Details

• Magda Ntouma, Aristotle University of Thessaloniki
• Date: Jan, 18, 2017 12:00 am
• Place: Sala d’Actes del Institut de Ciències de la Terra Jaume Almera (ICTJA)
• Location: C/ Solé i Sabarís s/n, Barcelona
• Further information:Dra. Marta Rejas

Abstract

The ophiolithic sequence of Stratoniki in Chalkidiki peninsula, in Northern Greece, displays a very interesting mineralization, consisted of Fe–Ni–Cu sulfides. This research concerns the formation of the iron–nickel–copper sulfide ores within the ultramafic body of a serpentinized dunite. The designation of how sulfides are formed can be the key to establish the conditions under which their genesis is detected. The main data obtained from the macroscopic and microscopic study of the dunite formation which desplays the mineralization, are listed below: The dunite presents primary minerals, like olivine and chlorite, with the last one being an unsubstantial one. Secondary silicate minerals, from the serpentinization of the dunite, like serpentinite, chlorite, talc and minor quantities of dolomite, are also present. Olivine displays bands, due to the differentiation of its chemical composition from the core to its periphery. The mineralization within the dunitic body, in Stratoniki area, is divided into two types, according their origin. The first group, is presented along a primary mineralization of banded spinels, consisted of a combination of chromites+pyrite+magnetite, while the second group corresponds to a secondary sulfide mineralization of Fe–Ni–Cu and infrequent oxides of Fe (magnetite), which is located mostly in serpentinized zones. The mineralization of sulfides does not exceed a value of 10% in relation to the whole rock and it can be recognized macroscopically with dispersed appearance or small veins. The microscopic examination of the samples, revealed that the mineralization is consisted mainly of pyrite, pentlandite, millerite and traces of pyrrhotite, chalcopyrite and bravoite. Among them, pentlandite presents two types, with different chemical composition. The first type is extended in the form of distinct bands or as aggregates on the pyrite, while the second type forms inclusions with pyrrhotite within the mass of pyrite. The origin of the mineralization of the sulfides is believed that is closely connected with serpentinization of the dunitic body and the minerals have been resulted from the screen of olivine. However, the presence of sulfur (S) in the sulfides is understood that originates from an outer source of a volcanic vent, like the sub–volcanic body presented in the close vicinity of the area, while the development of the sulfides are related to hydrothermal movement.