Curtin Applied Geology Seminar

Wed 21st September

@ 12 pm

Rm 312.222

Giada Iacono Marziono

Institut des Sciences de la Terre d’Orléans

Assimilation of sulfate and carbonaceous rocks: experimental study, thermodynamic modeling and application to the Noril’sk-Talnakh region.  

Most of the intrusions in the Noril’sk-Talnakh region (Siberia) are hosted in thick sedimentary sequences, including abundant evaporitic and terrigenous sedimentary rocks. Only three out of at least 22 mafic-ultramafic intrusions in the Noril’sk and Talnakh ore districts contain unusually thick massive sulfide deposits, which represent one of the world’s largest economic concentrations of Ni, Cu and PGE. The interaction of Siberian magmas with sulfate and organic matter-rich sedimentary rocks has been proposed as a possible mechanism for the origin of these exceptional sulfide deposits but never fully investigated. We conducted interaction experiments at conditions relevant to the emplacement of Noril’sk type intrusions to simulate the assimilation of sulfate and/or organic compounds by ultramafic magmas. We clarify how sulfate and organic matter assimilation occur in mafic-ultramafic magmas, affecting magma composition, crystallization and sulfide saturation. Gas-melt thermodynamic calculations were also employed to quantify the effect of these assimilations on the redox conditions and the S content of the magma, and investigate the role of temperature, pressure, and initial gas content of the magma in the assimilation process. Experimental and modeling results have been applied to the Noril’sk-Talnakh district to explain the occurrence of massive sulfide deposits, but also disseminated sub economic ones and barren intrusions. We conclude that exceptional conditions favoring substantial assimilation of sediments are needed to generate Noril’sk-Talnakh exceptional ore deposits.

Bio Details

Giada is an experimental petrologist currently working at the Institut des Science de la Terre d’Orléans. She did her PhD between the University of Palermo in Italy, and the BGI of Bayeruth in Germany on the degassing of phonolitic magmas. Since then she has been working on the behavior of volatiles in magmas (solubility and degassing of H2O, CO2, S, noble gases, halogens) and on the assimilation of volatile-rich sedimentary rocks. She joined the CNRS (French national center for scientific research) in 2011 and started working on the role of magma-sediment interactions and volatiles in ore processes.