Domain State Diagnosis in Rock Magnetism: Evaluation of Potential Alternatives to the Day Diagram

Abstract

The Day diagram is used extensively in rock magnetism for domain state diagnosis. It has beenshown recently to be fundamentally ambiguous for 10 sets of reasons. This ambiguity highlights theurgency for adopting suitable alternative approaches to identify the domain state of magnetic mineralcomponents in rock magnetic studies. We evaluate 10 potential alternative approaches here and concludethat four have value for identifying data trends, but, like the Day diagram, they are affected by use of bulkparameters that compromise domain state diagnosis in complex samples. Three approaches based onremanence curve and hysteresis loop unmixing, whensupervisedby independent data to avoidnonuniqueness of solutions, provide valuable component‐specific information that can be linked byinference to domain state. Three further approaches based onfirst‐order reversal curve diagrams providedirect domain state diagnosis with varying effectiveness. Environmentally important high‐coercivityhematite and goethite are represented with variable effectiveness in the evaluated candidate approaches.These minerals occur predominantly in noninteracting single‐domain particle assemblages inpaleomagnetic contexts, so domain state diagnosis is more critical for ferrimagnetic minerals. Treating thehigh‐coercivity component separately following normal rock magnetic procedures allows focus on the morevexing problem of diagnosing domain state in ferrimagnetic mineral assemblages. We suggest a moveaway from nondiagnostic methods based on bulk parameters and adoption of approaches that provideunambiguous component‐specific domain state identification, among which variousfirst‐order reversalcurve‐based approaches provide diagnostic information. Show more