Report from Chikyu
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"Lost in subduction"2018.12.03

When the opportunity arose to be a part of NanTroSEIZE expedition 358 I didn’t have to think twice about applying. Not only is this a unique opportunity to be a part of an immense scientific collaboration aiming to drill into a subduction zone, but it also has many crossovers with my current research interests.

I’m a postdoctoral researcher in rock mechanics at the University of Liverpool, UK, where I work in a laboratory performing friction experiments on a range of geological materials. These type of experiments involve sliding different rocks and minerals past each other under high pressures. We do this to simulate the type of sliding that might occur on a fault in nature kilometres below the surface. Laboratory tests have shown that we still have much to learn about how earthquakes occur as different rocks and minerals respond differently to frictional sliding. Some minerals slide past each other in a “smooth” stable manner whereas others slide in an unstable stick-slip fashion, analogous to what happens during an actual earthquake. The NanTroSEIZE project provides an invaluable opportunity to sample material directly from an active subduction megathrust at depth in the Earth. The materials that we recover can then be tested in the laboratory to determine their frictional response and will therefore help us understand more about the conditions that might lead to an earthquake on these type of fault.

The NanTroSEIZE project is a truly unique project that involves scientists from around the globe. It has been ongoing since 2003 (I was only 12 years old when it started!) and will culminate during Exp. 358 when we will hopefully drill through the main fault zone at the base of the accretionary wedge. As an on-board scientist I work as part of the Physical Properties team. We analyse the materials that are recovered during drilling and make a variety of measurements on them such as porosity, P-wave velocity and electrical resistivity. We do this as it tells us how the rocks are changing with depth and provides useful information about the structure of the accretionary wedge. This information along with that gathered by the structural geology, sedimentology and logging teams will be the first to provide over 5km of continuous data in a tectonic setting where such a complete dataset has never been acquired before.

Life on board so far has been really interesting and enjoyable. It has been inspiring to work with and learn from a variety of people with different backgrounds and specialties. It is also great to be part of team all working on the same common goal, something that we don’t normally get to experience in the academic world where much of our research can be independent or as part of a much smaller group.

As for the rest of the expedition, I hope we are able to drill through the accretionary wedge, I hope we manage to recover material from the main fault and I hope the research that is being carried out can inform and inspire future generations of scientists.

Working in the on-board lab measuring porosity of the recovered cuttings.

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"The Adventures of Pauline: When a French girl goes to sea…"2018.11.27

I am currently doing my PhD at the University College London (UK) in sedimentology and hydrodynamics. It is my third and last year of my PhD and before starting in a new direction such as a postdoc or a job in the oil industry, I wanted to try something different to give me another aspect and view of research in geology and more particularly in sedimentology. My PhD supervisor has been a part of several IODP expeditions (IODP Exp 131, 338, 362, etc …). When he told me about the IODP project, I immediately though that it was the perfect opportunity to discover something new in my domain of research. Participation in an IODP Expedition is a career-enhancing opportunity and experience.
The opportunity to work on a wide range of sedimentary materials with other shipboard scientists, both experienced and early-career, will improve my skill set and open up new collaborations and research opportunities. Therefore, when I saw that the NanTroSEIZE project was looking for a sedimentologist, I didn’t hesitate a second to apply. A few months later I got a positive response.

So far, it’s been a week that I am on board Chikyu and I am affiliated with the sedimentology team with two Japanese sedimentologists. The main goal of IODP expedition 358 is to deepen the Hole C0002Q and drill and sample the Nankai accretionary prism, to access the subducting plate and reach the plate interface fault system, located around 5,200 meters below sea floor. My job on board consists of describing and analysing the rock fragments produced during the drilling called cuttings and observing their variation with depth.
Cuttings are washed and sieved in order to take off the drilling mud and separate the rock fragments in different grain sizes. Cuttings are studied at different scales, from a macroscopic scale to consider the different lithologies and their proportion to a microscopic scale, using smear slides to identify the mineral composition.

It’s been three years that I have been focusing on my PhD topic (which is by the way, very exciting!) My PhD consists of improving our understanding of the hydrodynamics of bedform formation, such as dunes or antidunes, in deep-marine environments. Within these 3 years, I didn’t get the opportunity to work with geologists other than sedimentologists. On Chikyu, scientists have their own specialities such as structural geology, physical properties, mud gas analysis or logging analysis. Scientists from different horizons are working together on the same project. Therefore, it gives me a very good opportunity to learn a lot about disciplines other than sedimentology and to open my mind to new “geological ideas”. I am also improving my skills considerably in sedimentology by using new analytical techniques such as X-ray measurements. Here on Chikyu, we have access to a very impressive laboratory in terms of quality equipment. I had the occasion to work on different machines and methods that I had never used before.

A part of the science aspect, life on board is great. Facilities on board are excellent. We have access to a common room with plenty of games, a gym (even if we don’t need it, because climbing up and down the many stairs is my daily gym) and a sauna. The food is amazing with plenty of choices. One of the best moments of the day is to observe the wonderful sunset from the helideck!

A bientôt!

Amazing sunset from the helideck.

Microscope observation of some cuttings using smear slide.

Pauline Cornard (11.27,2018)

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"Activity for the last week (Oct. 23-28)"2018.10.31

We are still preparing for the 'side-tracking' toward deepening a hole. Riser pipe is already connected between Chikyu and BOP on top of the hole. During the weekend, the drill string went down inside the hole beyond the riser pipe. The bit is cleaning up the cased hole.

As such, we have only 2 scientists onboard Chikyu now; Kyu Kanagawa and Masa Kinoshita. They take a role as 'Science Leaders' with the help of Expedition Project Manager (EPM) Lena Maeda. The main role of us is to 'be here' just in case where any major trouble happens which could impact our scientific goals. Meanwhile, we are preparing for the coming shipboard scientists (checking sample and data request; drafting the Methods chapter for our cruise report). Marine techs are already onboard and simulating how they process the cuttings (small pieces of rock cut by the drill-bit) for scientific use.

Probably the best news of the week is that we had an update on the Kuroshio prediction; it will continue meandering until the end of our expedition (next March). This is really great because here we have a weak current (less than 1 knot) which is very 'gentle' for the riser pipe. In other words, we can save lots of time for drilling and have much more chance for success.

This week we start side tracking at 2874 meters below seafloor and deepening a hole. In 2014 this hole reached down to 3058 meters below seafloor, and found the lithology there (~10 Ma old accretionary prism formation) is tough to drill. A lot of improvements have been achieved since then by the operation team (CDEX), and we are sure we can obtain new data and samples soon.

(drafted by Masa Kinoshita onboard Chikyu)

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