Discrimination of TRM and CRM by blocking-temperature spectrum analysis

Overlap of blocking-temperature spectra can be caused by three factors: chemical overprinting, the presence of partial thermoremanences (PTRM's) in two coexisting magnetic minerals, and the presence of PTRM's in coexisting multidomain and single-domain states of the same mineral. Multidomain relaxation mechanisms are not well understood and therefore quantitative estimates of overlap due to the coexistence of single-domain and multidomain states of the same mineral cannot be made, although it is evident that such overlap may be large. The maximum overlaps which would be expected at various temperatures due to coexisting single-domain magnetite and hematite are calculated. Where it can be shown that multidomain remanence is negligible, blocking-temperature overlaps which exceed these limits are, therefore, indicative of CRM overprinting.