Overview of Copper, Lead and Zinc Exploration in India
India holds substantial reserves
of copper, lead and zinc, which are primarily located in the regions of
Rajasthan, Jharkhand, and Madhya Pradesh. Despite having significant reserves,
the exploration intensity, measured by exploration expenditure per square
kilometer, is relatively low compared to global standards. This indicates
substantial growth potential in exploration activities.
India's relatively low
expenditure per square kilometer can be attributed to several factors including
less intensive exploration activities, regulatory challenges, and sometimes the
focus on expanding known deposits rather than greenfield exploration.
Exploration Efforts
India is deficient in its
resources for base metal and has a poor resource-cum reserve base despite
having the geological potential for large resources. The scarce resource base
for base metals needs special attention for their exploration as they consume a
lot of foreign exchange for their imports.
A strategy has to be evolved for
an integrated approach towards exploration of these minerals. Data generated in
course of geological mapping activities has helped GSI in identifying favorable
geological domain (OGP) for base metal mineralisation over an area of 192606.49
sq. km area in India. GSI has renewed its efforts for systematic exploration
for base metals throughout the country by focussing on the OGP areas in various
states.
An area of 1.926 lakh sq. km
(0.19 million sq. km) area has been delineated in the year 2020 to be potential
for base metal occurrence in the country based on distribution of more than 200
prospects, nearly 920 occurrences of base metals, genetic association,
geological set-up etc. The base metal potential areas are distributed in the
States of Rajasthan, Karnataka, Gujarat, Madhya Pradesh, Jharkhand,
Chhattisgarh, Odisha, Arunachal Pradesh, Andhra Pradesh, Maharashtra, West
Bengal, Uttar Pradesh, Goa, Haryana, Kerala, Tamil Nadu, Manipur, Telangana,
Himachal Pradesh, Sikkim, Meghalaya, Nagaland, Jammu & Kashmir, Bihar,
Assam and Uttarakhand in the order of extent of geologically potential areas.
|
Copper, Lead and Zinc exploration projects by GSI since 2012 |
|
|
Year |
No. of Projects |
|
2012-13 |
22 |
|
2013-14 |
41 |
|
2014-15 |
67 |
|
2015-16 |
92 |
|
2016-17 |
117 |
|
2017-18 |
150 |
|
2018-19 |
187 |
|
2019-20 |
244 |
Resources:
Copper
The total resources of copper ore
as on 1.4.2015 (as per IMYB 2018) is estimated at 1.51 billion tonnes as per
UNFC system. Of these, 207.77 million tonnes (13.74%) fall under 'reserves'. Of
the total ore resources, 8.28 million tonnes (0.55%) comprise ore containing
1.85% Cu or more and 657.92 million tonnes (43.53%) 1% to below 1.85% Cu grade.
With regard to reserves, there were no reserves above 1.85% Cu grade. However,
203.83 million tonnes fall under 1.0% to below 1.85% Cu grade.
The total copper metal content in
the resources is 12.16 million tonnes of which 2.73 million tonnes constitute
reserves. Largest resources of copper ore to a tune of 813 million tonnes
(53.81%) are in the state of Rajasthan followed by Jharkhand with 295 million
tonnes (19.54%) and Madhya Pradesh with 283 million tonnes (18.75%). Copper
resources in Andhra Pradesh, Gujarat, Haryana, Karnataka, Maharashtra, Meghalaya,
Nagaland, Odisha, Sikkim, Tamil Nadu, Telangana, Uttarakhand and West Bengal
accounted for remaining 7.9% of the total all India resources.
Lead-Zinc
The total resources of lead and
zinc ores as on 1.4.2015 as per UNFC system, are estimated at 749.46 million
tonnes. Of these, 106.12 million tonnes (14.16%) fall under 'reserves' category
while balance 643.34 million tonnes (85.84%) are classified as 'remaining
resources. The resources of ore containing + 10% Pb & Zn were estimated at
124.23 million tonnes, ore containing 5 to 10% Pb & Zn were 329.88 million
tonnes and ore containing less than 5% Pb& Zn were 295.35 million tonnes.
The total metal content in
resources of lead is 13 million tonnes Lead and that of zinc is 36.36 million
tonnes and for lead zinc metal is 0.14million tonnes. In terms of reserves,
2.48 million tonnes of lead metal and 9.99 million tonnes of zinc metal have
been estimated. Rajasthan is endowed with the largest resources of lead-zinc
ore amounting to 670.34 million tonnes (89.44%), followed by Andhra Pradesh
22.69 million tonnes (3.03%), Madhya Pradesh, 14.84 million tonnes (1.98%),
Bihar 11.43 million tonnes (1.52%) and Maharashtra 9.27 million tonnes (1.24%).
