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Lead-alpha age determinations have been made on the accessory zircons and monazites of granitic rocks from the Fukuoka area, North Kyushu, and the eastern Aichi district and the Takato area, Central J...apan. Six results for granitic rocks from the Fukuoka area range from 80 to 115 m. y. with all average of 97 m. y. Of these results, zircon and monazite from a single granite have the same age of 90 m. y. This good agreement between different minerals from the same rock indicates the reliability of the lead-alpha method. Four zircon ages and two monazite ages from the eastern Aichi district range from 70 to 105 m. y. with an average of 90 m. y. and nine zircon ages from the Takato area from 80 to 165 m. y. with an average of 106 m. y.; of these ages, 165 m. y. that is for the Takato quartz diorite engages the attention of the writers, because it is older than other granitic rocks in the same area. Since our results of age determinations are, though with a few exceptions, consistent with geological evidences and other isotopic ages, the granitic rocks from North Kyushu and the Ryoke belt in Central Japan are believed to be of Cretaceous age.続きを見る
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1.Introduction and Acknowledgements 2.The Lead-Arpha Method 3.Preparation and Processing of Samples 4.Field Relation of the Source Rocks 5.Discussion of Age Determinations 6.References Cited
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Mendeley出力
16_03_p249