Magnetism and anisotropy of magnetic susceptibility of gabbroids of the Volodarsk-Volynskyi massif of the Korosten pluton of the Ukrainian Shield

• Datum: 2025
• Hauptverfasser: Bakhmutov, Volodymyr, Mytrokhyn, Oleksandr, Cherkes, Semyon, Poliachenko, Ievgen
• Format: Artikel
• Sprache: Ukrainisch
• Veröffentlicht: S. Subbotin Institute of Geophysics of the NAS of Ukraine 2025
• Schlagworte: anisotropy of magnetic susceptibility; rock magnetism; Korosten pluton; Volodarsk-Volynskyi massif; Palaeoproterozoic
• Online Zugang: https://journals.uran.ua/geofizicheskiy/article/view/335689
• Назва журналу: Geofizicheskiy Zhurnal

We studied the magnetic parameters of more than 500 samples of Palaeoproterozoic anorthosite-mangerite-charnockite-granite complexes of the Volodarsk-Volyn massif. The massif was formed about 1.76 billion years ago and corresponds to the main anorthosite phase of the Korosten Pluton. By the average values of magnetic susceptibility and natural residual magnetisation, anorthosite and gabbro are indistinguishable within the standard error, but the latter is much smaller in gabbro. Magnetic susceptibility values >10‒3 SI characterize more than 90 % of the studied samples of gabbroids, which indicates the advantage pivotal part of the ferromagnetic component in magnetic properties of rocks. Granitoids are relatively depleted in the ferromagnetic minerals. Their magnetic susceptibility and natural residual magnetisation are, on average, half as small. Near-stoichiometric magnetite in the rocks has been confirmed. The single-domain and pseudosingle-domain grains of magnetite are the best carriers of the characteristic component of remanent magnetisation, as have been shown in previous investigations. For the first time, data on the anisotropy of magnetic susceptibility have been obtained for the anorthosite-mangerite-charnockite-granite rocks of the Korosten Pluton. They mainly indicate magnetic textures typical of plutonic rocks. For gabbro, the directions of the main axes of the anisotropy of magnetic susceptibility ellipsoids are well grouped, while for anorthosites the directions have large 95 % confidence angles, complicating further interpretation. Magnetic textures directions in gabbro are consistent with magmatic lineation and foliation, which are crucial in understanding flow mechanism and emplacement history of plutons. Further study of the magnetic texture of gabbro (and partly granitoids) in different parts of the pluton can be extremely useful for obtaining important information about the directions of magma intrusion. The anisotropy of magnetic susceptibility results can be used to select reliable palaeomagnetic directions for calculations of palaeomagnetic poles. The combined magnetic parameters of magnetic susceptibility and natural residual magnetisation can be used to model magnetic anomalies.