Dr.Thrivikramji.K.P.,
Professor of Geology (Retd.) C/32, Sankar Lane,
Sasthamangalam, Trivandrum
695 010
ABSTRACT.
Sand is of to two types,
viz., the fine aggregate used in cement mortar and cement concrete and mineral
sand primarily containing one or more valuable ore or industrial minerals and
gravel, the coarse aggregate. Both are either natural (coming off modern
alluviam) or machine made (by crushing stones and rubble of suitable quality).
Most of the sand (size
= 2000 - 62.5 microns), is composed of the common rock forming mineral quartz,
which dominates nearly all known accumulations of sand in the world, whether in
beaches of seas and lakes or in modern or ancient river alluviam or in deserts.
Fluvio-glacial deposits of the outwash plains in regions at higher latitudes
and shallow-seabed have also been other important sources of sand.
Quartz, ubiquitously
and abundantly present (say from about a quarter to a third by volume) in
common crustal rocks (like granites, granite gneisses, diorites and as quartz
veins), is a light mineral (sp.g @ 2.65) of good durability (due to chemical
inertness, lack of cleavage, hardness @7, and conchoidal fracture).
Chemically inert
quartz is liberated from its parent rocks (both igneous and metamorphic) chiefly
by the process of chemical weathering (an extremely slow process) or chemical break-down
of other rock-forming silicate minerals like feldspars and ferromagnesians. Weathering
product of a rock is a mixture of clays, quartz and minor accessories like the
heavy minerals (sp.g = >2.9).
Some better-known
examples of mineral sand are: a) diamond bearing sands in certain beaches in
western .Africa, b) ilmenite bearing black-sands of Travancore - now part of
Kerala, c) red-sands of erstwhile Tirunelveli Dist., Tamil Nadu, d)
dark-beach-sands of Narcondam Is., in the Andaman Is. chain, and e) gypsum
sands of White Sand National Monument,
in s.w. USA.
Processes of erosion
and transport by running water or wind, work on the weathered rock particles to
concentrate the sand grade quartz and deposit it in continental environments
like flood plains and river channels, transitional environments like deltas, beaches
of lakes and shallow seas or sometimes even as sheet sands in deserts.
However, mining of aggregate
(i.e., sand and gravel) and its use are the foundation of prosperity of any
nation and quality of life of the population. Nevertheless geological “lottery”
has favoured at least some nations against others in respect of distribution of
mineral sands.
Impacts of sand and
gravel mining are very much similar to those of open cast mining or large scale
quarrying or dredging sans drilling and blasting. Granular, poorly or semi-consolidated
sandy sediment is excavated manually or with a power-shovel or such other
machines. Chief environmental impacts of sand and gravel mining are very
visible, like noise and dust from machineries and operations, trucks operating
in and out of the sites, changes in water quality due to settling of dust, stress
on aquatic life, lower esthetic value of natural settings, changes in surface
water and groundwater regimens. Some plant or animal species may face certain adversities.
Chemical pollution is practically absent in such operations.
Key words: aggregates, weathering, crushing and
screening, manufactured ballast
INTRODUCTION
Sand and gravel or aggregate
mining is as old as the first building of brick and mortar. Aggregate, defined
as the material added to cement, lime, gypsum, bitumen or other adhesive to
form concrete or mortar, can be classified into two types, viz., coarse gravel
and fine sand (Table 1). Addition of aggregate provides volume, stability and
lower wear and tear. Broken stones, pebbles, blast furnace slag, broken
clinkers, burnt shale and burnt clay (e.g., in Mullaperiyar dam) are examples
of coarse aggregate. Obviously, aggregates originate directly or indirectly
from the rocks and sediments of the earth’s surface.
