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Geochronological study of the Monte Amiata Lavas (Central Italy) |
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| Authors: | G Bigazzi O Giuliani F P Bonadonna C Ghezzo F Rita F Radicati Di Brozolo |
| Institution: | 1. Laboratoro di Geocronologia e Geochimica Isotopica, CNR, Pisa, Italy 2. Laboratorio di Geocronologia e Geochimica Isotopica, CNR, Pisa 3. Laboratorio di Geologia Nucleare, Università di Pisa, Italy 4. Istituto di Mineraogia e Petrografia, Università di Siena, Italy 5. Gentro di Studi Orogeno Alpi Occidentali, CNR, Torino, Italy |
| Abstract: | K/Ar and fission track age measurements were performed on lava samples of Monte Amiata volcano (Central Italy) which is formed by a sequence of lava flows and lava domes ranging in composition from trachybasalts to high-SiO2 quartzlatites. The ages obtained, except for the oldest volcanic products, range from 290,000 to 180,000 years. Excess40Ar was found in some mineral separates, especially biotite, causing apparent rather old ages. The correct ages were calculated by means of K/Ar isochrons, and were found to be very similar to the ages calculated on sanidine separates. The volcanic activity that built up the outcropping Monte Amiata units seems to have lasted a relatively short time. |
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