Movement Rates of Metamorphic Fronts in Rocks near Magmatic Intrusive Bodies

Abstract

The rate of mineral transformations in rocks near magmatic intrusions may be estimated using mathematical modeling for study of the duration of metamorphism and geological and mineralogical data. At the contacts of the Anakit trappean massif on the Nizhnyaya Tunguska River, where the temperature reached 900°C, the rate of growth of a wollastonite rim at the boundary between the limestone and the siliceous nodule was ∼3 × 10–10 cm/s. The zone of “spotted” hornfels with a width of 300‒400 m was formed during metamorphism of chlorite–sericite–epidote–albite–quartz schist near the Kharlov gabbro massif in the foothills of the Altai Mountains. The movement rate of the metamorphic front during the formation of rock may be estimated as ∼2 × 10–8 cm/s. It is suggested that the rate of metamorphism is controlled by the temperature and rock composition. As a whole, the rates of metamorphism of rocks near magmatic intrusive bodies exceed the rates of regional metamorphism. Upon accumulation of the actual data, this may be applied for diagnostics of the types of metamorphism.