1 R/V Natsushima Cruise Report NT15-15 Off Tanegashima, southwestern Japan Biogeochemical and geomicrobiological investigations of submarine mud volcano off Tanegashima, southwestern Japan -implication for research on the potential of huge hydrocarbon resources- Aug.12,2015-Aug.17,2015 Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
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R/V Natsushima Cruise Report
NT15-15
Off Tanegashima, southwestern Japan
Biogeochemical and geomicrobiological investigations of
submarine mud volcano off Tanegashima, southwestern Japan
-implication for research on the potential of huge hydrocarbon
resources-
Aug.12,2015-Aug.17,2015
Japan Agency for Marine-Earth Science and Technology
(JAMSTEC)
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●Contents 1. Cruise Information
2. Researchers
3. Observations
3.1 Background
3.2 Objective
3.3 List of observation equipment
3.4 Research results
4. Notice on Using
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1. Cruise Information ● Cruise ID NT15-15
● Name of vessel: R/V Natsushima
● Title of the cruise: Biogeochemical and geomicrobiological investigations of submarine mud
volcano off Tanegashima, southwestern Japan
-implication for research on the potential of huge hydrocarbon resources-
●Title of proposal: Biogeochemical and geomicrobiological investigations of submarine mud
volcano off Tanegashima, southwestern Japan
-implication for research on the potential of huge hydrocarbon resources-
Submarine mud volcanoes occur along the margins of convergent plates and are formed by the
vertical intrusion of low density, deformable sediments from the deep subsurface to the seafloor (Milkov,
2000; Kopf, 2002). The common geochemical characteristics of submarine mud volcanoes are
diagenetically altered pore fluid by dehydration of clay mineral and presence of hydrocarbon gases
derived from thermocatalyte decomposition of sedimentary organic matter (Ijiri, 2009). These
characteristics suggest that the mud volcano fluid must originate at a deep depth in the sedimentary layer
where these chemical reactions typically occur (>60˚C). The mud volcanoes are, therefore, important
pathway of deep sourced materials, especially natural source of methane, which is one of the green house
gases, to hydrosphere and atmosphere (Milkov, 2000; Kopf, 2002).
Several ten mud volcanoes have been found Island have been found off Tanegashima along the
Ryukyu Trench (Ujiié, 2000). During 2012-2014, our research group (Geobio-Engineering and
Technology Group, Research and Development Center for Submarine Resources), had conducted
submarine topography survey to clarify the spatial distribution of mud volcanoes off Tanegashima. In
these cruises, we observed mud flow from the top of mud volcano No. 1 (MV#1) (30˚53´N, 131˚46´E・
water depth: 1536 m) by side scan sonar image. At MV#1, one piston core was retrieved on 2002.
However, newly erupted mud was not reported (Nakaya et al. 2010). Thus, the mudflow possibly
indicates recent eruption of the mud volcanoes after 2002. Because relatively large earthquakes (M4-M5)
were observed after 2002, the mudflow may be related with these earthquakes. Furthermore, if we take
the mud sample from the top of MV#1, we can get fresh sediment directly supplied from deep realm of
the mud volcano.
Reerences
1. Milkov, A. V. (2000) Worldwide distribution of submarine mud volcanoes and associated gas
hydrates. Mar. Geol. 167, 29–42.
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2. Kopf, A. J. (2002) Significance of mud volcanism. Rev. Geophys. 40, 1005,
doi:10.1029/2000RG000093.
3. Ijiri, A. (2009) Origin of fluid in submarine mud volcanoes. J. Geography, 118, 435–454 (in Japanese
with English abstract)
4. Nakayama et al. (2010) Source of pore water in a Tanegashima mud volcano inferred from chemical
and stable isotopic studies. Geochem. J. 44, 561–569.
3.2 Objective
The objectives of this cruise are investigation of 1) eruption history, activity of eruption, and
origin of mud fluid of MV#1, and 2) biogeochemical processes sustained by the supply of deep origin
materials associated with mud volcanism.
3.3 List of observation equipment
(1) Pressure Corer
This coring system allows retrieving sediment core samples without releasing the in situ hydrostatic
pressure (max. 50 MPa) during core recovery.
Fig.2 Photo of pressure corer.
(2) Push corer
(3) Niskin sampler
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(4) Water temperature recorder (ANTARES)
Serial# 1854306 Depth rating 6000 m Material of pressure case stainless steel Length 160 mm Diameter 15 mm Number of thermistor 1 Accuracy < +/- 0.1 °C
Sampling interval 10 min
Measurement start August 14, 2015 08:00:00
Total weight *1 10.8 kg in air and 8.6 kg in seawater
*1 The value of total weight includes weight values of a platform
Fig. 3 Schematic figure and photo of water temperature recorded.
Deployment of bottom-water temperature monitoring systems
In heat flow measurement in shallow sea area, bottom-water temperature variation (BTV) with
large amplitude prevents to measure accurate temperature gradient with a geothermal probe. For future
measurement of geothermal gradient (hence heat flow), we deployed bottom-water temperature
monitoring systems to obtain long-term bottom-water temperature data for removal of the effects of BTV
from measured sub-bottom temperatures.
