Irish Marine Institute Shiptime: Tosca CE18008

Description

The acquisition of an extraordinary piece of reconnaissance data, collected in 2015 by the Marine Institute (MI), from the central CGFZ, provided a unique opportunity to study what is probably the longest-lived and best exposed section of oceanic crust formed by tectonic spreading in the Atlantic. The remarkable multibeam images from the RV Celtic Explorer of the central eastern part of the transverse ridge show it to be an exceptionally large mound that, given the setting, could be an OCC which would confirm the prediction that spreading here is tectonic. As a result, the CGFZ presents a unique opportunity to study the effects of tectonic spreading over millions of years from continental break-up to full ocean spreading.
The TOSCA expedition was an interdisciplinary study of the CGFZ that included multibeam mapping, multichannel seismic reflection imaging, ROV Holland I dives and sampling and gravity coring.
The overarching objectives were: (1) to determine the structure and composition of the lower crust and mantle; (2) to understand the interaction between seawater and peridotite and any resulting hydrothermal activity; (3) record the history of seismogenesis at long-offset strike slip faults; (4) to examine the structural effects of changes in spreading direction; (5) to investigate the role of mass wasting and slope instability in deconstructing mid-ocean ridges; and (6) establish the impact of basement topography, lithology and fluid flow on deep- water sessile and chemosynthetic biota.

Period	13 May 2018 → 08 Jun 2018
Degree of Recognition	International