Archean detrital zircon's age at the active East-volcanic zone of Kamchatka

• Published in: Geochimica et Cosmochimica Acta
• Main Authors: Kostitsyn, Yuri, Belousova, Elena
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2010
• Subjects: Kamchatka Peninsula; Kamchatka
• Online Access: https://researchers.mq.edu.au/en/publications/9b668d20-5e8b-439a-bb9f-d2e0fd6d6698; https://doi.org/10.1016/j.gca.2010.04.036

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.