Carriers of magnetism and vertical inhomogeneities in ultramafic-mafic rocks of the Kondyor Massif (Aldan shield)

• Published in: Izvestiya. Physics of the solid earth Vol. 46; no. 4; pp. 358 - 363
• Main Authors: Istomin, V. E., Prugov, V. P., Duchkov, A. D.
• Format: Journal Article
• Language: English
• Published: Dordrecht SP MAIK Nauka/Interperiodica 01.04.2010; Springer Nature B.V
• Subjects: Boreholes; Crystallization; Earth and Environmental Science; Earth Sciences; Geochemistry; Geophysics/Geodesy; Igneous rocks; Ions; Magnetic properties; Magnetism; Mineralogy; Spectrum analysis; Kondyor Massif; Aldan Shield; ESR spectra; nature of magnetism carriers; dunites; magnetic susceptibility
• ISSN: 1069-3513; 1555-6506
• DOI: 10.1134/S1069351310040087

Dunite samples from a borehole drilled in the platiniferous concentrically-zoned Kondyor Massif are studied by electron spin resonance (ESR). The spectrum profiles, relative intensities I , and volume magnetic susceptibilities κ are analyzed. These values experience strong irregular variations, sometimes by an order of magnitude, in the upper and medium parts of the column, at depths from 100 to 400 m; and the variations decay at greater depths. The magnetic properties of the samples are determined by iron (II) ions in the olivine lattice and by iron (III) ions in the magnetite and pyrrhotite microphases and in the products of breakdown of the solid solution: chromiferous magnetite, chromoferrite, etc. The I and κ values are directly related: κ max = 27.8 × 10 −3 SI units, κ min =2.63 × 10 −3 SI units, and κ mean = 12.7 × 10 −3 SI units. The maximum κ values are found in the zones with elevated contents of magnetite and pyrrhotite particles, and the minimum ones, in zones with few medium and small clusters with Fe 3+ ions. The uneven distributions of solid solutions and magnetic phases over depths are suggested to be related to the disturbances in the conditions of crystallization.