|LEAD - ZINC DEPOSITS
the section on Lead Zinc in “Mineral Specification” section
on this website
M/s Hindustan Zinc Ltd (HZL) ., a former Government
of India Undertaking, is involved in mining, beneficiation, smelting,
and marketing of zinc, lead and its byproducts in India. The following
text is based on HZL in-house publications further details could
be had from their website: www.hzlindia.com
Lead-Zinc deposits in India are localized mainly in the Precambrian
formations of the Peninsular Shield and to a smaller extent in the
lesser Himalayas. The important economically viable deposits are
located in two main regions of India viz., Western Region and Southern
Region with some scattered deposits in other parts such as North
and Eastern Regions.
The Western Region comprises Rajasthan and Gujarat
States. Copper-lead-zinc mineralization occurs as bi-and multi-metal
deposits and 95% of National Ore Resource is confined to this region.
There are two distinct metallogenic provinces; the north-eastern
parts characterized by predominantly copper rich province, confined
to the rocks of Delhi Supergroup, whereas in South Rajasthan and
North Gujarat, the mineralization is chiefly lead-zinc ores with
subordinate copper in the rocks of Pre- Aravalli, Aravalli and Delhi
Supergroup (Table 1).
Table : 1
(2.0 b.y.-1.2 b.y.)
Ajmer lead-zinc belt
Deri-Ambaji lead-zinc-copper belt
(2.5 b.y.- 2.0 b.y.)
Zawar lead-zinc belt
Pur-Banera lead-zinc-copper belt
(3.2 b.y. – 2.5 b.y.)
The Rajpura-Dariba-Bethumani belt is considered
to form the western limb of Banera-Bhinder synform extending from
Bhinder in the south to Banera in the north over a distance of about
The Dariba-Bethumani belt, extending from Bethumani
in the north and Dariba in the south is composed of a group of folded
metasedimentary rocks belonging to the Bhilwara Supergroup of pre-Aravalli
age. Numerous old workings, gossans and ferruginous breccias have
been recorded in the southern part of the belt in the Rajpura-Dariba
area. The ore deposit is stratabound and is enclosed in a sequence
comprising metamorphic equivalents of ortho-quartzite, carbonates
and carbonaceous facies which are flanked by a thick monotonous
sequence of meta-argillites. Rajpura-Dariba ore body owes its importance
to its multi-metal sulphide-sulphosalt associations within the ores.
Zinc is dominant metal followed by lead and copper.
The important trace metals are cadmium and silver. The sulphide
ores at Dariba mine show conspicuous mineralogical zoning. Copper,
lead-zinc and iron rich zones appear successively from the footwall
to hanging wall. Two important lodes viz., Main and East lode, separated
by a parting of 150 m, occur at Rajpura-Dariba. The main lode is
further divided into South lode and North lode.
Rajpura-Dariba has been developed as a 3000 TPD
underground mine with matching beneficiation facilities. The other
less significant deposits are Mokhanpura North and South, Sindesar
Kalan (East) and Malikhera block which are low in metal content
and hosted by graphitic schist.
HZL is also exploring at Bamnia Kalan, which is
14 km north of Rajpura-Dariba mine, where the lead-zinc mineralization
occurs in calc-silicate/dolomite and garnet bearing carbonaceous
schist. Two distinct zones of mineralization viz., Main Zone and
West Zone occur in this area. In the Main Zone, ore lenses are of
variable dimensions, disposed in enechelon pattern with dextral
overlap in sympathy with complicated fold pattern.
Rampura Agucha Lead-Zinc
The Rampura Agucha lead-zinc deposit is located 15 km southeast
of Gulabpura in the Bhilwara district, Rajasthan. The village Rampura,
originally located adjoining the western flank of the deposit was
rehabilitated in 1990, prior to the commencement of open pit operation
and Agucha village is about 1.5 km southwest of the deposit. The
proximity of these two village led to the naming of its as”
Rampura-Agucha deposit”. Since its discovery in 1977, the
deposit has attained significance because of its large potential
and geological setting not known to be conducive for mineralization.
The deposits forms a part of pre-Aravalli Banded Gneissic Complex
consisting of gneisses, schist and intrusive of acidic and basic
igneous rocks that occupy, predominantly, the southeastern plains
of Ajmer and Bhilwara.
Discovery and History of Exploration:
Garnet is found in almost all rock types around Rampura-Agucha deposit.
In connection with a assessment of the potential of semi-precious
and abrasive varieties of garnet of the area, T.C. Rampuria of Directorate
of Mines and Geology, Government of Rajasthan (DMG), observed multicolored
gossan bands, slag dumps and a linear shallow depression in the
vicinity, in August, 1977. Preliminary geological, geophysical and
geochemical surveys were made by DMG Rajasthan in 1978 and 1979,
which resulted in indications of good potential and surface drilling
in May, 1979.
Such indications attracted the attention of Hindustan
Zinc Limited (HZL), which proposed detailed exploration through
15,500 m of surface drilling and 500 m of underground development,
which was approved in February 1980, at estimated expenditure of
Rs. 12.5 million.
