Voyage Plans and Summaries

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Franklin Voyage Plan No. FR08/2001

Title

VAVE-2001 (Vanuatu and Australia Vents Expedition)

Seafloor hydrothermal activity in arc and backarc settings, Vanuatu, SW Pacific.

Itinerary

Depart Noumea 0800 hrs, Wednesday 5 September 2001
Arrive Brisbane 1000 hrs, Monday 24 September 2001

Principal Investigators

Dr Timothy F McConachy (Chief Scientist)
Principal Research Scientist
CSIRO Exploration and Mining
PO Box 136 North Ryde NSW 1670
Tel: 02 9490 8813
Fax: 02 9490 8921
Email: t.mcconachy@syd.dem.csiro.au

Dr Ray Binns, CSIRO Exploration and Mining, Sydney 

Scientific Objectives

The major scientific objective is to locate and study seafloor and sub-seafloor hydrothermal ore-forming activity in order to develop improved methods of exploring for ancient mineral deposits on land that originally formed by similar processes.

Specific objectives are:

1. To locate and sample sediment-hosted hydrothermal mineralisation, and gold-copper-zinc-rich massive sulfide deposits associated with submarine volcanic calderas in a backarc setting. Vanuatu has geological settings with excellent potential to host this range of hydrothermal ore systems.

2. FR08/2001 will not in itself be testing major hypotheses. Rather, it represents expeditionary "field work" to hunt for and locate "natural laboratories" and to collect data and samples that will be the subject of a range of laboratory investigations. These include assessments of tectonic setting, petrological and geochemical studies of volcanic rocks and sediments, examination of mineralisation and alteration phenomena, comparison with other submarine settings etc., all of which help build up actualistic models of hydrothermal processes and products in relation to their overall geological environment.

3. FR08/2001 is also vital for the definition of future ODP drilling targets to further clarify deep subsurface hydrothermal processes; our Manus Basin ODP Leg 193 in 2000/2001 having led the way.

Cruise Objectives

We aim to survey selected sites in the Coriolis Troughs and their extensions, centred about 180km SE of Vila, using CTD-transmissometer profiling to detect zones of active venting, followed by bottom camera tows, grab sampling, dredging and sediment coring.

Our strategy is to work from south to north (Fig. 1 & 2) which will optimise transit times and make the most efficient use of RV Franklin's time at sea. Decisions on which operations are conducted will be made at sea, depending on results.

The Coriolis Troughs located east of the Erromango, Tanna and Anatom Islands offer scope to investigate a number of volcanic-hosted hydrothermal fields. These troughs or basins were surveyed by the Metals Mining Agency of Japan in 1994, and good quality seabeam bathymetry and magnetic data are available over an area of 350 x 120km.

Unfortunately, this survey coverage does not extend to 100km SSE of Anatom Island where submarine volcanic activity is marked on published nautical charts at depths of less than 1000m. We interpret this activity as being at the southern extension of the Coriolis system and may therefore represent new or reinvigorated submarine volcanism. We plan (as the first way point) to survey this area using echo-sounding and CTD data to identify possible dredging and camera tow targets.

Two of seven prominent submarine ‘cones’ dotted along a 110km chain in the south east of the Japanese survey area, about 40km east of the small island of Fortuna, will be surveyed. The biggest cone rises to about 800m below surface with the others around 1000-1500m. No obvious caldera structures are evident but there may be potential for hydrothermal activity.

In addition we plan to survey targets within submerged portions of the Vanuatu volcanic arc. This will include sampling of reputed sulfide-bearing altered lava from near the site of an 1453AD massive caldera eruption (Kuwae) near Epi Island in the central part of the arc, where a small post-caldera parasitic cone emerges occasionally. So far, no shipboard hydrothermal indications are known. This site is scheduled as the final scientific waypoint of FR08/2001.

Specific activities include:

• Dredging major features to 'ground truth' them and if necessary upgrade their geological interpretation.

• CTD-transmissometer tow-yos and single dips to detect hydrothermal particulate plumes and locate the 'eyes' of any plume discovered, to define hydrothermally active edifices and sites. Seawater from plume "peaks" will be collected by Niskin for subsequent chemical analysis onshore.

