A new Ectasian event of basitic magmatism in the southern Siberian Craton

• Published in: Doklady Earth Sciences
• Main Authors: Donskaya, T. V., Ernst, Richard E., Hamilton, M. A., Mazukabzov, A. M., Pisarevsky, Sergei A., Kamo, S., Gladkochub, D. P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: сибирский кратон; эктазийский период; базитовые интрузии; Listvyanka; Levaya Shirokaya; Victoria Island; Siberia
• Online Access: https://doi.org/10.1134/S1028334X19050222; http://vital.lib.tsu.ru/vital/access/manager/Repository/vtls:000721977

On the basis of U–Pb dating of zircon and baddeleyite from gabbro–dolerite of the Goloustnaya dyke swarm (southern margin of the Siberian Craton) the age of basites was established as 1338.0 ± 2.9 Ma. It is shown that the basite intrusions of close ages from the Goloustnaya and Listvyanka areas (southern Siberian Craton) and Victoria Island (northern Laurentia Barking Dog complex) could have been formed under the influence of the same mantle plume and belong to the same Large Igneous Province of Ectasian (Middle Mesoproterozoic) age. The time interval 1.70–0.75 Ga is often called a “period of global uncertainty” [1] or a “boring billion” [2] in the geological literature. P.A. Cawood and C.J. Hawkesworth [3] showed that neither global glaciations occurred in this period nor did large deposits of orogenic gold iron and sulfides form. However this period was marked by the widespread appearance of intrusions related to Large Igneous Provinces. The modern paleogeographic reconstructions for the time interval of 1.70–0.75 Ga demonstrate the close spatial locations of the southern flank of the Siberian Craton and the northern part of Laurentia (cratonic part of North America) [4‒6]. However Large Igneous Provinces of the Mesoproterozoic are quite widespread in Laurentia [3 6] whereas data on magmatism in the southern Siberian Craton are still scarce. In 2016 R.E. Ernest and his colleagues [6] presented data on the ages of two singular dykes from the southern flank of the Siberian Craton (~1.35 and ~1.26 Ga). But even then the amount of data on the Siberian margin remained insufficient for reliable correlations of the Mesoproterozoic evolution of Siberia and Laurentia contrary to the abundant data on northern Laurentia. The present communication provides the results of geochronological studies of zircon and baddeleyite from gabbro–dolerites of the recently found Mesoproterozoic dyke swarm including more than ten dykes and located in the Goloustnaya block (southern Siberian Craton). The Goloustnaya block is located in the southern part of the Baikal salient of the basement (southern Siberian Craton) and is composed of predominantly Paleoproterozoic migmatized gneisses and granite gneisses intruded by undeformed granites of the Primorskii complex of about 1.86 Ga in age [7 8]. Paleoproterozoic rocks of the Goloustnaya block are intruded by dykes of several generations: Early Paleozoic Neoproterozoic and as was shown by the present study Mesoproterozoic. A series of dykes ranging from half a meter to 100 m in thickness was revealed in the areas of Dyrovataya and Pad’ Levaya Shirokaya bays on the western coast of Lake Baikal to the north of Bolshoe Goloustnaya settlement (Fig. 1). The dykes are subvertical bodies characterized by steep cutting contacts with the hosting Paleoproterozoic rocks and composed of dolerites and gabbro–dolerites. The trends or dykes are 230° to 300°.