MAGNETIC CHARACTERISTICS OF METAMORPHIZED ULTRABASITES OF THE OCEANIC LITHOSPHERE

Abstract

As part of the study of the nature of magnetic anomalies associated with the deep layers of the oceanic crust, a comparative analysis was made of the petromagnetic characteristics of serpentinized mantle ultrabasic samples taken from oceanographic expeditions of the Institute of Oceanology and the Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences in various morphotectonic regions of the World Ocean. The purpose of the work is to obtain information on the composition, concentration, crystallization temperature and structural features of ferromagnetic minerals, which are formed in different conditions of the post-magmatic metamorphism of ultrabasites. Sample collections are divided into three groups. 1. Oceanic peridotites from the rift zones of the mid-ocean ridges and transform faults. 2. Peridotites of the submarine ridge Gorringe, located within the Azoro-Gibraltar zone of faults. 3. Dunites of the Pekulney complex (Chukotka) formed in the island arc system. It has been established that in all selected regions, samples of serpentinized hyperbasites have high values of natural residual magnetization, magnetic susceptibility and saturation magnetization. The highest values of magnetic parameters are the dunites of the Pekulney complex. Estimation of the dependence of the concentration of ferrimagnetic materials C% of the degree of serpentinization of the SS%. showed that it is practically of little significance. The main factors contributing to the increase in the concentration of magnetite are the increased iron content of olivine in ultrabasites and the temperature of metamorphism. The question of the period of formation of magnetites and the stability of their primary residual magnetization requires further study.