Geology of the Deposit
Since a greater part of the area is capped with soil cover and fresh
rock exposures are scanty, much of the information for detailed
geology was gathered from the drill cores. The rock units show NE-SW
strike with steep dips in hanging wall (75°-80°) and moderate
dips in footwall (60°-65°) towards south-eats and plunges
towards NNE. The sequence of rocks, from hanging wall to footwall,
can be broadly grouped as under:
1. Garnet-biotite-sillimanite gneiss with intermittent bands of
calc-granulites, amphibolites and aplites/ pegmatites
2. Garnet-mica-sillimanite gneiss/ schist
3. Garnet-biotite-sillimanite gneiss with lenses of quartzo-felsphathic
bands, amphibolites, pegmatites and aplites
4. Granite gneiss, and
5. Mylonitic rocks.
Economic mineralization is predominantly in graphite-mica-sillimanite
gneiss / schist over a strike length of 1550m. The ore zone has
a sharp contact with the hanging wall and footwall. The hanging
wall side of the lode is the richest and also wide, followed by
comparatively lean grade in the middle and a narrow, rich, footwall
zone. Coarse-grained crystalline galena, associated with pyrite
and pyrrohitite are seen in the hanging wall rocks. The mineralizations
in hanging wall and footwall contacts is invariably fine to coarse-grained,
and is made up of sphalerite and galena with numerous inclusions
or rounded to sub-rounded discrete grains of feldspar, quartz, hornblende,
sillimanite and dark green chlorite.
Attitude of the ore zone:
The general strike of the ore zone is parallel to the enclosing
rocks, which is roughly NE-SW. The dip of the ore zone varies along
the strike and depth. Near the surface, the dip of the hanging wall
contact is steeper (75° to 80°SE) as compared to footwall
contact (about 60° SE). In depth, dips of both the hanging and
footwall contacts show a tendency to flatten. In general, the dip
varies from 50° to 80°. The ore zone shows a variation in
width, both along the strike and dip. The width of the ore zone
gradually widens to about 95 to 100m between latitudes S-200 and
Mineralogy of the Ore
The graphite-mica-sillimanite schist hosts the economic mineralizations
in Rampura-Agucha deposit. The economic minerals in the order of
decreasing abundance along with their ranges of modal percentages
are: sphalerite (15-20%), pyrite (15-18%), pyrrhotite (12-14%),
galena (1-2%) and sulphosalts (0.1-0.2%). Graphite is ubiquitous
in the ore body (7-10%). The gangue minerals that amount up to 45%
to 50% of the ore zone constitute quartz, feldspar (orthoclase,
plagioclase), various micaceous minerals (sericite, chlorite, biotite),
sillimanite with significant amount of garnets, amphibole, pyroxene,
rutile, apatite etc.
The Rampura Agucha deposit at comparatively shallow depth is ideally
suited for open pit mining using conventional equipment. The ore
body is comparatively narrower and richer in grade in the northern
part and wider in the southern. Thus open pit operation can go deeper
only in the southern part.
Zawar Lead-Zinc Belt
The Archaean basement comprising of gneiss, schist, amphibolite,
quartzite and granite dating back to 3.2 to 2.5 b.y. showing unconformable
relationship with the Aravalli cover rocks, is clearly marked in
and around Udaipur. Stratigraphic succession, established by Roy
et.al., (1984,b) for the Aravalli Supergroup of the type area around
Udaipur and Zawar show two major groups separated by an unconformity.
The Upper Aravalli Group consists of greywacke-slate-phyllite, quartzite,
dolomite and silty arenite (host for sulphides of zinc and lead)
while carbonaceous and pelitic phyllites, dolomite, quartzite, stromatolyte,
phosphorite, chlorite schist, amphibolite, quartz arenite and local
conglomerate belong to Lower Aravalli Group.
In general, Aravalli rocks in Udaipur-Zawar region
show a low-grade metamorphism. The recrystallisation of the silicate
minerals suggests the grade of metamorphism to be of greenschist
facies. A few dyke-like bodies, intrusive in Aravalli rocks of Zawar,
occur as totally undeformed.
The present structural disposition of Zawar area
is the manifestation of two distinct major periods of tectonic cycles,
each of which was characterized by intense folding and faulting.
In Zawar area, the north and south limb of cross fold is represented
by Mochia, Balaria and Bowa, whereas Baroi and Zawarmala represent
the north-south trending and northerly plunging first generation
The mineralization occurs as sheated zones, veins stringers and
disseminations, forming lenticular bodies arranged in overlapping
enechelon pattern. The individual ore shoots persist along strike
between 50 and 500 m, dip between 50° and vertical and plunge
between 30° and 60° west or north. The ore body varies in
width between 1 and 40 meters.
The mineralization is restricted solely within
dolomitic horizon along with the structural control, but regional
stratigraphic and lithological control is also evident. The main
sulphide minerals are sphalerite, pyrite and galena. Chalcopyrite,
pyrrhotite and arsenopyrite are the associated minerals. Appreciable
amount of silver and cadmium occur within the ore minerals.
Zawar belt has been the oldest centre of lead-zinc
production in the world. The producing deposits are- Mochia, Balaria,
Zawarmala and Baroi. Zawar group of mines has a capacity of 4000
TPD from underground mines with matching beneficiation facility