Summary:
Sindesar Khurd deposit is in the central part of the eastern limb of the major Dariba-Bethumni synformal fold and the Sindesar Khurd Mine is in the central part of the eastern limb of the fold. The best exposed rock unit in the area is interbedded mica-schist / chert / quartzite and forms a prominent NNE-SSW trending ridge. This is a lenticular orebody with multiple lenses surrounding the main orebody. The economic concentrations of lead-zinc-silver mineralisation are hosted by calc-silicate bearing dolomite and graphite mica schist. The host rock is completely concealed about 100 below the surface. The economic concentrations of lead-zinc-silver mineralisation are hosted by calc silicate bearing dolomite and graphite mica schist. The host rock is completely concealed about 100 below the above unit. The rock types of the area as follows:
- Quartz Mica Schist with bands of chert/quartzite;
- Graphite Mica Schist with Fe-Pb-Zn sulphides;
- Calcareous Garnet Biotite Schist with dolomite;
- Calc Silicate Bearing Dolomite with Fe-Pb-Zn sulphides;
- Calcareous Quartz Biotite Schist;
- Basement Rock (Feldspathoid schist/gneisses).
Base metal deposits of various sizes and grades occur throughout the belt in calc-silicate bearing dolomite and graphite mica schist horizons, the latter in general containing low grade disseminated sulphides of large volumes. At the south end of the belt, contains multi-metallic sulpho-salt association.
The Sindesar Khurd deposit consists of multiple horizons, up to 50 m thick, with a complex folded geometry and internal grade distribution due to intercalation of higher-grade dolomite-hosted ore and low-grade mineralisation in mica schists, in addition to discrete narrow ‘minor’ lenses. The mineralisation has been traced over almost 2 km along strike and 1 km vertical extension. In the mine area of the main deposit, the dip is steep towards the west, which rotates into an easterly direction in the lower-southern part of the deposit. The current “mine block” extends over 1200 m along strike and up to 500 m depth extension.
Deposit type
The mineralisation forms the western limb of a concealed NNE-SSW trending broad, open and asymmetric antiformal fold with sub-horizontal to gently northerly plunging fold axis. This is a Lenticular orebody deposit with multiple lenses surrounding the main orebody. The upper limit of mineralisation lies at a depth of about 100m below surface. The recent exploration from surface within leasehold between 5700 – 8200N, revealed the continuity of mineralisation in the southern extension. Besides main lens, 15 auxiliary lenses have also been delineated.
The ore bodies dip westerly in the upper part (up to 200 mRL) and dip changes to steep easterly in the lower part thereafter. The ore body has been proved up to -800 mRL level. The ore body lies close to the contact of quartz mica schist envelope with dolomite/ graphite schist.
The general strike of the ore body is N10°E to N15°E while dips vary from 45° to 60° towards west and in deeper levels steep easterly. Pinching and swelling are also observed in the ore body. The thick footwall barren dolomite, occurring east of mineralisation along the strike, is sparsely mineralised. Average width of the main ore body is about 30 m and shows remarkable variation both along strike and dip. The ore body is open at a depth of 1,200 m below surface in the southern extremity of the leasehold.
Mineralization
Mineralisation exhibits lithological, stratigraphic and structural controls and occurs in the form of fracture-filling veins, stringers and disseminations forming tabular to lenticular ore bodies. The mineralisation is in a highly folded and faulted strata-bound (in metamorphosed dolomite) sulphide assemblage. The mineralisation has been described as of SEDEX origin; however, the ore seems rather a carbonate-hosted remobilisation than the original SEDEX with blackshale affinity, remainders of which can be found in the stratigraphic footwall of the deposit. In addition to the main deposit, which is generally dolomite hosted, higher grade and elevated in silver, there are a number of separate but important mineralised lenses. The other lenses are: SKA1, SKA2, SKA4, SKA5, SKA6, SKA7, SKA8, SKA11, and SKA17. These lenses are generally hosted in mica schists, which often have higher graphite which has implications on processing. The main economic base metal minerals at SK Mine are sphalerite and galena with a relatively high level of pyrrhotite indicated (12% Fe as pyrrhotite). Two ore types are identified: dolomite hosted, which constitutes the majority of the anticipated ore feed (90%); and graphite mica schist.