Anisotropy of magnetic susceptibility and rock magnetism of high-grade rocks from Eastern Ghats Mobile Belt, India: Constraints to tectonics.

The present study deals with the Fe–Ti oxides, rock magnetic and anisotropy of magnetic susceptibility (AMS) carried out to determine the magneto-mineralogical characteristics and the nature of the magnetic fabrics of the high-grade metamorphic rocks from Chilka Lake area, Eastern Ghats Mobile Belt (EGMB), India. Petrography depicted the presence of both primary and secondary magnetite and titano-magnetite as the chief magnetic minerals. Different generations of magnetite were found in these rocks corresponding to different conditions of temperature that prevailed during their oxidation, having tectonic implications depicting the crustal upliftment. Thermomagnetic analysis, isothermal remanent magnetization (IRM), hysteresis loops and backfield IRM demagnetisation show the presence of ferrimagnetic minerals of different origin. The magnetic domain is determined by Day plot, using the remanence and coercivity values from hysteresis curves, dominated by stable single domain (SSD), which reveals the potentiality to record the ancient magnetic field. AMS studies unravelled the nature of the magnetic fabrics in the region. The magnetic susceptibility ellipsoids are dominantly oblate as revealed from the Pj–Tj shape plots. The magnetic lineation is highly variable which states the multiple phased tectono-metamorphic conditions. The similarity between the magnetic and mesoscopic fabrics in the granulite is significant, whereas the anorthosites result from felsic magmatism, which occurred after the deformational phases and thus did not record any mesoscopic tectonic significance. [ABSTRACT FROM AUTHOR]