Magnetic mineral characterization of the easternmost Indus Molasse sedimentary succession, Ladakh Himalaya: Implications for depositional environment and provenance

Rock magnetic analyses of easternmost Indus Molasses of Nyoma–Rhongo section, Ladakh Himalaya have been performed. The thermomagnetic curve gives Curie point (Tc) information on the constituent magnetic minerals, which vary between 574° and 592°C. The hysteresis loops are harmonious and the resultant remanence ratio (Mrs/Ms) ranges between 0.10 and 0.19 and the coercivity ratio (Bcr/Bc) between 1.91 and 3.07. The domain states of magnetic grains majorly belong to the pseudo-single domain (PSD) state. The isothermal remanent magnetization (IRM) acquisition curves show saturation ranges between 250 and 300 mT, and the coercivity spectra show coercive force ranging between 24 and 41 mT. These investigations indicate that magnetic mineralogy in samples is predominantly controlled by fine to medium-sized PSD state magnetite and accessorily Ti-poor magnetite, pyrrhotite, and greigite. This magnetic mineralogy seemed homogenous and was not considerably affected by weathering, lithogenesis and geotectonic events, suggesting their deposition over well-developed palaeogeography with small-scale tectonic modulations. The best possible source for Indus Molasses, as identified in the current study is the Ladakh batholith having an affinity to the Eurasian Plate and these interpretations are in line with the literature.