The crystal chemistry of hibonite: an indicator for oxygen fugacity during Solar nebula condensation?
type: CreativeWork
description: Meteorites represent the main source of materials which can give information on the early history of our Solar System. In particular, Calcium-Aluminium-rich inclusions (CAIs), which are usually found in carbonaceous chondrites, yielded the oldest measured ages of our Solar System. CAIs can contain records of the conditions and the events that characterised their formation, therefore they can provide essential information on the early Solar Nebula, which is believed to have been an environment so reducing to allow the occurrence of Ti(3+). For these reasons, the oxidation state of titanium in different minerals present in CAIs has attracted considerable attention over the years as it could be used to constrain the oxygen fugacity, fO2, at the time of Solar Nebula condensation. CAIs contain minerals which appear earlier in the condensation sequence of a hot gas having Solar composition. Among these minerals, Ti-rich clinopyroxenes, Ca(Mg,Al,Ti)(Si,Al)2O6, and hibonite, Ca(Al,Mg,Ti)12O19, have been used to estimate the fO2 during the Solar Nebula condensation, producing contradictory results, with pyroxenes suggesting reducing and hibonite oxidising conditions. The particular interest on hibonite is due to the fact that it is, together with corundum, the very first mineral to condensate in the Solar Nebula. Therefore, as compared to clinopyroxenes, which have formed subsequently, hibonite potentially carries information on the earliest stages of the Solar System formation. However, little is known on the crystal chemistry of hibonite, on the influence on hibonite structure of the Ti(3+)-Ti(4+) incorporation, and on the possible interactions of Ti with other cations substituting for Al such as, for example, Mg. The aim of this thesis is, therefore, to correctly determine the cation distribution of Ti in synthetic and meteoritic samples and to quantify their Ti(3+)/Ti(tot) ratios from spectroscopic data. Correlating the information on the crystal chemistry and the Ti(3+)…
abstract: Meteorites represent the main source of materials which can give information on the early history of our Solar System. In particular, Calcium-Aluminium-rich inclusions (CAIs), which are usually found in carbonaceous chondrites, yielded the oldest measured ages of our Solar System. CAIs can contain records of the conditions and the events that characterised their formation, therefore they can provide essential information on the early Solar Nebula, which is believed to have been an environment so reducing to allow the occurrence of Ti(3+). For these reasons, the oxidation state of titanium in different minerals present in CAIs has attracted considerable attention over the years as it could be used to constrain the oxygen fugacity, fO2, at the time of Solar Nebula condensation. CAIs contain minerals which appear earlier in the condensation sequence of a hot gas having Solar composition. Among these minerals, Ti-rich clinopyroxenes, Ca(Mg,Al,Ti)(Si,Al)2O6, and hibonite, Ca(Al,Mg,Ti)12O19, have been used to estimate the fO2 during the Solar Nebula condensation, producing contradictory results, with pyroxenes suggesting reducing and hibonite oxidising conditions. The particular interest on hibonite is due to the fact that it is, together with corundum, the very first mineral to condensate in the Solar Nebula. Therefore, as compared to clinopyroxenes, which have formed subsequently, hibonite potentially carries information on the earliest stages of the Solar System formation. However, little is known on the crystal chemistry of hibonite, on the influence on hibonite structure of the Ti(3+)-Ti(4+) incorporation, and on the possible interactions of Ti with other cations substituting for Al such as, for example, Mg. The aim of this thesis is, therefore, to correctly determine the cation distribution of Ti in synthetic and meteoritic samples and to quantify their Ti(3+)/Ti(tot) ratios from spectroscopic data. Correlating the information on the crystal chemistry and the Ti(3+)…
author: Giannini, Mattia
date published: 2014-08-28
date modified: 2026-07-27T18:49:36Z
provider: Universität Bayreuth
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Universität Bayreuth