PARAGENESES OF MINERALS AND FORMS OF THEIR RECOGNITION REFLECTING THE STAGES OF FORMATION OF CUPRIFEROUS SANDSTONES AND SHALES DEPOSIT

Abstract

The relevance of the research. The views on the genesis of cupriferous sandstones and shales deposits have been widely discussed in subject-related literature. Even if diverse research approaches are available, the study on the parageneses of major ore minerals of deposits remains the main criterion for credibility of proposed hypotheses. The main aim of the research is to reveal the stages of formation of cupriferous sandstones and shales deposits using acquired data on the relationships between major ore minerals. Objects: deposits and ore occurrences of cupriferous sandstones and shales deposits of the Kodar-Udokan zone and comparative analysis of the obtained results on the other 74 Cu-bearing zones. Methods: geological survey for uncovering the setting, conditions of formation, specifics of structure, mineral composition of deposits and ore occurrences of cupriferous sandstones and shales, mineragraphy research of major ore minerals parageneses. Results. It was found that ore of the cupriferous and sandstones and shales deposits contains numerous minerals, which when merged, produce paragenetic associations subdivided into major, secondary and rare, and considering formation conditions classified as sedimentation-diagenetic, post-diagenetic and hypergenic ones. The minerals display diverse structural relationships (lamellar, lattice-like, counter-penetrating boundaries, subgraphic, replacements, granule, corrosion, porphyroblastic, etc.). The mostly common forms of recognizing individual minerals and their parageneses are: disseminated, spot, layer (parallel, rhythmically layered, wavy, oblique), concretion-globule, streak, rim, lens, nest, flaser, colloform, earth-powder and incrustations, reflecting the main stages for rock and ore formation of cupriferous and sandstones and shales deposits: sedimentogenesis–diagenesis–catagenesis–metamorphism–hypergenesis. Formation of minerals, their parageneses and forms of recognition are defined in sedimentogenesis by: pH value, carbonate media, lithology-facies setting, climate; in diagenesis: values of Eh and pH media of ore formation, solubility of sulfides, concentration of metals, sulphate-ions and H2S; in catagenesis and metamorphism: increased temperatures and pressures, action of metamorphic and post-magmatic solutions; in hypergenesis: reactions of oxidation and reduction, electrochemical and bacterial processes dependent on hypsometry, tectonics, lithologic features, climate, mineral composition of primary ores.

Keywords

• cupriferous sandstones and shales deposits
• paragenesis of minerals
• structure
• texture
• forms of recognition
• stages
• conditions of formation