Placer Deposits --Final Contents: 1. Introduction 2. Classification 3. Formation of placers 4. Conditions favourable for placer deposit development 5. Factors controlling formation of placers 6. Ages of placers 7. Mineral concentration and accumulation 8. World Distribution of placer mineral deposits 9. Indian distribution 10. Conclusions

Objectives: The objectives of learning this module are to understand the placer deposits by studying their characteristic, physical properties, classification, formation of placers, factors that are controlling the formation of placers, world distribution and Indian distribution of placer deposits in particular.

1.0 Introduction Placers are very important economic minerals found in the near shore environment. These are detrital minerals which have been transported to their sites of deposition, in a particular form. Placers are mineral deposits that have been formed by the mechanical concentration of detrital mineral particles in subaqueous environments.They occur, in beaches, , dunes and offshore areas. The minerals that constitute the placer deposits are resistant to chemical breakdown and have high and durability. Placer minerals include elements in their native state such as , and , and resistant minerals such as , , , , , , and corundum.

Most of placer minerals occur within a few kilometers of their source. Thus marine placers are confined to near shore zone. However, placers also occur on ancient submerged beaches or in drowned valleys far away from shore line or on raised beaches.

The most commonly used definitions of placers refer to the concentration of valuable detrital minerals formed by sedimentary processes. Theses minerals are distinguished by the relatively high specific gravity that serves as the principal cause of concentration.

1.1 Mineral : Deposits of mineral sands are gaining economic importance on many occasions. Today people concentrate on mineral placer deposits occurring along beaches. Most of the mineral sands are exploited for in the form of rutile and ilmenite, with by products of zircon and commonly kyanite, sillimanitestaurolite, or garnet. At one time, the mineral sands were shipped as concentrates of three naturally occurring minerals like rutile, ilmenite, and leucoxene.

1.2 Economic importance: The economic mineral in placers are those with a specific gravity greater than 2.65, i.e., that of the main gangue mineral, . Individual placer deposits are exploited for gold, minerals, cassiterite and . Each of these may also occur as an accessory,as by-product concentration with another dominant mineral. Less commonly, placers also include sheelite, , bismuthinite, native copper, cinnabar, magnetite, , anatase, columbite-tantalite and pyrochlore. Since the 1970’s, Australia has overtaken India and the United States and now dominates the world’s production of ilmenite, together with rutile.

1.3 Historical importance: Placers have been mined on all continents except Antarctica. Historically, placers have yielded a very significant part of the world’s total supply of gold, platinum, , and diamonds. Page 1 of 10

They are presently the source of most of the world’s titanium. With the exception of mineral sands, the productive role of placers declined considerably during the 20th century and continues to decrease overall as reserves diminish. Diamond especially in the environment, being the only sector exhibiting growth in recent years.

The history of placer deposits as a source of economic minerals began with the discovery of monazite in the beach sands of Manavalakurichi (Tipper, 1909). This was first worked in 1911 and rapidly developed with the establishment of Ti02 (titanium) pigment industry in Europe and America. In early 1930's, India accounted for 80% of the total ilmenite production in the world. However, by the 1950's the ilmenite production marked a sudden decrease in the country. This owes, in part to the discoveries of new deposits in Australia and Canada and the presence of undesirable impurity like chromium and ferric in Indian ilmenite. Many features of Placer deposits and their evaluation were known a century ago.

2.0 Classification of placers: Placers may be classified according to the main mineral constituent, the physical and chemical properties of the mineral, age, size, tectonic history, means of formation, or geomorphological form. Kazakevich proposed a classification based on placer’s genesis. Lindgren gave due credits to geological location and tectonic history.

2.1 Emery and Noakes(1968) classified placer minerals into: i. Heavy- heavy minerals with specific gravities of 6.8 to 21 ii. Light -heavy minerals with specific gravities of 4.2 to 5.3. iii. Gems with specific gravities of 2.9 to 4.1

2.2Classification Based on physical properties Gold, platinum and cassiterite are important heavy- minerals; ilmenite, rutile, zircon and monazite are important light-heavy minerals and diamond is the most important gem placer mineral. The following table gives the physical properties of some common placer minerals.

