| dc.description.abstract | The nickel bearing komatiites from the Black Swan mine have undergone multiple phases of hydrothermal alteration in the form of a serpentinization event, followed by talc-carbonation. The aim of this research is to determine how nickel bearing phases are affected by the hydrothermal alteration from serpentinized rock to talc-carbonated rock. Thin sections, created from Black Swan mine rock samples, are used to obtain information about mineral assemblages and their chemical compositions. The analysis has been performed with the use of EMPA, SEM and Raman Spectroscopy. The nickel in serpentinized samples is primarily stored in nickel- and nickel iron sulfides. Along with the iron sulfides/oxides, these minerals form the opaque mineral assemblage of magnetite, pyrite, millerite, violarite, chromite, hematite, pentlandite, pyrrhotite and chalcopyrite. The opaque minerals observed in the talc-carbonated samples consist of magnetite, pyrite, millerite, chromite and polydymite. The difference in opaque mineral assemblage is linked to the rise of oxygen and sulfur fugacities, along with a decrease in αH2,aq and αH2S,aq that is caused by talc-carbonation. Lizardite and antigorite form the matrix mineral phases of the serpentinized samples. Iron gets released form lizardite and antigorite during talc-carbonation, which is partly taken into the sulfide minerals. This increases the total amount iron stored in sulfide minerals, but decreases the amount of nickel stored in sulfide minerals. The result is an increased amount of nickel stored in the talc matrix of talc-carbonated rock. Other talc-carbonated related mineral phases, in which nickel is stored, include millerite and polydymite. | |
