| Summary: | The Pb - Zn - Ba - F deposits of the Southern Pennine Orefield comprise stratabound rakes, pipes, and flats which are developed exclusively in Lower Carboniferous (Dinantian) Limestones and dolomites lying on a basement of Lower Palaeozoic rocks. The distribution of these deposits is largely controlled by the occurrence of favourable lithofacies, located on structural highs, in the uppermost (Brigantian stage) shelf limestones. These include pseudobreccias, shell beds, reefs, stylolitically-bedded limestones, erosion surfaces, and coarse crinoidal biosparrudites. A number of other lithologies acted as aquicludes and include lavas, tuffs, clay wayboards, shale, and chert beds. A review of studies of paragenesis, fluid inclusions, and isotopes has shown the mineralisation probably originated by deep circulation of connate Dinantian waters which leached base metals, barium, and fluorine, from a variety of crustal rocks. Deep seated sources provided sulphur in some of the sulphide minerals whose origin was related to crustal rifting in the area during the opening of the North Atlantic and the formation of the North Sea Basin. The mineral solutions were acidic and produced a system of integrated hydrothermal karst cavities known as pipes. Precipitation of the minerals occurred by an increase in pH, cooling, and decrease in pressure. Many of the pipes continued through the Tertiary and Pleistocene to act as water courses, where alluvial placer deposits of galena, fluorite, and baryte accumulated.
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