Mineral Composition and Structure of the Sverdlovsk Meteorite (H4-5)

A fragment of the Sverdlovsk Meteorite, which was found in 1985 in the Central Urals, is studied by modern analytical methods. It belongs to H chondrites of petrologic type 4–5; shock stage of meteorite is S1-2, terrestrial weathering is W1. The composition of minerals of the meteorite is studied. It is found for the first time that the metal and sulfides are concentrated in fine veinlets of the recrystallized matrix of the chondrite and are accompanied by segregations of metal and troilite inside these veinlets. The distribution of trace elements of the metal phase of the meteorite is studied.

     

Nature of the Clinoenstatite Rim in Refractory Forsterite-Rich Objects from Carbonaceous Chondrites: First Results of Study by the Method of Electron Backscatter Diffraction (EBSD)

Doklady Earth Sciences - A clinoenstatite rim occurs in many refractory forsterite-rich objects; however, specialized studies of it have not been carried out. The first data from the study of...     

中亚造山带中斑岩铜钼矿的Re，Pt，Pd和Au含量

Precious metal(Pt,Pd and Au)and Re contents in rocks,ores and flotation concentrates of Siberian(Russia)andMongolian porphyry Cu-Mo and Mo-Cu deposits were studied.The following deposits are discussed:Early Devonian porphyry Mo-CuSora deposit(Kuznetsk Alatau Mountains,Russia)and porphyry Cu-Mo Aksug deposit,(northeastern Tuva,Russia);Triassicporphyry Cu-Mo Erdenetiin Ovoo deposit(northern Mongolia).The samples analyzed include unaltered host rocks of plutons,porphyryrocks of ore-bearing series,different types of altered rocks,mineral separate analyses of molybdenite,chalcopyrite and magnetite,aswell as flotation concentrates.Pt,Pd,Au and Re contents were determined using ICP/MS,AAS and inversion voltammetric analysis.PGE abundances in rocks and poorly mineralized samples span a large range from below detection limit to 65 ppb Pt and 74 ppbPd.Re concentrations in whole rock samples range from below detection limit to 89 ppb.Molybdenite has been shown to be the majorhost phase for Re.The results presented show that Aksug deposit reveals elevated PGE and Au contents in ore minerals and flotationconcentrates.High Pd contents in ores of the Aksug deposit are in accordance with the presence of palladium mineralization in the formof palladium telluride merenskyite(Pd,Pt)Te_2.The variety of precious metals and Re contents in the studied deposits could be caused by a complex interplay of several factors,including importance of primary metal concentrations derived from the source,transport of metals to the deposition area,physicochemical properties of the fluid(fo_2,pH,fs,T,P),and depositional conditions.Higher Re contents in molybdenite andchalcopyrite separates are typical for copper-rich Aksug and Erdenetiin Ovoo deposits.Rhenium concentration in sulfides frommolybdenum-rich Sora deposit is significantly lower.Highly oxidized,Cl-rich fluid style at Aksug and Erdenetiin Ovoo was favorable forhigh rhenium solubility and transport to depositional area.The occurrence of significant precious metals contents at Aksug were likelydue to:1)PGE and Au enriched source,2)favorable fluid style(high fo_2,high Cl-activity),promoting high solubility andtransportation of precious metals in ore-forming fluid as chloride complexes;3)moderately reducing depositional conditions from PGE-bearing solutions containing As and Te,facilitating PGM deposition.As for the porphyry systems at the Sora and Erdenetiin Ovoodeposits,they were probably devoid of precursors favorable for the enrichment in PGE and Au or the role of such precursors wasinsignificant.     

Finding of Refractory Inclusions in the North Kolchim Meteorite (H3)

Doklady Earth Sciences - For the first time among Russian meteorites, refractory forsterite-rich inclusions are determined in the North Kolchim meteorite (H3). Forsterite-rich inclusions are found...     

Timing of Back–Arc Spreading of the Paleozoic Island Arc of the Urals: Implication of Sm–Nd and U–Pb Dating of Dolerites and the Composition of Inclusions in Zircon

Doklady Earth Sciences - Dolerites of the parallel dikes formed in a back-arc spreading setting have been dated by Sm–Nd to the Silurian (426 ± 34 Ma) for Mount Azov in the Central...