The two companies first announced their intention to work together a year ago to the day when they signed a heads of agreement to discuss potential collaboration in mineral exploration, both inside and outside China.

They then signed a technical collaboration contract in November.

The JV's immediate priority would be the mineral targets identified, but not shared, under the November agreement, with future collaboration aimed at expanding to global exploration.

It said the JV's registered capital would be US$31.3 million, with initial contributions of $5.5 million by each party in about six months from establishment.

Any further capital contributions will be subject to the unanimous approval of both parties and linked to agreed target areas.

The JV itself is also subject to regulatory approvals.

Rio CEO J-S Jacques said formalisation of the exploration JV was an important milestone in the growing partnership between the two companies and with China.

"Our complementary strengths in exploration put us in the best possible position to find metals and minerals essential to human progress," he said.

Minmetals president Guo Wenqing said the collaboration was "significant" for the trader.

"Rio Tinto has rich prospecting experience and [has made] great discoveries worldwide, while Minmetals has solid technical expertise and extensive experience - the two strong partners will drive breakthroughs, pioneer progress, and promote the exchanges and collaboration of the global resource industry," he said.