『Abstract
The results of investigation of the Bikkulovskoe manganese deposit
confined to volcanosedimentary piles of the Magnitogorsk paleovolcanic
belt s\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); burial and
low-grade (T = 200-250℃, P = 2 to 3 kbar) regional metamorphism
of rocks (D2-3-C1);
(3) tectonic deformation 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.』
(Introduction)
Geological wetting of the Bikkulovskoe deposit
Mineral composition of manganese rocks
Chemical composition of metalliferous sediments
Isotopic composition (δ 13C, δ18O) of carbonates
in manganese rocks
Method of isotope analyses
Isotope data and their interpretation
Discussion
Model of the formation of ore-bearing rocks
Conclusions
Acknowledgments
References