Sergey Ivanov's homepage

Research

My research project is concerned with the Kumtor lode gold deposit in theTien-Shan Mountains of the Kyrghyz Republic, one of the ten largest gold deposits in the world (288 t of gold). 

The primary objectives of the research include understanding the evolution of fluids in the hydrothermal system, and identification of the chief controls on the location of the metasedimentary-hosted vein mineralization. 

Mineralization occurs in the hangingwall of a second or third-order regional shear zone, is hosted in a Neoproterozoic carbonaceous phyllitic sequence, and consists of multistage veins, stockwork, hydrothermal breccias, and associated pervasive alteration. Parallel to the phyllitic foliation quartz-carbonate veins, and later carbonate-quartz tension gashes veins are related to the ductile deformation coeval to the lower greenschist peak metamorphism and brittle-ductile deformation, respectively, and are barren. They preceded auriferous mineralisation, which is related to brittle deformation and occurred late in mineral paragenetic and deformational histories of the region crosscutting the three deformational fabrics developed in the host rocks. The latter constraints maximum relative mineralisation age to Late Paleozoic. 

The auriferous veins and alteration chiefly consist of quartz, carbonates, potassic and sodic feldspars, sericite, chlorite, hematite, and barite. Four main stages of auriferous mineralization different in composition and style have been recognized based on crosscutting and overprinting relationships of veins and alterations. Later stages tend to be progressively enriched in pyrite and carbonates, whereas depleted in quartz and potassium feldspar. Intense stockwork and hydrothermal breccia development are more common for later stages. 

Gold minerals include its native form and gold and gold-silver tellurides, are intimately related with pyrite and occur in two main modes: primary inclusions in pyrite grains and texturally late phases forming films and filling fractures in pyrite. The textural relationships of the auriferous minerals with pyrite, hematite, magnetite and barite indicate that an increase in oxygen fugacity may have been important in gold deposition from the auriferouis fluids. 

The oxygen stable isotopes geothermometry based on the quartz-hematite/magnetite pairs has indicated temperatures ~300°C for the Stage 2. Also, the d¹⁸O values for quartz from Stage 2 veins are higher and less variable (15.4+/-0.65‰, n=14) than those for Stages 3 and 4 (11.4+/-1.8‰ , n=8);d³⁴S values for pyrite from Stage 2 (-0.6 to 1.6‰, n=7) exhibit a tighter range than for Stages 3 and 4 (-1.1 to 3.1‰, n=7). 

The isotopic and mineralogical differences between stages indicate changes in physicochemical environment of the evolving hydrothermal system, which possibly included variations in P-T conditions and/or associated changes in the fluid chemistry by the means of influx of different fluids, interaction with the host rocks, or fluid unmixing. 

In order to more rigorously constrain the nature of these processes, mechanisms of gold deposition, and fluid sources more data on fluid inclusions, stable isotopes of carbon, oxygen, hydrogen and sulfur, and detailed microscopical and quantitative data on mineral assemblages are needed. These data, when coupled with absolute and relative time limits on mineralization will provide important constraints on its relationships to the geological processes operative at a regional scale, a link that is now poorly understood for the gold mineralization in the Tien-Shan. This knowledge can also have applications for the metasedimentary-hosted lode gold mineralisation in other geologically similar terrains worldwide.

My research forms a part of a larger study.  Albert Abeleira,  another graduate student at the Department of Geological Sciences, U of S, focuses on regional-scale aspects of Kumtor's geology.  Kevin Ansdell is both my and his supervisor.  

The research is sponsored through an NSERC-Cameco grant to Kevin Ansdell.