Timing of Carbonatite Ultramafic Complexes of the Eastern Sayan Alkaline Province, Siberia: U–Pb (ID–TIMS) Geochronology of Ca–Fe Garnets

Abstract

In this study, we present the results of U–Pb (ID-TIMS) geochronological studies of calcic garnet from the alkaline ultramafic complexes of Eastern Sayan province (eastern Siberia). New U–Pb ID–TIMS garnet ages obtained from different rocks of Bolshaya Tagna (632 ± 2 Ma) and Srednaya Zima intrusions (624 ± 5 Ma), as well as previously published garnet ages of the Belaya Zima complex (646 ± 6 Ma), allow us to constrain the timing and duration of episodes of alkaline ultramafic magmatism in Eastern Sayan province (619–651 Ma). Variations in the chemical compositions of rocks from three massifs indicate that the parental melts were separated from different magmatic chambers generated during the same episode of mantle melting. This study further highlights garnet U–Pb dating as a potentially robust, high-resolution geochronometer to constrain the evolution of the main pulse of alkaline ultramafic magmatism in the large magmatic provinces.

Neoproterozoic Lysan Alkaline–Ultramafic Complex in the Eastern Sayan, Southern Siberia, Russia: Mineralogical Constraints of Carbonate Rocks and Albitite for Petrogenesis

“…In the Neoproterozoic period (670-630 Ma), there was widespread intraplate magmatic activity along the western, southwestern, and southeastern (in modern coordinates) margins of the Siberian craton [29][30][31]. This phenomenon resulted in the formation of several alkaline complexes with carbonatites (Figure 1) [29,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. The Lysan Complex intrusions were also formed during this period [28].…”

“…These are small plutons within the Tatarka Complex [32,33]. The East Sayan alkaline carbonatite massifs are situated within the Early Proterozoic Urik-Iya graben and the Late Archean Zhidoy Block of the Sharyzhalgai basement uplift of the Siberian craton [34][35][36][37][38]. The Urik-Iya graben is located in the southern part of the Siberian craton, between the Sharyzhalgai and Biryusinsk basement uplifts.…”