Sediment-hosted Ore Deposits Tour – Part 7

Time underground at Nyrstar’s ETM operations. A classic Mississippi Valley Type (MVT) carbonate-hosted set of mineral deposits hosted in the Cambrian-Ordovician Knox Formation. Spectacular examples of solution-collapse breccias and bed replacement in a karstified limestone-dolostone sequence that were then later mineralized by Zinc-rich hydrothermal fluids circulating during Perimian-Pennsylvannian tecontism. Precise dating of the age of mineralization in such deposits is notoriously difficult, but one can distinguish between the early ground preparation created by karsting, which is then followed by later introduction of hydrothermal fluids.
Mineralogically very simple with very high purity, honey yellow sphalerite which is in high demand for products such as surgical steel. Gangue minerals include dolomite, silica and rare pyrite. Working underground makes one appreciate the complex geometries associated with such deposits.

Mining is conducted using the room and pillar method. Ore materials are processed at a mill using heavy medium separation and flotation, followed by shipment to the nearby Nyrstar-owned smelter in Clarksville. The byproducts of this operation are used for aggregate and agricultural lime, making for a very low waste operation with little environmental impact.  #KFFellows


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