Home Page of Geochemistry Department, Geological Survey of Japan (GSJ).
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GEOCHEMISTRY
The Geochemistry Department undertakes geochemical studies in relation to many geological research projects.
Topics & Keyword
Geochemical Atlas (1:200,000) North Kanto area
Geochemistry of the Earth's Crust
The Geochemistry Department does basic geochemical research on the behavior and distribution of major and trace elements and isotopes in rocks and minerals including extraterrestrial material, and organic and gaseous components in sedimentary rocks and groundwater. The studies of radiometric dating and geochemical reference samples conducted in this department are indispensable for many geological researches. Useful data for environmental and exploration work are provided through the applied geochemical research on the abundance and behavior of elements, isotopes and organic compounds in soils, rocks and minerals.
Analytical Methods
GSJ develops analytical methods of determining the chemical and isotopic composition of rocks, minerals and other natural materials. They include Atomic Absorption Spectrometry (AAS), X-ray Fluorescence Spectrometry (XRF), Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), ICP-Mass Spectrometry (ICP-MS), Instrumental Neutron Activation Analysis (INAA), Thermal Ionization Mass Spectrometry (TIMS) and Secondary Ion Mass Spectrometry (SIMS). SIMS project involves many researchers of GSJ, mainly from Mineral Resources Department and Geochemistry Department.
Secondary Ion Mass Spectrometry (SIMS)
K-Ar and 40Ar/39Ar dating
K-Ar and 40Ar/39Ar geochronology is useful to determine age relationship between various geologic events. In GSJ, we are conducting K-Ar and 40Ar/39Ar dating using three mass-spectrometers, each of which is operated with a different analytical procedure; 1) conventional isotopic dilution method for the general K-Ar dating, 2) unspiked sensitivity method particularly for young volcanic rocks, and 3) laser-fusion technique for a single grain 40Ar/39Ar dating. With these methods, we can accurately and precisely date various kinds of igneous and metamorphic rocks older than a few tens of thousand years old. Current research activity in the GSJ K-Ar laboratory is forcused on solving temporal and spatial variations of Quaternary-Tertiary volcanism in Japanese Islands.
laser-fusion technique for a single grain 40Ar/39Ar dating
Standard Material
The GSJ prepares many geochemical reference samples for major and trace elements, isotopic compositions, and radiometric dating. JG-1a (granodiorite) and JB-1a (basalt) are the examples of these standards that are internationally used in many studies.
Geochemical reference samples
Organization
Geochemical department is divided into two sections with 18 researchers.
- Director : Dr. Shigeko TOGASHI
- Geochemistry Section : Chief Dr. Noboru IMAI and 8 researchers
- Isotope Geoscience Section : Chief Dr. Kozo UTO and 7 researchers
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Last Modify 00.8.2
