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.