Copper-containing magnesioferrite in vesicular trachyandesite in a lava tube from the 2012–2013 eruption of the Tolbachik Volcano, Kamchatka, Russia

Cu-rich magnesioferrite was found in vesicular basaltic trachyandesite in one of lava tubes (Duplex) that formed during the 2012–2013 eruption of the Tolbachik volcano, Kamchatka. This mineral is commonly associated with hematite, tenorite, halite, sylvite, and Ca-rich silicates (mainly, esseneite a...

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Bibliographic Details
Published in:Minerals
Main Authors: Sharygin, VV, Kamenetsky, VS, Zhitova, LM, Belousov, AB, Abersteiner, A
Format: Article in Journal/Newspaper
Language:English
Published: MDPIAG 2018
Subjects:
magnesioferrite
cuprospinel
hematite
tenorite
trachyandesite
lava tube
Tolbachik volcano
Kamchatka
Tolbachik
Online Access:https://eprints.utas.edu.au/41281/
https://eprints.utas.edu.au/41281/1/129123%20-%20Copper-containing%20magnesioferrite%20in%20vesicular%20trachyandesite%20in%20a%20lava%20tube.pdf
Description
Summary:Cu-rich magnesioferrite was found in vesicular basaltic trachyandesite in one of lava tubes (Duplex) that formed during the 2012–2013 eruption of the Tolbachik volcano, Kamchatka. This mineral is commonly associated with hematite, tenorite, halite, sylvite, and Ca-rich silicates (mainly, esseneite and Na-rich melilite) in high-temperature (800–1000 °C) reactionary zones (up to 100 µm) covering vesicular rocks and lava stalactites in the Duplex tube. The mineral relationships of this assemblage indicate the following crystallization sequence: Ca-rich silicates + hematite → Cu-rich magnesioferrite → tenorite → chlorides. This formed due to the reaction of hot gases containing Cu, alkalis, and Cl with solidified lava rock. The composition of magnesioferrite varies strongly in CuO (5.8–17.3 wt %; cuprospinel end-member—15–47 mol %), whereas the contents of other oxides are minor, indicating the main isomorphic substitution is Mg2+ ↔ Cu2+. Compositions with maximal CuO content nominally belong to Mg-rich cuprospinel: (Cu0.48Mg0.41Mn0.09Zn0.02Ca0.02) (Fe3+1.94Al0.03Ti0.02)O4. Increasing CuO content of the Duplex Cu-rich magnesioferrite is reflected in Raman spectra by moderate right shifting bands at ≈700–710 and 200–210 cm−1 and the appearance of an additional band at 596 cm−1. This supports the main isomorphic scheme and may indicate a degree of inversion in the spinel structure.

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