Resources are also established in Gujarat, Meghalaya, Odisha, Sikkim, Tamil
Nadu, Uttarakhand and West Bengal (IBM YB 2019).
Planning for the next five years
should involve exploration strategy to
1. Discover deeper extensions
(>500m) of known deposits and prospects and also to identify potential
mineralization under cover. Application of 3D seismic and magneto-telluric
surveys which are increasingly used to discover base metal mineralization >300m
from the surface.
2. For regional-scale, an
integrated approach involving geology, geochemistry, remote sensing and aero geophysical
data, with focus on volcano-sedimentary sequences of Archean and Proterozoic
age can help delineate zones for more detailed exploration. A first order
empirical guide will be to prioritize areas with altered submarine volcanic
rocks for VMS deposits and carbonate-associated sedimentary sequences for SEDEX
and MVT-type deposits. For vein-type and intrusion-related Cu-mineralization
younger granites of calc-alkaline affinity should be seen as source rocks.
3. Focus on large greenstone
belts and volcano-sedimentary belts for VMS, SEDEX and intrusion related base
metal deposits. For example, Central Indian Tectonic Zone is important with
several volcanic and sedimentary sequences such as Betul Belt, Sausar Belt and
Mahakoshal Belt.
4. Emphasis on Archean Dharwar
greenstone belts for Cu-Au VMS deposits and younger calc-alkaline granitoids
for porphyry-type Cu ± Au ± Mo deposits.
5. Search for base metal deposits
in the Archaean cratonic part of Jharkhand - Odisha region and Singhbhum shear
zone.
6. Margins of Archean Cratons
like Bastar, Dharwar and Bundelkhand to search for IOCG-type mineralization
7. The Aravalli-Delhi belt still
remains one of the most prospective terrains for discovering large VMS, SEDEX
and IOCG-type deposits. The exploration strategies for these areas should
involve targeting concealed mineralization through potentially covered
unconsolidated sediments of a general thickness of 80m to 150m.
8. New exploration strategies to
be applied for the covered terrains (greenfield areas) for the entire concealed
part of Rajasthan State for expanding mineral search space for base metal
mineralization by carrying the techniques being evolved in UNCOVER (India),
northern transect.
9. The selective greenfield
targeting projects for covered terrains of Western Region should involve
creation of buried topography, predictive geological map, distal foot printing
of mineralization, application of integration geoscience and mineral system in
the covered terrains of Western Region and later to the other areas.
Exploration Opportunities
Augmentation of copper ore
resources in the country can be achieved through further inputs for intensive
exploration with an aim of firming up and upgradation of reserve figures in
known prospects and in the extension areas of the known or established deposits.
The three prominent belts, where copper deposits are located include Singhbhum
Copper Belt (SCB), Khetri Copper Belt and Malanjkhand Copper Belt. In
Rajasthan, copper mineralisation is mainly associated with Delhi Supergroup.
Many occurrences of copper have been recorded in the basement rocks as well.
Some copper prospects are located in the lead-zinc belts associated with the
Aravalli rocks. In central India, search for granite host rocks similar to
Malanjkhand with Mesoproterozoic age and calc-alkaline signatures can be a
potential tool.
|
Obvious Geological Potential Areas for
Copper, Lead and Zinc |
|
|
States |
OGP Areas (in sq. km) |
|
Rajasthan |
67995.71 |
|
Karnataka |
35572.67 |
|
Gujarat |
12948.79 |
|
Madhya
Pradesh |
12144.29 |
|
Jharkhand |
10227.95 |
|
Chhattisgarh |
8781.29 |
|
Odisha |
6574.91 |
|
Arunachal
Pradesh |
6354.49 |
|
Andhra
Pradesh |
6336.41 |
|
Maharashtra |
5174.21 |
|
West
Bengal |
3010.54 |
|
Uttar
Pradesh |
2795.89 |
|
Goa |
2361.73 |
|
Haryana |
2346.9 |
|
Kerala |
1440.42 |
|
Tamil
Nadu |
1302.37 |
|
Manipur |
1135.36 |
|
Telangana |
1093.11 |
|
Himachal
Pradesh |
1033.86 |
|
Sikkim |
992.04 |
|
Meghalaya |
852.86 |
|
Nagaland |
712.98 |
|
Jammu
& Kashmir |
454.42 |
|
Bihar |
288.44 |
|
Assam |
224.27 |
|
Uttarakhand |
90.83 |
|
All India
OGP-2020 for Base metals |
192606.49 |
Keeping in view the prospects,
future targets of exploration for copper and associated metals may be
identified in Dariba-Bethumbi Belt, Jahazpur Belt, Pur-Banera Belt for
copper-lead-zinc-gold, Jasma-Akola-Bhinder Belt, parts of South Delhi Fold
belt, South Khetri Belt, Ajmer metallogenic district and Salumber-Dhariwad belt
in Rajasthan and in extension areas of South Delhi Fold Belt in Gujarat. The
South Khetri Copper Belt is relatively less explored.
