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  • 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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    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-

    Cruise period: Aug.12,2015-Aug.17,2015

    Ports of departure: Kagoshima, Kagoshima prefecture / arrival: Naha, Okinawa prefecture

    Research area: Off Tanegashima, southwestern Japan

    Research Map

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    Fig. 1 Cruise truck of the NT15-15 cruise

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    2. Researchers Chief scientist Akira Ijiri (JAMSTEC) Representative of Science Party Akira Ijiri [JAMSTEC]

    Associate chief scientist Fumio Inagaki (JAMSTEC) Scientist Hideaki Machiyama (JAMSTEC)

    Scientist Yuki Morono (JAMSTEC)

    Scientist Yuka Masaki (JAMSTEC) Scientist Nan Xiao (JAMSTEC) Marine Technician Yuji Fuwa (NME Ltd)

    3. Observations 3.1 Background

    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 (>60C). 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 (Ujii, 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) (3053N, 13146Ewater 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, 2942.

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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, 435454 (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, 561569.

    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

    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 d

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