SILVER CONTENT IN SOME ROCKS OF BARMER AND PALI DISTRICTS IN RAJASTHAN STATE
BY RAKESH GIRI GOSWAMI
In terms of land area Rajasthan state is the largest state in India with varied geographical features. Major part of this i.e. 61% area is covered with desert or semi desert including 11 districts. Climate in this part is dry with scanty rainfall, as such lifestyle of people is very tough. Despite these negative aspects nature has been very kind to this state in the sense that it has showered state with rich mineral wealth. State as on today stands at par with other mineral rich states like MP, Karnataka, AP, Chattisgarh, Jharkhand. As a result of mineral surveys of last 100 years, number of useful minerals identified in the state is 79, out of which only 59 are produced commercially in this state. Almost every type of metallic to non metallic minerals are available in Rajasthan, except high grade iron ore/high grade coal. Earlier it was thought that state is devoid of oil and gas but that deficiency has been cleared with oi discovery in Barmer district. The state govt. receives 3000 crores annually as royalty, mining industry gives direct indirect employment to 2 lakh people in the state. The sale value of all types of minerals produced is around Rs.15000/- crores.
In any state mineral search is a continuous activity which is mostly conducted by state as well as central government agencies. After change in recent years now private companies can also go for mineral search, even they can also go for mining of Gold and Tungsten. Geologically desert has Mesozoic and younger rock formations but Pali area also has Pre Cambrian rocks. This piece is about possible occurrences of Silver bearing rocks in 2 districts of Rajasthan, i.e. Barmer and Pali.
Barmer occurrences :- This is a border district which shares its border with a neighbouring country. This area has been in limelight since 2004 when 1st oil discovery was made in Gudha Malani tehsil of this district, and Barmer basin is now a major oil producing area in the nation. 8 years after oil was 1st struck, this district again became centre of attraction when a private prospector and some research workers reported rare earth minerals which was also a hugh scientific achievement. Recent mineral survey by a government of India agency- Atomic Mineral’s Directorate,Hyderabad has identified unusual silver concentration in some rocks of Barmer district. Brief details are as under.
Silver has been identified in the various rocks of Siwana ring complex (SRC) in Siwana tehsil of the district. This ring complex is located in the easternmost corner of the district. Now Siwana ring complex represents an assemblage of many types of igneous rock which occur in the field in a circular manner having 30kms. X 25kms. Dimensions. Speciality of siwana area is the fact that rocks ranging from basic to acidic and alkaline nature are found here. Major rock types are basalt–rhyolite–pyroclastic sequence intruded by peralkaline–aegirine–reibeckite-rich granites along the sub-circular fractures (Rajeev Bidwai et.al. 2014 in Current Sc.magazine). These rock units are traversed by rare earth rich granites. The rocks in SRC are exposed along Ramaniya–Mokalsar–Deora–Kitno Indrana–Siner–Kundal area in the Survey of India toposheet numbers 45 C/2, 6, and 10. Silver has been identified in different rock types at following localities.
Bhati khera,Nal-Ramaniya, Mawri Magreshwar,Sheetala mata,Indarana, Phulan Siwana, Dantla, Devandi.
Rock type-wise silver concentration in SRC Ag (ppm)
Rock type Range Average (ppm) Average abundance in nature(ppm)
Basalt 1–2 1.7 0.1
Rhyolite 2–5 3. 2 0.07
Granite 4–7 5.0 0.037
granitoid 1–4 2.2 0.05
Tuff 1–3 2 .0 0.07
and felsite 1–15 4.9 0.05
feldspathic 2-4 3.0 0.05
This silver concentration in rocks of Siwana area is higher than the natural average found in these rocks as such area need further scientific investigation to prove deposits.
Geological map of Siwana Ring complex
Pali occurrences:- Pali district is located in central part of Rajasthan.It has heterogenous assemblage of metamorphic rock types representing Pre Cambrian rocks of Delhi Super Group intruded by younger granites. The occurrences of Silver bearing rocks was reported few years ago by author of this article while performing his duties as geologist with state mines department. The main localities are area 2kms. north of Jadan village, 2 and 4kms. south of Jadan,i.e. up to Kharadi village included in survey of India topo sheets 45G/5,9. Jadan is located on Pali-Jaipur 4 lane national highway NH 14 . The rock types around Jadan include Slates,Silt stone, Quartzites, quartz veins with both Rhyolite and Basalt. The all the rock types show ferruginous stains. The samples of Slate and Silt stone have shown presence of Silver content varying from 3.1 ppm. to 17.50 ppm. Geophysical survey is necessary in this area to identify anomalous zones of silver concentration. If favourable results are found in this survey then drilling can be planned.
Satellite image showing Jadan village