Aggregates are truly the
backbone of development of any nation and its annual consumption is yet another
index of development-status, rate of growth and quality of life of the population,
and hence of the nation. All constructions with cement mortar, plain and
reinforced concrete (wherein aggregate constitutes @85% by volume) would not have
been possible in the absence of sand and gravel. Further, construction and maintenance
of a country’s infrastructure like runways, roads, rail-roads, bridges, canals,
various sorts of commercial and residential buildings and such others call for
input of aggregates. In developed countries of the world like USA, Canada, Germany, Japan, China and
others, annual consumption of sand and gravel is on the rise with rise of their
GDP. Any addition to such facilities like
houses, multi-storey complexes, schools, colleges, hospitals, churches,
cemeteries, highways, rail roads, road and rail bridges, bus and train
terminals, airport runways, harbours and
so on, annually consume large volumes of coarse and fine aggregates.
Equally important is
the role of mineral sands in manufacturing and other industries where in a
derivative of mineral sand finds hugely significant applications (for e.g.,
titanium of ilmenite goes into making of airplanes and white paint). But one
advantage with mineral sand is that in its absence, local or temporary
shortfall, the particular metal or mineral can be imported from another country,
which is untrue in respect of aggregates as the volumes involved are simply
stupendous.
In India, the
post-globalization emphasis on upgrading transportation sector, like making of 4-lane
highways and 6 lane express ways, conversion of meter-gauge into broad-gauge
lines, doubling of single lines to double-lines, construction of new Greenfield
airports and expansion of existing airports etc., is calling for huge and ready
supply of good quality aggregates. Like any other mining operation, mapping,
assessment of volumes and grades, development, production and stockpiling to
ensure delivery-on-demand to the client through a supply chain has a gestation
time. One other great advantage of quarries or mines producing aggregates is
that no drilling or blasting is involved. Instead bulldozers, front end loaders,
dragline buckets etc are used in the excavation, followed by washing, screening
and stock-piling. However, in a country like India, with very low occurrence of
fluvio-glacial deposits, hard crystalline rocks need to be quarried for
manufacturing of coarse and fine aggregates to meet country’s needs.
In what follows,
various attributes of gravel and sand, like origin, formation of gravel and sand
bodies, mining or quarrying of sand and impacts of mining are reviewed along
with an overview of importance of sand and gravel to the nation and society.
GEOLOGIC BASIS OF AGGREGATES
The process of Weathering
attacks the rocks in a dual manner in that one is a physical modification and
the other a chemical action, which jointly readies the rock for erosion by
geological agents like wind, water and glaciers. Physical weathering or
disintegration weakens the surface rock (Table 2) by alternate heating during
the day and cooling at night, frost wedging by the pressure exerted by ice formed
from water and moisture trapped in cracks and joints of rocks in colder
climates, and wedging apart of blocks of rock by growing tree roots. These
afford newer avenues for agents of chemical weathering (decomposition) to act
on the constituent minerals.
Engines of chemical weathering
are various natural chemical reagents, like, alkaline solutions, carbonic acid
and humic acid. Dissolution, oxidation, hydrolysis and acid hydrolysis are the
chief weathering processes. Despite their low concentrations, the constituent silicate
minerals (but with the exception of quartz), are attacked steadily for very long
periods of time (several 100,000s of yr)
which finally transforms them to newer hydrous silicates or clays that are stabler
at the earth’s surface conditions (Table 3). Process of denudation or chemical weathering
is proverbially slow that we humans do not perceive any visible or even
measurable change in the appearance of rocks or its constituent minerals.
Moreover, as the process of weathering is climate, relief and rock dependent,
it is less logical to come up with one single number for the rate. Though,
estimates of weathering rates are nearly difficult to make, some site or climate
specific estimates have been made.
