Recent topics on the rare-earth element (REE) geochemistry of zircon are reviewed in this article.
With SIMS (secondary ion mass spectrometry), we can obtain the REE composition for a spot area (<40μm) of zircon. These SIMS studies have revealed that the LREE are much more depleted in zircon crystals than was previously believed as indicated by conventional bulk zircon analysis. SIMS studies also indicate that the REE patterns of terrestrial zircon generally have Ce anomaly. The implications of the Ce anomaly for the evolution of the atomosphere are discussed.
Because zircon crystals are resistent to decomposition with HF in an open beaker, open beaker decomposition yields erroneous results in some cases. We discuss several examples in the case of analyses of sediments.
The resistence of zircons to erosion and weathering, and its high concentration of Hf constrain sediment recycling into the mantle and the evolution of continental crust. We discuss such issues in this paper, based chiefly on Lu-Hf isotope systematics.
We conclude in our “Reviews in Zirconolgy” that SIMS is the ultimate tool for U-Pb dating and the prerequisite equipment for the study of element partitioning. Therefore, we must utilize SIMS more extensively in geochemical studies in Japan in order that our ideas will not to be outdated. And furthermore, we should create new ideas.

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Kurofuji Volcano occupies the northwestern margin of the Kofu Basin and the older Cenozoicvolcanic rocks are distributed in the eastern part. The oldest Taragatoge Volcanic Rock consisting of subaqueous andesite effused at 7.9 Ma in the central part of the area. During 6.1-4.3 Ma, the Higashiyamanashi Volcano-Plutonic Complex was formed by eruption of rhyolite-dacite welded tuffs and minor andesite lava followed by intrusion of granodiorite in the eastern part. The Mizugamori Volcanic Rock of andesite composition occupied the central part derived from many vents, while the magnetic polarity changed from Gauss Normal Epoch to Matuyama Reversed Epoch in 2.4-1.7 Ma.
Kurofuji Volcano began its dacitic activity at 1.0 Ma forming the main shield of five pyroclas-tic-flow sheets and lava domes built up at the top at 0.5 Ma. The youngest andesite cone, the Kayagatake stratified cone, formed at the west flank of the main shield at 0.2 Ma.
These volcanic activities suggest that the volcanic front around this area moved about 20km from the east in 8-2 Ma to the west in 1.0-0.2 Ma, farther away from the Japan Trench.

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Chemical Th-U-total Pb isochron (CHIME) ages were determined on monazite, xenotime and zircon from coarse-grained leucogranite, quartzose pegmatite and residual arkose (weathered granite) of the Okuhinotsuchi granitic mass (Okuhinotsuchi Mass) in the South Kitakami terrane, Northeast Japan. Leucogranite, characterized by higher K₂O/Na₂O and lower CaO/(Na₂O+K₂O) ratios, yields latest Permian ages of 250-260 Ma for monazite and/or zircon. Some of the granite contains xenocrysts of Th-rich monazite or zircon that yields late Silurian to early Devonian ages of 400-410 Ma. Quartzose pegmatite or quartz vein, cutting in places leucogranite and rarely sediments of the Lower-Middle Silurian Okuhinotsuchi Formation, yields unequivocal CHIME ages of 240-250 Ma for Th-poor monazite, zircon and/or xenotime. Residual arkose that occurs immediately below the unconformity, is more disintegrated, altered and depleted in K₂O than leucogranite. The arkose contains Th- and U-bearing minerals with different CHIME ages: (1) both Th-rich (420 Ma) and Th-poor (260 Ma) monazites, (2) zoned xenotime grains with 410-420 Ma core mantled by 350 or 250 Ma rim, (3) euhedral ca. 250 Ma zircon, or (4) rounded inherited zircon grains of ca. 500-1000 Ma. All the CHIME age data demonstrate that the Okuhinotsuchi Mass is unlikely to be the pre-Silurian basement.
The CHIME geochronology also reveals that the leucogranite of the Okuhinotsuchi Mass is a remnant of the source rock for some Permian granitoid clasts in the Usuginu Conglomerate in the South Kitakami terrane, whose provenance has long been an open problem.

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