EarthRef.org Reference Database (ERR) -- Stokking & Tauxe 1990

We synthesized hematite under controlled conditions of the applied magnetic field in order to test the behavior of chemical remanent magnetization (CRM) predicted on the basis of theories developed to explain thermoremanent magnetization (TRM). We restrict this investigation to the remanence acquired during mineral crystallization (grain-growth CRM) and do not consider chemical remanence acquired during mineral alteration. The material produced by our technique is hematite, up to 10 ¿m in diameter. Thermal demagnetization to 200 ¿C removes the viscous component acquired under identical field/temperature conditions to those prevalent during synthesis. As predicted by analogy to TRM, the CRM acquired parallels the orientation of the magnetic field applied during growth. The intensity of chemical remanence is a linear function of the field in which it grew, BCRM, up to 7.5 mT, the maximum growth field investigated. Furthermore, the ratio of intensities of CRM to TRM acquired in the same field is independent of the strength of that field. The intensity of BCRM controls the growth and orientation of hematite crystals, a result not predicted from theory derived by analogy to TRM. The control on crystal growth by the field is reflected in the dependence on BCRM of the orientation of ellipsoids of anisotropy of isothermal remanence and the acquisition of isothermal and anhysteretic remanence. ¿ American Geophysical Union 1990 We synthesized hematite under controlled conditions of the applied magnetic field in order to test the behavior of chemical remanent magnetization (CRM) predicted on the basis of theories developed to explain thermoremanent magnetization (TRM). We restrict this investigation to the remanence acquired during mineral crystallization (grain-growth CRM) and do not consider chemical remanence acquired during mineral alteration. The material produced by our technique is hematite, up to 10 ¿m in diameter. Thermal demagnetization to 200 ¿C removes the viscous component acquired under identical field/temperature conditions to those prevalent during synthesis. As predicted by analogy to TRM, the CRM acquired parallels the orientation of the magnetic field applied during growth. The intensity of chemical remanence is a linear function of the field in which it grew, BCRM, up to 7.5 mT, the maximum growth field investigated. Furthermore, the ratio of intensities of CRM to TRM acquired in the same field is independent of the strength of that field. The intensity of BCRM controls the growth and orientation of hematite crystals, a result not predicted from theory derived by analogy to TRM. The control on crystal growth by the field is reflected in the dependence on BCRM of the orientation of ellipsoids of anisotropy of isothermal remanence and the acquisition of isothermal and anhysteretic remanence. ¿ American Geophysical Union 1990