<i>MINERALOGICAL </i>AND GEOCHEMICAL FEATURES OF THE "JOHN STONE" - A BLOCK OF METACONGLOMERATE IN EPICENTER OF THE TUNGUSKA EVENT OF 1908
Mineralogical-petrographic and geochemical study has revealed the terrestrial origin of the large block of quartz meta-conglomerate from the vent of paleovolcano located near epicenter of the Tunguska event of 1908. This investigation has allowed restoring the hidden history of pre-catastrophe hydrothermal-metasomatic alterations of the Upper Permian conglomerates of Pelyatkinskaya formation: their fragment is represented by the «John stone». Its alterations took place under influence of reduced juvenile fluids with crystallization of telluric native iron, as well as Ni, Pb, Zn, REE bearing minerals and the newly-formed hydrothermal zircon.