Petromagnetism of ores and host rocks in the Southern Omolon ore district (Northeast Russia)

• Published in: Russian journal of Pacific geology 2015-07, Vol.9 (4), p.312-321
• Main Authors: Ivanov, Yu. Yu, Minyuk, P. S., Tret’yakova, N. I., Kolesov, E. V., Fomina, M. I.
• Format: Article
• Language: English
• Subjects: Earth and Environmental Science; Earth Sciences; Geology; Hydroxides; Magnetic properties; Magnetism; Petrology; Quartz; Rock properties; Rocks
• ISSN: 1819-7140; 1819-7159
• DOI: 10.1134/S181971401504003X

The petromagnetic properties of rocks from the Verkhnii Omolon, Magnetitovyi, Innyaga, and Alekseeskii areas of the Southern Omolon iron-ore district located in the southern part of the Omolon Massif (Northeast Russia) are investigated. The maximum values of natural remanent magnetization (NRM) and magnetic susceptibility ( k ) of 22.8–1196 A/m and 1046 × 10 –3 SI on average, respectively, are typical of ferruginous quartzite from the Innyaga site. The amphibolites exhibit high values of these magnetic parameters: J n is approximately 28.6 A/m and k is 45 × 10 –3 SI. The magnetic properties ( J n and k ) of the plagiogneisses and granite gneisses are highly heterogeneous and variable. The migmatites, rhyolites, and dacites are submagnetic. Magnetic minerals are largely represented by multidomain and pseudosingle-domain magnetites and their oxidation products such as maghemite, hematite, and iron hydroxides. It is revealed that the amphibolites are characterized by normal polarity of the remanent magnetization, while the ferruginous quartzites demonstrate normal and reverse polarities. These rocks may serve as sources of magnetic bipolar anomalies.