For e.g., in our
tropical climate, with alternating wet and dry spells, most rocks and sediments
are transformed to Laterite - the typical ubiquitous cover in the midland of
Kerala and many parts of India. Laterite is also seen in other parts of the
world, where tropicality prevails. In French Guyana, studies by a French team
(Freyssinet and Probst, 1998), led them to believe in a rate of weathering of 3.0
m/Ma. But in another report from Up.Niger basin, Boeglin and Probst (1998) estimated
a rate of 1.3 to 3.7 m/Ma. Menard (1966) estimated the rates of erosion for the
Appalachian region, Mississippi
valley and the Himalayan region in the geologic past and present time. The data
is very instructive in that the unsettled Himalayan region perhaps sheds the
largest volume of sediment (118.47 m3/km2/yr or 0.12 mm/yr) to the tune of 0.12
mm annually (Table 4). Therefore, availability of erodible gravelly sand is
much less than the expectations of a generalist. In fact, it is this truism regarding
the rate of supply of sand to the rivers that never was correctly understood or
perceived by citizens outside of the geological profession. Instead, the rule
of thumb happened to be that the river bed is not only an everlasting reservoir
of sand, but it is automatically annually renewed on a use-it-or-loose-it
basis, unaffecting the river’s physical or biological systems.
Thus erosion of
weathered rock material is what creates sand and gravel deposits in the stream
bed. Gravel is characteristic of up stream reaches of the drainage; while in
the middle and lower reaches finer gravel and sand are very characteristic.
However, unlike the glaciated terrains of higher latitudes, the tropical
terrains (including India) are bestowed with much less volumes of naturally
washed stream bed gravel, and hence the needs for gravel or coarse aggregate have
been met from rock-crushing-screening-units (manufacturing gravel) in the
vicinity of quarries, or even manually breaking the rubble to required size.
PERSPECT: INDIAN SCENARIO
Soon after
independence, with the vehicle of V-year plans India launched an ambitious
program of building, very large cement and concrete structures (to the tune of several
hundred thousand square meters) to house schools, colleges, hospitals,
factories and office space as well as large number of dams, power stations, bridges,
runways etc. In a vast majority of such cases, river sand was the fine
aggregate while manufactured gravel equated with coarse aggregate. But private
houses very strictly stuck to river sand. However, as cited in the foregoing,
production of sand by nature being an extremely slow process, rate of removal
of sand from river channels more often than not out-paced the rate of supply. The
combination of waster water from homesteads and industry were piped into or discharged
into one or other channel network, and removal of sand led to an “ecological demise”
of a large number of rivers (at least in Kerala) and in rest of the country?.
Some of the
consequences of removal of river channel sediment or sand documented Thrivikramji
(1986) are summarized below. Sand borrowing affected a physical system of the river
chiefly in 3 ways. Firstly, it led to fining of the texture of channel bed
sediment, due to preferential removal of coarser sand fraction, resulting in a
loss of spawning ground of the aquatic fauna. Secondly, abundance of finer sediment
caused a decline or fall in the depth of the photic zone risking the abundance
of primary producers. Thirdly, removal of sand resulted in deeper channels, causing a
disequilibrium between the banks and bed of river or in a higher freeboard for
the channel walls with reference to channel floor. Such slumps brought down and
destroyed several hundred standing coconut trees over a river length of 20.0
km. and on either banks of the Neyyar (Thrivikramji, 1986). All these jointly
caused a sharp decline of faunal diversity and as well as fall in population density
of the riverine-aquatic-life. Over reliance on river channel sand both in
public and private constructions deprived the rivers of Kerala, from their legitimate
load of sand, resulting in the transformation of physical and biological health
of the river. Moreover, this in combination with effluents originating from towns
and villages, caused the “ecological demise” of most of the rivers of Kerala. In
he Neyyar basin, sand borrowing activity reached hectic levels (i.e., 180,000
tons/yr, in 1985 calendar yr.), which truly was far in excess of the combined
annual discharge of dissolved and suspended loads to Neyyar. Loss of income due
to uprooting of standing crops like coconut palm by wall collapse or slumping,
was estimated as Rs.750,000/- per annum.
Yesteryears: pre-1990’s
India lives in the
villages and the state of homes, sanitation and quality of streets, schools and
health centres on the one hand and that of the irrigation systems on the other
serving the population of 400,000 or more villages of India are the best indices
of quality of life of majority of Indian citizens. In fact, paved streets,
permanent buildings to house the families, school classes and health care facilities
have not yet been fully met with. For a long while, the well-to-do, accounting
for a smaller percentage of the population, lived in good houses that used masonry.
