Electron microscopic study of the composition, the microstructure and defects of natural dense hydrous minerals and of phases that crystallize from high density fluid inclusions in diamond.

• Applicant: Professor Dr. Frank Erich Brenker
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 264128933

Inclusions in diamond with super deep origin enable unique insights into the local chemical composition of the asthenosphere, the transition zone or even the lower mantle and therefore into the global transport processes and recycling mechanism.A large part of the studied samples from the Juina area (Brazil) show evidence for an origin within the transition zone (410-660km) or the Earth´s lower mantle (> 660km) (Harte und Harris, 1984; Stachel et al., 2000b; Kaminsky et al., 2001; 2012, Brenker et al., 2005, 2007; Harte, 2012, Walter et al., 2011, Pearson et al., 2014, Bulanova, 2010).Within the last years two unusual suites of inclusions in so called super deep diaomnds were recognized. These show evidence for the occurence of fluids or fluid transport (e.g. hydrous Ringwoodite with up to 1,4 wt% water, Pearson, Brenker, et al., 2014; Phase EGG, Wirth et al., 2007) and on the other hand for sedimentary parts (z.B. Phase EGG, Wirth et al., 2007; CF-Phase + K-Hollandite + SiO2, Bulanowa et al., 2010) down to the transition zone of the Earth´s mantle. The investigation of these water-bearing dense high pressure minerals, dense hydrous minerals and phases that cristallize from high density fluids enables to acquire the chemical composition of fluids within the deep Earth´s mantle from their respected source region and of the physico-chemical conditions during formation and later exhumation.The diamond samples studied during a preproject by the means of non-destructive in-situ techniques yield a high amount of syngenetic fluid components, several dense hydrous minerals (e.g. Phase Egg, Wirth et al,. 2007) and water-bearing minerals (e.g. waterbearing ringwoodite, Pearson et al, 2014). These findings will be studied in great detail for their chemical composition and their crystal structure in order to get more information about the conditions during formation and exhumation of the unique samples.The main focus will be on the TEM investigation of the samples. This will include the study of precipitates, exsolution, deformation, as well as phase transformations, like stacking faults and antiphase domains.

• DFG Programme: Research Grants
• International Connection: Belgium, Canada, United Kingdom
• Participating Persons: Professor Dr. Jeff Harris; Dr. Felix Kaminsky; Dr. Bart Vekemans; Professor Dr. Laszlo Vincze