Mineral Hardness Specific Resistance to (Moh’s scale) gravity Cassiterite 6.7 6.8-7.1 High Diamond 10 3.52 Very high Garnet 6.5-7.5 3.5-4.3 Moderate Gold 2.5-3 19.3 Very high Ilmenite 5-6 4.5-5 High Magnetite 5.5-6.5 5.1-5.18 High Monazite 5 4.9-5.3 High Platinum 4-4.5 21.46 Very high (chemically pure) and 9 3.95-4.10 Very high Zircon 7.5 4.5-4.7 Very high

2.3Folk (1971) has divided the heavyminerals into three groups, based on their physical and chemical naturenamely, opaques, ultra-stables and meta-stables.

2.4Routhier (1963) classified Placers into a simpler type of subdivisions. Placers are classified into (1) eluvial, (2) alluvial or fluvial, (3) eolian, (4)beach placers, and (5) fossil placers based on their mode of transportation and site of deposition.

1) Eluvial placer: A placer deposit that is concentrated near the decomposed outcrop of the source.This is the embryonic stage in the development of placers. Page 2 of 10

2. Alluvial placers: Placers or its associated valuable mineral, formed by the action running water. The heavy minerals are introduced into the fluvial system by the action ofrunoff, gravity or by the erosion process of streams themselves.

3. Eolian deposits: They occur in arid or semiarid regions, where the influence of wind is strong and sufficient vegetation does not exist to cover the soil.

4. Beach placers: Such placers are formed by the interact on of the terrestrial processes with the coastal hydrodynamics

5. Fossil placers: Placers formed in the geologic past, which were removed from the sub aerial environment by factors like changes in climate and/or epirogenic movements and eustasy are called fossil placers or submerged placers.

2.5Kartashov(1971) identified two types of placer, autochthonous and allochthonous on the basis of their formational processes. He described the former as predominantly proximal to the sources and formed mostly during fluvial downcutting. Allochthonous placers are concentrated during an aggradation stage after some significant transport.

2.6Burton and Fralick(2003) preferred to classify placers as erosional or depositional.

3.0Formation of placers: For any placer deposit to form the conditions to be satisfied are the following: 1) a primary source for the mineral placers, which are usually crystalline rocks. 2) a suitable weathering environment, which is required to liberate the minerals from the source rocks and 3) agents of transportation like running water, wind etc. which move the placer-forming minerals to the zones of concentration where they are deposited.

3.1 Sources: The formation of placer mineral deposits requires a primary source and involves process of erosion, transportation and concentration. The main environments of placer mineral deposition are rivers, beaches and the offshore area. The formation of placer mineral deposits on beaches results essentially from the selective sorting of the beach deposits in the intertidal zone by wave and current action with the velocity of the backwash being sufficient only to remove light minerals, thus leaving the heavy minerals behind (dunham 1969). Placer minerals can occur in several situations in the offshore area.

3.2 Discontinuous episode: Formation of placers is a cyclic process of erosion and deposition. It is a result of series of discontinuous episodes completed within an epoch, a period, or an era. The cycle commences with exposure and weathering of a minerals source. Two processes, like physical and chemical are involved, alone or together. The result commonly is the creation of a regolith, a mantle of loose , fragmental rock debris, soil or clay, which covers the more coherent bedrock from which it is derived.

3.3 Physical weathering : Physical weathering, especially periglacial forms, with little chemical weathering, is dominant in subarctic regions. It is not as specific as the chemical weathering in favouring the release of certain minerals. Acting alone, physical weathering produces a fractured rock crust without any change in the mineralogy.

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3.4 Chemical weathering: Chemical weathering occurs during warm, preferably humid, conditions. It is most intence and extends to the greatest depth, tens of meters in tropical climates. Resistant placer and accessory minerals are liberated with quartz, whereas rock-forming silicates are altered. In situ weathered mantles that contain economic concentrations of placer minerals constitute eluvial placer deposits.

