GEOLOGY OF MAHARASHTRA
The State of Maharashtra encompasses on
area of 307713 sq.km. Out of which likely mineral bearing area is about 58465
sq.km. i.e. 19% of the total area of the State. Divisionwise distribution of
mineral bearing area is
1) Nagpur
- 60%
2) Amravati
- 10%
3) Konkan
- 20%
4) Aurangabad -
5%
5) Pune
- 3%
6) Nasik
- 2%
GEOLOGY OF THE STATE
The entire area of the State forms a part of the “Peninsular
Shield”, which is composed of rocks commencing from the most ancient rocks of
diverse origin, which have undergone considerable metamorphism. Over these
ancient rocks of Precambrian era lie a few basins of Proterozoic era and of
permocarboniferous periods which are covered by extensive sheets of horizontally
bedded lava flows comprising the Deccan trap. More than 80% area of the State
is covered by these Deccan trap, which have concealed geologically older
formations. The most important economic minerals such as coal, iron ore,
manganese ore, limestone, etc. are found in the geologically older formations.
STRUCTURE :
Structurally, the entire area of the state forms a part of the “Peninsular
Shield” of India which represents a fairly stable block of earth crust that has
remained unaffected by, mountain building movements, since the advent of the
Palaeozoic era. Some of the subsequent movements in the crust have been of the
nature of normal and block faulting which have laid down certain portions
bounded by tensional cracks of faults giving rise to basins in which sedimentary
beds of the Gondwana age have been deposited. Particularly in the Vidarbha
region giving rise to the the important limestone as Penganga beds and
coalfields of the Pench-Kanhan valley, the Umred – Bander field the Wardha
valley and Vidarbha valley. It is generally accepted that the Western coast has
been formed as a result of the faulting. Along this coast from Ratnagiri to
Mumbai, and further north in Thane district there exists a series of hot springs
arranged almost in linear fashion which suggests that they are situated on a
line of fracture. Further evidence regarding the formation of west coast by
faulting is offered by the Western Ghats comprising Deccan trap lava flows,
which are several hundred metres thick near the coast and which gradually thins
out east wards. Near Panvel, near the west coast the Deccan traps show
westerly slopes indicating designated as Panvel flexure.
Association of Economic Minerals
with Gological Formations and their Geographic Distributions in the State
An intimate knowledge of geological formations and their
geographic distribution provides a very important clue not only to the
occurrence of minerals, but also forms the basis on which all future search for
economic minerals could be based. From the genetidc and structural point of
view, there is a definite relation between the geological formations or rock
types in any region and the type of economic minerals that are associated.
Thus, the most important iron ore and manganese ore deposits of India occur
closely associated with the formations of Precambrian era and the most important
limestone and dolomite deposits are associated with the rocks of Penganga,
Pakhal and Kaladgi groups. Similarly, the most important coalfields are
associated with the sedimentary rocks of the Gondwana sequence. The important
oil deposits of India are associated with rock formations of the Tertiary
period and so on. It is, therefore, of prime importance to know intimately the
nature of occurrence and distribution of different geological formations that
occur in the various parts of the State in order to have a proper knowledge of
the potentialities of mineral wealth and for guiding the search for future
location of mineral deposits.
The stratigraphical sequence of the various rock formations
that occur in Maharashtra State and the important minerals that are associated
with each formation are shown in the Table given below :
TABLE
Time units (Period)
|
Type rock formation
|
Associated mineral
|
1
|
2
|
4
|
Recent, Sub-Recent and Pleistocene
Miocene-Pliocene
|
Alluvium Laterite Soil Sand etc.
Tertiary sediments lignite, shales
|
Kankar, Brick and pottery clay, sand
illmenite,inferior grades of iron ore and manganese ore, ochres, bauxite
lithomarge, etc.
Clays, Lignite
|
Lower Eocene-upper cretaceous
|
Deccan trap with the intertrappeans and
infratrappeans (Lametas, Bagh beds)
|
Building stone road meatal, inferior limestone,
agate, jasper, opal, rock crystal, calcite, zeolites, gypsum etc.
|
Jurassic (Upper Gondwana)
|
Limestone, Chikiala and kota formation
|
Limestone
|
Triassic
|
Clays, Sandstones and Maleri formation
|
Sandstone and clays
|
Permian (Lower Gondwana)
|
Sandstone and shales Mangli beds Sandstone and Shales
Kamthi formation. Micaceous sandstone with clays.
|
Clays
|
|
Motur formation (Sandstone and Shale). Barakar
formation (Sandstone Carbonaceous shale and coal)
|
Coal fire clays
|
Upper Carboniferous
|
Talchir formation
|
----
|
Pre-Cambrian
|
Limestone, Shales and Sandstones (prenganga beds).
Limestone and shales (Pakhal group).
Sandstones, limestone Conglomerates, quartzites and
shales (Kaladgi Group).
Sausar Group
|
Limestone, Fluorite
Limestone, Baryte
Limestone, Clays, Glass sand, foundry sand
Manganese ore, calcitic and dolomitic crystalline
marble, quartz
|
|
Dongargarth Group/Sakoli Group, Iron ore Group
|
Iron ore, Chromite, Tungsten ores, Copper ore, Zinc
ore, Gold Manganese ore, Kyanite, Sillimanite, Corundum, Pyrophylite
etc.
|
Precambrian (Older)
|
Older Schists and gneisses (unclassified crystallines)
|
Barytes, chromite, felspar, sillimanite, quartz,
soapstone, antimony, corundum, copper, mica, etc.
|