MINERALOGICAL AND GEOCHEMIСAL FEATURES OF CHALCOPYRITE FROM THE YUBILEYNOE MASSIVE SULFIDE DEPOSIT (SOUTH URALS): LA-IСP-MS DATA

Abstract

Relevance. The LA-ICP-MS analysis of sulfides is one of the promising directions in study of ore deposits. The understanding of mineralogical-geochemical evolution of sulfides allows interpretation of differentiation of components at stages of hydrothermal sedimentogenesis and further lithogenesis of massive sulfide deposits. This work is important for development of models of sulfide authigenesis. The main aim of the research is to compare mineralogical-geochemical features of chalcopyrite types to identify the evolution of sulfide ores from the Yubileynoe massive sulfide deposit (South Urals). Methods. The morphogenetic types of chalcopyrite were identified using ore-facial mapping in the open pit of the deposit. The mineralogical features of ores were studied under an Olympus BX51 optical microscope. The chemical composition of minerals was analyzed on a Tescan Vega 3 SBU scanning electron microscope equipped with an Oxford Instruments X-act energy dispersive analyzer. The trace element contents of chalcopyrite were determined using LA-ICP-MS on an Agilent 7700x mass spectrometer equipped with a New Wave Research UP-213 laser ablation device at the SU FRC MG UB RAS and University of Tasmania (Hobart, Australia). Results. Chalcopyrite was subdivided into two genetic types: hydrothermal and post-sedimentary. The hydrothermal type includes subhedral chalcopyrite from chalcopyrite-pyrite, chalcopyrite-pyrite-sphalerite, and sphalerite-pyrite-chalcopyrite smoker chimneys. The post-sedimentary type of pseudomorphic, interstitial, nodular, and veinlet (dynamometamorphic) chalcopyrite is typical of clastic ore. Each chalcopyrite type is characterized by various mineral assemblages and trace element contents, reflecting different formation conditions. Themorphology of chalcopyrite changes from spear-like and dendritic crystals to graphic and epitaxial intergrowths of chalcopyrite and sphalerite in a range from chalcopyrite-pyrite to mostly sphalerite smoker chimneys. The median contents of high-temperature (Se, Bi), medium-temperature (Te, Sb) and low-temperature (Tl) trace elements of hydrothermal chalcopyrite decrease in this range. The post-sedimentary chalcopyrite has the lower Sn contents and exhibits minor variations in Se contents. The median Mn, Co, Ni, Mo, As, Tl, Au, Ag, Bi, and Te contents decrease in a consecutive range of post-sedimentary chalcopyrite: pseudomorphic→interstitial→nodular→veinlet.

Keywords

• chalcopyrite
• authigenesis
• la-icp-ms
• smoker chimneys
• sulfide turbidites
• sulfide nodules
• massive sulfide deposits
• south urals