An Integrated Model for Ilmenite, Al-Spinel, and Corundum Exsolutions in Titanomagnetite from Oxide-Rich Layers of the Lac Doré Complex (Québec, Canada)

Minerals. 2018;8(11):476 DOI 10.3390/min8110476

 

Journal Homepage

Journal Title: Minerals

ISSN: 2075-163X (Online)

Publisher: MDPI AG

LCC Subject Category: Science: Geology: Mineralogy

Country of publisher: Switzerland

Language of fulltext: English

Full-text formats available: PDF, HTML, XML

 

AUTHORS

Jean-Philippe Arguin (Sciences de la Terre, Université du Québec à Chicoutimi, Chicoutimi, QC G7H 2B1, Canada)
Philippe Pagé (Sciences de la Terre, Université du Québec à Chicoutimi, Chicoutimi, QC G7H 2B1, Canada)
Sarah-Jane Barnes (Sciences de la Terre, Université du Québec à Chicoutimi, Chicoutimi, QC G7H 2B1, Canada)
Réjean Girard (IOS Services Géoscientifiques, Chicoutimi, QC G7J 3Y2, Canada)
Charley Duran (Sciences de la Terre, Université du Québec à Chicoutimi, Chicoutimi, QC G7H 2B1, Canada)

EDITORIAL INFORMATION

Blind peer review

Editorial Board

Instructions for authors

Time From Submission to Publication: 11 weeks

 

Abstract | Full Text

The titanomagnetite of the Lac Dor&#233; Complex, an Archean layered intrusion that is located in the Abitibi greenstone belt in Qu&#233;bec (Canada), contains a wide variety of exsolution textures, which are the remnants of a complex cooling history. In the present study, we reconstitute the decomposition stages of the original solid solution in order to explain the formation of ilmenite, Al-spinel (hercynite and gahnite), and corundum exsolutions in magnetite. This was conducted through a detailed mineralogical and textural examination and in situ determination of mineral chemistry. Our investigation reveals two discrete types of ilmenite exsolutions, which are ascribed, respectively, to the oxidation of ulv&#246;spinel at temperatures above and below the magnetite-ulv&#246;spinel solvus. Exsolutions of Al-spinel result from either a decrease in the solubility of the (FeZn)Al<sub>2</sub>O<sub>4</sub> components upon cooling, or local excesses of Al and Zn due to the removal of ulv&#246;spinel during the early oxidation. The origin of corundum is ascribed to the oxidation of pre-existing hercynite exsolutions. The trace element composition of the titanomagnetite indicates stratigraphic reversals in Cr, Mg, Co, Ti, and Si and important changes in redox conditions. We interpret this as a direct consequence of a major event of magma chamber replenishment, which strongly influenced the distribution of exsolutions.