Weathered ground may move downslope under the influence of gravity alone, lubricated by ground water, or washed by flowing surface water, to form a colluvial deposit. The various means of mass movement are determined by the physical nature of the ground, climate, elevation, and slope gradient.

3.5 Topoographiccontrols : Placers may form in higher elevation, low order, headwater creeks, gullies, gulches and canyons in all of which placers have been mined. Beach placers result from the concentration of heavy minerals by waves on the foreshore, the active portion of the beach between low-tide level and the level attained by storm waves. Mineral sands are most efficiently concentrated by wave action on the foreshore.

4.0 Conditions favourable for placer deposit development: Three events, alone or in combination, initiate the formation of a placer, some form of tectonic activity, a change in climate, and a change in relative sea level.

4.1Tectonic activity: Plate tectonics results in continental collision within plate boundaries, creating a combination of horizontal and vertical uplift. Uplift causes a fall in relative sea level and immediately affects coastal rivers, increasing their gradients. Uplift alternates with subsidence and localized down warping , causing an on-and off-lap surrounding oceans with accompanying deposition of platform sedimentary sequences.

4.2 Climate change: Climate change is created by external factors, such as the Earth’s orbital variations that are thought to have triggered global ice ages, and internal factors. Climates, their changes and their role in placer formation differ globally in both time and place. Four basic climates are arid and cold, arid and warm, humid and warm, and humid and cold.

Colder climates encourage physical weathering with solifluction and, at high elevations coupled with sufficient snowfall, glaciation. Warmer climates, especially in combination with humidity, result in chemical weathering.

Change in climate may be more important than the climate itself at any one time and place and encourages alternating effects of weathering and erosion. A change from arid to semiarid conditions increases the availability of water in source areas, increasing the rate of sediment transport. Erosion is assisted by the lack of vegetation cover.

4,3 Change in sea level: A fall in relative sea level reduces the base level of coastal rivers, the elevation below which fluvial erosion cannot occur. The sea regresses, withdraws from shallow areas preserving beaches, and changes the length and gradient of rivers that, with renewed energy, become incised. A reversal, or transgression, reduces a ’s gradient and its sediment carrying capacity, and coastal are inundated. Change in sea levels has been cyclic, reflecting ice ages and interglacial periods, with the rises being more rapid than the falls. Evidence of the variablepermanence of different relative levels remains in coastal areas as still stands, which have been recorded during marine placer exploration. Page 4 of 10

5.0Factorscontrolling formation of placers: Some of the geological and geomorphological factors that control the concentration of heavy minerals along the Indian coast are as follows:

5.1Geological control: The physico-chemical behaviour of provenance rocks, i.e.,igneous, metamorphic or sedimentary and the effect of various geological processes have played avital role in contributing sediments to form a placer deposit.

5.2 Climatic Factor: The climate of the region has a great role to play in decomposing and disintegrating the rock and mineral fragments that get liberated and concentrated. Tropicalto sub-tropical climate promotes deep chemical weathering along coastal region. These conditions also favoured the formation of laterites that, in effect, is a process of pre-concentration.

5.3 Drainage Pattern: The availability of young and youthful rivers and their high density,coupled with climatic factors, played a prominent role in the supply of material forconcentration along favourable locales, especially along the Ghat section of Kerala and Tamil Nadu coasts. The rivers joining the Bay of Bengal on the east coast, however, have attained maturity and in many cases delta systems have developed; e.g. Mahanadi,Godavari, Krishna, Cauvery etc.

5.4 Coastal Processes: Wave velocity, long shore currents and wind speed also have their effects in littoral transport, sorting and deposition of placer minerals. Emergence and submergence of the coast during geological past also affected the beach placer formation. Apart from these, numerous other factors that helped in the formation of these deposits are coastal processes.

6.0Ages of placers: Primary sources, including those of gold, that generated placer deposits cover most of earth history.Some important gold placers owe their origin to orogenic gold deposits formed during the Paleozoic, but the maximum frequency of all sources is in younger Mesozoic settings. The frequency declined in the Cenozoic butprimary sources continued to form through to the Pliocene and Pleistocene epochs. Evidence exists that greater number of placers were formed during the Paleozoic and Mesozoic eras.

