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Highly carbonated mantle xenoliths have been found in rift-related alkaline basalts at the Wadi Natash area in the southern part of the Eastern Desert of Egypt. Although all olivine and most orthopyroxene was replaced by carbonate and/or quartz, textural and mineral chemical features show that they are plagioclase-free spinel peridotites (lherzolite to harzburgite). Cr and Mg numbers (Cr#, Mg#) of Cr-spinel vary from 0.06 to 0.45 and 0.73 to 0.81, respectively. The correlation between Cr# and Mg# of the Cr-spinel in the studied xenoliths is weakly negative and its TiO2 content is slightly higher than in abyssal peridotite that was not affected by melt injection. The chemistry of ortho- and clinopyroxene suggests enstatite and chromian diopside compositions, respectively, with distinct signatures of a sub-continental mantle source. In particular, the Na2O contents (>1.0 wt%) and AlVI/AlIV ratios (1.2–2.6) of chromian diopside suggest such an origin. Two-pyroxene geothermometry indicates a temperature of about 900 °C, which is slightly lower than that of ordinary spinel peridotite xenoliths from other rift zones. It is evident that the studied peridotite xenoliths had experienced mantle processes (e.g. decompression melting, magma upwelling and metasomatism) at higher pressure than abyssal peridotites. The trace-element chemistry of clinopyroxene, e.g. high LREE/HREE ratios {(Ce/Yb)n = 7}, high LREE contents (>3.6 ppm and up to 30.0 ppm Ce) and high Sr between >85.6 ppm and 466 ppm, indicates metasomatic alteration of the peridotite. Clinopyroxene in one sample has very low Ti/Eu and high LREE/HREE ratios. Clinopyroxene with (Ce/Yb)n higher than 3–4 and Ti/Eu ratio lower than 1500 may have experienced carbonatite or carbonate-rich melt metasomatism prior to their incorporation into the host basalt. The basalt itself is almost devoid of any carbonatization and hence the studied mantle peridotites were carbonatized before the generation of the basaltic magma but following an earlier event of K-metasomatism as indicated by the presence of phlogopite. The studied peridotites from the Wadi Natash area were altered by a carbonate-rich melt during a rifting stage. The results of the present paper indicate that the Natash basalts with their peridotite xenoliths extruded along transversal fractures of the NW-trending Nuqra-Kom Ombo-Kharit continental rift on its western shoulder in the south Eastern Desert of Egypt.

Even though desert dust is the most abundant aerosol by mass in Earth's atmosphere, the relative contributions of the world's major source regions to the global dust cycle remain poorly constrained. This problem hinders accounting for the potentially large impact of regional differences in dust properties on clouds, the Earth's energy balance, and terrestrial and marine biogeochemical cycles. Here, we constrain the contribution of each of the world's main dust source regions to the global dust cycle. We use an analytical framework that integrates an ensemble of global aerosol model simulations with observationally informed constraints on the dust size distribution, extinction efficiency, and regional dust aerosol optical depth (DAOD). We obtain a dataset that constrains the relative contribution of nine major source regions to size-resolved dust emission, atmospheric loading, DAOD, concentration, and deposition flux. We find that the 22–29 Tg (1 standard error range) global loading of dust with a geometric diameter up to 20 µm is partitioned as follows: North African source regions contribute ∼ 50 % (11–15 Tg), Asian source regions contribute ∼ 40 % (8–13 Tg), and North American and Southern Hemisphere regions contribute ∼ 10 % (1.8–3.2 Tg). These results suggest that current models on average overestimate the contribution of North African sources to atmospheric dust loading at ∼ 65 %, while underestimating the contribution of Asian dust at ∼ 30 %. Our results further show that each source region's dust loading peaks in local spring and summer, which is partially driven by increased dust lifetime in those seasons. We also quantify the dust deposition flux to the Amazon rainforest to be ∼ 10 Tg yr−1, which is a factor of 2–3 less than inferred from satellite data by previous work that likely overestimated dust deposition by underestimating the dust mass extinction efficiency. The data obtained in this paper can be used to obtain improved constraints on dust impacts on clouds, climate, biogeochemical cycles, and other parts of the Earth system.

International audience; The European Journal of Mineralogy (EJM) is owned by four European learning Societies (DMG, SEM, SFMC and SIMP). The journal, published under a commercial publisher, used the open access hybrid model. Early 2018, it was decided to move to full open access. In this talk, we discuss the transformation challenges and its impact. It took us two years to fully complete this transformation. Since 2020, the journal is published as gold open access by a reputable open access publisher offering very moderate APCs. The quality and attractiveness of the journal has improved considerably, namely: wider dissemination, reduction of the processing time for publication, reduction of the cost of production by more than 50%. Notwithstanding, the first nine months of 2020, the number of submissions decreased compared to previous years, but we are now back to the same submission rate as before. It means that the implementation of APCs, which was new for many authors, has only marginally affected the attractiveness of the journal. Nevertheless, in order to help authors adjusting, the current APCs rates are still below the real cost of production. The nominal cost will be reached only in a few years. The learning societies have also launched APCs waiver programs to help authors who have difficulties to pay full rates.The open access revolution of EJM is work in progress. We still have to transform the past hybrid volumes into open access formats. This will be implemented as soon as APCs generated funds fully cover the running cost of the journal. Once all EJM volumes are in open access, the cost of a paper published in EJM will be fully transparent to authors, institutions and tax payers. It will correspond exactly to the APCs paid. It was never the case in the previous hybrid system. This is a major achievement thanks to gold open access.