Features of Frictional Melting of Rocks and Melt Crystallization in a Seismic Process: Case Study of Pseudotachylites of the Ladoga Regionстатья
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Дата последнего поиска статьи во внешних источниках: 26 июня 2024 г.
Аннотация:In this paper, pseudotachylites (PST) from mica schists and plagiogneisses of several metamorphic zones of the Ladoga region from the greenschist to granulite facies are studied to identify and characterize the peculiarities of frictional melting of metaterrigenous rocks at increased shear stress and displacement velocities with subsequent melt crystallization during the presumed paleoseismic slip. It is established that mineral melting in the polymineral aggregate occurred in the sequence determined in the non-equilibrium conditions by individual melting temperatures of separate minerals and by their thermomechanical strength (the Spray’s series). The crystallization of melt occurred not in the order of decreasing solidus temperatures but in the same order as in the case of mineral melting—from fusibles (mica) to refractories (quartz). The temperatures of melting and crystallization of minerals from melt are determined, and the aspects of the effect of aqueous fluid and redox conditions on melting and crystallization processes are considered. Model calculations of viscous parameters and shear stresses in the frictional melt during seismic slip are carried out, and their complex functional dependence on chemical composition of melt, proportion of lithic fragments in it, the achieved melting temperature, lithostatic load parameters, displacement amplitude and velocity is demonstrated.