THE COMPARATIVE-ANALYSIS OF BASALTS MAGNETIC-PROPERTIES OF MID-ATLANTIC RIDGE AND JUAN-DE-FUCA RIDGE

Amplitudes of Mid-Ocean Ridges magnetic anomalies vary in the wide range: from 500nT on Mid-Atlantic Ridge (MAR) to 1600nT on East Pacific Rise (EPR). In order to explain this difference of magnetic anomalies values, magnetic properties of two collections are considered. The basalts were sampled by MIR submersibles from Mid-Atlantic Ridge near Kane fracture zone (MAR) and from Juan de Fuca Ridge (JFR). Natural remanent magnetization (In) of JFR basalts is three times greater than that of MAR basalts. Basalts of MAR are more oxidized then basalts of JFR (Z(mar) = 0.51; Z(JFR) = 0.42). The different degree of basalts oxidation appears to be the main reason causing the difference between the magnetic properties of collections samples. In consequence of oxidation of MAR basalts titanomagnetites primary thermoremanent magnetization (TRM) was partly replaced by secondary chemical remanent magnetization (CRM) during oxidation that decrease NRM intensity. Comparison of our basalts magnetic properties with results of other investigators obtained from MAR and EPR allows us to point out at twe least certain petromagnetic provinces of modem basalts in system of rifts Mid-Ocean Ridges. The reasons that caused the differences of basalts magnetic properties from JFR and MAR, Permit to explain the low values of natural remanent magnetization of modem rift basalts, that are observed sometimes.