Insights into the mineralogy and distribution of Co, Ni, As and Bi in the sediment-hosted polymetallic ores of the Kupferschiefer in Lusatia, Germany

The Kupferschiefer ores of Central Europe have long served as an important source of Cu and Ag, but have also yielded a number of important by-product metals, including Pb, Zn, Co, Ni, Ge, Re, and Au. However, little is known about the mineralogy and distribution of such by-product metals. The present study provides a comprehensive assessment for the mineralogy and distribution of potential value-adding by-products (Co and Ni) and deleterious elements (As and Bi) in drill-cores from the Spremberg-Graustein-Schleife prospect in Lusatia, Germany. Detailed mineralogical investigations were conducted using scanning electron microscope-based automated mineralogy to identify and quantify the abundance of minerals hosting Co, Ni, As, and Bi. Major sulfide minerals were analyzed by laser ablation-inductively coupled plasma-mass spectrometry to constrain their trace element compositions and to assess their contribution to the bulk content of the four target elements. The results show that the bulk of Co and Ni is hosted in major sulfides, discrete Co and Ni minerals, as well as the gangue minerals. In the copper-mineralized samples, most of the recoverable Co and Ni occur as fine cobaltite – gersdorffite inclusions within Cu-sulfides. The two deleterious elements illustrate a very different distribution. Arsenic occurs primarily in cobaltite – gersdorffite and pyrite, whereas Bi is mainly incorporated into Cu-sulfides. The results have important implications for the recovery of these four target elements during industrial mineral processing. Recovery of Ni and Co will be limited by their deportment to gangue minerals (including pyrite). Bi as well as As will effectively report to the Cu concentrate. Because of low bulk concentrations in the ore, Bi contents in the copper concentrate can be expected to remain below smelter penalty levels. This is markedly different from As contents in Cu concentrates that may, in fact, approach smelter penalty levels. • SEM-based automated mineralogy quantifies Co, Ni, As, and Bi minerals in the ores. • LA-ICP-MS quantifies trace occurrences of target elements in major sulfides. • Gangue-hosted Co and Ni represent a non-recoverable metal fraction. • Arsenic approaches smelter threshold penalty limits, while Bi remains below.