Zircon U-Pb Zircon U-Pb (& Lu-Hf) (& Lu-Hf) isotope isotope geochronology of the geochronology of the Hidaka Metamorphic Belt, Hidaka Metamorphic Belt, Hokkaido, NE Japan Hokkaido, NE Japan Tony KEMP, Toshiaki SHIMURA Tony KEMP, Toshiaki SHIMURA Department of Geology, Niigata University Department of Geology, Niigata University
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Zircon U-Pb (& Lu-Hf) isotope geochronology of the Hidaka Metamorphic Belt, Hokkaido, NE Japan Tony KEMP, Toshiaki SHIMURA Department of Geology, Niigata.
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Zircon U-Pb Zircon U-Pb (& Lu-Hf) (& Lu-Hf) isotope geochronology of isotope geochronology of
the the Hidaka Metamorphic Belt, Hidaka Metamorphic Belt,
Hokkaido, NE JapanHokkaido, NE Japan
Tony KEMP, Toshiaki Tony KEMP, Toshiaki
SHIMURASHIMURADepartment of Geology, Niigata Department of Geology, Niigata
UniversityUniversity
• Tomokazu Hokada, Daniel DunkleyNational Institute for Polar Research, Tokyo, Japan
• Richard HintonEdinburgh Ion Microprobe Facility, Edinburgh University, UK
• Chris HawkesworthDepartment of Earth Sciences, University of Bristol, UK
CollaboratorsCollaborators
Micro-chronology of Micro-chronology of zirconzircon
U-Pb isotopesU-Pb isotopes
Crystallisation Crystallisation ageage
Lu-Hf isotopesLu-Hf isotopes
Source ageSource age
Ion Ion microprobemicroprobe
LaserLaserAblationAblation
42°N
143°E
43°N
143°E
0 10 20 30
km
Hokkaido
Cape Erimo
Hidaka Metamorphic Belt
Poroshiri Ophiolite
upper metamorphic rocks
lower metamorphic rocks
upper granitoid
middle tonalite
lower tonalite
basal tonalite
gabbro & diorite
peridotite
Geological Map of the Hidaka Metamorphic Belt
Hidaka Metamorphic Hidaka Metamorphic BeltBelt
‘an exposed crustal slab derived from an immature island arc’(Komatsu et al. 1986; Osanai et al. 1991)
Hidaka Metamorphic Hidaka Metamorphic BeltBelt
Idealised succession of the
metamorphic and igneous
rocks in the ‘Hidaka Crust’
(modified from Komatsu et al. 1986)
1. What is the temporal framework?
2. Magmatic
differentiation
mechanisms? Crustal evolutionary
processes in arcs
Most K-Ar and Rb-Sr mineral ages cluster around 40-28 Ma and 20-15 Ma
• Owada et al 1991 : peak metamorphism and anatexis at 56 ± 6.1 Ma (WR Rb-Sr isochron)
• Usuki et al 2002 : granulite facies metamorphism at 23-18 Ma (SHRIMP U-Pb on thin zircon rims)
• Maeda et al. 1990: Gabbro-diorite-granite K-Ar WR ages of 19.6-17 Ma. Cooling/exhumation ages (??)