Date: 4.00pm-5.30pm, Friday, 3 March 2017
Place: Room 1302, Main Chemistry Build.
Speaker: Rustam Lukmanov
Title: Determination of the iron oxidation state in mantle minerals.
Mantle xenoliths brought up to surface by kimberlites, alkali basalts and related magmas provide direct and nearly comprehensive information about the structure and composition of the upper mantle at the time of the eruption. Recent and past studies of mantle xenoliths have provided a big amount of information about mineralogy and chemical composition of upper mantle its thermal and redox state, wich has enabled important inferences on mantle processes like partial melting, metasomatism, and deformation. In addition to P (pressure) and T (temperature) oxygen fugacity (fO2) plays a key role in the lithospheric processes. The determination of the Iron oxidation state in mantle minerals could help us to directly determine oxygen fugacity.
Nowadays, in-situ observation of Iron oxidation state in mantle minerals requires measurements in hardly accessible facilities, like synchrotron radiation sources. Widely presented Mossbauer spectroscopy used to determine the Iron oxidation state, but the method can work only with separated amount of mineral fractions, however, the method is still useful but unfortunately not local. The key parameter – ratio of ferric iron to total iron, can be also roughly estimated from microprobe analyses assuming mineral stoichiometry. Furthermore, this ratio could be precisely determined by using a Flank method based on EPMA measurements.