Title of article :
Ferromagnetic resonance and low-temperature magnetic tests for biogenic magnetite
Author/Authors :
Weiss، نويسنده , , Benjamin P. and Sam Kim، نويسنده , , Soon and Kirschvink، نويسنده , , Joseph L. and Kopp، نويسنده , , Robert E. and Sankaran، نويسنده , , Mohan and Kobayashi، نويسنده , , Atsuko and Komeili، نويسنده , , Arash، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2004
Pages :
17
From page :
73
To page :
89
Abstract :
Magnetite is both a common inorganic rock-forming mineral and a biogenic product formed by a diversity of organisms. Magnetotactic bacteria produce intracellular magnetites of high purity and crystallinity (magnetosomes) arranged in linear chains of crystals. Magnetosomes and their fossils (magnetofossils) have been identified using transmission electron microscopy (TEM) in sediments dating back to ∼510–570 Ma, and possibly in 4 Ga carbonates in Martian meteorite ALH84001. We present the results from two rock magnetic analyses—the low-temperature Moskowitz test and ferromagnetic resonance (FMR)—applied to dozens of samples of magnetite and other materials. The magnetites in these samples are of diverse composition, size, shape, and origin: biologically induced (extracellular), biologically controlled (magnetosomes and chiton teeth), magnetofossil, synthetic, and natural inorganic. We confirm that the Moskowitz test is a distinctive indicator for magnetotactic bacteria and provide the first direct experimental evidence that this is accomplished via sensitivity to the magnetosome chain structure. We also demonstrate that the FMR spectra of four different strains of magnetotactic bacteria and a magnetofossil-bearing carbonate have a form distinct from all other samples measured in this study. We suggest that this signature also results from the magnetosomesʹ unique arrangement in chains. Because FMR can rapidly identify samples with large fractions of intact, isolated magnetosome chains, it could be a powerful tool for identifying magnetofossils in sediments.
Keywords :
Biogenic magnetite , Moskowitz test , Ferromagnetic resonance , magnetotactic bacteria
Journal title :
Earth and Planetary Science Letters
Serial Year :
2004
Journal title :
Earth and Planetary Science Letters
Record number :
2323710
Link To Document :
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