Abstract
We present results of U-Pb isotopic and trace-element geochemical studies of detrital zircons collected in the area of Quaternary and the modern volcanic activity at the East-Volcanic Zone of the Kamchatka peninsula, Russia: Karymsky, Maly Semiachik, Central Semiachik, Uzon, Kihpinych and Krasheninnikov volcanoes located within the area of the Kronotsky National park. Pre-Quaternary volcanic or sedimentary rocks are not known in the area of sampling and there are no pre-Cretaceous rocks exposed in the Kamchatka peninsula.
The main goal of the study is to test a hypothesis of older basement rocks existence under the volcanoes in the melting area and to assess age of these source rocks. Recovered detrital zircons were studied by LA-ICP-MS technique using Element-XR ICP-MS and UP-213 laser ablation system.
Many of zircons were too young (much less than 1 Ma) to get quantitatively measurable U-Pb ages using LA-ICP-MS method, however a number of robust older age clusters were discovered. The most intriguing result is that more than a hundred zircon grains from three samples collected near the Karymskoe Lake produced a good discordia with ages 1940±50 Ma and 2980±20 Ma. Other less populated clusters are close to 330 Ma, 78 Ma and 2.4 Ma.
There is a correlation found between age and trace element composition of the studied zircons: older zircons have higher Th/U ratios and more pronounced Eu anomaly than younger populations.
Obtained results reveal existence of the Achaean basement (ca 2980 Ma) under the East-Volcanic Zone of the Kamchatka peninsula as well as younger, particularly Cretaceous rocks that are known only within the Central Kamchatka Range.
The main goal of the study is to test a hypothesis of older basement rocks existence under the volcanoes in the melting area and to assess age of these source rocks. Recovered detrital zircons were studied by LA-ICP-MS technique using Element-XR ICP-MS and UP-213 laser ablation system.
Many of zircons were too young (much less than 1 Ma) to get quantitatively measurable U-Pb ages using LA-ICP-MS method, however a number of robust older age clusters were discovered. The most intriguing result is that more than a hundred zircon grains from three samples collected near the Karymskoe Lake produced a good discordia with ages 1940±50 Ma and 2980±20 Ma. Other less populated clusters are close to 330 Ma, 78 Ma and 2.4 Ma.
There is a correlation found between age and trace element composition of the studied zircons: older zircons have higher Th/U ratios and more pronounced Eu anomaly than younger populations.
Obtained results reveal existence of the Achaean basement (ca 2980 Ma) under the East-Volcanic Zone of the Kamchatka peninsula as well as younger, particularly Cretaceous rocks that are known only within the Central Kamchatka Range.
Original language | English |
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Pages (from-to) | A534-A534 |
Number of pages | 1 |
Journal | Geochimica et Cosmochimica Acta |
Volume | 74 |
Issue number | 12 |
Publication status | Published - Jun 2010 |
Event | Goldschmidt Conference (20th : 2010) - Knoxville, United States Duration: 13 Jun 2010 → 18 Jun 2010 |