Physical and geological modeling of dolerite intrusion at collisional suture of Siberian craton – Olkhon terrane system (Western Baikal region)

The Olkhon region is a key structure (geodynamic polygon) straddling the boundary between the Siberian craton and the Central Asian folded belt. In this regard, finding out the history of their interaction in time and space is an interesting and relevant task, the solution of which provides a good opportunity to discuss the prospects for a different interpretation of the array of new geological and geophysical data for the Western Baikal region. The purpose of physical and geological modeling is to clarify the geological structure of the collisional suture of the Siberian craton – Olkhon terrane system to create next-generation geological maps. For this purpose, ground magnetic surveys and petrophysical studies have been conducted at the Anga river section where collisional suture metamorphic features are prominent. These studies included the collection of oriented samples from blastomylonites of various types and the intruding dolerites, aged 500–470 and 290 million years, respectively. According to geologists, dolerites form a dike of northeastern strike, no more than 5 m thick and up to 2 km long. New information on geochronology, petro- and paleomagnetism of the considered dolerites contradicts this hypothesis. The performed physical-geological modeling showed that the dolerites form an intrusive body of a more complex shape than the dike (most likely a sill about 200 m thick), and made it possible to find a compromise solution for the interpretation of previously obtained material. On this basis, it is possible to conclude that fairly active tectono-magmatic events occurred here in the Early Permian, which most likely were associated with the formation of the Angara-Vitim batholith in Transbaikalia. According to the obtained samples (N = 19), after introducing a tectonic correction for the bedding elements of the main fault plane of the Primorsky fault, a virtual geomagnetic pole has been calculated for the Early Permian (295–275 Ma) with coordinates: F = 45° N, L = 133° E, dp/dm = 18.2/19.0°. Thus, to clarify the Aerospace geological map and the history of geodynamic development of the Olkhon region, it is proposed to include a wide range of geophysical methods in the research.

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