The recognition of depositional bed-forms on fine sediments in some hydrothermal veins in central Wales

摘要

Old mine tips around Bryn-y-rafr mine in the central Wales Pb-Zn mining district yield small numbers of blocks with a fine (0.2 to <0.05 mm, most <0.05 mm, where identifiable) sediment accompanying the normal hydrothermal quartz, quartz + galena and quartz+ marcasite infills that characterise the A2 assemblage of Mason (Mason 1997). These show geopetal structures similar to those seen in situ at Tyndrum (Platten and Dominy 2007) but with more residual pore space, allowing structures to be seen in 3 dimensions. Descriptions here are based on the approximate orientation inferred from the geopetal indicators.