Stability of Cu-Sulfides in Submarine Tailing Disposals: A Case Study from Repparfjorden, Northern Norway

Abstract

Mine tailings that were produced during the exploitation of the Ulveryggen siliciclastic sediment-hosted Cu deposit in northern Norway were disposed into the inner part of Repparfjorden from 1972 to 1978/1979. This study focuses on the mineralogy and geochemistry of the submarine mine tailings and underlying natural marine sediments from the inner part of Repparfjorden, as well as on the primary Ulveryggen ore. The ore mineralization from the neighboring Nussir carbonate sediment-hosted Cu deposit was studied too, due to the forthcoming mining of both deposits. Bornite and chalcopyrite are the major Cu-sulfides, and are characterized by low concentrations of potentially toxic elements including Cd, Hg, and As. The tailing material occupies the uppermost 9 cm of Repparfjorden sediments. It is characterized by predomination of a silty component with elevated Cu (up to 747.7 ppm), Ni (up to 87 ppm), and Cr (up to 417 ppm) concentrations. The high Cu concentration is related to the deposition of mine tailings. In contrast, Ni and Cr concentrations are close to those in naturally occurring stream sediments from the feeding river, Repparfjordelva, reflecting the compatibility of these elements with hosting mafic volcanics, which are widely spread in the Repparfjord Tectonic Window. Copper in the uppermost part of the sediments is bound to the acid-soluble fraction while Ni and Cr are bound to the residual fraction. Artificial placement of large masses of fine-grained material, i.e., smothering, resulted in a diminished biological activity and/or physical distortion of mostly benthic fauna, which was reflected in total organic carbon (TOC) values as low as 0.15% in the uppermost strata. Sulfide minerals are found both in natural marine sediments and in the mine tailings. They are generally well-preserved with an exception for chalcopyrite from the uppermost part of the submarine tailing, which shows signs of incipient weathering. Thermodynamic modeling confirmed that redox potential and pH are important factors in the weathering of sulfides. Available ligands contribute to the Cu speciation. In near-neutral to slightly alkaline conditions a presence of carbonates can lead to the mobilization of Cu in form of CuCO3 complexes.

Ore Minerals and Metal Distribution in Tailings of Sediment-Hosted Stratiform Copper Deposits from Poland and Kazakhstan

“…The means of material deposition determines the lateral variability in grain size distribution (coarse deposits accumulate at the crown of the dams, fine deposits accumulate in ponds). This pattern also concerns other tailings in Poland [41,44] and around the globe [45]. In terms of mineral composition, deposits in the tailing pond reflect the ores occurring in the deposit-they are largely composed of the same ore components (copper sulphides, copper and iron sulphides)-and rocks: fragments of dolomites, sandstones, and shales, single grains of quartz and feldspars in ZM, and sandstones and quartz grains in B and OS (Figures 1-4).…”

“…Zinc content varies from 29 ppm in ZM-N to 225 ppm in ZM-W (western dam), and in OS from 150 to 2500 ppm (Table 1, Tables S1 and S2). The content of Co, Cs, Ba, and Sr is somewhat higher in ZM than in OS, despite the presence of Ba and Sr sulphates as important components of SSC deposits in Poland [26,31,45]. Silver, as one of the primary metals recovered in Poland, shows high concentrations in ZM.…”

The Role of Mineral Assemblages in The Environmental Impact of Cu-Sulfide Deposits: A Case Study from Norway

“…The Nussir deposit is hosted by a thin (no more than 5 m thick) metadolostone layer that can be traced for several kilometres (Figure 1A,C), intercalated with metasandstone, metasiltsone and metapelites. The metasedimentary complex is overlain by a several hundred meters thick metavolcanic sequence [49,50,53]. Despite the close geographical occurrence of the Nussir and Ulveryggen deposits, they have different lithologies.…”

“…In addition, to determine the concentration of potentially toxic elements including Cu, Zn, Ni, Hg, Cd, and As (e.g., [64]), the bulk chemical compositions of hand-picked Nussir, Røros chalcopyrite as well as Ulveryggen bornite were analyzed (Table 2). The Nussir and Ulveryggen results are taken from [53]. 3 RSL-Røros; Bn-bornite, ccp-chalcopyrite, LD-limit of detection, LLDlower than limit of detection, ND-no data.…”

Seepage field characteristic and stability analysis of tailings dam under action of chemical solution

“…However, during the mining-mineral process, there are residual heavy metals and chemical reagents in the tailings waste residues after the grinding and fine crushing and flotation processes, which have changed the hydrochemistry environment in the reservoir 19 . Under such circumstances, the tailings is always immersed in the acid and alkaline reservoir water, while the long-term immersion and chemical reaction have partially changed the tailings particle size, pore size, mineral composition and surface morphology 20 , 21 . Therefore, the permeability and mechanical property of the entire dam are changed to some extent.…”