Quartz veins and silver-containing crushing zones in the exocontact of Solur granite stock (Kularsky district, Yakutia)

Abstract

The purpose of the work is a investigation of quartz varieties present in quartz veins and crushing zones in order to establish the formation conditions and the possibilities of using quartz varieties to study the distribution of mineralization during exploration. The work was stimulated by the discovery of gold and gold-silver mineralization in adjacent areas and the possibility of using some new methods for studying quartz. Research methods. Samples for the study were taken during the mineralogical mapping of the studied area in the course of work to assess the prospects for its ore potential. The characterization of quartz from veins and crushing zones was carried out on the basis of its field descriptions and laboratory microscopic study, as well as measurements of X-ray luminescence (RL) of vein quartz in the region of 350–550 nm. Fluid inclusions in quartz and sulfur isotope composition in sulfides from quartz veins were also studied. Results and conclusions. The granite stock, surrounded by a zone of contact hornfels with cordierite and andalusite, lies among terrigenous sedimentary rocks that have undergone metagenesis (anhimetamorphism). Veins of glassy coarse-grained quartz and recrystallized (granular) quartz are located directly in the granites, partially recrystallized gray quartz – among the contact cornea, and veins of deformed milky-white quartz - in terrigenous sedimentary rocks outside the contact halo. As the transition from veins located among granites to veins located outside the granite massif, the intensity of quartz RL decreases sharply. The nature of the RL indicates the probable presence in the crystal lattice of quartz from veins in granites of their own defects – vacancies of oxygen or silicon, and in gray and milkywhite quartz – cation-compensated [AlO4 /M+]-centers. Sulfide mineralization in quartz veins is mainly represented by arsenopyrite with an isotopic composition of sulfur close to the meteorite standard. In addition to quartz veins, later crushing zones with hydrothermal injection breccias are also common in the area. In breccia cement and in breccia-intersecting veins, early non-split hypidiomorphic quartz and later split comb-shaped and chalcedony quartz are present. In micro-cryptogrаined chalcedony quartz with grain size up to 0.05 mm contaminated with inclusions of finely crushed rock particles and kaolinite grains, the inclusions of the pyrargyrite – one of the main silver-containing minerals on a number of gold-silver deposits of the region – were found. Based on the known vertical zonality of epithermal gold-silver deposits with the confinement of kaolinite-containing ores and chalcedony quartz to the upper horizons of the deposits, and due to the presence of micro-cryptograined chalcedony quartz containing kaolinite and pyrargyrite in the considered crushing zones, it can be suggested that these crushing zones may be confined to the upper parts of the silver mineralization development zone.