• Bottom-tow camera-video traverses along promising features, looking for hydrothermal deposits (chimneys, mounds, crusts) and faunal concentrations.

• Precision dredging to sample any deposits found.

• Sediment coring and grabbing (Smith-McIntyre) for subsequent geochemical analysis in order to look for anomalies indicative of hydrothermal activity and also identify sites to test for indications of subsurface sediment-hosted mineralisation.

We have previously used the above techniques at depths to 2500m and occasionally 3300m. Our camera-video system is rated to 3000m and therefore some targets in the deeper Fortuna Basin will not be accessible but these sites will be studied using sediment coring and the ship's CTD.

Special attention will be devoted to any locations that appear during the cruise to have potential for sediment-hosted mineralisation (including within altered epiclastics). A discovery of the latter nature would open up a major new research field highly relevant to land-based mineral exploration.

Cruise Track

From Noumea, sail around the southern end of New Caledonia and then NE towards Waypoint "A" (100km SSE of Anatom Island; 21° S, 170° 15'E) where submarine activity is recorded on published nautical charts. From there working our way NNW (with local zig-zags) surveying and sampling selected targets in the East Coriolis Seamount Chain, Fortuna, Erromango and Vate Basins and then to near Epi Island to investigate the Kuwae caldera (16° 50'S, 168° 30'E) before departing for 4-day transit to Brisbane. The general cruise track is shown in Figure 1 and more detailed plan in Figure 2.

Time Estimates

Table 1. Summary

Table 2. Summary of Planned Number of Operations

The actual number of operations will depend on the results at sea. Except for echo sounding, time for each operation is a function of depth. The length of echo sounding traverses will depend on the accuracy and detail of existing bathymetric coverage. Where coverage is minimal (eg Waypoint "A") more time will be allocated to echo sounding to produce workable bathymetric maps.

As estimated from experience, the following times (hours) include positioning and set-up.

Table 3. Time Estimates for Operations

Franklin Equipment

All winches, deck crane, deck machinery, all laboratories (including container lab and darkroom), differential GPS, scientific sounder (narrow and broad beam receivers), CTD-transmissometer, Niskins, computers, 12 kHz pingers (2), Smith-McIntyre grab, trackPlot software, fridge and freezers. Clean air cabinet. VUNL is required (NB: closing mechanism on Niskin bottle needs attention).

User Equipment

From CSIRO North Ryde unless indicated.

Bottom sampling: Dredges and depressor weights (x2), small gravity corer.
Bottom photography: Deep tow video system and related equipment including sled, and two nitrogen bottles (one bottle for clean air cabinet). Sealite batteries. Recording CTD-transmissometer.
General: Microscopes, PCs. Equipment for filtering and analysing hydrocast and vent fluid samples, buckets for rock samples.

We will not be using the geophysical arrays mentioned in the original proposal.

Special Requests

1. To help defray transport costs to Noumea, store gear in Franklin's hold in Brisbane prior to departure of FR07/2001 on Tuesday 28 August 2001. This has been discussed with Dr Patrick DeDeckker (Chief Scientist FR-07/2001). We plan to ship gear (4 wire cages, 3 wooden pallets (dredges and weight), one wooden box (corer), camera cage, and consumables (white plastic buckets)), to arrive by 21 August 2001, one week before scheduled departure from Brisbane.

2. Prior checking and calibration of wire-out and tension measurement.

3. Second colour printer always recording exactly what is displayed on SIMRAD monitor. Echoview display on separate monitor.

4. Real-time output of nav and winch data as spreadsheet, for recall after each operation (e.g. for planning the next operation)

5. Rapid creation of digital CTD data (down and upcast) in spreadsheet form, for detailed comparisons between casts for planning purposes.

6. Synchronisation between SIMRAD and ship time.

Personnel List

This cruise plan is in accordance with the directions of the National Facility Steering Committee for the Research Vessel Franklin.

John Wallace
Ships Manager

Updated: 31/01/03