Outline of Main Research Theme for
Research Vessel “MIRAI” during fiscal year 2008

1. Cruise Code :
MR08-06

2. Main research theme:
Studies on geophysics and paleoceanography in the South Pacific.
1) Oceanic crust formation around the Chile Triple Junction.
2) Large-scale mantle flow,‘superplume’around the Society hotspot in Polynesia.
3) Paleomagnetic study in the South Pacific.
4) Evolution of climate changes in the Chilean continental marginal area.

3. Objectives:
This research cruise is composed of four sub-themes (see 2. Main research theme). Objectives of each theme is followings:
1) To characterize the geological processes of the ridge subduction and to understand the processes of the continental crust growth interacted with ridge subduction systems.
2) To understand the mantle dynamics and mass transfer between the upper and lower mantle around the Society hotspot in Polynesia with determining the seismic structure and conductivity structure.
3) To understand geomagnetic inclination anomaly, which would be caused by non-dipole in the South Pacific over the past geological period.
4) To investigate past changes in the biological pump, which transports carbon from the surface to the deep ocean, sea-surface water temperatures, and the ventilation rate of the intermediate water with high time resolution.

4. Outline of observation:
1) Hard rock sampling using by dredge system, sediment coring will be done around Chile Triple Junction and transform fault. Sub-seafloor structure survey with single channel seismic experiment, Seabeam mapping, surface gravity and magnetic surveys are also planed.
2) Six BBOOBS (broadband ocean bottom seismograph) and six OBEM (ocean bottom electro-magnetometer) will be deployed around the Society hot spot.
3) Bathymetric survey using Seabeam system and sediment coring are planed in the South Pacific
4) Bathymetric survey using Seabeam system, sediment coring, CTD/RMS water sampling, plankton tows, drifting sediment trap experiment are planed along the Chilean coast.


5.Main research area:
1) Chile Triple Junction and transform fault: 44。S-53。S and 70。W-82。W.
2) Society hot spot in Polynesia: 16。S-23。S and 140。W-148。W.
3) South Pacific: 40。S-60。S and 70。W-95。W
4) Chilean coast including fjord: 45。S-56。S and 67。W-76。W

6.Cruise period:
Nov. 25. 2008〜Mar. 16. 2009
Leg.1 (sub-theme of 1): The end of November 2008- the beginning of January 2009
Leg.2 (sub-themes of 2, 3 and 4): The beginning of January 2009-the middle of March 2009

7.Ports of call (tentative):
Valparaiso, Papete

8.Proponent of main research theme:
Sub-themes of 1), 2), 3): Natsue Abe (IFREE, Jamstec)
Sub-theme of 4): Naomi Harada (IORGC, Jamstec)

9. Contact person for questionnaire on this cruise:
Sub-themes of 1), 2), 3): Natsue Abe (IFREE, Jamstec)
Sub-theme of 4): Naomi Harada (IORGC, Jamstec)