Publication Date:
2021-02-05
Description:
Understanding the viscosity of mantle-derived magmas is needed to model their migration
mechanisms and ascent rate from the source rock to the surface. High pressure–temperature
experimental data are now available on the viscosity of synthetic melts, pure carbonatitic to
carbonate–silicate compositions, anhydrous basalts, dacites and rhyolites. However, the viscosity
of volatile-bearing melilititic melts, among the most plausible carriers of deep carbon, has not been
investigated. In this study, we experimentally determined the viscosity of synthetic liquids with
~31 and ~39 wt% SiO2, 1.60 and 1.42 wt% CO2 and 5.7 and 1 wt% H2O, respectively, at pressures from
1 to 4.7 GPa and temperatures between 1265 and 1755 C, using the falling-sphere technique combined
with in situ X-ray radiography. Our results show viscosities between 0.1044 and 2.1221 Pa s, with a
clear dependence on temperature and SiO2 content. The atomic structure of both melt compositions
was also determined at high pressure and temperature, using in situ multi-angle energy-dispersive
X-ray di raction supported by ex situ microFTIR and microRaman spectroscopic measurements.
Our results yield evidence that the T–T and T–O (T = Si,Al) interatomic distances of ultrabasic melts
are higher than those for basaltic melts known from similar recent studies. Based on our experimental
data, melilititic melts are expected to migrate at a rate ~from 2 to 57 km yr1 in the present-day or the
Archaean mantle, respectively.
Description:
Published
Description:
267
Description:
3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
Description:
JCR Journal
Keywords:
magma
;
rheology
;
viscosity
;
ascent rate
;
04.01. Earth Interior
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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