Boninites as Mercury lava analogues: Geochemical and spectral measurements from pillow lavas on Cyprus island

Abstract

In the absence of Mercurian rocks or meteorites in our collections, komatiites and boninites are often proposed as the best analogue rocks to Mercury lavas. However, despite previous work on the possible analogy between komatiites and Mercury rocks, similar work has not been done for boninites. In this work, we investigate the whole-rock geochemistry and visible/near-infrared (VNIR) spectroscopy of boninitic material collected at three specific areas of the Troodos Massif (Cyprus island). The objective is to evaluate if collected boninites, these along with other boninites present in the literature, can be analogous to Mercury geochemical terranes. On average, we find an unusually high MgO/SiO₂ ratio (0.68) for the boninites from the Troodos Massif compared with previous boninite analysis. This MgO/SiO₂ value is most closely related to the high-Mg regions of Mercury, while the average Al₂O₃/SiO₂ ratio (0.25) is consistent with the Mercurian intermediate terrain and to Mercury's largest pyroclastic deposit. In addition, further affinity to the high-Mg regions and the intermediate terrains of Mercury are shown in regard to Si vs. Mg, Si vs. Ca, and Si vs. Fe content for one sample in particular. We then conduct magmatic modeling on this specific sample to provide a possible parental melt composition for analogue Mercurian magmas. In conclusion, we suggest these specific locations on the Troodos Massif in Cyprus as good geochemical analogue sites for the high-Mg regions of Mercury and explain how boninites could be important benchmark samples for the chemical and spectral data expected from the BepiColombo mission.