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Research Group Division of Earth and Planetary Materials Science

 

Volcanology and Geofluids Research Group

http://epms.es.tohoku.ac.jp/arcmag/top_e.html
•Professor Michihiko Nakamura,
specializing in Magma and earth’s crust fluid science, and Rock texture formation theory
•Asst. Professor Satoshi Okumura, specializing in Magma, Volcanic eruptions, and Water

 

This group conducts research on geochemistry, petrology, and volcanology. Its ongoing research involves correlative studies of granitic rocks in continental and island-arc crusts, spatial and temporal variations in the composition of island-arc igneous rocks, and petrological and geochemical studies of quarternary island arc volcanic rocks.
 
 
Arc Magmatism Research Group Tohoku University is located right on a typical island arc called the Honshu arc and above a nearby trench. The magma activity that is taking place there is a notable geological phenomenon associated with plate sinking. It is an important subject that demands our hard work. In fact, we feel we must research the issue because we all live there with our families and colleagues. Our laboratory is geared to understanding, comprehensively, the activities of the magma and the super critical fluids of this active sinking zone, which is typical of the Honshu arc. This geological type of fluid carries heat and the chemical elements efficiently, and strongly influences the physical properties of the associated rocks. To understand how such fluids move inside the earth in addition to its mechanism interacted with rocks in terms of chemical reactions is also our laboratory’s theme to work on. Some examples of the themes we are researching include the following: the immense structure extending from the earth’s crust level to the mantle level and its formation history over a scale of 10 million years back to 1 million years; its association with mineral floor formation; the structure of surface layers and of the deep inside the earth in terms of magma chamber, rock wall, and caldera; the mechanism and types of volcano eruptions; material movement phenomena such as those involving chemical elements spreading and infiltrating and the original process of re-crystallization of rocks with its application for geochemistry and rheology; and fluid behavior at places where an earthquake occurs. In pursuit of our study of these research themes, we are proceeding with various methods and techniques to be used, including a field investigation and a chemical analysis of rocks and rock-forming minerals (regarding main and trace chemical elements, and radio-isotopes and stable isotopes), high-temperature and high-pressure experiments, and numerical simulations. The education given at the graduate school emphasizes that students acquire basic materials science systematically. Moreover, it is aimed to have them acquire the capability of performing leading edge research work.

 

Arc Magmatism Research Group The laboratory of this group captures associated earth science phenomena from a multilateral perspective: from micro-scale to a macro-scale. For example, observing the exposed plutonic rocks and the dissected vent in which the magma passes, or chemically analysis of the eruptions of an active volcano would provide us many ideas of how to conduct a high-temperature and high-pressure experiment. Conversely, any hypothesis that might be obtained from an experiment or a simulation must be demonstrated by comparing it with the real chemical organization of the associated natural rock. Thereby, the use of numerous methods including examination form the perspectives of geology, earth science, experimental petrology, and numerical analysis, and acquiring the sense of recognizing characteristics as well as strong and weak points of each method are all extremely advantageous for us to understand phenomena that are occurring deep underground right now, in addition to those that happened so far in the past that we have no history of them. All are expected to help us produce additional future predictions, which we are expected to do.

 

Arc Magmatism Research Group Regarding the real situation creation environment, using externally heated gaseous pressure equipment, and high-temperature and high-pressure deformation “on the spot” observation equipment in addition to piston cylinders. Using that apparatus, we are conducting experiments using methods were created with respect to the precise phase equilibrium, the organizational equilibrium, the magma deformation fluidity, and open system type degassing, all of which are performed within the temperatures and the pressures available from the ground surface down to the uppermost position of the mantle. An evaluation of every specimen is made in collaboration with domestic and international research workers using such a technique as permeability measurements, analysis of chemical compounds, and isotopic compounds for all rocks and for small parts of them, in addition to tissue analysis of them using X-ray tomography, for example. Lately, we are also concentrating on research work, for example, related to the gassing and degassing mechanism of the magma at the time when an eruption occurs––particularly the origin of water that drives a volcanic eruption––assisted by the system implemented to analyze the isotope compound by extracting and refining the hydrogen gas that is emitted out of the rocks, minerals, and the experimentally resulted products.