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Rb-Sr and Sm-Nd Mineral Isochron Ages of the Metamorphic Rocks in the Namaqualand Metamorphic Complex, South Africa |
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| Authors: | M Yuhara T Miyazaki J Ishioka S Suzuki H Kagami N Tsuchiya |
| Institution: | aDepartment of Earth System Science, Faculty of Science, Fukuoka University, Nanakuma 8-19-1, Jonan, Fukuoka 814-0180, Japan bInstitute for Geothermal Sciences, Kyoto University, Noguchihara, Beppu 874-0903, Japan cGraduate School of Science and Technology, Niigata University, Ikarashi 2-8050, Niigata 950-2181, Japan dDepartment of Geoscience and Technology, Graduate School of Engineering, Tohoku University, Aramaki, Aoba, Sendai 980-8579, Japan |
| Abstract: | Rb-Sr and Sm-Nd isotopic studies were carried out for metamorphic rocks in the Namaqualand Metamorphic Complex, South Africa. The metamorphic rocks give the Rb-Sr mineral isochron ages (whole-rock - biotite - felsic fractions) of 844±85 Ma and 811.6±6.6 Ma for the lower granulite zone and of 776.5±5.4 Ma for the upper granulite zone. The rocks yield the Sm-Nd mineral isochron ages of 1071±18 Ma (whole-rock - garnet - felsic fractions) and 1067±158 Ma (whole-rock - hornblende - biotite rich fraction - felsic fractions) for the lower granulite zone and of 1052.0±3.6 Ma and 1002.5±1.4 Ma (whole-rock - garnet - felsic fractions) for the upper granulite zone. These age data suggest that the granulite facies metamorphism took place at 1060-1000 Ma, and that the rocks cooled down at 850-780 Ma. The Sr and Nd isotopic compositions of metamorphic rocks are different between the lower and upper granulite zones. |
| Keywords: | Rb-Sr whole-rock - mineral isochron age Sm-Nd whole-rock - mineral isochron age Namaqualand South Africa granulite |
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