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3.4 Research results
○ Dive summary
In NT15-15 cruise, we conducted two dives (#1866 and #1867) of Hyper-Dolphin on 14 Aug
2014 (Fig. 3).
During the #1866, the ROV landed on near the summit of the MV#1 and surveyed around the
summit. We found out a small colony of Calyptogena (Fig. 4). Near the Calyptogena colony, we retrieved
sediment samples by using push corer. We also tried to take pressure-conserved sediment by using
pressure corer. But the pressure was not conserved probably because of leak from valve. The
hemi-pelagic sediment was not observed around the summit. Instead of that, several consolidated sandy
mudstone clasts (several cm to several ten cm) were observed (Fig. 5). Such clasts are probably mixed
with fractured sediments by diapiric mud intrusion. This suggests that the sediment around the summit is
composed erupted mud and not covered by hemi-pelagic sediments. Some clasts were taken to determine
their origin and age.
At second dive #1867, the ROV landed near the western foot of MV#1. The ROV climbed along
a gully and reached to the summit. At the Calyptogena colony, we took living Calyptogena as well as their
shell. Near the colony, we tried to retrieve pressure core (Fig. 2) and succeeded in the sampling.
Fig. 3 HD track during #1866 (red circle) and # 1867 (green circle)
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Fig. 4 Photo of Calyptogena colony found at the summit.
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Fig. 5 Photo of Sandy mudstone clasts.
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○ Cruise log
Date Local
Time
Note Position/Weather/Win
d/Sea condition
12-Aug-15 Sail out & started NT15-15. 8/12 12:00 (JST)
09:00 Let go all shore lines & left Kagoshima port for
Research Area.
Kagoshima bay
9:20 -
9:45
Carried out shipboard education & training for
scientists.
31-06.0N, 130-38.0E
13:00 Proceeded to west of tanegashima due to
research area is rough sea.
Cloudy
21:15 Arrived at west of tanegashima. SSW-6 (Strong
breeze)
4 (Moderate)
1 (Low swell short or
average)
Visibly: 6'
13-Aug-15 Avoided rough sea at west of tanegashima
and Carried out MBES survey.
8/13 12:00 (JST)
13:00
-
13:30
Scientists meeting. West of tanegashima
17:30 Proceeded to research area. 30-15.0N, 130-45.0E
22:30 Arrived at research area. Fine but Cloudy
22:41 Rereased XBT at <30-45.8322N,
131-32.8355E>
WSW-5 (Fresh
breeze)
23:18 Started MBES mapping survey. 4 (Moderate)
2 (Low Swell Long)
Visibly: 8'
14-Aug-15 Operation "HPD" Dive#1866 and #1867 8/14 12:00 (JST)
04:23 Finished MBES mapping survey. Off east of
tanegashima
10:30 Arrived at dive point. 30-53.0N, 131-46.0E
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11:16 Hoisted up HPD Cloudy
11:20 HPD Launched. West-4 (Moderate
breeze)
11:32 HPD dove and started her operation #1866. 3 (Slight)
12:42 HPD landed on the sea bottom (D=1418m). 1 (Low swell short or
average)
14:10 HPD left the sea bottom (D=1417m). Visibly: 6'
14:50 HPD floated.
15:06 Recovered HPD and finished her operation.
16:42 Hoisted up HPD
16:46 HPD Launched.
16:58 HPD dove and started her operation #1867.
18:09 HPD landed on the sea bottom (D=1683m).
20:56 HPD left the sea bottom (D=1417m).
21:36 HPD floated.
21:52 Recovered HPD and finished her operation.
23:00 Started MBES mapping survey.
15-Aug-15 Freefall of umbilical cable 8/15 12:00 (JST)
03:57 Finished MBES mapping survey and then
proceeded to freefall area.
Off south west of
tanegashima
12:45 Arrived at freefall area. 29-36.0N, 131-24.0E
13:14 Started freefall of umbilical cable. Cloudy
16:40 Finished freefall of umbilical cable. WSW-3 (Gentle
breeze)
16:41 Started freefall of umbilical cable. 2 (Smooth)
19:52 Finished freefall of umbilical cable. 1 (Low swell short or
average)
20:00 Proceeded to Naha port. Visibly: 7'
16-Aug-15 Proceeded to Naha port. 8/16 12:00 (JST)
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17-Aug-15 Disembarkation scientist group & completed
NT15-15
09:00 Arrived at Naha port. Then completed NT15-15.
○ Dive information
Dive log #1866
Dive Log of
HPD Dive #1866
2015/
08/14
Time
(JST)
Dep.
(m)
Alt.
(m)
Head
(Deg)
Pos.
Xm
Pos.
Ym
Description Rema
rks
12:41 1414 3.6 278 -89.7 388.7 Niskin (green) close
12:42 1418 0 275 -86 385.4 Arrived to bottom
12:59 1428 0.5 58 7.5 294.5 arrived event mark#14
13:02 1428 0.5 58 7.5 294.5 Rock sampling (R1)
13:15 1424 3.4 174 4.2 463.3 Change direction to south, head to event
#15
13:18 1423 1.2 172 -34.2 464.1 Gap structure was observed (260 degree)
13:20 1422 0.6 240 -53.9 467.6 Head to event #1
13:22 1419 0 237 -75.1 434.8 Wood chips were observed