Abstract
The Tharsis mining area is one of the largest mining centers of the Iberian Pyrite Belt, which covers a large area in the SW part of the Iberian peninsula. Sedimentary structures in the sulfide deposits of the Filon Notrte, Tharsis mine were studied in the field and under the microscope. The sulfide deposits are classified into two types based on internal structures: (1) massive pyritic ores; (2) pyritic ores with sedimentary structures. In the latter type, several kinds of sedimentary structures are observed, such as graded bedding, parallel and cross lamination and slump structures. Distribution of the sedimentary structures indicates that slump breccias are commonly observed in the lower horizons and in the country rocks, massive ores rather in the upper horizons and cross lamination in the middle horizons. Cross lamination is also obsevable in the calst of the slump breccias. From these, depositional process is considered to be as follows. In the early stage, ore solutions flowed out in the mud on the sea-floor from the feeders and sedimentary structures were formed after the outflow. Some ores were moved by slumping before lithification. In the late stage, massive ores were rapidly precipitated on the pre-existing ores.