7.0Mineral concentration and accumulation: The factors that determine the behavior of a rock or mineral particle in water or air are its size, shape, and density relative to its neighbors, and the prevailing energy level of its environment. The processes of erosion and deposition, and the dominance of one or the other lead to the formation of two distinct styles of placers. They are here termed as lag (erosional) and accumulation (depositional), expressions that are familiar to, and used in placer industry.

The two forms of placer deposit, lag and accumulation, reflect variations in energy created by rainfall, stream flow, marine currents, ocean swell, breaking waves, tides, and wind. They may exist alone or in combination in any placer type in progression from eluvial to the most distal and dispersed marine deposits.

8.0World Distribution of placer mineral deposits: 8.1 Placer deposits of Southeast Asia: In general the placer deposits are more productive, more economical and easier to mine than lode deposits. Cassiterite from which most tin is smelted occur in placer concentration which yields valuable amounts of niobium, tantalum and rare earth minerals. Offshore dredging proceeded dredging in land for tin. Page 5 of 10

Offshore tin placers are wide spread in shelf region. The Southeast Asia is the most important tin-producing area of the world. The source rocks are Mesozoic granite intrusive (Late Jurassic-Cretaceous) which are widely distributed in the area. The tin province extends over a distance of 2900kms from northern Burma through peninsular Thailand, western Malaysia to islands of Indonesia (Sigkep, Bangka and Billiton Islands).

Geological factors considered to have contributed to the unusual size and value of this belt includes: a) High concentration of tin bearing granite b) Deep and rapid tropical weathering, c) Formation of marine and alluvial placers many of which are now seaward of the present shoreline. d) Preservation of placers, resulting from relatively low terrain drained by low velocity streams. The most important offshore placers near the Indonesian tin islands are found in submerged river channel of glacial or post-glacial age, covered by younger sediments. Of the world’s annual production of about 0.23 million tones, 30 to 50% comes from Malaysia and 10% from Thailand and Indonesia.

The offshore dredging of submarine tin first began in 1908 in the shore line area of Puket Island, Thailand. Seabed mining for tin continued for many years near Indonesian tin islands and Phuket Island.

8.2 Placer deposits of Sri Lanka: In the north-eastern Sri Lanka, beach placers have been mined for 70 years. The offshore extension of Pulimoddai beach deposit was explored by a German company. It has shown that heavy mineral bearing near shore Holocene fine sediment overlies either biogenic coarse , Pleistocene sediment or gneiss. Heavy mineral concentration in surface sediments (maximum 58%) occurs in the near shore silt/fine sand zone. Heavy mineral content in fine sand varies from 11 to 14% and the water –depth is 0.5 to 15m. The reserve of ilmenite + rutile + zircon is 0.95 to 1.34 milion.metrictonnes.

8.3 Placer deposits of Japan: Offshore titaniferrous magnetite placers have been investigated in several places in Japan and some of them have been exploited (emery &Noaker, 1968). Heavy minerals concentration in offshore area of Japan and Korea have been investigated to prove more deposits.

8.4 Placer deposits of Northwest Europe: The cassiterite deposits off Cornwall have been mined for a short period in the past. The offshore deposits are both surficial and buried. Buried deposit consists of stream tin in buried river channel up to at least 12m below sea floor.

8.5 Placer deposits of North America: Alaska: Placer gold of economic significance occurs in the offshore of Nome, Alaska. It stretches for over 30kmsalong the coast and over 5 kms seaward. Water depth varies from 10 to 45 m. Gold placer is associated with gravel deposit which is derived from underlying glacial till. Platinum occurs in Good news area of Alaska as fine grained particles. The source is probably Red Mountain ultramafic body.

Oregon: Surface concentration of more than 10% heavy minerals lie at more than 200m water depth nearer to the river mouths of Oregon. Higher concentrations of 30% heavy minerals associated with 5 to 150ppb gold are located seaward of Rouge river mouth and off Cape Blanko. The heavy minerals are chromite, Ilmenite, zircon and gold.

