In the first dive we revisited the chimneys at Semenov 2 on the summit of the 13°30’ N detachment. This dive explored this hydrothermal vent system, and during the dive fluid samples and rocks where collected by VICTOR.
Next day we conducted a geological exploration dive at the western part of the detachment. Starting from the base of a scarp near the axis we proceeded up slope, to reach a fault scarp where the rocks from the detachment were exposed, giving us a great target for sampling and looking into this massif. A final dive is planned to investigate the top of the massif tonight, at the limit between the striated surface and the seafloor to the W, and to better understand what causes these striations.
For the first and second ROV dive we relied on the ship’s bathymetry for selecting dive targets. For future dives we will do AUV surveying prior to ROV dives, as these provide us with metre-scale bathymetry, significantly more detailed than the hundred metre-scale maps that can be acquired from a ship. Hence, features on the seafloor that can be then seen and recognized with Victor can be explored in detail. Any chemical anomalies from hydrothermal systems can also be detected by Abyss, using a variety of sensors to `sniff’ the seawater it passes through. Eventually, these sensors will allow us to the location of any active hydrothermal field prior to diving with Victor.
The next dive was a long traverse across the detachment at 13°30’N, from its eastern termination in the axial valley across much of the corrugated, striated surface of the massif. VICTOR was deployed on the hanging wall, right next to the detachment toe, before continuing over on the footwall of the detachment. This area turned out to be highly sedimented, with evidence of fossil hydrothermal activity.
Of two fault scarps mapped by Abyss, the first one was covered by talus, and the second gave us some spectacular outcrops. These we sampled and imaged for hours – looking into the core complex. Lastly, we traversed west to explore the nature of the E-W trending corrugations on the detachment, and hydrothermal mounds over it.
The next dive focused on the ridges between the 13°30’ N and 13°20’ N detachments. Exposed along the scarps of large faults we found basalts.
Now while Abyss is collecting bathymetry from the 13°20’N detachment, we are going to conduct our, for the moment, last ROV dive at the summit of the 13°30’N detachment. We will then move our investigations to the southern dome.