Looking For Graphite To Find Copper

Exploration for copper in the Zambian Copperbelt has been guided for most of the past hundred years by the search for a known favourable stratigraphic horizon known as the Ore Shale. Historical efforts have also been informed by a belief that the ores are syngenetic and stratiform. Both of these criteria are now known to be too restrictive. Economic mineralisation beyond the Ore Shale has been amply demonstrated by stratigraphically higher deposits close to the traditional Copperbelt, such as Frontier and Lonshi, as well as deposits such as Kansanshi and Sentinel that extend the Zambian Copper Belt all the way to the northwest of the country, and by the most recent discovery at Kamoa, in the DRC, by Ivanplats Ltd, far outside of, and above what was considered Copperbelt stratigraphy. The hydrothermal nature of many of the ores has also been validated, with the attendant role of structure, both deep-seated and local. These cases demonstrate that copper-bearing fluids precipitate their metals in (or near) the first reducing horizon they reach above the basement. The geophysical contribution becomes focused on mapping basement topography and graphitic (reducing) horizons, as well as crustal and local structure that can focus this fluid flow. Examples from a geographic spread of deposits along the Zambian Copperbelt highlight the role of electromagnetic imaging in the search for copper.