Strontium isotopic ratio in brines from the north-east of the Angara-Lenskiy artesian basin

¹ Institute of the Earth’s Crust, Russian Academy of Sciences, Siberian Branch, 664033 Irkutsk, Russia
² Irkutsk State University, 664003 Irkutsk, Russia
³ Isotope Tracer Technologies Inc, Waterloo, Ontario, N2V 1Z5, Canada
⁴ Department of Earth and Environmental Science, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
⁵ School of Engineering, University of Guelph, Guelph, ON, N1G 2W2, Canada

^* Corresponding author: lalex@crust.irk.ru

Abstract

The Sr isotopic composition was measured in a number of samples of highly concentrated oil-field brines from the Angara-Lenskiy artesian basin. The brines are contained in the salt-bearing and subsalt-bearing hydrogeological formations at a depth of 1,500-3,000 m. They have high salinity (385-530 g/L) and high Sr content (2.3-7.0 mg/L). The ⁸⁷Sr/⁸⁶Sr ratio ranges from 0.70800 to 0.713062. Most brine samples exhibit an isotopic composition similar to Vendian-Cambrian paleoocean water, however several samples from the Yaraktinskiy horizon are significantly more radiogenic than others. It suggests that a considerable amount of ⁸⁷Sr is likely to have been carried from terrigenous sediments due to a water-rock interaction.