The Onon manifestation of hydrotherms: a unique site of discharge of hot waters of Khentei-Daurian vault
A.I. ORGILYANOV, I.G. KRYUKOVA, P.S. BADMINOV
Institute of the Earth’s Crust, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
Keywords: vault uplift, thermal waters, microcomponents, helium, isotopic composition, depth of formation
Abstract
Presented are the new concepts of the structural-hydrogeological conditions and evolution of the underground hydrosphere of Khentei-Daurian vault which is considered as a unified hydrogeothermal system located on the neighbouring territories of Russia and Mongolia. The conclusions of these authors are based on factual evidence obtained during expedition work that was for the first time carried out in the winter period, on laboratory investigations as well as on the studies of archival material. Special attention is given to the Onon seat of discharge of hot waters. A detailed description of springs is provided, and information on macro- and microcomponent chemical composition of water is presented. The relationship between the concentration of microelements and the depth of formation of mineral waters is considered. An assessment is made of the predicted temperatures at the depth of formation by the method of silica geothermometer. It is pointed out that during the winter runoff low period, almost the entire volume of runoff of the Onon River is formed by the discharge of hydrotherms. The mantle part of gas composition of water from the spring under study was calculated by use of the isotopic relationship 3He/4He. It is noted that in spite of a high absolute concentration of water-dissolved helium, the relative value of the mantle component is only 0.3-0.4 %. This indicates the crust origin of the increased concentrations of helium. It was noted а high balneological value of the Ikh-Onon thermal spring is highlighted, and the need to organize the protection of this unique natural monument is emphasized.
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