River sand and to some extent river gravel, certainly met the local demand for
aggregates. However, predominant portion of coarse aggregate belonged to the
manufactured category, leaving the rivers to mend themselves.
Current trend
Currently, the picture
certainly changed (for good) drastically. Now, under the various programs of states
and center, massive investments are made in the village sector and as a
consequence demand for Portland cement and aggregates too skyrocketed. As per last
year’s data (2006), cement production in the country stood at 160 million tons,
accounting for an input of 906 million tons or 515 million cm3 of aggregates (@
a sp.g. 1.76). Use of “manufactured” aggregate is catching up in the
construction industry along with ready- mix concrete. Recently, several large
capacity rock-crushing-screeninging plants have come up in the various states,
including Kerala associated with what are called super-quarries.
.
Truly with the government’s
emphasis on modernizing the infrastructure in the surface transport sector, the
level of aggregate and cement production is getting ready for a quantum leap. But,
the rivers of India will not be in any position to meet the requirements of aggregate
by the new growth centers or sectors spread across the country. Unlike cement
and steel, as far as possible aggregate must be sourced locally, in order to
offer a low or attractive price to the end user. For example, builders in
Trivandrum dist, Kerala, due to non-availability of river sand, source it at a
very high price, from places like Sri Vaikuntam (in the shore of Thamraparni
Ar,) in TN – like 150 km. one way from the user site.
PROSPECTS: FUTURE DIRECTIONS
India, a large populous
country (Population = one billion; area =3,166,414 km2) occupying little more
than 2.0% of the land area of the earth, is developing at a relatively fast
pace of over 7.0%. Majority of the Indians live in the villages, a colossus of about
400,000. But, the distressing fact is that about 1/3 of the population still
lives below the poverty line. Truly in the first 4 decades after independence,
no immediate attention was bestowed on the development of infrastructure of the
country like modernization of roads, rail roads, airports, houses for millions etc.,
or securing a healthy environment in the villages.
Table 5 gives a
picture of the present status of surface transport facilities in the country. All
such constructions will require input of gigantic volumes of sand and gravel
along with cement and steel. Mining or quarrying or manufacturing of both sand
and gravel is bound to create environmental problems and this challenge can be faced
up and tackled by a team of geoscientists, leaders of the society, mining
company and regulators of mining. More over, with the ambitious plans in the
real estate and infrastructure sectors in India, we must examine the
possibility of sourcing aggregates from even the shallow seabed; mine waste
storages, cinder or slag of industrial smelters and recycling of building waste
etc. It is high time that construction sector buried the one-material-one-source
mindset and instead one-material-multiple-sources.
In fact, new-divided
4-lane-highways, new express ways and undivided-2-lane-national highways would have
consumed a large quantity of aggregate like 14.0 x 10 12 tons (or 14.0 trillion tons) only to build initially.
Renewal or maintenance would demand an additional input of a lesser volume like
a third of this, say once in three or four years. The story is not very different
in respect of the Indian railways either. Indian railroad net work is one of
the largest in the world (Table 5). In the rail road, ties and rails are placed
over a track-bed of crushed stone or ballast of 4.0-6.0 cm. size and over a thickness
of at least 30.0 cm. The construction of rail road system in India would have consumed
a volume of 132.0 billion cubic meters or 232.0 billion tons of ballast. The
renewal of track bed is one of the vital tasks of track maintenance, when older
worn out stones are replaced with new ballast, needing a relatively large
volume new material.
Mineral sand
The black sand (BS) deposits
are chiefly seen in the beach placers in the states of Kerala
(Chavara-Ambalapuzha), Tamilnadu (Manavalakurichi) and Orissa. Being what these
are, at least in Kerala, there is an ongoing controversy regarding mining of BS,
Due to the high population density (side of support squareof a person =32 .0 m)
of the coastal land, this valuable mineral industry is yet to get a legitimate
chance to expand or to permit entry of new private players.
