Tarasov Yaroslav Alekseevich
@diamond.ysn.ru
Laboratory of Geology and Mineralogy of Precious Metals
Diamond and Precious Metal Geology Institute, Siberian Branch, Russian Academy of Sciences
RESEARCH, TEACHING, or OTHER INTERESTS
Geology
Scopus Publications
Scopus Publications
Lena Polufuntikova, Valery Fridovsky, Yaroslav Tarasov, and Maksim Kudrin
IOP Publishing
Abstract The article presents the results of studying the sulfidization zone of the Charky-Indigirka thrust fault within the Vyun ore field in the Upper Adycha sector of the Yana-Kolyma metallogenic belt. The purpose of the research is to study the composition and distribution of basic and trace elements in terrigenous rocks of the Upper Triassic and Middle Jurassic, as well as in distal metasomatites on the territory of the Vyun ore field. The petrochemical features of weakly altered terrigenous rocks, conditions of their formation and changes of composition during epigenetic processes were analyzed. Three generations of pyrite were identified: diagenetic Py1, metamorphogenic Py2 and metasomatic Py3. Typomorphic trace elements and variations of their distribution in pyrites were determined. Composition analyses of weakly altered sedimentary rocks of the Upper Triassic (V/(V+Ni)=0.5-0.8, V/Cr=0.1-2.9 and Ni/Co=2.5-10.3) and Middle Jurassic (V/(V+Ni)=0.7-0.9, V/Cr=0.2-2.0 and Ni/Co=1.3-8.8) yielded the conclusion that changes in oxygen conditions to disoxic and anoxic, as well as the enrichment of terrigenous material with ore elements, lead to the formation of authigenic sulfide mineralization at the early stages of the sedimentary strata formation. The subsequent multistage development of the territory was accompanied by an active migration of chemical elements, their input and redistribution.
Valery Yu. Fridovsky, Lena I. Polufuntikova, and Yaroslav A. Tarasov
IOP Publishing
Abstract The Early Mesozoic clastic rocks the Kular-Nera terrane in the Verkhoyansk-Kolyma orogenic belt, northeast Russia, exhibit regional sulfidation zones. The most abundant mineral of the zones is pyrite. However, its origin (sedimentary-diagenetic, metamorphogenic-hydrothermal, metasomatic) and contribution to the formation of economically important gold deposits remain debatable. The localization of the sulfidation zones is still poorly understood. We have studied geological-structural and mineralogical-geochemical features of pyritization zones in bedrock outcrops on Khara-Yuryakh creek (a right-side tributary of the Nera river) within the Kular-Nera terrane, Verkhoyansk-Kolyma folded area. The pyritization zones are distant from the known gold deposits, and they extend along the Chay-Yureya regional fault. The deformation structure of the clastic rocks of the Chay-Yureya fault is defined by different-aged fold-thrust and strike-slip elements. The early deformations are isoclinal and tight folds up to a few hundred meters wide, with rounded and sharp crests and subhorizontal hinges. The early folds were refolded so that their crests may be seen on the limbs of later folds of the same NW strike. These structures were formed in the conditions of progressive deformation D1 in course of a single continuous (non-stop) tectonic regime during the frontal convergence of the Kolyma-Omolon superterrane with the eastern margin of the Siberian craton. These are commonly inclined or, more rarely, recumbent folds. Also present are late folds associated with dextral and sinistral strike-slip motions on the Chay-Yureya fault. The sulfide mineralization of the Chay-Yureya fault is represented by the disseminated idiomorphic pyrite crystals 1 to 10 mm in size. Metapyrites exhibit a cataclastic microtexture complicated by later corrosion processes. They contain zircon, rutile, and monazite microinclusions entrained in the process of growth. Microinclusions of galena, sphalerite, chalcopyrite, and other late sulfides are confined to defects in the pyrite grains. The chemical composition of pyrite was determined on the Camebax-Micro microanalyzer, using a standard X-ray spectral analysis (DPMGI, SB RAS, Yakutsk). Most of the grains have a stoichiometric composition. 30 percent of the analyses showed excess Fe. Metacrystals of pyrite demonstrate variations in the concentration of trace elements, which often leads to chemical zonality. Our investigations showed that pyritization zones of the rocks are localized in the trans-crustal Chay-Yureya fault which served as a transit path for ascending regional fluid flows. Typomorphic trace elements found in pyrites are Co, Ni, As, Sb, and Cu, with the total amount of 0.1 to 0.4%. They are characterized by the low concentrations and nonuniform distribution. Zonality in the distribution of trace elements is attributable to the poly-