Since 2018, the submarine east flank of Mayotte Island (Comoros archipelago) is the site of a major eruption located at 3.5 km depth bsl on a WNW-ESE volcanic ridge. Samples brought by oceanographic cruises carried out to monitor this seismo-volcanic crisis indicate that this volcanic ridge is built by a bimodal sodic alkaline magmatic series that includes basanites and phonolites. A petrological study of dredged samples allowed us to image the magmatic system feeding the volcanic ridge and to determine the link between basanitic and phonolitic magmas. The magmatic system feeding the volcanic ridge comprises multiple levels of magma storage. Basanitic magmas generated at 80–100 km mantle depth are stored in two or more deep reservoirs (≥ 37 km) and then in shallower basanitic and phonolitic lenses located close to the Moho interface before rising the surface. This study identifies three possible scenarios: (1) the deep basanitic magma rises directly and quickly to the surface from the deep mantle reservoir (as is currently happening 60 km offshore), (2) the basanitic magma stalls in a shallower reservoir near the Moho before resuming its ascent toward the surface and erupting as porphyritic basanite, (3) the basanitic magma stops and evolves to phonolite in these sub-crustal reservoirs. The phonolitic lavas are produced by approximately 80% fractional crystallization (34% clinopyroxene, 30% anorthoclase feldspar, 15.5% magnetite, 12.5% olivine, 5% apatite and 4% ilmenite) of a hydrous basanitic magma at mantle depths (P > 0.6 GPa) under reduced oxygen fugacity (~ FMQ-1). In this third scenario, the phonolitic magma might be reactivated by the arrival of a new batch of deeper basanitic magma.

自 2018 年以来，马约特岛（科摩罗群岛）的海底东翼是位于 WNW-ESE 火山脊上 3.5 公里深度 bsl 的主要喷发地点。为监测这次地震-火山危机而进行的海洋航行所带来的样本表明，这个火山脊是由双峰钠碱性岩浆系列构成的，其中包括巴桑岩和响岩。对疏浚样品的岩石学研究使我们能够对供给火山脊的岩浆系统进行成像，并确定玄武质岩浆和音质岩浆之间的联系。供给火山脊的岩浆系统包括多层岩浆储存。在 80-100 公里地幔深度产生的玄武岩岩浆储存在两个或更多深水库（≥ 37 公里）中，然后在上升到表面之前位于靠近莫霍面界面的较浅的玄武岩和音质透镜中。这项研究确定了三种可能的情况：（1）深部玄武岩岩浆从深部地幔储层直接快速上升到地表（目前在离岸 60 公里处发生），（2）玄武岩岩浆滞留在莫霍面附近较浅的储层中在恢复向地表上升并喷发为斑状玄武岩之前，(3) 玄武岩岩浆在这些亚地壳储层中停止并演化为响岩。音质熔岩由大约 80% 的分步结晶产生（34% 单斜辉石、30% 斜长石长石、15.5% 磁铁矿、12.5% 橄榄石、P  > 0.6 GPa) 在降低的氧逸度 (~ FMQ-1) 下。在这第三种情况下，新一批更深的玄武质岩浆的到来可能会重新激活音质岩浆。