Geochronology of Alkaline Rocks of the Aryskan Rare Metal Deposit,East Sayan

Doklady Earth Sciences - The temporal relations between alkaline rocks of the Aryskan rare metal (Y, REEs, Nb, Ta) deposit are determined using metamict zircon with high U and Th contents, which...     

Paleoarchean orthopyroxenites of the Bug granulite–gneiss domain at the Ukrainian shield

This report presents data on the geological structure and location of the orthopyroxenite inclusion in gneissic enderbites of the Bug granulite–gneiss domain. Three stages of orthopyroxenite formation were identified on the basis of studies of the mineral composition along with the U–Pb and Lu–Hf isotope systems of zircons.     

Isotopic-Geochemical Features of Zircon and Its Significance for Reconstructing the Geological History of Paleoarchean Granulites in the Ukrainian Shield

This paper presents the results of a complex study (morphology of grains, internal texture in cathodoluminescence and backscattered electrons, microprobe analysis, Lu–Hf data) of five groups (generations) of zircon crystals differing in age and separated from the same granulite sample pertaining to the Bug River Complex of the Ukrainian Shield. The data show that the oldest zircon crystals of the first group (3.74 Ga in age) are xenogenic and initially crystallized from a granitic melt; zircon of the second group (3.66 Ga) formed from a mafic melt contaminated by felsic country rocks. The third group (3.59 Ga) is represented by zircons that formed about 100 Ma later than the second group under conditions of granulite-facies metamorphism and with the participation of fluid-saturated anatectic melt. Two Paleoproterozoic zircon groups (~2.5 and 2.1 Ga) also formed under granulite-facies conditions; to a certain extent, their structure and composition were controlled by fluid. The geochemistry of all zircon generations provides evidence for their crystallization in the continental crust, but from the sources differing in the contribution of mantle-derived material and in oxygen fugacity.     

U–Pb SHRIMP II age and origin of zircon from lhertzolite of the bug Paleoarchean complex,Ukrainian Shield

Complex study of the U–Pb and Lu–Hf systems of zircon from a lhertzolite lens of Archean gneiss enderbites of the Bug complex, Ukrainian Shield, showed that ultramafic magma was contaminated by the material of the country gneiss enderbites. The age of the zircons of 2.81 ± 0.05 Ga corresponds to the period of ultramafic magmatism within the Bug complex. Previously, this peak of endogenic activity was considered the stage of manifestation of metamorphism and magmatism of mafic composition.     

Paleoarchean U–Pb (SIMS SHRIMP-II) Age of Mafic Granulites from the Bug Complex,Ukrainian Shield

Doklady Earth Sciences - Data on the U–Pb (SIMS SHRIMP-II) age (3628 ± 38 and 2845 ± 65 Ma) of zircon from the inclusion of mafic granulite in gneiss–enderbites of the Bug...     

Distribution of Moderately and High-Siderophile Elements in Sulfides as a Basis for Reconstructing the Evolution of the Archean Harzburgite of the Bug Complex,Ukrainian Shield

Geology of Ore Deposits - We studied the regularities of distribution of siderophile elements, including platinum group elements (PGE), in rock and in sulfides from Archean (2814 ± 51 Ma)...     

Wolframoixiolite in Lithium–Fluorine Granites of the Arga–Ynnakh–Khaya Pluton,Yakutia

Geology of Ore Deposits - A complex of accessory W-bearing tantalo-niobates (columbite-(Fe), columbite-(Mn), tantalite-(Mn), microlite group minerals, and Ta-bearing rutile) involving...     

An Extreme Concentration of Isomorphic Tantalum in Cassiterite from Lithium–Fluoric Granites (Arga-Ynnakh-Khaysky Massif,Yakutia)

Doklady Earth Sciences - The phenomenon of an abnormally high concentration of tantalum (5.3–17.9% of Ta2O5) in accessory cassiterite from lithium–fluoric granites of the...