Most of the lead zinc mines of
the country occur in the Proterozoic fold belts in the western Indian shield.
In the Precambrian shield of the western India as well as in the other shield
areas, several smaller and medium grade lead-zinc deposits have been identified
and explored. Number of occurrences of leadzinc have been recorded from the
Himalayan region, particularly in the Lesser Himalayan Zone, comprising
Precambrian rocks, tectonically disturbed and deformed during the younger mountain
building movements. Application of modern exploration techniques with emphasis
on airborne and deep – probing geophysical methods may help in identifying new
deposits in the above area. There are several occurrences associated with
greenstone sequences in the Dharwar Craton (Kalyadi, Ingaldhal etc). Base metal
deposits are also known in the Cuddapah sedimentary rocks (Agnigundala,
Zangamrajapalli, Markapur etc). Fault-related copper-mineralization is known to
occur in the granitic terrain of eastern Dharwar Craton (Tintini, Kallur etc).
Extension of these areas has to be studied in detail.
Potentially covered large terrains of Western India over North Delhi Fold belt, Aravalli Region is essentially a key Region giving opportunity for next generation base metal mineral deposits in the country. In these areas the targeted Geoscience Goals should include,
i. Basement surface elevation or buried topography.
ii. Exploring effectively and efficiently through cover.
iii. Managing drill hole data, magnetic data for mapping through cover.
iv. Preparation of predictive geological map and tracing the concealed structures.
v. Groundwater and Calcrete studies for distal foot printing of mineral deposits.
vi. Subsurface movement of groundwater and its possible linkage with mineral belts, host lithology, delineating buried rock type etc.
vii. Understanding mineral dispersion through cover.
viii. Designing and progressing efficacy of geochemical sampling techniques in the buried terrains.
ix. Establishing links to magnetic/ gravity anomaly in the subsurface with secondary dispersion record in calcrete, groundwater, lithology etc. and deriving metallogenic implications.
x. Exploratory drilling and characterizing geophysical domains and updating the predictive geological and buried topography map of the area in the second year of the project.
With an objective to deliver,
a.
First hand buried topographic map.
b.
First hand predictive geological map of buried
terrain.
c.
Making of structural interpretive map by
integration geoscience.
d.
Distal foot-printing of geochemical anomalous
zones in buried terrain.
e.
Delineation of areas for furthering dense
geophysical and geochemical data acquisition by integration geoscience.
f.
Exploratory drilling is expected to lead in
bringing out new buried belts, extension of known mineral belts below cover
etc.
g.
These works will result in exploratory drilling
to decipher the areas for characterizing geochemical, geophysical signatures
to increase the chance of concealed mineral deposits.
Challenges
Exploration:
The discovery of new deposits based
on surface indications will be extremely remote considering that most known
areas have already been explored. The challenge is to find base metal
deposits in new areas/ concealed terrain within volcano-sedimentary sequences
and those associated with intrusive rocks. This will require the acquisition of
high-resolution aeromagnetic data and its integration with other geological and
ground-geophysical data. Also, modern concepts of mineral systems and their
understanding is crucial in identifying potential terrains. Researching and
mineral targeting in green field regions is vital in the country. Discovering
new deposits/area is essential requirement to keep continuous supply of
minerals to fulfil country’s needs. Selecting the most suitable area,
geological field and terrain will assist in making the exploration easy, cheap
and quick. Geophysical studies play a vital role in exploration of buried ore
deposit.
Geophysical exploration may be
used with advantage to locate boundaries between different elements of the
subsoil as these procedures are based on the fact that the gravitational,
magnetic, electrical, radioactive or elastic properties of the different
elements of the subsoil may be different.
