福岡県竜円鉱山産閃ウラン鉱の産状の絶対年令

抄録

There are three pegmatites in Ryuen mine, Fukuoka Prefecture, which intruded in Masaki granite of the middle Cretaceous. The U-Pb age of uraninite from a pegmatite has been chemically determined as 100×10⁶ years by Kimura and Iimori (1937). Uraninite was collected from the other pegmatite, of which mode of occurrence was different from the above mentioned uraninite. It occurred in chlorite vein cut the pegmatite. In order to know whether or not any measurable time interval existed between the pegmatite solodification and the vein formation, isotopic U-Pb age was determined on the uraninite from the chlorite vein. The age of uraninite is 110×10⁶ years and the formation of chlorite vein continued immediately after the solidification of pegmatite.