Voyage Plans and Summaries

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Franklin Voyage Plan FR03/2002

Title

Submarine hydrothermal activity and volcanic petrogenesis associated with the birth of island arcs in the Solomon Islands.

Itinerary

Depart Rabaul 1000 hrs, Tuesday 26 March, 2002
Arrive Sydney 1000 hrs, Tuesday 23 April, 2002

Principal Investigators

Dr Tim McConachy (Chief Scientist)
CSIRO Exploration and Mining
PO Box 136 North Ryde NSW 1670
Tel: 02 9490 8813
Fax: 02 9490 8921
Email: Tim.McConachy@csiro.au

Dr Ray Binns, CSIRO Exploration and Mining, Sydney

Professor Richard J Arculus, Department of Geology, Australian National University, Canberra

Scientific Objectives

1. To study 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.

2. To extend our research on seafloor hydrothermal ore systems to additional and different tectonic provinces in the western Pacific, and in particular to nascent volcanic arc environments where there are strong possibilities of finding gold-copper-zinc-rich massive sulfide deposits associated with calderas.

In detail, we are seeking answers to the following questions:

1. What are the distribution and association of rock types (both locally and regionally) in submarine arc volcanoes and what is their relationship to tectonic/structural features?

2. What styles of eruption and submarine volcanism characterize the San Cristobal-Santa Cruz volcanic arc? Are they related to volatile content?

3. Do nascent arc-related hydrothermal systems fundamentally differ in morphology and composition from mid ocean ridge and back arc systems and if so, why?

4. A by-product of the research will be the location and preliminary documentation of the diverse biota that surround seafloor hydrothermal systems which will assist and foster baseline environmental studies and ultimately ensure protection of biological diversity. How common are vent biologic communities in submarine arc volcanoes? How do they compare with mid ocean ridge vent communities? What is the longevity of life-supporting hydrothermal systems in arc environments?

The cruise will not in itself be testing speculative hypotheses. Rather, it represents expeditionary "field work" where, after hunting for and finding "natural laboratories", we will collect data and samples that become 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, etc., all of which help build up actualistic models of hydrothermal processes and products in relation to their overall geological environment.

The major hypothesis underlying our overall research program is that magmatic sources of hydrothermal fluids and contained metals are vital for the development of "world-class" orebodies in the subvolcanic-epithermal-subhalative-exhalative spectrum. Magmatic-source concepts are now becoming more popular, but it remains important to test them in new seafloor hydrothermal settings such as nascent arcs, particularly in order to develop the best possible geochemical and isotopic criteria and related exploration technologies for use by mineral companies in land-based exploration programs.

The proposed work is also vital for the definition of future ODP drilling targets that will further clarify deep subsurface hydrothermal processes.

Additional Project

In addition to the main research objectives above, an extra two days of ship time is planned to study the abundance, speciation and residence of metals and trace elements in the waters and sediments in the Empress Augusta Bay area, located on the west side of Bougainville Island, PNG. Funding for this project is yet to be finalised.

See appendix for further information.

Cruise Objectives

We plan to use CTD-transmissometer profiling to detect zones of active venting, bottom camera tows, dredging and sediment coring to study (1) the San Cristobal-Santa Cruz synrift volcanic zone and associated magmatic arcs located between the north dipping San Cristobal Subduction zone and the Vitiaz trench to the north, and (2) the magmatic arc as it swings south towards Vanikoro island, (3) revisit the eastern rift zone at Vella Lavella, the Kavachi submarine volcano and possibly other features which were studied during FR04/2000 to examine what changes have occurred during a 2 year period.

Please note that the original scientific proposal made provision to study a number of recently discovered submarine volcanoes near Malaita. To date, we have been unsuccessful in obtaining maps of these occurrences, so they are not one of the prime objectives of this current provisional cruise plan. However, should we be successful in obtaining more information about these occurrences, then one or two days could be given to their study, without materially altering the track and cruise plan.

Detailed recent bathymnetric surveys of the eastern Solomons, led by Dr Loren Kroenke (University of Hawaii; on behalf of the South Pacific Applied Geoscience Commission (SOPAC)), have revealed a remarkable transtensional zone with more than 50 submarine volcanic edifices distributed over a strike length of about 250 km. Our interpretation of the morphology and synrift setting of these volcanoes is that they are likely to be basaltic to andesitic in composition, growing upon a basaltic substrate, and represent a nascent island arc in an area of extending (and lengthening along-strike) crust. The likelihood of hydrothermal activity and deposition of sulfide deposits in the San Cristobal-Santa Cruz synrift volcanic zone and associated magmatic arcs and extensions to Vanikoro Island is considered to be high but to the best of our knowledge such a topic has not been investigated before anywhere in the world’s oceans. By working in this area, we will be expanding the range of geotectonic settings incorporated in our long-term research program whose outcomes will be improved knowledge of ore forming systems, with applications to land-based mineral exploration strategies and technologies.

Specifically the cruise will aim:

• To collect new marine geoscientific and geotectonic information on a hitherto little-explored but significant island-arc region, in the eastern Solomon Islands. Among the island arc-backarc systems of the southwestern Pacific, considerable petrologic and geochemical effort has been expended in the Solomon Islands and Vanuatu. However, there is an apparent gap of fundamental knowledge, between the eastern end of the Solomon arc and the northwestern end of the Vanuatu arc in terms of known subaerial volcanism, with the exception of one known volcano (Vanikoro)

• To document changes over a two year period of the active submarine Kavachi volcano

• To document the state of seabed sediments and water quality in Empress Augusta Bay, 13 years after the cessation of mining on Bougainville.