Interestingly, the
offshore of Kerala is a vast reservoir of a silty-muddy-sand carrying fairly
large percentage of black heavies. The recent Tsunami of Dec, 26, 2005, offered
the smoking pistol on the abundance of BS in the offshore. Very large volumes
of BS were washed over the backshore by the Tsunami wave, blocking the coastal
roads for days together and withholding the entry of automobiles carrying
relief supplies. JCB’s had to be brought in to clear the road pavements in
order to allow entry of 4 wheeled vehicles.
In fact, the mindset of
public in respect of BS mining needs change as Kerala has one of the best-known
BS rich sediment of the world sitting in the offshore, a portion of which is deposited
on the eroded beach-face when the waves start rebuilding of the beaches after
the initial erosional phase of SW monsoon. This renewal of BS placer takes
place annually in association with the SW monsoon. The seabed sand deposit is a
vast reservoir of sand deposited in the inner shelf during the last 65.0 ma
(Vinodkumar, 2004). According to
Anthraper et al., (2005) worth of the BS in Kerala, after mining and
concentration and at to day’s price is in excess of Rs.40,000 crores during the
next 30 yr. or at 10 or 5% royalty a whopping 4000 or 2000 crores of rupees. A portion
of this money can be used for constructing first rate township/s for re-settling
the population of the coastal tract of Kollam-Alappuzha sector, who otherwise
are herded to and sheltered in school buildings or similar places to escape the
wrath of monsoon waves.
IMPACTS OF MINING
Aggregate mining by
quarrying or open cast mining is no different from strip mining, where the
overburden is initially removed to expose the valuable deposit which can be
accessed with mining machinery. It is not quite true in respect of granular,
unconsolidated, accumulations of sand from the modern river beds and flood
plains or from deserts. Conversely, in the Indian context, when all the
aggregate needs to come from quarries after crushing, sizing and washing, a
degree of drilling and blasting precedes making of gravel. The important environmental concerns are the
following.
a) Noise pollution from the blasting, operation of large machineries in
manufacturing aggregate (both fine and coarse); by the large trucks and moving
in and out of the site
b) Dust pollution from operations like drilling and blasting; crushing,
sizing, stocking and handling; as well as from the traffic of heavy duty trucks
c) Disfigurement of landscape due to the scars left behind by abandoned
mines and quarries.
d) Modification of ground water as well as surface water regimens and geometry
of stream network, and finally
e) Pollution of surface and ground waters due to unscientific disposal of
used oil, grease and other petroleum products.
f) Waste water with fine dust laden water from the battery of screens
g) All mining activities will result in small and large scars of abandoned
pits as well as some amount of stony waste.
Measures recommended
for containment of negative impacts of strip mining are:
a) Some of the measures suggested to contain these negative aspects of
strip or open cast mining are building of a green belt or living barrier along
the perimeter of the mining and operational areas. Fencing by some
strip-planting of fast growing tree species are generally recommended
b) Establishing a more or less continuous tree belt, around the mining and
processing area to hold back considerable volumes of fine dust, as well as good
deal of noise caused by the machinery. Tree strips also function as an
effective barrier against air-flow or wind whipping the dust into the air.
c) Sprinkling or spraying water on the truck tracks and other possible
sources of dust. Vegetating with suitable species of natural turf to minimize
the bare patches or parcels of loosened soil.
d) Battery of water clarification tanks will create water that is suitable
for wet screening. Ponding or storage of waste water in low capacity reservoirs
is a process to be strictly adhered to prior to release of this water essential
to lare essential to . reusable washing.
e) Careful design of mine plan must be adhered to ensure avoidance of
blocking of stream courses, however small they be and especially in areas
dominantly with wet and humid climate.
f) Large and small pits abandoned after mining needs to be restored to the original
near natural state in respect of the soil horizons and vegetation, by placing
the overburden back in, strictly adhering to the natural order of succession of
the sediment layers. But in respect of aggregate quarries, it is nearly
unfeasible due to the near total salability of practically all the material
coming out of the mining operations. Further, the abandoned mine pits in
crystalline rock areas, it is more impractical. On the other hand, such pits
can be intelligently converted to huge water storage facilities, if required by
applying some “friendly” seal to enhance water tightness of the basin. It can
then be a site for water sports as well as recreation and picnicking. All it
takes is an ingenuity of people in the immediate neighbourhood to come up with
practical positive uses of abandoned strip mines. The sand and gravel pits are
no different in this respect.
