Mixing Zephyr Program
Dive 2923

Port Observer: Robigou
Starboard Observer: Butterfield
Pilot: Hickey
Date: 5/27/95

Summary

Dive Goals: Establish which transponders are picked by the submersible for in-hull navigation purposes and collect positioning data to start establishing the navigation net for the rest of the cruise and summer program. Go to Transponder A and ping to the others. The goals of this first dive were to find the Main Endeavour vent field as soon as possible. Finally to sample hydrothermal fluids from 1991 previously-sampled active sulfide structures and mark all orifices or areas sampled with new 1995 markers (white small triangles).

Summary: On the way down, impossible to hear transponder at 14.5kHz. We landed at 9:28 at 6492, 6534 and D2097. We do not know exactly where yet. We are experiencing navigational problems because of lack of response from transponder 14.5, so instead of going to transponder A to ping on other transponders and establish the net as well as can be for the first dive, we head roughly west for the valley floor and find the first sulfide structure that needs to be sampled (Hulk). As we are coming down the eastern wall and traversing the valley floor, we encountered dead sulfides and noticed that the valley floor is pillow-basalt mostly. Because of navigational uncertainty we crossed the valley (narrow is this area (200-300m?) and went up the western wall for a while. From our calculations we seem to be off by 600m to the north and 150-200m to the west of where we thought we should be. Correcting for this offset we come back down (east) to the valley floor and look for some familiar feature that we can use to orient ourselves. We traveled to depth 2100m on the western wall. Despite the surface sent recommendation that we should keep going north, we turn around and follow the edge of the western wall. Around noon, still north of the MEF we find a dead sulfide spire about 7-8m high, and several other dead sulfide structures until we reach 5153, 5702 where we spot the LOBO cement bag which serves as permanent marker to the north of the MEF. We know where to go now and we spend a little time gathering good fixes at the cement bag to correlate this dive track with our older maps.

In 2 minutes we are at Hulk, by marker J. The structure looks less active in terms of hydrothermal activity but it is still doing well (less black smoker activity and many tube worm areas covered by brownish bacteria). Market J is at 5190, 5638, D2193, H202, A13. Manifold sampling at Hulk on black smoker with small orifice. High-T temp is 332°C. New marker A3 is deployed.

Next we fly to Dante passing TP and noticing a very nice overflowing flange on the eastern side of the southern lobe of TP. At Dante we find marker X, 5120, 5545 D2178, H137, A15 (on the northern lobe of Dante). High-T temp. 348°C. We sampled with major 10 and 4, and gas-T 5, 2 and 6. Marker A7 was deployed at the sampling site at 5122, 5540, D2178, A15 m.

Upon ascent sampling Niskin bottles over Dante at 1m (red), 3m (green) and 10m (blue). During ascent checking on transponder 14.5 kHz and still can not hear it.