Epigenetic lead-zinc mineralization in miocene pebbly mudstones, Sierra de Cartagena, Spain

Abstract

The Pb-Zn-ores of Minas de Cartes, Sierra de Cartagena, Spain, occur in a zon along the lower boundary of a Miocene sequence and along post-Miocene faults. Pebbly mudstone beds in the Miocene are slump sediments, which by their lithological properties form preferred horizons for the spreading of the mineralization. Faulting and flexuring have caused cavernous fault breccias in the relatively competent pebbly mudstones, while dissolution of carbonate pebbles and carbonates in the matrix of these rocks has resulted in solution cavities. The brecciated cavernous pebbly mudstones form channelways for ore solutions and sites of deposition of ore streaks with marcasite, pyrite, galena, sphalerite and quartz. The mineralization is of typical cavity-filling nature and so-called “ore pebbles” are fillings of pebble-shaped voids resulting from selective dissolution of carbonate pebbles. The ores were formed by near-surface subvolcanic-hydrothermal processes in relation with Late Tertiary trachyandesitic volcanism in the region.