T106 Celebrating Dr. John W. Valley's Contributions to Isotope Geochemistry and Beyond, from the Hadean to the Holocene I

Monday, 23 October 2017
8:00 AM - 12:00 PM
Skagit 2

VALLEYITE: A NEW MAGNETIC MINERAL IN BASALTIC ROCKS

Paper number: T106-16
Program: Technical Sessions
Time: 11:45 AM – 12:00 PM

Authors

Abstract

Valleyite (Ca4Fe6O13) is a strongly magnetic mineral that was discovered in late Pleistocene basaltic scoria from Menan Volcanic Complex near Rexburg, Idaho, USA. The Menan Volcanic Complex consists of broad, flat volcanoes, formed by low-viscosity eruptions, with tholeiitic basalts dominating the outcrops. Both brown and red scorias contain valleyite. Empirical chemical formula of valleyite is (Ca3.60Mg0.39)(Fe3.97Al1.91Ti0.10)O13. It coexists with hematite (α-Fe2O3), luogufengite (ε-Fe2O3), maghemite (γ-Fe2O3), and quartz.

Valleyite has a cubic symmetry (a = 8.8852 Å) with the space group I 3m. This mineral has a sodalite-type structure, which consists of a framework of corner-sharing FeO4 tetrahedra with Ca2+ cations occupying the cavities. The (Fe,Al)-O bond distance and unit cell edge are slightly larger than those reported for synthetic Ca4Al6O13, presumably due to the occurrence of the larger Fe3+ cations, compared with Al3+, in the structure. The new mineral phase with a unique structure and magnetic properties may also be a potential functional material.

The newly discovered mineral species of Ca4Fe6O13 is named after Prof. John W. Valley (born in 1948) of the University of Wisconsin – Madison. Prof. Valley was President of the Mineralogical Society of America (2005-2006). His contributions to mineralogy, petrology and geochemistry lead to a deeper understanding of crustal evolution from early Earth to the Anthropocene. Both the mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-297685

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