Voyage Plans and Summaries

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Franklin Voyage Plan No. FR01/2001

Title

GABSEEPS. Warm seeps at the shelf margin of the Great Australian Bight: Indications of a new analogue for ore environments.

Itinerary

Depart Fremantle 0700 hrs, Wednesday 31 January 2001
Arrive Adelaide 1000 hrs, Thursday 15 February 2001

Principal Investigators

Dr Ramond A Binns
Chief Research Scientist
CSIRO Exploration and Mining
PO Box 136
North Ryde NSW 1670
Tel: 02-9490 8741 (H) 02-4883 6069 Fax: 02-9490 8921
r.binns@syd.dem.csiro.au

Dr Tim McConachy
CSIRO Exploration and Mining
PO Box 136
North Ryde NSW 1670
t.mcconachy@syd.dem.csiro.au 

Scientific Objectives

Our prime objective is to test (by exploration) the hypothesis that hydrothermal "warm seeps", venting basin brines or fluids rising up faults from basement, exist along the edge of the Great Australian Bight. Such sites may host mineral-rich deposits, or the fluids may have compositions implying operation of subsurface ore-forming processes. If seep sites are found, the environment will be assessed as a modern analogue of "Mississippi Valley type" lead zinc mineralisation, and also for a form of uranium mineralisation.

A second objective is to maximise value of data and samples collected during the cruise, for example by treating and preserving material to allow shipboard and shore-based studies that will add to the national petroleum prospectivity and biodiversity databases.

Cruise Objectives

The aim, using existing reflection seismic profiles as a guide to suitable structural sites, is to locate, photograph and sample "warm seeps" at three transects across the outer shelf margin of the Great Australian Bight:

• Recherche Transect, 640-3900m

• Eucla Canyon Transect, 600-1500m

• Nullarbor Canyon Transect, 1700-3500m

Following confirmation of the presence and location of scarps, slumps and "holes" by precision echo sounding, selected areas within these transects will be tested for proximity to venting with CTD-transmissometer hydrocasts (including salinity and dissolved oxygen sensing), collecting profiles of near-bottom seawater for on-board analysis (calibration) of salinity, methane content (and higher hydrocarbons if detectable by gas chromatograph) and selected "nutrient" elements (P+?). Highly anomalous waters will be preserved for shore-based isotopic analyses.

Sediment samples will also be collected by tube corer, box corer and grab near CTD stations and at other prospective sites. Tube core samples will be opened, logged and analysed ashore for indications of metal and hydrocarbon enrichments, while lithology and biomass will be assessed on board for box core and grab samples, with aliquots frozen for onshore organic analyses .

Bottom-tow video photography will be conducted at appropriate sites, looking first for rising abundance of macrofauna expected around vent sites or seeps, then homing in on these. Once identified and accurately located, the sites will be sampled by precision dredging and box coring.

Dredging will also be conducted on some steep scarps expected to expose rocks, particularly at the "holes" recently identified in the Nullarbor Canyon. Two possible volcanoes in the Nullarbor Canyon Transect area will be dredged to establish their identity and will be photographed (if time allows) for faunal associations.

Additional sediment cores may be taken during the later transits to obtain background/reference samples and data.

Biodiversity studies require underway and on-station thermosalinograph and fluorescence measurements and vertical deployments of a bongo or ring net for collecting pelagic plankton.

Fauna collected will be preserved by freezing for biological research and appropriate samples will be treated to retain microbe assemblages.

Cruise Track

From Fremantle, we will round Cape Leeuwin and proceed directly to the first transect site, then the second, then the third, then proceed to Adelaide. Coordinates of the centres of the three transect areas are as follows.

Time Estimates

Time required for any sediment coring during transits will come from the contingency allowance, or be deducted from time on station at transects. Time required for individual operations will depend on depth. As estimated from experience, the following times include positioning and set-up:

Decisions on which operations are conducted will be made at sea, depending on results. The desirable minimum numbers listed above (45 operations) would require 5.5 days if no problems develop, while the maximum numbers (68 operations) would use all the time available allowing for a few hours sounder profiling at each transect. Conservatively, since there will be some activities in shallower water, 15 operations are anticipated for Recherche, 15 for Eucla, 22 for Nullarbor and 3 during transits (total 55 operations).

Piggy-back Projects

Petroleum-related (sedimentological and geochemical) and biodiversity-related studies involving the Australian Geological Survey Organisation and Environment Australia, respectively, will use the same samples and data as are acquired for the main scientific objective. Biodiversity studies will need underway thermosalinograph-fluorescence measurement (no extra ship time involved) and deployment of a plankton-collecting net at each transect area. AGSO and EA personnel are being carried to ensure maximum value is obtained from the planned activities as outlined in proposal, especially in the event of locating chemosynthetic communities at seep sites.

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, under-way and on-station thermosalinograph and fluorimeter. Fridge and freezers.

Chemistry – salinity, P (+?)

User Equipment

From CSIRO North Ryde unless indicated.

• Bottom sampling: Dredges and depressor weights (x2), small gravity corer, 6m gravity corer and deployment cradle (AGSO), box corer (AGSO).
• Bottom photography: Deep tow video system and related equipment including sled. Sealite batteries. Recording CTD-transmissometer.
• Biodiversity: Bongo/ring net (EA-CMR). Apparatus for collecting and preserving microbial samples.
• Analytical: Portable gas chromatograph and ultrasonic gas extraction system. Possibly a benchtop fluorimeter (AGSO)
• General: Microsopes, PCs. Equipment for filtering and analysing hydrocast and vent fluid samples.
• VUNL is not required, and we will not have a towed radiometric system (mentioned in proposal)

Special Requests

• Ergonomic readout of trackPlot at winch station
• Prior checking and calibration of wire-out and tension measurement
• Second colour printer always recording exactly what is displayed on SIMRAD monitor (ie slaved)
• Prior checking that modified SIMRAD firmware will allow rapid deployment of camera to bottom, and effective altimetry using pinger
• Real-time output of nav and winch data as spreadsheet, for recall after each operation (e.g. for planning the next)
• Rapid creation of digital CTD data (down and upcast) in spreadsheet form, for detailed comparisons between casts for planning purposes; ability to recalibrate salinity
• Better synchronisation between SIMRAD and ship time

We request that AGSO corers and cradle be stored in hold after FR01/2001 for use during FR03/2001 (agreed by Prof Tomczak).

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
CSIRO Marine and Atmospheric Research

Updated: 31/01/03