Abstract

Manganese deposits of Balaghat belt of Madhya Pradesh, India, occur as shear parallel quartz-manganese interlayers restricted within the mylonite zones of the area. The interlayered ore bodies, along with the shear planes, maintain a co-axial, non-coplanar relationship to the S₁ schistosity of the country rock. They also exhibit folding along S₂ and S₃ axial trends and attain a sinuous map pattern. These ore bodies also show widespread felspathization of the wall rocks and pneumatolytic activity along their periphery, resulting in the development of tourmaline, apatite, chlorite, fibrolite bearing quartz-mica schists/ gneisses. Dimensional orientation of the constituents of the ore bodies along ‘S’ and ‘C’ planes of the mylonites is characteristic with all the deposits, indicating ductile to brittle ductile movement along these mylonites.
It is envisaged that the rocks of the area, belonging to Sausar Group of metamorphites, were subjected to shearing during late D₁ deformation. These shear zones were then occupied by hydrothermal bodies related to late D₁ pink magmatism. These hydrothermal bodies were either rich in residual manganese, or scavenged manganese oxides from the manganese silicates of the country rock. The calcium rich manganese silicates ‘Gondites’ are possibly produced by interaction between the felspathic components of the hydrothermal bodies with the manganese oxides and the randomly occurring calc-silicate enclaves of biotite gneiss. The hydrothermal hypothesis towards the origin of manganese explains satisfactorily the anomalous occurrence of high temperature oxide ores with intergrowth textures in the low temperature region of Sausar metamorphites. It also explains the absence of other members of the Sausar metamorphites from the so called ‘narrow furrows of deposition’ as advocated for the biotite gneiss hosted manganese deposits

Keywords: Mylonites; Pink magmatism; Hydrothermal emplacements; Boron metasomatism;Griesening; Gondite.