The Bikkulovskoe manganese deposit (South Urals): Geological setting,composition of metalliferous rocks,and formation model |
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| Authors: | A I Brusnitsyn I G Zhukov V N Kuleshov |
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| Institution: | 1.Faculty of Geology,St. Petersburg State University,St. Petersburg,Russia;2.Institute of Mineralogy, Ural Division,Russian Academy of Sciences,Miass, Chelyabinsk oblast,Russia;3.Geological Institute,Russian Academy of Sciences,Moscow,Russia |
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| Abstract: | The results of investigation of the Bikkulovskoe manganese deposit confined to volcanosedimentary piles of the Magnitogorsk
paleovolcanic belt are presented. The paper characterizes the geological setting of the deposit and mineral-chemical compositions
of ores and enclosing rocks (volcanomictic sandstones; ferruginous, manganiferous, and ferruginous-siliceous tuffites; and
jasperites). Analysis of the data obtained made it possible to identify four sequential stages of deposit formation: (1) accumulation
and diagenesis of ore-bearing sequences (D2–3); (2) burial and low-grade (T = 200–250°C, P = 2 to 3 kbar) regional metamorphism of rocks (D2–3-C1); (3) tectonic deformations of volcanosedimentary piles (C2-P); and (4) hypergenesis and partial denudation of rocks (MZ-CZ). According to the model proposed for the accumulation of
ore-bearing rocks, the productive member was formed in a zone of hydrothermal solution outflow to the seafloor surface. Discharge
of solutions and precipitation of Fe and Si began below the seafloor surface (rather than above the surface) in the near-bottom
sequence of volcanomictic sediments. Upon reaching the seafloor, the impoverished solutions mixed with seawater and gave up
metals completely: Fe and Mn were transferred to sediments to make up the ore-bearing bed. Thus, zonal sediments with ferruginous
tuffites at the base and manganese ores at the top were formed. |
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