A Non-Magnetized Chondrite Parent Body Revealed by Paleomagnetic Investigation of LL6 Chondrite NWA 14180

Abstract

Magnetic records from meteorites provide valuable information about the formation and evolution of the solar system and planets. The parent planetesimals of chondrites are typically considered to be undifferentiated based on their primary chemical composition and texture. However, recent paleomagnetic investigations of various chondrites indicate that they carry a primary remanence generated by a dynamo, suggesting partial differentiation of their parent planetesimals. The presence of a dynamo within the parent planetesimal of LL chondrites remains uncertain due to the ambiguous origin of the remanent magnetism. Here, we report petrographic, paleomagnetic, and rock magnetic properties for the novel LL6 chondrite NWA 14180. The high metamorphic temperature experienced by NWA 14180 could have removed the pre-accretionary remanence. The fusion crust baked-contact test suggests that NWA 14180 preserves primary magnetic information about its parent body. Alternating field demagnetization results from interior subsamples reveal distinct low- and medium-coercivity components that may represent a viscous remanent magnetization acquired in the geomagnetic field. No natural remanent magnetization was unblocked in the high coercivity range, implying that NWA 14180 cooled in zero-field conditions. Therefore, we suggest that the parent body of NWA 14180 did not have a dynamo. Furthermore, this result suggests that the LL chondrite parent planetesimal accreted later and was smaller in size than other chondrite classes.