The Dariba Main Lode of Rajpura-Dariba Zinc-Lead-Copper Belt, Udaipur District, Rajasthan

The Dariba Main Lode is characterized by a complex assemblage of metallic sulphides and sulphosalts. Primary sedimentary fabric is evident by the occurrence of sphalerite, pyrite and occasionally galena, and rarely chalcopyrite, in the form of conformable layers, interbedded with the host rocks throughout the exposed length in the underground mine. Early diagenetic pyrite is found as tiny isolated grains as well as framboids, in which the first form is always dominating. This reflects two different pathways of pyrite formation.

Distinct mesoscopic folds are found in the bedded ores which show their general trend congruous to the "major folds of the region. ' Healed' breccias and fractures often occur associated with the folded and conformable ores in which the sulphides appear mobilized and recrystallized.

Folded pyrite-graphite schist laminites show excellently developed axial and bedding plane cleavages along which the pyrite has been recrystallized into aggregates of elongated crystals due to outlasting effect of shears. Pressure shadow structures showing elongated crystals of pyrite bordered by sphalerite and/or galena are also frequently observed along the bedding plane cleavages. Typical metablastic textures are exhibited by large euhedral crystals of pyrite and arsenopyrite and triple-point junctions shown by sphalerite and pyrite.

The ore features suggest that the Rajpura-Dariba-Bethumni deposits are essentially syn-sedimentary.