Rock Magnetic Characterization of Lavas Erupted From Haleakala Volcano, Maui, Hawaii

We have studied rock magnetic properties of 103 lava flows erupted from Haleakala Volcano on the Island of Maui in Hawai'i. Ages of the flows range between 365±40 years to 52,900±1800 years BP, as determined by 14C dating and comparisons to paleomagnetic directions between flows. Sherrod et al. [JGR, 111, 2006], and Herrero-Bervera and Valet [PEPI, 167, 2007] have previously undertaken paleomagnetic investigations of these lava flows. Few rock magnetic experiments, however, have been done on samples from these flows other than alternating field (a.f.) and thermal demagnetization experiments. Thus, we have performed saturation isothermal remanent magnetization (SIRM), hysteresis loop, coercivity, and Curie-point determinations for the lava flows in question, using a variable field translation balance (VFTB) instrument. The results indicate that 90 percent of the magnetic grain sizes are within the pseudo- single domain (PSD) range, with the remainder being of either single domain (SD) or multi-domain (MD) grain size. Curie point determinations have identified diverse magnetic mineral phases ranging from Ti-rich, pure magnetite to Ti-poor magnetite grains within the lava flows. After the performance of these rock magnetic experiments, in addition to a.f. and thermal demagnetization procedures, we conclude that only about 10 percent of the flows are suitable for absolute paleointensity determinations using the Thellier method.