The beach placer iron deposit of Portman Bay, Murcia, SE Spain: the result of 33 years of tailings disposal (1957–1990) to the Mediterranean seaside

Abstract

Between 1957 and 1990, the Peñarroya Mining and Metallurgical Company (SMMPE) disposed about 60 million tonnes of tailings materials directly to the Mediterranean Sea. A substantial part of it (12.5 Mt) was dragged back by the sea currents progressively infilling the Portman Bay (Murcia, SE Spain), thus making the shoreline advance between 500 and 600 m seaward. The Roberto froth flotation plant processed mineral from manto-type deposits belonging to the Sierra de Cartagena-La Unión lead-zinc district. One of the mineral assemblages present in these deposits comprises greenalite, magnetite, sulfides, carbonates, and silica. Despite that magnetite recovery was undertaken by SMMPE between 1959 and 1967, we estimate that magnetite contained in the tailings hosts a substantial resource that could be as large as 2.3 Mt of iron ore. The ore contains magnetite ± hematite ± siderite. Tidal waves and sea currents led to gravimetric classification of the tailings material, with concentration of the dense iron oxides in the sandy fractions, eventually forming a coastal placer iron deposit. A major problem for magnetic separation is the intimate intergrowth between magnetite, hematite, and siderite. Besides, the sands contain large concentrations of Pb (0.27 %), Zn (0.72 %), and As (559 ppm).

Rock magnetic characterization of the mine tailings in Portman Bay (Murcia, Spain) and its contribution to the understanding of the bay infilling process

“…This suggests that alterations, diagenetic processes or transformations due to the sedimentary aging are not important (Evans and Heller, 2003). One should note, however, that the infilling was very rapid, so that the upper most layers have not yet started to undergo alteration; this does not preclude alteration of deeper strata, considering the total thickness of the mineral deposits which is estimated to be 10 m (Martínez-Sánchez et al, 2008;Manteca et al, 2014). (b) Fig.…”

“…As a result, the Portman Bay was completely filled in a few decades affecting significantly the shoreline, which receded about 1 km. The mineralogical composition of the beach iron concentrates has been determined to be 17% of quartz, up to 35% of magnetite, 12% of hematite and 36% of siderite (Manteca et al, 2014). Furthermore, the Bay, presently, shows high concentrations of metals such as lead, copper, zinc, cadmium and mercury as well as sulfur and iron oxides (Martínez Orozco et al, 1993;García et al, 2003).…”

“…In this particular aspect, the tailing has been estimated to contain up to 444 × 10 3 t of magnetic iron concentrate in the form of magnetite, hematite and siderite. Finally, if the present beach black sands represent approximately 1/6 of the total bay infilling, the actual amount of iron in Portman Bay could be much larger, at least on the order of 1 × 10 6 t (Manteca et al, 2014).…”

A descriptive and quantitative approach regarding erosion and development of landforms on abandoned mine tailings: New insights and environmental implications from SE Spain

“…Ferricretes and hardpans are a common feature in tailing deposits from SE Spain (e.g., Oyarzun et al, 2013;Manteca et al, 2014), capping the deposits with a hard, brownishcoloured, erosion-resistant cover. These erosional forms are the result of raindrop impact on weakly consolidated mine deposits.…”

“…Even relatively small-scale operations may alter the landscape so profoundly as to eliminate an entire bay with its harbor facilities as it happened in Portman (Spain) , not far from our study area. The Peñarroya Mining and Metallurgical Company disposed at Portman Bay about 60 million tons of tailing materials directly to the Mediterranean Sea between 1957 and 1990; a substantial part of it (12.5 Mt) was dragged back by the sea currents progressively infilling the bay, making the shoreline advance between 500 and 600 m seaward (Manteca et al, 2014) thus creating a massive, physical and chemical environmental impact .…”