Gold Fields, the world's fourth largest gold producer, has upgraded the mineral resource estimate for its Chucapaca joint-venture project in Peru by 35 percent to 7.6 million ounces.

The company also said in a presentation sent to Reuters on Tuesday that it remained on track to diversify its operations and was aiming to get 60 percent of its global output from outside South Africa by 2015, up from 50 percent now.

South African gold miners are keen to reduce their exposure to their home base because of growing mine depths, rising costs and political risks such as nationalisation talk by radical elements of the ruling African National Congress.

South America is key to Gold Fields' global ambitions and the company aims to get 1 million ounces of production from the region by 2015, which would almost double its share of group output to 20 percent from 11 percent now.

A senior executive said earlier this month that Gold Fields' Chucapaca mine, a $750 million joint venture with Peru's Buenaventura , was on track to start construction by the second quarter of 2013 and initiate operations in 2015.

In its presentation, which was given on Monday by chief executive Nick Holland at the Denver Gold Forum, the company also said a pre-feasibility study was underway for its arctic platinum project in Finland.