Granite island mountains: morphology, tectonic structure and genesis

Rubric: Geology
Journal: GEOMORPHOLOGY Number: 3 Year: 2017

Presented data show that granites after they become a part of consolidated crust do not remain passive units and move upwards, finally forming separate ridges or mountain groups, often surrounded by more resistant to weathering rock assemblages. Geological and geomorphological evidences suggest impulsive nature of the massif’s uplift that continued during the neotectonic stage, ahead of denudation processes. The internal structure of the considered “island mountains” (inselbergs) of the Northern Tien-Shan, Transbaikalia and Mongolia testifies to the intense postmagmatic structural reworking of granites, which led to complete or partial disintegration of rock massifs at the macro, meso and micro levels. This structural feature of the exhumed massifs is a crucial link when considering possible mechanisms of post-magmatic movements of granite mass in the upper horizons of the crust and the formation of the positive topography. When rocks convert to discrete masses, their effective viscosity decrease and shear strength reduces, that causes three-dimensional mobility of rocks. Spatial redistribution of “fluid” rock masses take place due to the viscosity inversion: masses flow and squeeze to decompressed areas, in particular, toward the day surface in the direction of less lithostatic pressure.
Keywords: гранитный массив, островные горы, морфотектоника, дезинтеграция, протрузия, объемная деформация.