Adsorption of Rare Earth Metal Cations by Base Metal Sulfides in the Broken Spur and TAG Hydrothermal Fields, Atlantic Ocean

The article presents the results of sorption of rare earth metal (REM) cations on samples of deep-sea base metal sulfides in the Broken Spur and TAG hydrothermal fields (Mid-Atlantic Ridge). The studied samples contain the following major minerals: marcasite, pyrrhotite, pyrite, and sphalerite in the Broken Spur field; chalcopyrite, pyrite, and marcasite in the TAG field. It has been established that these Fe–Cu–Zn sulfide minerals are natural absorbents. The exchange capacity of sulfide minerals for REM cations is 0.006‒0.061 mg-equiv/g. The exchange complex of sulfide minerals comprises the cations of alkaline, alkali-earth metals, and main cations of metals in the crystal lattice – Fe, Zn, Cu (in very limited quantities). The mechanism of the REM cation absorption is ion-exchange equivalent to the exchange cations of sulfide minerals. It was found that REM cations occur in the sulfide minerals almost completely in the sorbed form (more than 90% of the total amount). Apparently, the chemically bound form is possible only for Lu and Dy cations. The mineral composition of sulfide deposits is preserved in the exchange reaction products, and new phases do not appear.