Hydrothermal Activity in the Baikal Rift Zone: Recent Hot Springs and Deposits of Paleothermal Waters

摘要

Thermal springs, which are widely developed within the Baikal rift zone (BRZ), form a NE-trending zone extending from the upper course of the Olekma River in the northeast to the Selenga River mouth in the southwest (Fig. 1). Thermal springs are rare west of Lake Baikal. Springs, mainly represented by nitric thermal waters of variable composition, mark recent hydro-thermal activity in the BRZ. This zone also contains deposits of paleothermal water represented by travertines and geyserites. Travertines can be deposited within a wide range of temperatures, from cold water inclusive. However, they are mostly deposited from thermal water, the temperature of which in the study region can vary from 20 to 70℃. As to geyserites, the minimal temperatures of their formation do not fall below 70℃. We found geyserites on the western coast of Lake Baikal at the southwestern extension of the above-mentioned zone of hydrothermal activity. The amount of siliceous deposits in the Ol'khon region is much higher as compared to previously described geyserite occurrences on the eastern coast of Lake Baikal, where only thin crusts of opal-like chalcedony were found in fragments of bedrocks with silica as cement. Recently, travertines have been found in association with geyserites and as independent veins in the Ol'khon region.