Differences in Rock Magnetic Properties From Heterogeneous Weathering of the LL7 Chondrite Northwest Africa 12780

Abstract

Meteorites preserve valuable remanent magnetization from the early solar system. However, the residence on the Earth's surface often leads to the formation of iron oxides, which can alter or obliterate the primary remanence and complicate the paleomagnetic data interpretation. The weathering degree varies significantly depending on residence time, location, climate, and the chemical composition of the meteorite. Additionally, individual meteorites can exhibit varying oxidation degrees within a single stone due to partial burial in soil. This study examines the LL7 chondrite Northwest Africa 12780, revealing heterogeneous weathering across different parts of the meteorite. While one part shows extensive metal oxidation, another remains unoxidized. Although most oxidized subsamples contain paramagnetic iron oxides, maghemite is observed in some oxidized subsamples. Our findings highlight the presence of heterogeneous weathering in meteorites, which leads to the formation of various iron oxides, including maghemite, potentially acquiring chemical remanent magnetization and overprinting primary remanence. This also indicates that certain subsamples may retain their primary remanence even in weathered meteorites. However, systematic investigations are necessary to eliminate the influence of ferromagnetic iron oxides.