ИСТИНА

One of the threats to obtain incorrect paleointensity (PI) data is the risk to misidentify NRM as TRM while in reality the studied rock carries CRM or TCRM. The danger is aggravating by the inability to distinguish CRM (TCRM) from TRM by any known means including the Thellier procedure. It was shown experimentally (Draeger et al., 2006; Gribov et al., 2017) that PI values determined from samples carrying laboratory induced CRM underestimate PI about 2 times. But equally important kind of chemical remanence, TCRM, created during slow cooling of igneous rocks due to oxidation of titanomagnetites was not investigate. Here we report results of such studies performed on laboratory. TCRM was created in a thermomagnetometer first by quick heating to 570 C following by slow cooling in air at rate of 1 C/hour in the presence of an external field of B = 50 μT. A complex magneto-mineralogical studies, comprising electron microscopy and X-ray diffractometry, have shown that creation of TCRM is associated with the formation of highly oxidized titanomaghemites and the magnetite due to their exsolution. Simulation of the Thellier method on these samples revealed that the application of this technique to samples carrying TCRM yields a magnetic field very closed to the true one giving the error of determination not more than 6 %. This result radically differs on that of obtained for the CRM and provides a good hope that contrary to the common fears, TCRM and TRM may be equivalent sources for true paleomagnetic information.