Magnetic properties in an ash flow tuff with continuous grain size variation: a natural reference for magnetic particle granulometry

Geochemistry, Geophysics, Geosystems
By: , and 

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Abstract

The Tiva Canyon Tuff contains dispersed nanoscale Fe-Ti-oxide grains with a narrow magnetic grain size distribution, making it an ideal material in which to identify and study grain-size-sensitive magnetic behavior in rocks. A detailed magnetic characterization was performed on samples from the basal 5 m of the tuff. The magnetic materials in this basal section consist primarily of (low-impurity) magnetite in the form of elongated submicron grains exsolved from volcanic glass. Magnetic properties studied include bulk magnetic susceptibility, frequency-dependent and temperature-dependent magnetic susceptibility, anhysteretic remanence acquisition, and hysteresis properties. The combined data constitute a distinct magnetic signature at each stratigraphic level in the section corresponding to different grain size distributions. The inferred magnetic domain state changes progressively upward from superparamagnetic grains near the base to particles with pseudo-single-domain or metastable single-domain characteristics near the top of the sampled section. Direct observations of magnetic grain size confirm that distinct transitions in room temperature magnetic susceptibility and remanence probably denote the limits of stable single-domain behavior in the section. These results provide a unique example of grain-size-dependent magnetic properties in noninteracting particle assemblages over three decades of grain size, including close approximations of ideal Stoner-Wohlfarth assemblages, and may be considered a useful reference for future rock magnetic studies involving grain-size-sensitive properties.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Magnetic properties in an ash flow tuff with continuous grain size variation: a natural reference for magnetic particle granulometry
Series title Geochemistry, Geophysics, Geosystems
DOI 10.1029/2011GC003648
Volume 12
Issue 7
Year Published 2011
Language English
Publisher AGU
Publisher location Washington, D.C.
Description Q07Z26
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Geochemistry, Geophysics, Geosystems
Country United States
State Nevada
Other Geospatial Tiva Canyon Tuff