Yuji Sano has made fundamental contributions to isotope geochemistry, volcanology, and earthquake monitoring. His study of the distribution of helium isotopes in Japan constitutes an extraordinary advance in our understanding of the structure of volcanic arcs. Yuji clearly established the relationships between magmatism, fore-arc and back-arc basins, and the volcanic front. With detailed studies of individual volcanoes, he demonstrated the focusing of magmatic gases under volcanic edifices and the dilution of magmatic gases by crustal volatiles at increasing distances. His monitoring of the composition of volcanic gases over decadal periods laid the foundations for the geochemical monitoring of volcanic activity. In particular, his long-term study of the isotopic variations of gases at Ontake volcano opened the way to predict with helium isotopes the eruptive activity of a volcano. Yuji also developed the basics of seismic prediction by geochemical methods. With his group, they detected radon anomalies before the Kobe earthquake in 1995, and more recently they identified fluid circulation paths in relation to the large Tōhoku-Oki earthquake in 2011.

Combining noble gas isotopes with those of carbon and nitrogen in natural emanations, Yuji provided for the first time a means to identify and quantify the different sources (mantle, crust, atmosphere/hydrosphere, slab, sediments, etc.) contributing volatile elements to volcanism. By establishing with rigor geochemical relationships between major volatiles and noble gases, he quantified the cycle of carbon and nitrogen at arcs. Such estimates are crucial for understanding the exchanges of volatile elements between the mantle and the surface of our planet. These milestone works are now used worldwide by all geochemists working on active volcanism.

Besides his noble gas and stable isotope seminal works, Yuji Sano developed novel lines of research in the fields of cosmochemistry on the one hand, and of biogeochemistry on the other hand. He established the first ion probe laboratory in Japan at Hiroshima University, and later installed a NanoSIMS instrument at the Atmosphere and Ocean Research Institute of the University of Tokyo. He developed the U-Pb dating method of apatite, which has found a large number of applications such as dating fossil teeth, apatite that hosted the first evidence of life, and lunar/Martian rocks. I think Yuji Sano’s career is very much in the spirit of Norman L. Bowen: He always sought to identify important problems, and gave himself the means to take extremely difficult measures to solve them.

—Bernard Marty, Université de Lorraine, Nancy, France

It is a great honor for me to receive the Norman L. Bowen Award and Lecture from AGU. I also consider this a joint award, not only for me but also for all those who have worked with me over a long period of time. I am sincerely very happy. My research began with helium isotope ratios, which I studied in my doctoral program in geophysics at the Faculty of Science, University of Tokyo. In the early 1980s, helium isotope measurements of terrestrial materials were performed at two oceanographic institutes in the United States, a university in Canada, and a laboratory in the former Soviet Union. Under Prof. Minoru Ozima and Hiroshi Wakita, my research focused on the measurement of helium isotope ratios in volcanic gases and groundwater. I constructed a metallic ultrahigh-vacuum line to extract and purify helium from samples and tuned a noble gas mass spectrometer. The nominator, Prof. Bernard Mary, was a postdoctoral fellow at the time. Since then, we have been collaborators for 40 years. After receiving the Ph.D. degree, I conducted numerous studies on earthquakes and volcanoes using helium isotope ratios. Later, with the support of the Japan Society for the Promotion of Science, I stayed at the Open University in the United Kingdom in 1989–1990, where I was taught a highly sensitive carbon and nitrogen isotope measurement method by Prof. Colin Pillinger. By combining this light-element isotope analysis technique with noble gas measurements, I was able to study the deep circulation of carbon and nitrogen from the surface into the mantle. In 1991, I moved to Hiroshima University, where I installed a large ion probe (SHRIMP) and developed U-Pb dating methods for apatite. This method was applied into dating of early life and lunar meteorites. In 2001, I moved to the Atmosphere and Ocean Research Institute, University of Tokyo, where I studied the deep-ocean circulation by analyzing noble gases and introduced a high-resolution ion probe (NanoSIMS) to study marine paleoenvironment reconstruction and Martian meteorites. In retrospect, my research was conducted by installing state-of-the-art analytical equipment at the time and maximizing its performance to achieve the best results. In order to install expensive equipment, support from the heads of institutions and funding agencies is essential. I am very fortunate and grateful in this regard. Finally, I would like to thank my family and former students for supporting me over the long term. —Yuji Sano, Kochi University, Kochi, Japan

For his study on volatile isotopes of volcanic and environmental systems, and invention and application of ion microprobe U-Pb dating of apatite.