On the iron isotope heterogeneity of lithospheric mantle xenoliths: implications for mantle metasomatism, the origin of basalts and the iron isotope composition of the Earth

摘要

With the aim to better understand the cause of the iron isotope heterogeneity of mantle-derived bulk per-idotites, we compared the petrological, geochemical and iron isotope composition of four xenolith suites from different geodynamic settings; sub-arc mantle (Patagonia); subcontinental lithospheric mantle (Cameroon), oceanic mantle (Kerguelen) and cratonic mantle (South Africa). Although correlations were not easy to obtain and remain scattered because these rocks record successive geological events, those found between δ~(57) Fe, Mg#, some major and trace element contents of rocks and minerals highlight the processes responsible for the Fe isotope heterogeneity. While partial melting processes only account for moderate Fe isotope variations in the mantle (<0.2 %o, with bulk rock values yielding a range of δ~(57)Fe±0.1 %o relative to IRMM-14), the main cause of Fe isotope heterogeneity is metasomatism (>0.9 %o).