Transformation of the mineral composition of ferromanganese crusts under the influence of hydrogen sulfide

Abstract

Experiments devoted to interaction between the material of ferromanganese crusts (FMC) of Pacific seamounts and hydrogen sulfide at temperatures ranging from 100 to 600°C unraveled the formation of pyrite microcrystals at 100°C. Upon heating, the pyrite acquires more perfect crystalline form at 200°C and breaks down at 600°C. The formation and breakdown of magnetite take place according to the same similar scenario. At 200°C, one can see the formation of lumpy aggregates of the slightly crystallized alabandine transformed at 600°C into lamellar crystals, which accumulate the whole Mn and part of Fe hosted in rock. At maximal temperature, platinum and gold are crystallized selectively as lamellar particles and native sulfur is accumulated. The composition of these newly formed minerals is incomparable with the mineralogy of natural FMCs. This is inconsistent with the assumption about the possible influence of hypothetic hydrosulfuric emanations on the formation of minerals mentioned above. However, experimental results demonstrate an extremely high sorption capacity of FMCs relative to hydrogen sulfide, suggesting great prospects of the practical application of FMCs for the industrial and ecological purposes.