期刊
GEOPHYSICAL RESEARCH LETTERS
卷 46, 期 22, 页码 12841-12850出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2019GL084715
关键词
red beds; remagnetization; hematite; magnetite; goethite
资金
- Institute for Rock Magnetism (IRM) at the University of Minnesota - Instruments and Facilities program of NSF
Red beds are well-known for recording stable natural remanent magnetization (NRM). However, discriminating primary NRM from secondary remanence in red beds is difficult. The Paleogene Nangqian red beds in eastern Tibetan Plateau variably record an overprint related to nearby magmatism and thus provide a great opportunity to characterize remagnetization in red beds. Through comprehensive rock magnetic, Mossbauer spectroscopic, and petrographic analyses, we find that remagnetization was controlled by temperature. Remagnetized red beds contain abundant authigenic hematite and goethite, with some larger grains unblocking at the Neel temperatures and the remainder (nanoparticles) unblocking at lower temperatures. In contrast, red beds retaining primary NRM are characterized by dominance of detrital hematite and magnetite, presence of fine-grained authigenic hematite, and absence of authigenic goethite and magnetite. High temperature behaviors of NRM/susceptibility are indicative of remagnetization, but the presence of goethite appears to be a more sensitive criterion for diagnosing remagnetization in red beds.
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