g) In respect of black-sand mining in the west coast (both
Chavara-Kayamkulam tract in Kerala and Manavalakurichi in TN), operations are
firstly along the beaches built by the latest monsoon wave climate, and
secondly by using earth moving machinery like bulldozers, front end loaders,
heavy duty scrapers/levelers and dump trucks to transport the mineral sand to
the stockyard. Mining never goes below low-water-mark. Year after year
blacksand placers are consistently rebuilt by the monsoon waves, However,
mineral sand mining in the east coast of TN is primarily focused on the ancient
coastal dunes, and hence a certain degree of disfigurement of the natural
landscape is unavoidable. However, backfilling of the lows or shallow pits are
with the waste from the mineral separation plants.
h) Yet another way of reducing the impact on the community could be by
locating lease areas outside of the region of visibility of the members of the
community. In general an alliance of the leaders of the community, mining
company, local and state mining regulator and geoscientists can certainly
contribute to minimize and even largely forestall the negative impacts from
mining and related operations.
SUMMARY
“If you can not grow
or buy it, you got to mine it”. This Chinese proverb aptly and bluntly tells us
the need to mine the resources on or below or deeper below the surface in the
crust. Distribution of minable minerals
is far less uniform in the rocks that some continents and nations have more
mineral wealth than others. Any mining activity is a special effort focusing on
a target of anomalously large natural concentration of one or more minerals in
the solid earth and results in a “huge” accumulation of waste. The latter will
have deleterious and occasionally unpredictable impacts on the biosphere by the
mediation of pedosphere and/or parts of hydrosphere. It is sort of an
occupational hazard.
Yet, like any mining
operation, aggregate mining can be pursued very scientifically and
intelligently to provide for the ever growing needs of the society to build and
maintain large infrastructural projects in the sectors like, transportation, housing,
recreation and trade and commerce. For e.g., conversion of the undivided single
lane National Highways of India, to divided, two and four lane highways and
superhighways will initially call for nearly a trillion tons of aggregates. The
requirement aggregates for the new generation airport runways and
modernizations and maintenance of rail roads also point to a staggering bulk. CONSIDERING
the large population base, needs of housing and commercial and recreation
sectors are also bound to be very huge. With approximately 160 million tons of
cement produced last year, the requirement of aggregates would be hovering
around 906 or let us say 900 million tons (=511 million m3).
Scientific planning, design
and execution of mines along with active co-operation of community leader,
scientists and administrators, the requirements of aggregate of a district/s
can be easily secured, ensuring minimal adverse impacts on the environment. But
mining or gathering or aggregating black sand in the west coast (Kerala and TN)
is targeting the blacksand placers annually accumulating in the beaches, during
the latest monsoon. Contrary to this, Garnet separation plants in the east
coast utilize the mineral sand in the ancient sand dunes in the inland, and modern
backshore. But refilling of the lows or scars with the waste sand to a large
extent restores landscape to near natural contours.
It is high time, to examine the feasibility of
overburden of Neyveli Lignite Corporation or the granular waste came off the
erstwhile Kolar Gold Mines are suitable substitutes for fine aggregate after a
pre-treatment or clarification.
ACKNOWLEDGEMENTS
I sincerely thank the
organizers especially Prof.(Dr). Ambazhgan (Periyar University) for
encouragement and Mr. Praveen Kumar, a young geologist, for library search.
Many of my thoughts in this regard heavily lean on a status study of the Neyyar
in south Kerala, in the eightees, with funding from the MOEF, GOI.