The principal investigators will endeavour:

• To document numerous aspects of modern, actively-forming mineralised environments, leading to improved interpretation of ancient sequences and orebody settings

• To provide new understandings of hydrothermal mineralising processes at geological settings differing from those so far discovered, thereby adding to the compendium of knowledge about orebody genesis

• To provide resultant strategies for land-based mineral exploration, especially within the sphere of interest of Australian-owned or Australian-based companies

Activities will include:

• Identification of targets using available bathymetric and preliminary geological interpretation

• Dredging major features to "ground truth" and if necessary upgrade the geological interpretation

• CTD-transmissometer tow-yos to detect hydrothermal particulate plumes and determine location of the "eyes" indicative of hydrothermally active edifices and sites. Seawater from plume "peaks" will be collected by Niskin bottle for on board methane gas analysis using a gas chromatograph and subsequent chemical analysis onshore

• Bottom-tow camera-video traverses along promising features, looking for hydrothermal deposits (chimneys, mounds, crusts) and faunal concentrations or "biological haloes" around vent sites

• Precision dredging to sample any deposits found

• Sediment coring and grabbing (Smith-McIntyre) for subsequent geochemical analysis seeking anomalies indicative of hydrothermal activity, and also at appropriate sites to test for indications of subsurface sediment-hosted mineralisation

• Access permitting, it is planned to sample water in the Jaba River using the ship's rescue boat. These water samples will also be tested for pH and a range of trace elements including copper.

We have previously successfully used these techniques at depths to 2500m and occasionally 3300m. Our camera-video system is rated to 3000m. Thus the targets mentioned above are accessible.

Cruise Track

Refer to Figures 1 and 2. We plan to sail from Rabaul to the Empress Augusta Bay on the western side of Bougainville Island, PNG where we will conduct echosounding traverses, camera tows, grab sampling, sediment coring and water sampling.

We then will enter Solomon Islands' waters, sailing to the eastern side of Vella Lavella, and making our way to the Kavachi submarine volcano in the SE of the New Georgia Group Islands. From there we will sail in a ESE direction to the east of San Cristobal Island (and provisionally E of Malaita, subject to obtaining suitable maps) where we will conduct the majority of our survey work towards the Santa Cruz and Vanikoro Islands in the far eastern Solomons. The cruise track shown in Figures 1 and 2 is approximate and will vary in detail depending on results and decisions made at sea. The planned final way point is a topographic high and suspected submarine volcano near 11° 20'S 166° 55'E, before commencing a 6 day transit to Sydney on Franklin's ultimate research leg.

Time Estimates

The actual number of operations will depend on results, and decisions 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, 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.

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, 11x 10-litre Niskins

• 12 kHz pingers (2), Smith-McIntyre grab

• Computers, trackPlot software

• Fridge and freezers, clean air cabinet

• Underway pH and ADCP.

User Equipment

From CSIRO North Ryde unless indicated.

• Bottom sampling: Dredges (x2) and depressor weight , 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.

• Analytical: Portable gas chromatograph and ultrasonic gas extraction system.

• G-size Hydrogen, G-size Helium, G-size Air and D-size standard cylinders (the 3 G-size will need to be delivered by BOC to Cairns). PH meter 

Special Requests

1. Except perhaps for the gas chromatograph and associated gas bottles, all our equipment will be used on the earlier FR02/2002 cruise to the west Bismarck Sea (Dr Ray Binns Chief Scientist, and who is also a Co-Principal Investigator on FR03/2002). Our plan is to ship gear (4 wire cages, 3 wooden pallets (dredge), and consumables (white plastic buckets), to arrive by 27 February 2002, two days before scheduled departure from Cairns. Arrangements were also made to leave a dredge and depressor weight and camera cage on the fore deck, and sediment core (3 boxes) in the scientific hold following FR08/2001.

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.

Provisional Personnel List

* Chief Scientist
** Co Principal Investigator
Note: A third ORV Franklin technician is not required.

This cruise plan is in accordance with the directions of the National Facility Steering Committee.

Dr Tim McConachy
Chief Scientist

4 October 2001

Figure 1. FR03/2002 cruise track.

Figure 2. Bougainville (PNG) and Solomon Islands showing areas for planned operations on FR03/2002 and approximate cruise track.

APPENDIX

Additional Project on FR03/2002

Title

Abundance, speciation and residence of metals and trace elements in the waters and sediments in the Empress Augusta Bay area, Bougainville Island, PNG.

Principal Investigators

Dr Tim McConachy, CSIRO Exploration and Mining, Sydney
Dr Ray Binns, CSIRO Exploration and Mining, Sydney

Research Objectives

To document the state of sea bed sediments and water quality in Empress Augusta Bay, 13 years after the cessation of mining on Bougainville.

This project is planned to study the abundance, speciation and residence of metals and trace elements in the waters and sediments in the Empress Augusta Bay area, located on the western side of Bougainville Island, PNG.

Cruise Objectives

To conduct echosounding traverses, camera tows, grab sampling, sediment coring and water sampling in the Empress Augusta Bay area. An extra two days of ship time has been requested to undertake this work. Access permitting, it is planned to sample water in the Jaba River using the ship's rescue boat. These water samples will also be tested for pH and a range of trace elements including copper.

The ship would have to pass Empress Augusta Bay on its way to Vella Lavella and Kavachi submarine volcano and the eastern Solomons, therefore operations in Empress Augusta Bay involve virtually no change to the cruise track plan. Furthermore, discussions with the Master of Franklin have confirmed that the Franklin is able to access Empress Augusta Bay. It is around a 20 hour steam from Rabaul and will be the first operations conducted on FR03/2002.

Updated: 31/01/03