windfall levy on mining firms.
"The state must capture an equitable share of mineral resource rents and deploy them in the interests of long-term economic growth, development and transformation," an ANC policy document seen by Reuters said.
It said the government should consider export taxes on "strategic" minerals, reflecting the ANC's wish to expand the domestic factory sector to tackle the 25 percent unemployment rate that poses arguably the biggest threat to its 18-year grip on power. The party has faced increased popular protests against its failure to reduce poverty, deliver services and create jobs.
The ANC has talked for years about getting more value out of South Africa's vast mineral wealth, without much action.
This led some analysts to downplay the impact of the policy document but they said it sent a worrying message to investors.
"It looks like a very autarchic approach to the economy rather than an open one. It is interventionist... and it is not going to encourage investment," said Peter Leon, a mining expert at Johannesburg law firm Webber Wentzel.
At the conference, the ANC also picked millionaire businessman Cyril Ramaphosa as Zuma's deputy, a choice seen as favourable to investment and the economy, particularly if Ramaphosa can push through plans to boost long-term growth.
Despite Ramaphosa's background as an anti-apartheid mineworkers' leader, his business image will serve as a counterweight to the unions that have seen their influence grow during the 70-year-old Zuma's 3-1/2 years in office.
Zwelinzima Vavi, head of the powerful COSATU trade union federation, went on the offensive on Wednesday by reminding South Africans that 'Cyril' - as Ramaphosa is widely known - is no longer a champion of the poor and downtrodden.
"He is now a multi-millionaire reflected by the empire that he has created over the few years he has been in business," he told Talk Radio 702.
"It is always the material conditions of men that influence their conscience. That is where we would be a little bit concerned."
Ramaphosa came in for strong criticism after he was shown to have lobbied the government in mid-August to act against thousands of strikers at Lonmin's Marikana platinum mine, in which he has a large personal stake.
The next day, 34 miners were shot dead by police in the bloodiest security incident since apartheid.
In another sign of possible tensions to come, the ANC also said the central bank should stick with inflation-targeting, squashing calls from unions and its Communist Party allies to switch the bank's mandate to include jobs and growth.
Ramaphosa, who was tipped as a possible successor to Mandela in the 1990s before turning his attention to business, has an estimated fortune of $675 million and sits on the boards of some of Africa's biggest companies.
In a statement issued via his Shanduka investment company, he said he would review his extensive business ties in the wake of his appointment as ANC deputy to ensure no conflict of interest. (Additional reporting by Sherilee Lakmidas in Johannesburg; Writing by Ed Cropley; Editing by Pascal Fletcher and Janet McBride)