Abstract

A review of the available literature on Sausars points to a number of disagreements amongst the workers. This includes-Stratigraphic status of Tirodi biotite gneiss; correlation of the low grade phyllite-sericite schist of Bharweli-Ukwa belt; sedimentary versus autoclastic nature of conglomerates and igneous versus metamorphic origin of the amphibolites/granulites, especially of the western part of the belt. Metacarbonate bodies present in the western part of Balaghat district and belonging to Bichua Formation of Sausar Group preserve contact metamorphic assemblages, distributed in distinct zoned aureoles, having lower temperature assemblages in the core and highest temperature assemblages along the periphery. This zonation is more pronounced where metacarbonate lenses are wider. The peripheral area of such lenses are rich in calcite-dolomite-forsterite (serpentinized)-diopsidechondrodite- spinel-tremolite assemblage followed by an intermediate calcite-dolomite-tremolite-biotite-white mica-spinel assemblage and an inner calcite-dolomite-tremolite -white mica-chlorite assemblage. The outer high temperature zone extends for about 250m of width and grades into the intermediate zone of about 500m and finally passes into a core of low temperature assemblages. The high temperature peripheral zones, at places, show presence of dark greyish-green coloured patches with predominance of diopside over calcite/dolomite and accessory quartz, sphene, zoisite, epidote and calcic plagioclases.

These patches, probably representing the special variety of calc-silicates, known as ‘skarns’ [1] are possibly formed by metasomatic interaction between marble and the enclosing biotite gneiss of probable intrusive origin. They have striking mineralogical and textural similarity with the numerously occurring calc silicate lenses present within the surrounding biotite gneiss. Presence of contact metamorphic assemblages in the Sausar metacarbonates, embedded within biotite gneiss of western Balaghat area, and their arrangement in an increasing metamorphic order, from core to periphery, is a clear indication of thermal effect caused by the enclosing biotite gneiss. Additionally, development of calc silicate assemblages at the contact zones and their ubiquitous presence, as lenses, along with the presence of numerous smaller metacarbonates patches, well within the surrounding gneiss further strengthens the possibility of the biotite gneiss being intrusive within the calcareous rocks of Sausar Group.