Virginia-Georgia coast: Economic deposits are expected to occur off Virginia-Georgia coast where onshore strandline deposits are being mined.

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Reconnaissance surveys of Virginia were conducted in the inner shelf for over 3 years from 1986. The chief economic heavy mineral is ilmenite (27%) with minor quantities of leucoxene, rutile, zircon and monazite.

8.6 Placer deposits of British Columbia (Canada): Heavy minerals are reported in the continentalshelf. The avareageconcentrataion is about 10% with maximum concentration of 28% in Queens Sharlotte sound. Heavy mineral concentrated in fine sand (0.15 to 0.2mm). The Heavy mineral fraction contains 30 to 50% amphibole, 5 to 25% opaques (chiefly ilmenite) and 5 to 15% sphene. Other Heavy minerals are garnet, epidote, chlorite, and titano-magnetite.

8.7Placer deposits of Australia: Australia is the major producer of rutile, zircon and monazite in the world. Australia accounted for about 95% of rutile, 87% of zircon, 50% of monazite and 25% of ilmenite out of the world production in 1971. The main placer deposit occurs along 400km long coastline north and south of Perth in Western Australia and coast of Queens land and New South Wales in Eastern Australia. All are essentially beach and fore dune deposits formed by wind and wave action.

Gold occur as accessory mineral in beach sand heavy mineral concentrates at a number of places in eastern Australia. The gold placers may extend offshore either in drowned river channel or in ancient beaches. Offshore investigations in late 1980 have showed the presence of insignificant traces of gold and the operation was abandoned.

8.8 Placer deposits of Africa: Mozambique coast: Sands with heavy mineral content of more than 3% in Pleistocene terrigenous and biogenic relic sediments in the shelf surrounding the Zambezi River have been located in 1974. It covers an area about 800 sq.km. The chief heavy mineral is ilmenite.

South African coast: Diamonds in raised beaches were first discovered along the coast of southeast Africa in 1908. Since the diamond bearing sand extends down to the shore line, it was thought that they might also occur on the sea floor. During 1961, the Marine Diamond corporation of South Africa commenced commercial offshore operations. They located several areas of diamond concentration. Mining was subsequently undertaken in three areas. The other heavy minerals present are similar to those reported from the east coast of Africa.

Senegal:Offshore surveys have brought out the presence of ancient shorelines at 25 m, 40 m and 65 m waterdepth. Heavy mineral concentration is in fine sands which contains 2 to 5% of ilmenite and zircon. Heavy mineral concentration occurs as lenses parallel to shoreline.

9.0 Placer deposits of India: However, after the nationalization of all the major deposits, the national production of ilmenite and rutile has increased over the years. The current production rate is of the order of 140,000 tons for ilmenite and 6000 tons for rutile. Governmental concerns like the Indian Rare Earths Ltd. and Kerala Minerals and Metals Ltd. are involved in the production and marketing ofthe placer minerals.

Over the last few decades new deposits have been discovered in placerslike, Chattarpur in Orissa, Vishakapatnam in Andhra Pradesh in the east coast and Ratnagiri in Maharashtra in the west coast of the country. Along the coastal stretches of Tamil Nadu, deposits of heavy minerals occur in the inland areas in the form of Teri sands.

The current reservesof the placer minerals in India, are as follows; 278 million tonnes of ilmenite 13.49 of rutile, 18 million tonnes of zircon, 7 million tonnes of monazite, 84 million tonnes of sillimanite and 86 million tonnes of garnet. The major placercon centrations of India are located along the east and west coasts. Page 7 of 10

9.1 Placer deposits ofRatnagiri,Maharastra High concentrations of placer minerals occur along Jaigarh and Vijaydurgin Maharastra particularly in the bays of Kalbadevi, Mirya and Ratnagiribays. Heavy minerals range from 1-91% with 1-52% of ilmenite. Ilmeniteassays about 50-52% TiO2 (Titanium oxide). The placers in Bhatya, Purangad andGoankhede contain high content of magnetite (40-60%) and limonite/haematite (25-35%) with relatively low ilmenite(5-25%). Thetotal reserves of the heavy minerals are estimated to be around 3.45 million tonnes.

