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IODP Expedition 324:
Shatsky Rise Formation
Week 1 Report (6-12 September 2009)
PDF file is available for download.
14 September 2009
324 started on 4 September at the port of Yokohama. In addition to the routine
resupply of expendables and the offloading of Expedition 323 cores and
returning freight, some items of note were the loading of 1800 MT of marine gas
oil, the overhaul of the passive heave compensator, and service visits by
Novenco (air conditioning), RigNet (VSAT), and Hose-McCann (ship
phone/intercom/alarm system) field engineers. This port call was also noteworthy for the extensive number of visitors that were treated to a tour of the vessel.
port call, we were not able to send or receive email or use the ship's phone
system because of local electromagnetic interference, which prevented VSAT
operation. Although some maintenance was possible on the aft antenna, the
RigNet engineer was unable to perform a systems check and calibration to the
VSAT system because of the interference.
last line was released at 0950 hr on 9 September, the vessel was underway to
the pilot station. The RigNet engineer stayed aboard and attempted last minute
adjustments while working with rig-based technicians. The pilot and RigNet
representative disembarked at the pilot station at ~1130 hr. A short time after
this, VSAT operation was restored and remained until the first course change.
At this time, the signal was lost and in spite of the best efforts of on-board
technicians communicating with the RigNet engineer in the hotel via the
Inmarsat GMDSS satellite phone, the VSAT system could not be restored to normal
working order. After discussing the situation with the agent and the port call
coordinator, the decision was made to reverse course, return to a convenient
rendezvous point close to Yokohama, and bring the RigNet engineer back to work
on the system.
engineer was welcomed aboard shortly before 0600 hr on 10 September and
remained for nearly two hours restoring the VSAT to operation. Once he departed at 0740 hr, the vessel began the voyage to Prospectus Site SRNH-2.
voyage the clocks were advanced one hour placing the vessel in the same time
zone as Townsville. There will be no further adjustments to the clock during
the expedition. By midnight on 12 September, the vessel has sailed 730 nmi at
an average speed of 11.6 knots. The expected time of arrival at Prospectus Site
SRNH-2 is slightly before noon on 14 September.
Expedition 324 aims to contribute to the ongoing controversy about large
igneous (oceanic) plateau formation by drilling at several sites on the Shatsky
Rise, located ~1500 km east of Japan. Igneous oceanic plateaus, such as
Shatsky, present one of the largest known volcanic episodes on Earth but can't
be easily explained by conventional plate tectonic models.
hypothesis for the origin of oceanic plateaus is that they reflect eruptions
from a "mantle plume head". Despite the wide acceptance of this hypothesis, a
convincing case for a plume head origin has not been made for any oceanic
plateau. Some scientists therefore question the existence of deep (lower)
mantle plumes and attribute the origin of oceanic plateaus and other large
igneous provinces to shallow processes related to (shallow) plate tectonics.
For example, oceanic plateaus could form where mid-oceanic spreading ridges
form a special geometry (a so called triple-junction).
great difficulty for answering this question is that the original setting,
relative to mid-ocean ridges and plate tectonics, is poorly known for most
plateaus because they were formed during the mid-Cretaceous magnetic quiet
zone. Shatsky Rise is unique in being the only large oceanic plateau formed
during a time of frequent magnetic reversals, permitting its tectonic setting
to be resolved. The magnetic lineations reveal that Shatsky Rise formed along
the trace of a triple junction, intimately related to ridge tectonics. On the
other hand, existing data demonstrate that several aspects of Shatsky Rise's
history (e.g., massive, rapid initial growth; transition from large to small
magma flux; capture of ridges) fit the plume head model. Its unique combination
of features makes Shatsky Rise the best location on Earth to test plume versus
plate-tectonic hypotheses of ocean plateau formation.
IODP Expedition 324 we plan to penetrate ~800 m of igneous basement at five
sites on Shatsky Rise to examine the history, magma source(s), and evolution of
this plateau. From the results of this expedition, we hope to address the
question of whether oceanic plateaus like Shatsky Rise were formed from
deep-sourced mantle plumes or interaction of plate boundaries and the
lithosphere with the shallow mantle.
all drill sites only rotary core barrel (RCB) drilling and single penetration
is planned. To further save operational time, sediment coring will not start
until about ~50 m above expected igneous basement. Three holes with 100 m, one
hole with 200 m and one hole with 300 m igneous penetration are anticipated. If
hole conditions allow, each hole will be logged with the standard triple combo
and the Formation Micro Scanner (FMS). Employment of an Ultrasonic Borehole
Imager (UBI) is planned for the deepest hole.
scientific party arrived on board on Sept. 5. They spent the first week of this
expedition learning their laboratories, instrumentation, documenting methods,
and practicing core flow and sampling procedures. Descriptive information will
be entered into the database using the new DESClogik application. By the end of
this week, each descriptive lab group (sedimentology, petrology, alteration,
structure) and the biostratigraphers completed the set up of their specific
templates in DESClogik, which are used to compile and enter any descriptive
information. The igneous core describing groups used Leg 198 cores (igneous
sections from Site 1213 are available on board) to practice core flow and
description in DESClogik. In addition, each lab group submitted their first
draft of the Methods chapter (explanatory notes) for the Proceedings volume.
scientists met with the curator, co-chief scientists and staff scientists for a
first sampling meeting for postcruise research. A procedure for developing a
coordinated sampling plan was developed. It was agreed to defer all personal
sampling of igneous cores until the transit to Townsville, where we will
conduct coordinated sampling parties.
September 12, the Japanese educator successfully broadcasted a live video
interview from the ship to the National Museum of Nature and Science in Tokyo,
which was screened before an audience of more than 30 museum visitors. The
audience could ask questions to scientists on board of the vessel.
Technical Support and HSE Activities
Expedition 324 technical staff boarded the vessel on September 4 at 1600 hrs.
Crossover and training with the off going crew began the next day, September 5,
and continued through the remainder of port call. Surface freight and
airfreight were loaded. Off going freight was sent to College Station. Cores
were off loaded on September 7 and trucked to the repository in Kochi, Japan.
On September 6 an introduction meeting was held with the science crew. All trash was collected and offloaded before departure. Equipment and laboratory spaces were secured for sea.
transit to the first site the technical crew have been preparing the shipboard
laboratories for the commencement of coring. The scientific staff was
introduced to the labs and technical staff. The magnetometer on loan from WHOI
was mounted and the magnetometer deployed successfully on September 10.
Underway watches were started at this time.
A boat and fire drill was held for all hands on September 10.