A large part of basement areas of
Rajasthan, Gujarat, Haryana, Uttar Pradesh etc., are covered with unclassified
sediments posing challenges to the mineral exploration geoscientists.
Geological basement favourable for mineralization in parts Rajasthan are mostly
covered with windblown sand having variable thickness. Generally, the thickness
of cover sediments is thinner near outcropping areas and the depth of cover
range from 80m to 150m in parts of Churu, Jhunjhunu, Sikar, Alwar districts of
Rajasthan. The basement geology of major parts of Gujarat, Uttar Pradesh,
Haryana, Bihar is masked with unclassified sediments.
Processing and Analysis
Since base metals are associated
with a wide-range of associated ore metals it is important to have high-quality
analytical support for analyzing the entire spectrum of associated trace
elements. These trace elements form important by-products and add value-addition
to the primary ore assemblages. High precision ICP-AES analyses is essential
for low concentration (ppm) levels.
Beneficiation:
As per SOP, the mineralized cores
are sent for beneficiation studies to the Mineral Processing Laboratory like
IBM for beneficiation study to understand the metal recovery from a particular
ore type. About 50-100 kg of each mineralized core samples having assay above
cut off values is to be collected for bench scale beneficiation study with an
objective to assess the feasibility of Cu, Pb or Zn up- gradation suitable for
smelter. Bond’s ball mill work index of the host rocks is to be determined at
the ground product -150# (-105 microns), which is the product size as per BWI
standard procedure (DID base metal2012).
Beneficiation of base metals face
several constraints including 1. Complex nature of ores, 2. intergrowth of
silicate and ore, 3. Presence of deleterious elements like graphite etc. In
this scenario, the beneficiation is more or less custom-made for individual
mines and plants taking into account the nature of ore and associated gangue
minerals.
Copper ore from the mine is
processed to yield copper cathodes which are basically 99.99% pure copper.
Common type of copper ore is copper oxide and copper sulphide, which undergo
different processes. Copper oxide is processed through hydrometallurgy whereas,
copper sulphide is processed through pyrometallurgy. Lead and zinc ores are pre
concentrated by gravity methods, employing heavy mineral separation, jigging
and tabling depending on liberation size and ultimately concentrated by
xanthate flotation. Usually lead sulphides are selectively floated from the ore
followed by activation and separation of zinc in case of complex lead-zinc
ores. Bulk flotation followed by separation of lead and zinc differential
flotation is not uncommon.
Mineralogical characterization:
A complete and comprehensive
analyses and characterization of the associated ore minerals and alteration
assemblages are vital to develop exploration strategies in existing
prospects/mines as well as regionally to select areas for more detailed
exploration. Petrographic studies of the host rocks and the ore mineral assemblage
bears significant role in understanding the nature and control of
mineralization in a particular mineral system. Besides these, the paragenetic
sequence, textural relationship and ore mineral assemblages tell a lot about
the deposit type and genesis of the ore deposit. Ore mineral assemblages of a
deposit and their geochemistry have great significance in describing the type
of depositional environment. SEM/EPMA studies of ore assemblage will help in
identifying trace elements, for example, to identify presence of Au, Ag, Re,
Pt, Pd in Cu-rich porphyry systems. It is well-known that several alkaline
porphyry copper deposits are sometimes also enriched in Pt-Pd, which can be
recovered as valuable by-products. LA-ICP-MS analyses of sulphides are increasingly
used to understand ore-genesis, thereby facilitating the fingerprinting of
depositional processes and mineral system type. This can be effectively used as
a rapid assessment tool in base metal exploration to distinguishing
economically important prospects/zones from those of relatively lesser
significance.
Future Research &
Development
The mineral system concepts and
models can be translated into effective exploration targeting criteria and
serve as the basis of forceful, testable exploration models. Base metal
deposits are predominantly hydrothermal in nature and mineral system concepts
of source, driver, pathway and depositional gradients are particularly
pertinent. In this scenario, emphasis should be laid on mineral-system wise
targeting. In the Indian scenario, mineral system classification has not
gained much importance and application. Initially, all known deposits and
prospects should be re-assessed from the point of modern basis of
classification schemes. A mineral-system scheme provides important clues and
proxies for extending exploration regionally (district-scale) as well as
locally (deposit-scale).
References:
- A Brief on Exploration for Base metal Mission in India – 2020 – GSI Publication
- Mineral Exploration in India at a Glance -2020 – GSI Publication
