TY - JOUR

T1 - Magnetic characterization of the Daule chondrite (Ecuador's first meteorite fall): The case of elusive tetrataenite?

AU - Bristol, K.E.

AU - Smirnov, A.V.

AU - Piispa, E.J.

AU - Navas, M.R. Ramirez

AU - Kosterov, A.

AU - Kulakov, E.V.

PY - 2023/11/1

Y1 - 2023/11/1

N2 - We investigated the magnetic properties of Ecuador's first reported meteorite fall (March 23, 2008), the Daule ordinary chondrite (L5, S4, W0) using thermomagnetic analyses at high and cryogenic temperatures, analyses of magnetic hysteresis and first-order reversal curves, and thermal and alternating field (AF) demagnetization of natural remanent magnetization (NRM). The mineralogical and chemical composition of Daule was examined using scanning electron microscopy with energy-dispersive x-ray spectroscopy. Most methods indicate that the magnetic properties of Daule are dominated by multidomain FeNi alloys (kamacite) with Ni content varying between ∼4% and ∼17%. However, backfield demagnetization (BFD) analyses revealed the presence of high-coercivity tetrataenite that survived shock metamorphism. The differential survival of tetrataenite at the millimeter scale indicates heterogeneity of the impact-related temperature and pressure fields within the Daule meteorite. BFD curves may serve as an efficient tool for identifying minor amounts of tetrataenite that otherwise cannot be discerned from the signal from magnetically-soft FeNi mineral phases by methods based on induced magnetization. Thermal demagnetization experiments unveiled the presence of a well-defined characteristic component of NRM, which remains resistant to AF demagnetization. We interpret this component as a pre-impact thermochemical remanence carried by tetrataenite and acquired during the thermal metamorphism of the parent body. At cryogenic temperatures, the magnetic properties of Daule are dominated by low-Mg magnesiochromite with the Curie temperature at 60–70 K.

AB - We investigated the magnetic properties of Ecuador's first reported meteorite fall (March 23, 2008), the Daule ordinary chondrite (L5, S4, W0) using thermomagnetic analyses at high and cryogenic temperatures, analyses of magnetic hysteresis and first-order reversal curves, and thermal and alternating field (AF) demagnetization of natural remanent magnetization (NRM). The mineralogical and chemical composition of Daule was examined using scanning electron microscopy with energy-dispersive x-ray spectroscopy. Most methods indicate that the magnetic properties of Daule are dominated by multidomain FeNi alloys (kamacite) with Ni content varying between ∼4% and ∼17%. However, backfield demagnetization (BFD) analyses revealed the presence of high-coercivity tetrataenite that survived shock metamorphism. The differential survival of tetrataenite at the millimeter scale indicates heterogeneity of the impact-related temperature and pressure fields within the Daule meteorite. BFD curves may serve as an efficient tool for identifying minor amounts of tetrataenite that otherwise cannot be discerned from the signal from magnetically-soft FeNi mineral phases by methods based on induced magnetization. Thermal demagnetization experiments unveiled the presence of a well-defined characteristic component of NRM, which remains resistant to AF demagnetization. We interpret this component as a pre-impact thermochemical remanence carried by tetrataenite and acquired during the thermal metamorphism of the parent body. At cryogenic temperatures, the magnetic properties of Daule are dominated by low-Mg magnesiochromite with the Curie temperature at 60–70 K.

KW - Geophysics

KW - Magnetic fields

KW - Meteorites

KW - Mineralogy

KW - Planetesimals

U2 - 10.1016/j.icarus.2023.115684

DO - 10.1016/j.icarus.2023.115684

M3 - Article

VL - 404

JO - Icarus

JF - Icarus

SN - 0019-1035

M1 - 115684

ER -