The provenance of the heavy minerals is attributed mainly to the DeccanTrap provinces. The Kaladgis consist of both granitic and metamorphic rocks and the gneissic basement of south Konkan forms a secondary source of heavy minerals. Extensive areas of Deccan Traps are overlain by laterites.

The Konkan coast extending for about 230 km from Dabhol through Ratnagiri to Vengurla is marked by a number of rocky promontories with interveningarcuate bays and tidal inlets. The occurrence of ilmenite placers on the beaches of these bays and estuaries have been known since 1935. The Department of and Mines of Maharashtra estimated the onland reserves of ilmenite to be 4 mt. in the area extending from Undi to Purangad for a stretch of 48 km. The offshore surveys of Konkan coast by National Institute of Oceanography (N.I.O.) in 1975 indicated ilmenite bearing sand cover more than 96 sq.km area between Jaigarh and Vijayadurg and the resources were inferred to be about 12.5 million tonnes for a sediment thickness of 1m from seafloor.

The resources estimated by National Institute of Oceanography(N.I.O) in the three bays of Kalbadevi, Ratnagiri and Mirya based on grab sampling and extrapolation to a depth of 1m from seabed were of the order of two million tones.

The total heavy mineral content varies from 2.5 to 66%. The chief heavy minerals are ilmenite (10 to 40%), magnetite (2.0 to 8%) and clinopyroxene (up to 8%). Hornblende, tourmaline, zircon and garnet are also present in minor quantities.

Conservative estimation of ilmenite and magnetite in Kalbadevi down to a depth of 2m from seabed is of the order of 2.29 to 3.12 and 0.44 to 0.68 million tone srespectively over an area of 6 to 8.45 sq.km.

9.2 Placer deposits ofChavara, Kerala The beaches of southern Kerala is well known for its rich deposits of heavy mineral sands. One of the highest concentrations of heavy minerals in the world occurs over a stretch of 22 km in Neendakara-Kayamkulam coast. The sands contain on an average 60 to 75% ilmenite, 4 to 7% rutile, 5 to 8% zircon, 0.5 to 1% monazite, 4 to 8% sillimanite and 1 to 1.5% leucoxene. It is being mined by the Indian Rare earths Ltd., at chavara.

This deposit, popularly known as Quilon deposit is one of the largest and richest in the world. It extends to about 22 km with a width of around500m. It stretches as a barrier beach between Neendakara, at the mouthof Ashtamudi estuary and Kayamkulam. The deposit has a maximum depth of 15m and is estimated to contain about 12.7 Million tonne of ilmenite, 1 million tonne of rutile, 1.9 million tonne of zircon and 0.41 million tonne of monazite and 6 million tonne ofsillimanite.

This offshore occurrence is of significance from economic point of view due to a) Its nearness to Neendakara seaport and Indian rare Earths (IRE) factory at Chavara, b) Its occurrence in shallow waters, c) Growing consumption of heavy mineral bearing sands by IRE authorities as sources of ilmenite, rutile, zircon, monazite, garnet and sillimanite,’ Page 8 of 10

d) Fast depletion of onland reserves and. e) Environmental aspects and difficulties of mining in thickly populated areas of Kerala. Hence exploration to evaluate the heavy mineral distribution in the offshore of Southern Kerala was taken up.

9.3 Placer deposits ofManavalakurchi, Tamil Nadu. Important placer deposits are located in theManavalakurichiarea of Kanyakumari district. It is one of the oldest known deposits, which was first worked for its monazite. The deposit extends to a length of about 6 km, from the north of Muttomto Kolachel, with an average width of 45m. The total average content of heavy minerals is around 39%. Of these, ilmenite forms the major constituent (24%), with rutile (1.8%), leucoxene(0.90%), zircon (2%), monazite (1%), sillimanite (3.5%) and garnet (5.5%).

