The Central African copper belt is one of the world’s most important copper producing districts, with dozens of deposits spanning a 400km length through the Democratic Republic of Congo and northern Zambia. Of these copper deposits, a select few contain significant quantities of cobalt, which is produced as a by-product of the ore refining process.
In June 2016 a field trip was undertaken to Zambia in order to examine cobalt-rich ore from the copper belt. Dr Alex Webber, Research Fellow at the National Oceanography Centre at the University of Southampton and member of the COG3 Consortium reports from the field trip.
One of the great things about the copper belt is how well explored the region is, and therefore the sheer amount of core that is available to sample. On our first and second days we visited the Kalalushi core shed, a facility that hosts the government’s core collection from the days when the mines were run by the state. Here, we examined and sampled core from cobalt-rich deposits.
In a lot of deposits, especially where cobalt is not exceptionally abundant, the cobalt is hosted in iron and copper sulphide phases. But when the deposits are very rich in cobalt, it can be found as phases such as carrolite (Cu(Co,Ni)2S4), and at Kalalushi we spotted our first small piece.
The next two days were spent at a core shed run by Rio Tinto’s exploration team. They showed us a core through some of the domes region stratigraphy, including massive sulphide veining.
The core shed was adjacent to the Kafue River, and so once our core logs and sampling were complete, we headed down to the river to look at the crocodiles and hippos. But unfortunately, because it was mid-day, all the crocs were in the river cooling off and we didn’t see any. But we found lots of tracks!
The final day was spent in some of Mopani Mines’open pits, looking at the mineralisation in-situ. Apart from the enormous dessication cracks, we were able to see stunning chalcopyrite and bornite veins, and the basement was exposed, giving access to a potential source of cobalt.
And, now the samples are back in the UK, the real work begins!