The article presents the first data on biotite-hornblende lamprophyres discovered at the Peshchernoe gold deposit. We consider the geological position of lamprophyre dikes in the deposit structure and the relationship of these rocks with tectonically weakened and mineralized zones. The data on the structural position of mineralized zones, faults, dike bodies, metasomatic halos, and host volcanogenic-sedimentary rocks confirm the tectonic nature of the Peshchernoe deposit alteration system. Lamprophyre dikes are pre-ore, as evidenced by the superimposed metasomatic mineral associations. We assume that dikes of andesitic rocks, lamprophyres, and subsequently hydrothermal fluids, including ore-bearing ones, were intruded along the fault zone of northeastern strike at different geological times. The description of mineralogical and chemical transformations of lamprophyres, which occurred as a result of alteration, is given. Two stages of metasomatism are distinguished: carbon dioxide (beresitization-listvenitization) and subsequent alkaline (sodic metasomatism). During carbon dioxide metasomatism, dark-coloured minerals are replaced by chlorite, albitization and sericitization of plagioclase occur, and ferruginous dolomite is formed under the influence of a signifi-cant supply of CO2. Alkaline (sodic) metasomatism is superimposed on the mineral metasomatic paragenesis of the first stage. We consider metasomatic zoning during sodic metasomatism, manifested in one of the spessartite dikes. Chlorite and relics of magmatic dark-coloured minerals are replaced by magnesite, the supply of Na leads to the appearance of newly formed albite, and the supply of S leads to the formation of pyrite, which concentrates iron from other minerals. As a result of the sodic metasomatism, iron content in carbonates decreases in the direction from the outer metasomatic zone to the inner one. We conclude that it was the alkaline-sulphide sodium solutions that performed the ore-bearing function, and beresitization and listvenitization prepared a favourable environment for ore deposition.
The results of the chemical composition of platinum minerals from ore body and placers of Nizhni Tagil massif of Ural Platinum Belt are summarized in the given article. Peculiar properties of the chemical composition of the platinum group minerals from ore body and placers are established and described. X-ray analysis data of the most common mineral species was ob-tained and the internal structure of granular aggregates and mono crystals was studied with due regard to the various irregularities.
In 1826 two unique icons were delivered to Saint Petersburg Mining Cadet corps from Zlatoust. They were named composed icons because of their background composed of different Ural stones. These icons have become the objects of the historical analysis which results are presented in this article. The documents which are kept in the Saint Petersburg and Zlatoust archives served as a basis for icons history reconstruction. The article describes the story of malachite and corund blocks delivery to the museum of the Cadet corps. This story is based on the information which was found in the one of archival documents.