REFERENCES:
Anthraper, BJ, et
al., 2005, Black sand deposits of Kerala: A cost-benefit analysis: Abst. of
Paper in “Mineral Resources of Kerala”, Feb. 2005. Trivqandrum
Boeglin,J.L, and
Probst,J, 1998, Physical and chemical weathering rates and CO2 consumption in a
tropical lateritic environment: the Upper Niger basin: Chem. Geol., 170,,
133-151
Freyssinet, P. and Farrah,
A.S. 1998, Geochemical mass-balance and weathering rates of ultramafic schists
in Amazonia, Chem.Geol., 170,113-121
Menard, HW, 1961,
Some rates of regional erosion, Jour. Geology, 69, 154-161
Thrivikramji.K.P, 1986,
River Metamorphosis due to Human Intervention: A Neyyar basin experience: Final
Report submitted to MOEF, GOI, 153p.
Vinodkumar, N, 2003,
Sedimentology of the Placer sands of Kerala coast: Unpublished Ph.D. thesis,
University of Kerala, 117p
Wedephol, K.H, 1969,
“Composition and abundance of common igneous rocks” in Handbook of Geochemistry, Wedephol,
K.H,(ed), Springer Verlag, 227-249
-------
Table 1. Size grouping of aggregates
(Encyclopedia Britanica)
|
Type
|
Size, mm
|
Size, in
|
|
Fine
|
0.025 – 6.5
|
0.001 -0.25
|
|
Coarse
|
6.5 – 38.0
|
0.25 – 1.5 or
larger
|
Table 2 Abundance of intrusive rocks in a standard
section of upper continental crust (Wedephol,1969)
|
Rock type
|
Abundance, %
|
|
Granite & Quartz monzonite
|
44.0
|
|
Granodorite
|
34.0
|
|
Quartz diorite
|
8.0
|
|
Diorite
|
1.0
|
|
Gabbro
|
13.0
|
|
Others
|
3.0
|
Table. 3 Mineral proportions in plutonic igneous rocks (Wedephol,1969)
|
Mineral
|
Granite
|
G.diorite
|
Q.diorite
|
Diorite
|
Gabbro
|
Up.crust
|
|
Plagioclase
|
30
|
46
|
53
|
63
|
56
|
41
|
|
Quartz
|
27
|
21
|
22
|
2
|
--
|
21
|
|
P.feldspar
|
35
|
15
|
6
|
3
|
--
|
21
|
|
Amphibole
|
1
|
13
|
12
|
12
|
1
|
6
|
|
O.pyroxene
|
--
|
--
|
--
|
3
|
16
|
2
|
|
C.pyroxene
|
--
|
--
|
--
|
8
|
16
|
2
|
|
Olivine
|
--
|
--
|
--
|
--
|
5.
|
0.6
|
|
Magnetite
Ilmenite
|
2
|
2
|
2
|
3
|
4
|
2
|
|
Apatite
|
0.5
|
0.5
|
0.5
|
0.8
|
0.
|
0.5
|
Table 4. Rates of regional erosion (Menard,1961).
|
|
Ton/acre/yr
|
Ton/km2/yr
|
M3/km2/yr
|
|
1
|
0.55
|
135.85
|
51.264
|
|
2
|
0.50
|
123.5
|
46.60
|
|
3
|
0.74
|
182.0
|
68.697
|
|
4
|
0.10
|
247.0
|
9.32
|
|
5
|
2.62
|
647.14
|
244.2
|
|
6
|
12.00
|
2964.0
|
118.47
|
Note: Geologic (1) and modern (2) deposition rates in
Mississippi basin- the rates are nearly same. Deposition rates (3) in the
Appalachian region in geologic past and modern day (4)
Geologic deposition rate (5) in the Himalayan region
and modern day rate (6)
Table 5. Road and
Rail road network, India ( from website of GOI)
|
Roads, Types
|
Length, km
|
Rail road
|
Length, km.
|
|
Express ways
|
200
|
Total track
|
62195
|
|
National Highways
|
66,590
|
Double track
|
12617
|
|
State highways
|
128,000
|
|
|
|
Major Dist. Roads
|
470,000
|
|
|
|
Rural & other
|
2,650,000
|
|
|
