The elemental sulfur ore deposit of Salmerón: Las Minas de Hellín basin (Late Miocene, SE Spain)

Abstract

Strata-bound elemental sulfur deposits occur in different circum-Mediterranean Miocene sedimentary successions containing evaporites and high amounts of organic matter. It is widely known that bacterial sulfate reduction processes are the triggering mechanisms involved in the origin of hydrogen sulfide and the subsequent native sulfur. However, in most of these sedimentary successions, there is controversy over whether elemental sulfur formed in the basin floor, as the same time as the sediments (biosyngenetic), or later, during diagenesis (bioepigenetic). Las Minas de Hellín basin, in the SE Spain, contains one of the largest elemental sulfur deposits in Europe. Based on data recovered from mining company (1903 -1960) and a borehole campaign performed by MINERSA between 1987 and 1988, two native sulfur ore bodies are recognized. The upper sulfur body is hosted by carbonates and diatom-rich levels, whereas the lower sulfur body, only exploited in underground mines now closed, is hosted by gypsum. This work shows a petrological and geochemical study of core samples from the upper sulfur body in the Salmerón area (Murcia), 500 m west of the widely exploited area of Las Minas de Hellín (Albacete). In Salmerón, elemental sulfur occurs as pseudomorphs after primary sedimentary gypsum as well as filling fractures and bed joints. The elemental sulfur replacement is also related to calcification and silicification of the sedimentary biomediated dolomite. The mineralization is considered bioepigenetic formed during early diagenesis. Contribution from hydrothermal waters circulating through adjacent faults are not ruled out.