Rb-Sr Whole Rock Ages of the Granites of Minami-osumi and Amami-oshima, Southwest Japan
1971; Kyushu University; Volume: 21; Issue: 1 Linguagem: Inglês
10.5109/1544091
ISSN0023-6179
AutoresTakeru Yanagi, Masaru Yamaguchi, Tamotsu Nozawa,
Tópico(s)earthquake and tectonic studies
ResumoThe Minami-osumi granite and the granites from Amami-oshima were analyzed for strontium and rubidium by the iso七〇pe dilution method． The ages calculated from the slopes on the isochron diagram are(64±11)m．y． with an initial strontium 87／86 ratio of O．7071±0．0002 for the Minami-osumi granite and(105±27)m．y． with an initial strontium 87／86 ratio of O．7065±0．0002 for the granites from Amami-oshima． An order of the difFerences『be七ween the whole rock ages and the K-Ar ages on biotite is about 50 m．y． These whole rocks ages represent the oldest limit of the time of differentiation of these granitic magmas． Relatively high initial strontium ratios of these granites along with other Iines of evidence are assumed to suggest the the existence of older rocks in the source region of these granites．
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