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We measured the natural remanent magnetization (NRM) and rock magnetic properties of 57 sediment samples and 38 basalt samples from Tūranganui Knoll on the Hikurangi Plateau collected at Site U1526 during International Ocean Discovery Program Expedition 375. NRM was measured on all samples before and after either progressive alternating field or thermal demagnetization. Principal component analysis was conducted to provide estimates of the characteristic remanent magnetization direction. Rock magnetic observations include measurements on select samples of the bulk magnetic susceptibility, susceptibility versus heating for Curie temperature assessment, magnetic hysteresis, backfield for coercivity of remanence determinations, isothermal remanent magnetization, and first-order reversal curves.
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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 been shown recently to be fundamentally ambiguous for 10 sets of reasons. This ambiguity highlights the urgency for adopting suitable alternative approaches to identify the domain state of magnetic mineral components in rock magnetic studies. We evaluate 10 potential alternative approaches here and conclude that four have value for identifying data trends, but, like the Day diagram, they are affected by use of bulk parameters that compromise domain state diagnosis in complex samples. Three approaches based on remanence curve and hysteresis loop unmixing, whensupervisedby independent data to avoid nonuniqueness of solutions, provide valuable component‐specific information that can be linked by inference to domain state. Three further approaches based on first‐order reversal curve diagrams provide direct domain state diagnosis with varying effectiveness. Environmentally important high‐coercivity hematite and goethite are represented with variable effectiveness in the evaluated candidate approaches. These minerals occur predominantly in noninteracting single‐domain particle assemblages in paleomagnetic contexts, so domain state diagnosis is more critical for ferrimagnetic minerals. Treating the high‐coercivity component separately following normal rock magnetic procedures allows focus on the more vexing problem of diagnosing domain state in ferrimagnetic mineral assemblages. We suggest a move away from nondiagnostic methods based on bulk parameters and adoption of approaches that provide unambiguous component‐specific domain state identification, among which various first‐order reversal curve‐based approaches provide diagnostic information.
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- PAR ID:
- 10457221
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Solid Earth
- Volume:
- 124
- Issue:
- 6
- ISSN:
- 2169-9313
- Page Range / eLocation ID:
- p. 5286-5314
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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