Geology, Metallogeny and Exploration of Concealed Lead-Zinc Deposit in Sindesar Khurd-Lathiyakheri Area, Rajsamand District, Rajasthan

The Sindesar Khurd-Lathiyakheri area is located in the middle part of the Dariba-Bethumbi-Surawas belt, which comprises Paleoproterozoic meta-volcano-sedimentary rocks (of Bhilwara Supergroup) forming a crescent shaped synform plunging due North-North-East. Cherty quartzite with schist bands are exposed in the area where as the rocks intersected in the boreholes are feldspathic gneisses with schist (basement rock), laminated marble bands, calc silicate marble/dolomite with lead-zinc mineralization and tuffaceous mica schist with bands of greywacke and carbonaceous schist with lead-zinc mineralization. These rocks show metamorphism of kyanite-almandine-muscovite subfacies of almandine-amphibolite facies and depict three phases of deformation out of which first and second phases are coaxial with NNE-SSW trend and third one is across.

The lead-zinc mineralization occurs in fine grained disseminated banded form in mica schist, tuffaceous mica schist and carbonaceous schist, where as in coarse grained form it occurs in calc silicate marble. In calcareous schist mineralization occurs in both forms. In fine grained form Pb, Zn, Cd and Ag elements show very good correlation among themselves (correlation coefficient from 0. 86 to 0. 94), where as in coarse grained these show poor or very poor correlation. The average sulphur isotopic values also show different values of 4. 39 and 13 permil in fine and coarse grained respectively. The coexisting aqueous and carbonic inclusions indicate deep source above 700 bar pressure at 350°C. The salinity versuse temperature plot indicates two distinct variations higher and lower salinity with temperature. The paragenesis, two types of mineralization, host rocks, elemental correlation, metamorphism, isotope and fluid inclusion studies indicate two phases of mineralization. The primary source was volcanic from deeper part and got deposited as fine grained layers along with volcano sedimentary rocks as protore. This was remobilised and deposited in the available locales as coarse grained mineralization due to metamorphism and deformation.

The Dariba and Bethumbi lead-zinc mines located respectively towards the southern and northern end of the Rajpura-Dariba-Surawas belt are characterized by old workings, gossans, mineralizations and surface exposures of the host rocks. In contrast, the Sindeswar Khurd-Lathiyakhen area lying between these two areas is distinctly devoid of these features. The ridge portion of the present area is covered by barren rock sequence of cherty quartzite and tuffaceous mica schist, whereas thick soil cover is forming plane area. In the Dariba mine and in old working area it is observed that the cherty quartzite and tuffaceous mica schist sequence is enveloping the host rocks i. e. carbonate and tuffaceous carbonaceous schist. Therefore, an exploration model generated on the basis of litho-stratigraphy, structure, depositional environment and the exploration data obtained from the adjoining blocks was employed to locate the mineralization below the barren rock sequence and thick soil cover. Based on this model the test drilling has located rich lead-zinc mineralization below 150 m thick barren rock cover from the surface. Further step by step successive exploration by accurate structure and lithological interpretation the mineralization is traced for 3.5 km along the strike and 1000 m across the strike with 100 numbers of boreholes proving 100 million tones of ore reserve with 4% to 8% average grade of lead and zinc.