Geophysical research: article

The effect of chemical magnetization on the paleointensity determined by the Thellier method: experimental study on titanomagnetite-containing basalts
S. Gribov
Borok Geophysical Observatory of Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Borok Yaroslavl region, Russia
Journal: Geophysical research
Tome: 18
Number: 1
Year: 2017
Pages: 37-48
UDK: 550.382
DOI: 10.21455/gr2017.1-3
Full text
Keywords: titanomagnetites, oxyexsolution, chemical remanent magnetization, Thellier method, paleointensity
Аnnotation: The simulation of the Thellier-Coe paleointensity experiments was performed on laboratory oxyexsolved titanomaghemite-bearing basaltic samples with either a separately created chemical remanent magnetization (CRM) or a partial thermoremanent magnetization (pTRM) or a combination of both. It is shown that the Thellier method makes it possible to determine the magnetic field of ‘pure’ pTRM with an error not exceeding 10 %. In contrast, the field estimate for CRM by this method is understated by 40-60 % relative to the true value. At the same time, however, CRM cannot be distinguished from TRM on the Arai-Nagata graphical construction of the stepwise heating Thellier-Coe procedure. In the paleomagnetic aspect, all of this means that igneous rocks containing magnetite formed through oxyexsolution of highly cation-deficient titanomagnetites and carrying thermochemical magnetization may be the source of a significant error in determination of the paleointensity of geomagnetic field by the Thellier method when a natural CRM is not recognized and is mistakenly interpreted as a TRM in the Thellier-type experiments.