Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

We have determined the concentrations of chalcophile and siderophile elements by LA-ICP-MS from sulphide droplets and fresh glass in contact with them from MORB pillow rims. MORBs play an important role in the understanding of mantle petrogenesis, providing information on chemical fractionation of elements in the mantle. However, chalcophile element behaviour is not completely understood, partly due to the lack of data for partition coefficients between sulphide and silicate melts. Some droplets present homogenous textures and others portions rich in monosulphide solid solution (Mss) and intermediate solid solution (Iss) indicating that they have undergone crystal fractionation. For homogenous droplets, concentrations of Ni and Cu are 10 to 1%; Co and Zn 1000 to 100 ppm; Se, Te, Ag and Pb 100 to 10 ppm; Cd, Sn, Pd, Bi and Pt 10 to 1 ppm; Au, Ru and Re 1 to 0.1 ppm. For some of these elements it was also possible to obtain data in fresh glass allowing the calculation of partition coefficients. These were calculated for Ni (745± 252), Cu (1219 ± 381), Co (42 ± 5.5), Zn (3.4 ± 0.9), Sn (10.4 ± 1.8) and Pb (55.6 ± 9.3). Values for Ni, Cu and Co are in agreement with literature [1], suggesting that values for Zn, Sn and Pb are realistic.