Mount Toromocho.html



Mount Toromocho (Chinese: 特罗莫克山 ^{1 2}) or in Spanish 'a bull without horns', (and it really does look like a bull when approached along the main road from La Oroya) is a mountain next to the long established mining camp of Morococha and hosts a large polymetallic metal deposit. It is now owned by the Aluminum Corporation of China (Chinalco) who are planning to establish a large open pit mine on the mountain to produce 210,000 tonnes copper annually. Available information is rather sketchy in the absence of an official announcement in English so the following must be taken as indicative rather than firm. Nor, as a wholly owned subsidiary of a company in a very secretive country, is it clear whether much more information will be released.

History

The mineralisation on Toromocho has been known and mined on a small scale for many years and was drilled by both the Cerro de Pasco Corporation and its successor (after nationalisation) Centromin³ between 1966 and 1976 but it was evidently not considered worth exploiting, probably due to lack of finance in the case of Centromin and the spectre of nationalisation in the case of Cerro, or maybe it just did not look economic at the prevailing metal prices.

Peru Copper Inc was formed in February 2004 and took over the Toromocho option that had been successfully bid for from Centromin by its predecessor company. The five year option required certain expenditures which Peru Copper completed satisfactorily and the option was exercised on 5th May 2008⁴. There is no indication of any further payment for the exercise of the option.

In the meantime on 11th July 2007 Chinalco purchased Vancouver listed Peru Copper Inc for C$840 million⁵ and it became a wholly owned subsidiary of Chinalco. Chinalco now plans to establish an open pit copper mine at a cost of US$2.16m to produce 210,000 tonnes of copper annually⁶.

The Deposit and its Resources

Much of the technical information below comes from a report prepared by Independent Mining Consultants of Tucson, Arizona entitled Toromocho Project Technical Report, Prepared For Peru Copper, Inc.⁷

The mountain of Toromocho is located about 140 km east of Lima on the main road to La Oroya. High tension power lines pass close by (although inadequate for Toromocho at present) as does the Central Railroad though part of this may have to be relocated as it runs over the projected limit of the open pit. It is next to the mining camp of Morococha where SIMSA and Pan American operate underground silver/lead/zinc mines. It is not clear how Toromocha will affect these operations but it has already been decided to move part of the Morococha mining camp. Chinalco is offering a new house and US$2,000 compensation and the offer has been accepted by a majority of the population according to a BBC report⁸

The deposit is very high with elevations over the deposit ranging from 4,700 metres (15400 feet) to 4,900 metres (16,100 feet). Neither humans nor diesel powered machinery work very well at that altitude as anyone who travels up from Lima on the main road over the 4,818 metre (15,800 feet) El Ticlio pass realises as the engine starts to struggle towards the top. Also there is anecdotal evidence of geologists being quite unable to understand their notes made on top of the mountain due to the befuddling of their minds by the lack of oxygen. The early years will not be easy.

The deposit is complex but has the general characteristics of a porphyry copper. It consists of a core of copper with molybdenum and silver, surrounded by a a lead/zinc zone then a lead/silver zone that is being mined to the north-east of Toromocho by various small companies. It has been mined on a small scale in the past and the underground workings have proved to be valuable drill sites. The ore reserves and resources released in the IMC Technical Report were as follows

Proven and probable reserves 1,375 million tonnes grading 0.51% copper, 0.018% molybdenum and 7.06 gms/tonnes silver. Resources were estimated at 601 million tonnes grading 0.37% copper, 0.016% molybdenum and 6.82gms/tnne silver.

Using the recoveries estimated by IMC, the recoverable metal from the reserves would be 5.7 million tonnes of copper, 148,000 tonnes molybdenum and 188 million ounces of silver, giving a life of over 25 years at an average production rate of 210,000 tonnes copper annually, plus another 8 years if the resources prove payable, a total of 35 years.

The Mine

Chinalco estimate that it will cost US$2.16m to bring the mine to production⁹ in 2012 and that annual production will be 210,000 tonnes copper¹⁰. It will be a medium sized mine by world copper mining standards. However, due to the relatively low copper grade the mill will have to be large at at least 140,000 tonnes per day.

Operating costs will probably be relatively high per pound of copper despite a low stripping ratio (the amount of waste that has to be moved to access the ore), again due to the low grade coupled with the adverse working conditions. On the other hand the molybdenum and silver will be very valuable sources of byproduct income which at current prices could cover operating costs.

Metallurgically the concentrate is likely to be relatively complex. It will contain arsenic which could well incur smelter penalties in the early years because of the enargite (Cu3AsS4) in the top of the deposit. The zinc and antimony are unlikely to be a problem. A more serious problem is the presence of variable quantities of talc which come out with the copper/molybdenum concentrate and tend to depress the copper grade of the concentrate. Sodium carboxymethylcellulose (CMC), will supress the talc in the flotation process but it has the unfortunate side effect of reducing molybdenum recovery. It gives a higher grade copper concentrate but also lower recovery. A high grade copper concentrate is very desirable because smelters generally deduct 1% from the copper content which is a higher percentage of a low grade concentrate than a high one.

Please see the note in Discussion regarding the above figures.

References