Voyage Plans and Summaries

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Franklin Voyage Plan No. FR02/2002

Title

Variability related to subduction style of submarine hydrothermal and volcanic activity in the Western Bismarck Island Arc, Papua New Guinea.

Itinerary

Depart Cairns 1000hrs, Friday 1 March 2002
Arrive Rabaul 1000hrs, Monday 25 March 2002

Principal Investigators

Dr Ramond A Binns (Chief 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 (soon to be Ray.Binns@csiro.au)

Dr Tim McConachy, CSIRO Exploration and Mining, Sydney

Prof Richard Arculus, Dept. of Geology, Australian National University

Scientific Objectives

General aims of our research program are to study modern 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. This approach avoids the problems of metamorphism and deformation which can confuse direct genetic investigations of ancient orebodies themselves. We are now at the stage where, following successes in the Eastern Manus Basin and elsewhere, we wish to extend our research to additional and different tectonic provinces in the Western Pacific so that results can be directly applied to a broader range of orebody settings.

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. Our early PACMANUS work proposed this (on the basis of laboratory work including isotopic and trace element analyses) when other groups were mostly ascribing such deposits to recirculated seawater with igneous activity acting primarily as a heat engine. Magmatic-source concepts are now becoming more popular, but it remains important to test them in new seafloor hydrothermal settings, 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. It is also important, for improved interpretation and exploration of ancient geological terrains, to improve our understandings of the links between tectonism and igneous characteristics in modern, undeformed terrains.

Cruise Objectives

Specific aims of Cruise FR02/2002 are to locate, study and sample submarine volcanoes with active hydrothermal systems in the Western Bismarck Island Arc of Papua New Guinea, in particular at sites having highly potassic characteristics and where summit calderas occur.

The cruise will not in itself be testing major hypotheses (apart from the presumption that an island chain of this character will possess active submarine hydrothermal centres). 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 and volcanic setting, examination of hydrothermal 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.

As by-products of this research, we aim to clarify the geochemical characteristics of the Western Bismarck Arc and to test the presence of systematic along-arc geochemical variations. We will be alert to the possibility of discovering that the arc is in fact broader than indicated by island volcanoes, and that there might be systematic cross-arc variations also. These results will feed into improved understandings of the complex tectonics and geodynamics of this important segment of the Indo-Australian Plate margin.

Another subsidiary aim will be to sample hydrothermal plumes in order to extend the understanding of hydrothermal components to the chemistry of the Bismarck Sea and environs.

Cruise Track

From Cairns, sail via China Strait or Jomard Entrance, then Vitiaz Strait, into the western Bismarck Sea. Operations will take place between Umboi Island (5° 30’S, 147° 30’E) to near Vokeo Island (3° 20’S, 144° 10’E), first moving generally westwards, then returning east back towards Umboi (see Figure 1).

If time permits and depending on the results in the western Bismarck, the PACMANUS site (3° 45’S, 151° 40’E) will be visited briefly on the final transit to Rabaul, checking two locations where strong indications of hydrothermal activity seen during our BINATANG-2000 cruise on RV Franklin remain to be sourced.

Figure 1. Principle area of operations, FR02/2002

Time Estimates

Methods

Techniques to be used during FR-02/02 will be the same as those employed to locate hydrothermal activity during our previous PACMANUS cruises:

• Identification of targets using available bathymetric, geophysics (seismicity, satellite gravity and magnetic intensity in particular), plus preliminary geological interpretation.

• Systematic echosounder profiling as required to further define these targets and seek new targets

• 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. Seawaters from plume "peaks" will be collected by Niskin bottle for subsequent chemical analysis onshore

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

Decisions on which and how many operations are conducted will be made at sea, depending on results.

Franklin Equipment

• All winches, deck crane, deck machinery

• Dynamic positioning aids, differential GPS

• All laboratories (including container lab and darkroom)

• Scientific sounder (narrow and broad beam receivers) with plotting software and printer

• CTD transmissometer, Niskin bottles, computers, 12 kHz pingers (2)

• Smith-McIntyre grab, trackPlot software, weak links for dredging

• Fridge and freezers.

User Equipment

Bottom sampling: Dredges (x2) and depressor weights, small gravity corer.

Bottom photography: Deep tow video system and related equipment including sled, Sealite batteries. Recording CTD-transmissometer.

General: Microsopes, PCs. Equipment for filtering and analysing hydrocast samples.

Related Cruises

Discussions are proceeding with Dr Sang-Mook Lee (KORDI, Korea) about coordinating this cruise with one he is contemplating with RV Onnuri later in 2002. Joint participation by personnel from CSIRO and KORDI in both cruises is proposed.

Some personnel from FR02/2002 will also take part in the following cruise FR03/2002 (Rabaul to Sydney: Chief Scientist, Dr Tim McConachy, CSIRO), which will focus on Solomon Islands waters.

Personnel List

Not finalised at this stage. We plan filling the 12 scientist berths as follows:

CSIRO Exploration and Mining, 3
ANU Geology, 1
PNG participants nominated by research partner GSPNG, 2
International collaborators (KORDI, LIPI), 3
CSIRO Marine (Vessel Staff), 3

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

Dr John Wallace
Ships Manager

Updated: 31/01/03