Monazite U–Pb dating and ⁴⁰Ar–³⁹Ar thermochronology of metamorphic events in the Central African Copperbelt during the Pan-African Lufilian Orogeny

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• 作者：C. Rainaud ; S. Master ; R.A. Armstrong ; D. Phillips ; L.J. Robb
• 关键词：Copperbelt ; Pan-African ; Geochronology ; Orogen
• 刊名：Journal of African Earth Sciences
• 出版年：2005
• 出版时间：July-September 2005
• 年：2005
• 卷：42
• 期：1-5
• 页码：183-199
• 全文大小：716 K

文摘

New SHRIMP U–Pb age data on metamorphic monazite, as well as step-heating ⁴⁰Ar–³⁹Ar ages on metamorphic biotite, muscovite and microcline, from Katangan metasedimentary rocks of the Central African Copperbelt are presented. These rocks were deformed and metamorphosed during the Pan-African Lufilian Orogeny. Three samples of metamorphic monazite from the Chambishi structural basin give ages of 592 ± 22 Ma, 531 ± 12 Ma and 512 ± 17 Ma, which correspond respectively to the ages of eclogite facies metamorphism, high-pressure talc-kyanite whiteschist metamorphism, and of a regional metamorphism/mineralisation pulse elsewhere within the Lufilian Orogen. A biotite population from Luanshya gives a ⁴⁰Ar/³⁹Ar plateau age of 586.1 ± 1.7 Ma, coinciding with the oldest monazite age. Several samples from the Chambishi basin and the Konkola area give ⁴⁰Ar/³⁹Ar biotite plateau ages in the range of 496.6 ± 0.6–485.2 ± 0.9 Ma, and a muscovite plateau age of 483.6 ± 1.1 Ma, which are a manifestation of regional uplift and cooling that affected the whole Katangan basin. The youngest apparent ⁴⁰Ar/³⁹Ar ages obtained are from microcline at Musoshi and range from 467.0 ± 2.7 Ma to 405.8 ± 3.8 Ma, reflecting continued slow cooling of the Lufilian Orogen.