Abstract Acquiring accurate absolute paleointensities of the geomagnetic field is essential for studying the evolution of the geodynamo in Earth's core and its thermal history. Thermoremanence is a preferred magnetic recording mechanism, but most igneous rocks are dominated by non‐single‐domain (non‐SD) ferromagnetic grains (e.g., magnetite larger than ∼100 nm), for which there is no strict theory for obtaining unbiased paleointensities. The Repeated Thellier‐series Experiment (RESET) method has been recently developed to specifically deal with non‐SD effects and thermal alterations so as to provide an accurate paleointensity. To test its capability, we studied a 1915 CE dacitic lava from Mount Lassen (located in northern California, USA, 40°29′N, 121°30′W, elevation ∼3,100 m) that contains micron‐sized titanomagnetites whose thermoremanence was acquired in a known geomagnetic field of 54 μT. This dacitic lava was previously investigated and found to exhibit concave and S‐shaped Arai diagrams along with unsatisfying paleointensities. In this study, out of 34 specimens, we successfully obtained 22 qualified RESET‐corrected paleointensity estimates that range from 50.6 to 57.4 μT with an average of 54.1 ± 1.6 μT. Our results show that the thermoremanence recorded in non‐SD‐dominated igneous rocks can indeed provide accurate paleointensity estimates using the RESET method. We demonstrate that the RESET method provides a promising approach to expanding the range of geological materials suitable for future paleointensity studies, enabling the recovery of accurate paleointensities from samples previously considered non‐ideal, which can significantly improve our understanding of the evolution of the geomagnetic field.
Chen et al. (Sun,) studied this question.