Parts of Andhra Pradesh
(North of 15° Lat.)
AMD, South Central Region, 1-10-153/156,
AMD Complex, Begumpet, Hyderabad - 500 016.
The Region was carved
out from Southern Region in 1988. Prior to it, all the investigations
were carried out from Southern Region, Bangalore. The
Office of the South Central Region was initially started in a
rented building in Hyderabad and since 1993 it is located within
the premises of AMD Headquarter, Hyderabad.
Broad Geological Features
following geological domains occupy major part of the region:
Basement rocks: They comprise (1)Peninsular Granite
Gneiss and (2) Eastern Ghat Mobile Belt consisting of charnockites
and khondalites in coastal districts of Andhra Pradesh.
Lower Proterozoic Green Stone Schist Belt such
as Nellore Schist Belt, Veligallu-Gadwal Schist Belt and
Ramagiri-Penakacherala Schist Belt.
Middle to Upper Proterozoic rocks: These
rocks are exposed in two major geographic domains, such as
sedimentary and igneous rocks of Cuddapah Super group and
the Kurnool Super group.
Upper Proterozoic sediments deposited in rift related environment
along the Godavari belt.
addition, Middle Proterozoic granites and mafic dyke swarms similar
to Closepet granite of Karnataka occur as discrete plutons within
the basement rocks.
Gondwanas (Mesozoic) along Godavari basin:
They overlie the Proterozoic rocks of Pakhal basin.
Beach Sand and Inland Placers: They are
the part of Quaternary group of rocks. Number of rich beach
sand mineral deposits are located in the coastal stretch
of Andhra Pradesh.
addition, very small exposures of Deccan Trap (Mesozoic age)
are exposed in the northwestern part of the Region.
Summary of Investigations :Important finds
survey in this part of the country was initiated in the early
50’s. Initially emphasis was given to locate vein type uranium
mineralisation in the basement rocks. Some uraniferous occurrences
were also located in the Mahabubnagar granite around Wanapurthy
during such surveys.
1990’s, however, with the changing concept of uranium mineralisation,
radiometric surveys led to the discovery of unconformity related
uranium mineralisation near the unconformity of fertile Mahabubnagar
granite and overlying Srisailam/ Banganapalle quartzite in the
northern part of Cuddapah basin. Subsequent detailed investigations
including borehole drilling resulted in the delineation of important
deposits. These are:
(1) Lambapur: It
is located in the Nalgonda district of Andhra Pradesh at
a distance of 140 km SE of Hyderabad. The mineralisation
is established over an area of 1.8 km x 0.7 km and is hosted
by Srisailam quartzite and the basement granite in the proximity
to the unconformity between them. It is a flat lying deposit
with a vertical depth of 45m.
(2) Peddagattu: It
is lying in very close proximity to Lambapur deposit. The uranium
mineralisation at Peddagattu occurs in an exactly similar geological set-up
and is spread over an area of 4.5km x 1km. Entire mineralisation
occurs within a vertical depth of 60m.
Present Thrust areas of Investigations
by the discovery of unconformity-related deposit, radiometric
surveys are targeted to locate such type of occurrences in the
similar geological environments. A few thrust areas, described
briefly, are as follows:
Srisailam-Palnadu basin: In
addition to the deposits already established, there are many
outliers of Srisailam and Banganapalle quartzite occurring
in the Srisailam-Palnadu basins, directly overlying the basement
granite. Since the unconformity between them has been established
as potential horizon for uranium mineralisation, the radiometric
and exploratory drilling are under way in many locations such
as Koppunuru in Guntur district and R.V. Tanda in
Nalgonda district, etc. Chitrial is another important
area. It is located in Nalgonda district of Andhra Pradesh
at approximately 130 km south-east of Hyderabad. The mineralisation
is confined to the unconformity between the basement granite
and Srisailam quartzite. The radioactivity is spread over an
area of 50 km2. Exploratory drilling is yet to be
taken up here.
Kurnool basin: Areas have been identified
where the Kurnool Supergroup of rocks are projected to overlie
the rocks of the Nallamalai fold belt with a pronounced angular
unconformity between them. Some of the earlier geochemical
surveys have delineated hydrogeochemical anomalies along
the Rudravaram line (contact between Nallamalai
fold belt and Kurnool Super group rocks). Mineralisation
is expected to occur at deeper levels in proximity to the
Pakhal basin: Interesting
geological set-up exists in Khammam and Warangal district of
Andhra Pradesh, where Proterozoic Pakhal group of rocks were
deposited over basement granite in rift related environment
(Godavari Rift). Gondwana sediments overlie these Proterozoic
Supracrustals. Radiometric survey are being carried out in
these areas to look for any unconformity related Uranium mineralisation.
supporting laboratory facilities are being provided from the
different laboratories located at AMD Headquarter, Hyderabad.