Molybdenum exploration target at the Bingham Canyon mine, Utah, USA

Recent brownfield exploration at the Bingham Canyon mine has identified a new molybdenum exploration target beneath the current open pit.

Diamond core drilling indicates a sub-vertical body of mineralisation extending at least 1000 metres below the floor of the pit. The average grade of molybdenum in the open pit reserve is 0.044 percent molybdenum while the grade of the material within the new exploration target is estimated to range from 0.1 to 0.15 percent molybdenum.

Location and Title

The new target lies within the footprint of the open pit and within patented mining claims owned by Kennecott Utah Copper.  Kennecott and predecessor companies have been conducting large scale open pit mining at Bingham for more than 100 years.

Location Map

Summary of Exploration Results

Sixteen diamond drill holes have intersected molybdenum mineralisation with assays available for 14 of the holes. Drilling suggests a steeply dipping arcuate body of >0.09 percent molybdenum mineralisation that appears to wrap around the barren core of the porphyry copper deposit in the northeast and southeast sectors of the deposit. There has not yet been any drilling directed at the deep molybdenum mineralisation in the northwest or southwest sectors of the deposit.

The molybdenum mineralisation locally reaches the surface on the eastern side of the pit bottom where it contributed to higher than average molybdenum head grades in the period 2004 through 2007. The mineralisation is mostly hosted by monzonite and occurs as quartz-molybdenite veinlets and as molybdenite disseminations or fracture fillings. Batch flotation testing of composite samples has indicated molybdenum recoveries of approximately 95 percent in rougher flotation, while preliminary testing indicates that the rougher concentrate can be upgraded readily by regrinding and cleaner flotation.

3D model showing molybdenum mineralisation extending beneath the Bingham Canyon mine
 

Table showing major intercepts

Exploration of the deep molybdenum mineralisation is part of on-going studies of future mine development options at Bingham. While it is likely that underground development could access both the deep molybdenum body and deep porphyry copper and skarn mineralisation, the feasibility of developing such a mine has not yet been established.

The potential quantity and grade of the molybdenum mineralisation is conceptual in nature. There has been insufficient drilling to define a Mineral Resource and it is not certain that further exploration will result in discovery of a Mineral Resource.

CP Statement

The information in this presentation that relates to Exploration Results is based on information compiled by Gerry Austin who is a member of the Australian Institute of Mining and Metallurgy (AusIMM). Gerry Austin is a full-time employee of Rio Tinto and has sufficient experience relevant to the style of mineralisation and type of deposit under consideration and to the activity which they are undertaking to qualify as a Competent Person as defined in the 2004 Edition of the ‘Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves’. Gerry Austin consents to the matters based on his information in the form and context in which it appears.