Processus de métallogénèse dans les amas sulfurés océaniques

Quantitative analysis of trace elements repartition in hydrothermal sulfide minerals has required a development in the method of microprobe analysis. Large investigations on the microprobe analysis conditions (reproducibility, mineral resistance, homogeneity, standards, background measurements, electron beam intensity, accelerating voltage and counting time) allow an improvement of the signal/background ratio during analysis of Se, As, Co, Cd and Ag in chalcopyrite, pyrite, sphalerite, isocubanite and pyrrhotite. Then, a minimal exploitation value has been defined for each element in each sulfide mineral with an analytical accuracy greater than 10%. These values vary from 200 ppm for the cobalt in chalcopyrite and sphalerite to 600 ppm for the selenium in sphalerite and pyrrhotite. Bulk chemical (XRF) and microprobe analysis on sulfides are complementary analysis investigations, which allow to follow the repartition and to know the behaviour of the trace elements during the maturation of a sulfide deposit more accurately