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    STUDIA GEOLOGIA - Ediţia nr.1 din 2007  
         
  Articol:   SULFUR ISOTOPES OF PRECAMBRIAN SULFATES AND SULFIDES IN THE FEDOROVSKAYA FORMATION (ALDAN SHIELD, YAKUTIA).

Autori:  VASYL’ M. GULIY, ALLA V. YAKYMYUK. 		 
       
         
  Rezumat:  The isotopic analyses of Precambrian sulfates and sulfides may provide important information about the chemical compositions of Precambrian oceans with respect to the evolution of the Earth’s biosphere and atmosphere. Sedimentary sulfates in Precambrian rocks are direct evidence that free oxygen was an important component in the atmosphere-hydrosphere system at that time and they may be reflections of evaporite deposition in old sedimentary basins. Rocks with sulfates were early identified in the Fedorovskaya Formation on the Aldan Shield by Vinogradov et al. (1975). Geological exploration works at the Seligdar apatite deposit and prospecting of analogous objects in other sectors of the Aldan Shield revealed a wide distribution of sulfur-containing phases in metamorphic sedimentary rocks of the Fedorovskaya Formation, which are represented by carbonate and calc-silicate varieties. They conformably intercalate with gneisses and crystalline schists and have similar structural styles. The rocks are metamorphosed to the granulite and amphibolite facies, and their U-Pb age is 1.8 – 2.0 Ga.  
         
     
         
         
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