Abstract
Seafloor massive sulfide deposits form in remote environments, and the
assessment of deposit size and composition through drilling is
technically challenging and expensive. To aid the evaluation of the
resource potential of seafloor massive sulfide deposits,
three-dimensional inverse modelling of geophysical potential field data
(magnetic and gravity) collected near the seafloor can be carried out to
further enhance geologic models interpolated from sparse drilling. Here,
we present inverse modelling results of magnetic and gravity data
collected from the active mound at the Trans-Atlantic Geotraverse
hydrothermal vent field, located at 26o08’N on the
Mid-Atlantic Ridge, using autonomous underwater vehicle (AUV) and
submersible surveying. Both minimum-structure and surface geometry
inverse modelling methods were utilized. Through deposit-scale magnetic
modelling, the outer extent of a chloritized alteration zone within the
basalt host rock below the mound was resolved, providing an indication
of the angle of the rising hydrothermal fluid and the depth and volume
of seawater/hydrothermal mixing zone. The thickness of the massive
sulfide mound was determined by modelling the gravity data, enabling the
tonnage of the mound to be estimated at 2.17 +/- 0.44 Mt through this
geophysics-based, non-invasive approach.