ИСТИНА

We present the results of complex study of magnetic minerals composition of speleothem Vor from Vorontsovskaya cave (Western Caucasus). Paleomagnetic archive of Vor flowstone contains the record of excursion event in high temporal resolution, which enables detailed description of geomagnetic field behaviour during excursion. In attempt to characterise the magnetic composition and the nature of NRM in Vor flowstone we implemented wide range of laboratory facilities. Sampling of flowstone was performed in situ with the help of portable core drill. Several representative pieces of drill-cores were then crushed into pieces and dissolved in acetate buffer solution (4:1 ratio of 2M CH3COOH and 1M CH3COONa) in order to remove calcite fabric. Resulting insoluble residue was collected and subjected to further laboratory analyses. In addition we collected soil samples from the cave stream and surface stream, which feed the studied flowstone, and subjected them to the same analyses. Applied techniques included thermomagnetic, coercivity spectra analyses, scanning electron microscopy imaging and XRD-analysis. Results demonstrate the presence of several magnetic minerals with low (8-16 kA/m), medium (50-60 kA/m) and high (250-1000 kA/m) coercivities and smoothed broad interval of deblocking temperatures in both - speleothem and soil - samples. SEM imaging also demonstrates several-micron-sized spherical grains composed of Fe and O. We discuss the differential identification of magnetic minerals which carry the NRM and associated question about it's origin .