T13 Sigma Gamma Epsilon Student Research (Posters)

Monday, 26 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

EVALUATING THE APPLICATION OF CE-IN-ZIRCON AS A MAGMA FO2 ESTIMATOR

Paper number: T13-17
Program: Technical Sessions
Time: 4:15 PM – 4:25 PM

Authors

Abstract

Zircon-melt partitioning behavior of Ce is sensitive to the redox conditions of magmas as zircon crystallizes, because Ce4+ is far more compatible than Ce3+ in zircon. Previous works suggest that the Ce concentration in zircon is an effective tool to estimate magma oxygen fugacity (Trail et al., 2012; Smythe and Brenan, 2016). The goal of this study is to understand the application and limitation of different Ce-in-zircon oxygen barometers and to quantitatively identify Ce4+ and Ce3+ in zircon and the contributions of inclusions to Ce measurements. We evaluate multiple experimentally derived models by applying them to natural sample data from a variety of systems: Mt. St. Helens, WA, USA (continental arc), Peach Spring Tuff, NV, USA (continental extension zone) and Iceland (mid-ocean ridge/hot spot). We estimate magma fO2 using different methods and compare the results with other measures of magmatic conditions for these systems. However, light rare earth element (LREE) concentrations in zircon analyses are easily inflated by inclusions. In order to more accurately estimate magma fO2 using the models, we try to quantify the contributions of inclusions to Ce concentrations measured in zircon. The Ce value (which we denote as Ce**) obtained by projecting a log-linear relationship from chondrite-normalized Sm value through Gd may better represent the concentration of Ce3+ in zircon, than the commonly used Ce*, calculated from La and Sm, as this reports Ce3+ in zircon plus the contribution from inclusions. Calculating Ce** allows us to use Ce as a more reliable tool to understand magma redox conditions.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-355115

© Copyright 2020 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.