Hiroaki
Sato
Brief research career
Hiroaki Sato's main interests are in the
application of mineral and rock texture analyses to the understanding of magmatic processes from its birth to tomb. Earlier works
are mostly concerned with geology and epma petrography
of Tertiary high-magnesian andesites(sanukite) in northeast Shikoku, Japan.
Finding of primary phenocrysts in these volcanic
rocks as well as other basaltic rocks on the terrestrial planet through NiO versus Fo
relations of olivine phenocrysts in 1974 was the most
exciting experience in his career. Finding of uphill diffusion of alkali
elements around quartz xenocrysts in the basalt and andesite of northeast Shikoku was another excitement in the 70th. Sato was on board the Glomer Challenger for DSDP Leg 46 in 1976 in the mid Atlantic to
examine MORB samples. He submitted his Doctor Thesis in 1982 on the geology and
petrology of high-magnesian andesite
and related volcanic rocks of northeast Shikoku, Japan.
Since 1985, Sato is concerned with
application of petrological methods to solve volcanological problems, especially eruption and degassing
processes of magmas. He also started melting experiments at 1 atm. on basaltic samples of ODP MORBs
and Izu Oshima 1986 lavas.
He first intended to determine phase equlibrium
relations, but eventually found that partitioning of iron between plagioclase
and melt strongly depends on oxygen fugacity, and could be used as an oxgen fugacity meter. During the survey of the 1986
eruption products of Izu-Oshima volcano, he
recognized that pahoehoe and aa lavas have different groundmass textures. He
conducted 1-atm melting experiments to duplicate the groundmass textures of the
basalts, and tried to understand quantitatively the effects of cooling rate and
initial overheating on the number density of plagioclase microlites.
Sato visited Cameroon volcanoes in 1988 as a staff of the Japan
research team for the Lake Nyos gas disaster, in which he served to perform sounding experiments
to survey water depth profiles of the lakes.
Since 1991, Sato is engaged in the watch
on the Unzen eruption. Because there are a lot of
volcanic domes in the southwest Japan
arc, he was excited to observe the growth processes of lava domes. He thought
that effusively issued lavas like Unzen have experienced
thorough degassing of volatiles before reaching to the surface. But at the first watch on the dome (August 1991) he found self
explosive nature of the dome lavas during collapse and pyroclastic
flow generation. He and some other colleagues at Unzen
were sure that the degassing of the magmas were
incomplete and the magma was overpressurrized, which
caused the self-explosive nature of the issued lavas. Two vulcanian
explosions during the 1991 effusive eruption of Unzen
volcano taught us that transition of explosive/effusive eruption of the dacite may occur just at water contents of 0.5-0.7 wt. %
from the analyses of the eruption products.
In 1995 Sato moved to Kobe University,
just after a big earthquake. He got a fund for installation of a gas-media high
pressure apparatus, and started melting experiments in water-bearing systems.
The first experiments are concerned with the low pressure stability of
amphibole in the Unzen groundmass, because we
observed amphibole microlites in the Unzen 1991 lavas. Although he has troubles in making buffured charges, he obtained some interesting results on
the stability of amphiboles in the dacite. He is also
interested in quntitatively understanding the effects
of volatiles in the element partitioning between plagioclase and melt, and to
duplicate zoning textures of phenocryst minerals in Unzen and other volcanoes.
Selected Publications
1.
Sato, H.(1975) Diffusion
coronas around quartz xenocrysts in andesite and basalt from Tertiary volcanic region in
northeastern Shikoku, Japan. Contrib.
Mineral. Petrol., 50, 49-64.
2.
Sato, H. (1977) Nickel content of basaltic magmas:
identification of primary magmas and a measure of the degree of olivine
fractionation. Lithos, 10, 113-120.
3.
Sato, H. (1982) Geology of Goshikidai
and adjacent areas, northeast Shikoku, Japan: Field occurrence
and petrography of sanukitoid and associated volcanic
rocks. Sci. Rep. Kanazawa Univ., 27, 13-70.
4.
Sato, H. (1989) Mg-Fe partitioning between
plagioclase and liquid in basalts of Hole 504B, ODP
Leg 111: A study of melting at 1 atm. Proc. Ocean
Drilling Program, Sci. Results, 111, 17-26.
5.
Sato, H., Fujii, T., and Nakada, S. (1992) Crumbling of dacite
dome lava and generation of pyroclastic flows at Unzen volcano. Nature, 360, 664-666.
6.
Sato, H. (1995) Textural difference between pahoehoe and aa
lavas of Izu-Oshima volcano, Japan - an experimental
study on the number density of plagioclase. J. Volcanol.
Geotherm. Res., 66, 101-113.
7.
Sato, H., Nakada, S., Fujii, T. Nakamura, M, and
Suzuki-Kamata, K. (1999) Groundmass pargasite in the 1991-1995 dacite of Unzen
volcano: phase stability experiments and volcanological
implications. J. Volcanol. Geotherm. Res., 89,
197-212.
8.
Sato, H.,
Holtz, F., Behrens, H., Botcharnikov, R., Nakada, S. (2005) Experimental petrology of the
1991-1995 Unzen dacite, Japan. Part II: Cl/OH partitioning between hornblende
and melt and its implications for the origin of oscillatory zoning of hornblende
phenocrysts. J. Petrology, 46,
339-354
Publication list
Contact
address: Department of Earth and Planetary Sciences, Faculty of Science, Kobe University, Kobe, 657-8501
phone: 81-78-803-5732, fax: 81-78-803-5757
e-mail: hsato(at)kobe-u.ac.jp
