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International audience; VLF (Very Low Frequency) events of the ongoing seismovolcanic crisis of Mayotte are detected through a single-station time-frequency detector with data that comes from local and regional stations around Mayotte. The correction of the OBH (Ocean Bottom Hydrophone) pressure data into acceleration allow us to perform analysis like location, modelling and observe the complexity of the source mechanism in the VLFs signal. After corrections, waveforms, frequency content and duration of VLFs shows the same history, it's an effect of the source. Event location is performed though spatial 3D back-projection of station-pair cross-correlation functions, assuming a velocity of 3.5 km/s. Well constrained horizontal location is set in the middle of the proximal swarm, depth resolution is poor. We explore depths through synthetics seismograms generated using a simple 1D model and an isotropic focal mechanism. They provide a good fit with the observed signals. We compared 75 detected VLF with synthetics : cross-correlation time delay and amplitude ratio are analysed in function of the epicentral distance. VLF possible depth range is reduce to 10-25 km.

International audience; Pb-Zn deposits and specifically Sedimentary-Exhalative (SEDEX) deposits are frequently found in deformed and/or metamorphosed geological terranes. Ore bodies structure is generally difficult to observe and its relationships to the regional structural framework is often lacking. In the Pyrenean Axial Zone (PAZ), the main Pb-Zn mineralizations are commonly considered as Ordovician SEDEX deposits in the literature. New structural field analyzes focusing on the relations between mineralization and regional structures allowed us to classify these Pb-Zn mineralizations into three types: (I) Type 1 corresponds to minor disseminated mineralization, probably syngenetic and from an exhalative source. (II) Type 2a is a stratabound mineralization, epigenetic and synchronous to the Variscan D1 regional deformation event and (III) Type 2b is a vein mineralization, epigenetic and synchronous to the late Variscan D2 regional deformation event. Structural control appears to be a key parameter in concentrating Pb-Zn in the PAZ, as mineralizations occur associated to fold hinges, cleavage, and/or faults. Here we show that the main exploited type 2a and type 2b Pb-Zn mineralizations are intimately controlled by Variscan tectonics. This study demonstrates the predominant role of structural study for unraveling the formation of Pb-Zn deposits especially in deformed/metamorphosed terranes.