A Heterogeneous Mantle under the African-Arabian Plate boundary revealed by boron and radiogenic (Sr-Nd-Pb) isotopes

Researchers from IGG, along with colleagues from Universities of Firenze and Roma, INGV and IGAG published a study reporting original geochemical data, including radiogenic isotopes and Boron (B) isotope data for a dataset of alkali basalts cropping out in a wide area close to the Arabia-Africa-Anatolia triple junction and on the Arabian Plate foreland. To measure the B isotope ratios on B-poor alkali basalts, the analytical procedure was significantly updated and improved.

The results of this study have global implications, because the peculiar geodynamic setting of the region allowed the emplacement of alkali basalts for a very-long time span, over 20 million years, and from the same source, that is subcontinental mantle asthenosphere. This allowed a diffuse and long-lasting sampling of this mantle source, and we find the occurrence of a sub-continental mantle that is heterogeneous not only in terms of geochemical characteristics and radiogenic isotopes, but also in terms of stable boron isotopes. Far from solving the conundrum of the isotopic composition of boron in the pristine mantle, this study provides an interesting contribution in this topic and includes an important element of novelty. Actually, most of the study targeted to define the mantle characters are based on oceanic basalts, which are mostly primitive and emplaced after a short trip in a thin crust. We here try to drive the attention of the scientific community to alkaline basalts emplaced in continental lithosphere: these are less studied because they are less diffuse and may have to travel along thick lithosphere and contaminate during uprising. However, in this paper we show that they can tell a different story from oceanic basalts, opening a window on a different point of view on the Earth interior. 

Bibliographic reference:

Agostini, S., Di Giuseppe, P., Manetti, P., Doglioni, C., Conticelli, S. A heterogeneous subcontinental mantle under the African–Arabian Plate boundary revealed by boron and radiogenic isotopes. Sci Rep 11, 

11230 (2021). doi.org/10.1038/s41598-021-90275-7.

Article available at: https://www.nature.com/articles/s41598-021-90275-7.

For further information:

Samuele Agostini - samuele.agostini@igg.cnr.it