Skyscraper sized hydrothermal vents and chimneys buried below the Mozambique Channel
Résumé
During intrusion of thermal sources in sedimentary basins fluids present in the pore space are expelled trough fracture, vertical and lateral geological discontinuities. When extrusion occurs, these fluids and remobilized sediments can be accumulated as chimney, mounds and associated with chemosynthetic organisms. Here we investigate the shape of mounds outcropping at the seafloor and buried in the sedimentary succession of the Davie Ridge and Morondava Basin. Two modes of geophysics data acquisition are use to describe the vent structures (1) multibeam bathymetry survey and (2) ship-based geophysical survey. We have found that mounds are rooted by hydrothermal vents sourced from the intrusion of volcanic sills in the sedimentary strata. However, other origin for these vents and associated mounds cannot be precluded due to limited samples. The most important point of this study is that the Sakalave mounds and vents compared to other identified hydrothermal vents and structures worlds wide, is to our knowledge the highest and steepest expression of hydrothermal vent-mounds yet discovered.