Ilmenite contains about 56% Ti02. The monazite has a total of 58% REE (rare earth elements)oxides and 8% Th02(). The total reserves of heavy minerals in the Manavalakurichi-Kolachel stretch are estimated to be about 1.6 million tonne. Ilemenite amounts to about 1 million tonne. The reserves of other mineralsestimated are as follows: 0.075 million tonne of rutile, 0.035 million tonne of leucoxene,0.082 million tonne of zircon, 0.043 million tonne of monazite, 0.23million tonne of garnet, 0.14 million tonne of sillimanite and about 6850 tonnes' of kyanite. The area north of Kolachelto Midalam has been found to contain workable deposits of heavy minerals estimated to about 0.5 million tonnes.

9.4 Teri sands of Tamil Nadu These inland deposits occur along parts of south eastern coast of TamilNadu in the form of Teris in parts of Tirunelveli, Chidambranagar, Ramanathapuram districts. They standout prominently in the area, atelevations of 30-60 m. They occur as widely separated isolated patcheswith dimensions ranging from a few hectares to about 6000 hectares.They are found about 0.1-10 km inland from the beach placers in a semiarid setting. Seven such deposits with an aggregate area of 144 km havebeen identified. Theaverage mineral grade is about 10% with reserves of 123 million tonnes. The Teris are believed to be formed due to aeolian action in an aridsemiarid climate. The sediments owe their origin to the Eastern and Western Ghats, tertiary sandstones and limestones and Cuddalore beds.

9.5 Placer deposits of Visakapatnam, Andhra Pradesh deposits occur in the Visakapatnam, Bhimunipatanam coastal stretch of Andhra Pradesh for a length of 37 km with a width ranging from 150m to 1 km. The average heavy mineral concentration is about20% with ilmenite (9%), rutile (0.6%), monazite (0.090/0), zircon (0.30/0),garnet (4%) and sillimanite (4%). The total reserves are worked out to be between 6.18-2.88 million tonnes of ilmenite and 0.005 million tonnes of garnet. The assay of this mineral is about49% Ti02. The coastal stretch between Kakinada and Tandavarivercontain a total heavy mineral content of about 70 million tonnes with a grade ofabout 12%. The reserves of ilmenite are about 30 million tonnes.

The lithology of the area consists of charnockite and khondalite group ofrocks of the Eastern Ghats Province. Granites and granitic gneisses also exist in the rock assemblages. A part of the sediment for the deposit formation may have been brought by large drainage systems like Krishnaand Godavari, which flow through a range of lithologic successions like Deccan Traps, Cuddapah sedimentary formations and tertiaries of Rajamundry sequence.

9.6 Placer deposits ofChattrapur, Odisha The occurrences of heavy mineral placers along the beaches of Orissa coast are well known. of sand with 20 to 25% of heavies along the coastal tract of Gopalpur-Chhatrapur. Utilization has already commenced in the foreshore area of Aryapalli near Chhatrapur by the I.R.E. . The economic heavy minerals present are ilmenite, sillimanite, garnet, zircon, monazite and rutile. Page 9 of 10

Important deposits of placers are located in the Chattarpur of Ganjam district near Gopalpur. Itextends to a length of 22 km with an average width of 1.54 km. The average grade of the heavy mineral is about 20% with ilmenite (8.80%),rutile (0.38%), monazite (0.27%), garnet (6.70%), zircon (0.31%) and sillimanite (3.40%). The total reserves are estimated to be 46.61 million tonnes with a grade of about 20.22%. Of these, ilmenite constitutes about 20.3 million tonnes. The assay ofTi02 inilmenite is around 50%.The heavy minerals are essentially derived from the Eastern Ghats province, which consists of khondalites, charnockites with their migmatised equivalents. Frequent exposures of anorthosites have been reported.

10.0 Conclusions: The most important economic attributes of placer deposits are size, density and grade, for their commercial extraction. Sometimes, placers are distributed far away from their source rocks. Diamond, rutile and zircon are found as placers after several hundred kms of their sources. Erosion, transportation and deposition of placer and heavy minerals are very interesting areas of study in Earth sciences.

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