MI2023 - 02 Ana Pagu: Investigating aqueous alteration in carbonaceous chondrites
Channel: MagNetZ
Date: 2023-01-16

Magnetic Interactions 2023 conference at the University of Cambridge
Session 1: Solar System and Asteroid Magnetism

Title: Investigating aqueous alteration in carbonaceous chondrites using magnetic measurements obtained with the QDM (Quantum Diamond Microscope)
Author: Ana Pagu from the University of Oxford, UK

Extensive studies of the magnetic properties of carbonaceous chondrites have been performed recently, providing a wealth of information on the magnetic fields present in the protoplanetary disk, with implications for planet formation and early Solar System dynamics. However, data from chondrites is challenging to interpret due to their complex aqueous alteration history and resulting mineralogy, and a thorough understanding of the alteration pathways that influenced magnetic mineralogy is required to extract reliable paleomagnetic information from chondrites.

Here, we analyse the mineralogy and magnetic recording of CM and CO chondrites, having two main aims: firstly, to characterise the individual signals of different magnetic carriers and determine whether magnetite carries an NRM; secondly, to investigate whether a magnetic signal can be inherited from the precursor mineral through alteration. We used a geo-quantum diamond microscope (QDM) to produce spatially resolved maps of the local magnetic fields of 7 CM chondrite and 3 CO chondrite thin sections, and we present preliminary results discussing their NRM and magnetic mineralogy in relation to the degree of alteration.

We find that the remanence of CM chondrites is carried by pyrrhotite, although rare metal grains are present and magnetised in the less altered samples. We applied several ARMs on one CM chondrite (MIL 090288) and we found that the field that imparted its NRM was stronger than 60 μT. In CO chondrites, the metal, magnetite and sulfides all appear to carry a signal, which is on average stronger than the signal from CM chondrites. However, CO chondrites appear to be heterogeneously magnetised. Future work includes more QDM measurements, micromagnetic modelling, and ARM and IRM experiments extended to other samples.

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00:00 - Intro
00:24 - Presentation
16:00 - Questions