Miscellaneous investigations on mineralisation in sedimentary rocks

Five areas on the outcrop of the Helsby Sandstone Formation (formerly Keuper Sandstone) and Tarporle y Siltstone (formerly Waterstone) (Warrington and others, 1980) coinciding with known mineralisation were selected as targets for a geochemical investigation. About 3750 soil samples were collected and analysed for copper, lead, cobalt and nickel. Geochemical maps are presented to show the occurrence and distribution of anomalous values. In all the five areas investigated the geochemistry of the soils identified the known areas of mineralisation. In several instances other small areas were also indicated where the soil values are anomalously high and are presumed to reflect local, hitherto unknown, mineralisation. None of these areas, however, appear to have the area1 extent necessary for economic deposits. The results of this preliminary investigation indicate that in all cases the mineralisation is very closely associated with permeable and porous sandstone units which are faulted against less permeable units forming trap structlzres for migrating mineralising fluids.