Open AccessExperimental Investigation of Diopside Melt Viscosity at High Pressure
Author(s) -
S. Banushkina,
А. И. Чепуров
Publication year - 2020
Publication title -
izvestiâ altajskogo gosudarstvennogo universiteta
Language(s) - English
Resource type - Journals
eISSN - 1561-9451
pISSN - 1561-9443
DOI - 10.14258/izvasu(2020)4-02
Subject(s) - olivine , viscosity , diopside , magma , homogeneous , materials science , thermodynamics , phase (matter) , mineralogy , analytical chemistry (journal) , geology , chemistry , composite material , physics , chromatography , geochemistry , organic chemistry , volcano
This paper presents the experimental evaluation of viscosity of the diopside-based model composition conducted at high P-T parameters (at the pressure of 4 GPa and in the temperature range of 1750°C - 1800°C) in the presence of olivine crystals. The experiments are carried out using the multi-anvil high-pressure apparatus of the “split-sphere” type (Russian acronym — BARS) according to the falling sphere method. The traveling time of a platinum (Pt) sphere in a melt is one of the parameters measured in experiments. Measurement of this parameter starts when the given P-T values are attained and stops when the electric current is turned off. There are three main positions of the Pt sphere observed in the experiments. Viscosity is calculated using the Stokes’ Law. It is found out that the Pt sphere velocity decreases expectedly as the relative viscosity of such heterogeneous compositions (liquid + solid phase) increases (in contrast to homogeneous melts). Viscosity values remain low when there is up to 7-10 wt-% of solid phase crystals in magma. The increase of olivine xenocrysts in magma leads to the progressive increase of viscosity values of the melt: by 1.5-2 orders of magnitude at 20-25 wt-%, by 3-3.5 orders of magnitude at 35-40 wt-%. The obtained experimental results allow concluding that the amount of solid phase in magma should be sufficiently low (less than 20-30 wt-%), otherwise, melts of the investigated composition can be moved only by explosive processes.