Date/heure
Date(s) - 28 février 2025
13 h 15 min - 14 h 15 min
Catégories
28 février 2025, 13h15 salle de réunion du CRPG | Jessy Dominique (LMV, Clermont-Ferrand)
How dry is the Kaapvaal craton?
Kimberlites give an exceptional insight of the deep cratonic mantle by exhuming at an extreme pace well-preserved peridotites from a wide range of depths. The fast exhumation velocity of peridotite limits diffusion of incompatible trace elements (REE, hydrogen) due to the interaction between the ascending kimberlite melt and the rock and allows to measure pristine water contents in nominally anhydrous minerals (NAMs). Water is regarded as a key parameter as it may impact, depending on its concentration, physical parameters such as rheology and partial melting. This study is focused on the petrology and water quantification of 17 spinel and garnet harzburgites scattered over a wide range of pressure (27 to 51 kbar) from Jagersfontein mine located at the rim of the Kaapvaal craton. Sampling was focused on poorly metasomatized, ultra-refractory harzburgites (Fo92-95) which are considered to represent the most preserved cratonic archean mantle. Water content was obtained from FTIR spectroscopy on the most representative phases: olivine, orthopyroxexe, clinopyroxene and garnet. The aim of this study is to investigate the relation between petrology, water content of non-metasomatized cratonic mantle.