Abstract

Contrary to the general belief of a sedimentary origin for the manganese deposits associated with the Paleoproterozoic ‘Sausar Group’ of rocks of Madhya Pradesh, India, the evidences like-invariable association of shear zones, very glaring in satellite images, with all the manganese deposits of Madhya Pradesh; the ‘S-C’ fabric shown by the mineral constituents of the ore inter-bands; pinch and swell arrangement of the ore bodies; presence of tongues of ore bodies in wall rocks of Tirodi mines with swerving around foliation in host Tirodi biotite gneiss; and the co-axial but non coplanar relationship of the shear parallel manganese ore inter-bands with the S1 foliation of the host phyllite in Bharweli Mines; as encountered during the course of present work, is more supportive of igneous emplacement of the ore bodies within the ‘Sausar Group’ of rocks of diverse origin (granitic gneisses and meta-sedimentaries).

The affirmative ore petrography, as also detailed by earlier workers, indicate presence of high temperature ore minerals within the ore bodies exhibiting textures better suited for rocks of igneous origin. The ‘strain sensitive fabric’ exhibited by the constituent minerals of the ore bodies supports for a progressive ‘simple’ shear deformation within the shear zones hosting manganese ore deposits of Madhya Pradesh. The noncoplanar relationship of the Manganese ore inter-bands with the S1 schistosity of the country rock, their being coplanar to the shear planes, and co-folding of the ore bodies and the shear planes along S2 and S3 axial traces, points to the fact that the Sausar rocks were affected by co-axial (S1) but non coplanar shearing and hydrothermal emplacements, at the waning phase of the D1 deformation. Evidences of pneumatolysis along the flanks of such ore zones indicate igneous activity responsible for the metasomatic changes in mineral composition along the periphery of the Mn-oxide bearing hydrothermal emplacements.