The U–Pb zircon and baddeleyite ages of the Neoproterozoic Volyn Large Igneous Province: implication for the age of the magmatism and the nature of a crustal contaminant

Abstract

The Volyn continental flood basalt province is situated on the western margin of the East European platform and constitutes a significant portion of the passive continental margin sequence formed along the Trans-European Suture Zone in response to Rodinia break-up in the Neoproterozoic. In Ukraine, the volcanogenic sequence is subdivided into suites called Zabolottya, Babyne and Ratne, which together with the lowermost terrigeneous Gorbashy suite comprise the Volyn series. Magmatic zircons from one high-Ti basalt sample yielded an age of 573 ± 14 Ma, whereas grains isolated from a rhyolitic dacite yielded an age of 571 ± 13 Ma. Baddeleyite from the olivine dolerite sample gave an older ²⁰⁶Pb/²³⁸U age of 626 ± 17 Ma, whereas the ²⁰⁷Pb/²⁰⁶Pb weighted average age of 567 ± 61 Ma is close to the zircon ages. Zircons separated from the other basaltic samples are much older and crystallized at c. 1290, 1470, 1820-1860, 1930-2050 and 2660 Ma. Ages in the 1820-1860 and 1930-2050 Ma time spans correspond to the ages of the Precambrian basement that underlies the Volyn province. However, the sources for the 1290, 1470 and 2660 Ma zircons are unknown, and these zircons must have been derived from more distal areas.

Keywords:

• Volyn
• basalts
• Vendian
• zircon
• baddeleyite
• geochronology

Acknowledgments – The first author acknowledges financial support from the Swedish Institute (Svenska Institutet). We are grateful to S.M. Tsymbal, K.I. Derevska and geologists of the Rivne geological enterprise for providing samples. Martin Whitehouse, Lev Ilyinski and Kerstin Lindén are thanked for their assistance at the NORDSIM facility. The NORDSIM facility is operated under an agreement between the research funding agencies of Denmark, Norway, Iceland and Sweden, and the Geological Survey of Finland and the Swedish Museum of Natural History. This article is NORDSIM contribution number 426. This is publication number 46 of the large igneous provinces – supercontinent reconstruction – resource exploration project (www.supercontinent.org; www.camiro.org/exploration/ongoing-projects). The manuscript benefitted greatly from careful reviews by two anonymous reviewers and Associate Editor Dr. Martin Klausen.