Iron sulfide precipitation sequence in Albian coals from the Maestrazgo Basin, southeastern Iberian Range, northeastern Spain

Abstract

Deposition of important coal accumulations in the proximal areas of a delta-estuary, occurred in the Maestrazgo Basin during the middle Albian (late Lower Cretaceous). These coals are characterized by high sulfur contents: 4.18% in coal from the Castellote subbasin, and 7.16% in coal from the Calanda subbasin (dry basis). A petrographic study of iron sulfide was carried out on the subject coals, to deduce an iron sulfide precipitation sequence for five principal stages: (a) early syngenetic stage; (b) late syngenetic stage; (c) syngenetic-diagenetic stage; (d) early epigenetic stage; and (e) late epigenetic stage. A sulfide precipitation control during the syngenetic stage, carried out by different compounds liberated from organic matter during its coalification stages, is deduced from the confrontation with other studies on coal differing in rank, depositional environment and geographical location.