MINERALOGY AND GEOCHEMISTRY OF IROAI ORES OF THAKURANI MINES, DISTRICT KEONJHAR, ORiSSA
DISSERTATION SUBMITTED IN PARTIAL FULFILMENT FOR THE DEGREE OF MASTER OF PHILOSOPHY IN GEOLOGY FACULTY OF SCIENCE, A. M. V., ALIGARH 1383
BY PARYAIZ AZAM QAQRI M.Sc.
DEPARTMENT OF GEOLOGY AUGARH MUSLIM UNIVERSITY ALIGARH ^r''','^ ;/j ^%
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^-•aj^ f"! Dedicated to my father JANAE S.G.A. QADRI who has been a strong source of inspiration to m® since ray childhood CONTENTS
DEPARTMENT OF GEOLOGY ALIGARH MUSLIM L NiVERSiTY A LIGARH-202001
Dated 2;b«^«U.934-'
Ibis is to certify that Mr, Barvaiz Az&m ;(,ada7l l)as coapXeted bis rase&rcb vc»'k under my sdps:!i:'Visioa ia partial fulfiliaeQt for the «i\Ard of degree of Mestar of Philosophy of tho Allgarh MusXiffi Qnivursity, AXigarh. Shis «(H'k is aa origioaX contrtbiitica to our koowXedg* of ii-on cares mifieraiogy Bad gsoehemistry, E« is aXXoved to submit th« vork for the H.Phil degrte of tna AXigarh Kuslia atjivsrsity, Aii2&::h,
uipl, Masraloi, (K. S.iUPbiX) Qniverait^ of Heidelborg west C-3j'aaoy Microstruoturss & Textures ••• 46 Paragenesis ••» 50
CHAPTER-V GEOCHEMISTRY ,•, 53 Distxlbution o£ major oxides ••• 55 Mutual Relationship o£ the significant 59 oxides with the V^o^a
Inter Element Relationship ••• 67
CHAPTER-VI SUMTIARY & COIICLUSIOiJ ... 73
TABLES ••• 78
HISTOGRAMS ••• 86 GRAPHS ••• 93 MAPS ••• 99 REFEREHCES •«• 102 PLATES •«• 113
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***** LIST OF TABLES
Table-I Oeological distribution of Indian ores.
Table-Il Stratigraphy
Table-III Iron Ore Reserve
Table-IV Paragenesis of the iron and associated manganese mizMtrals of Thaktirani mines,
Table-V Distribution of major oxides in the iron ores of ThaKurani mines*
Table-VI Correlation coefficient of the major oxides of Thakurani mines iron ores.
Table-VII Data showing the range of major oxides of Thakurani mines. District Keonjhar (Orissa).
Table-VIII Data showing the niean value and standard deviation of the major oxides of iron ores of Thakurani mines. ii
EXPIANATION OF PLATES
PLATE » I
Figure*! miotomicrograph showing micro>baiKling in granular hematite(55 X}« Figure-2 Photomicrograph showing replacement of Goethite by hematite and limonite at the margins of goethite crystals (55 X}. Figure-3 Photomicrograph showing the replacement of magnetite by hematite without any remnant of magnetite (55 X)»
PLATE » II
Figure-1 Photomicrograph showing replacement of martite crystals by goethite (Pseudomartite), (55 X). Flgure-2 Photomicrograph showing concentric bands of colloform goethite (55 X). Figure->3 Photomicrograph showing well developed cubic crystals of martite embedded in granular hematite (55 x).
PLATE » III
Figure-1 Photomicrograph showing hematite vein and at the margin replaceaient by goethite and limonite respectively (55 X). Figure-2 Photomicrograph showing colloforra pslloraelane and pyrolusite (55 X), Figure-a Wiotomicrograph showing segregation bands of hematite and massive goethite (55 X), lil
LIST OP FIGURES
Figure 1 Location map o£ the area Figure 2 Geological map o£ Thakurani mines* district Keonjhar* Orissa Figure Map shoving iron ore area o£ Singhbhum, Keonjhar and Bonai Figuxre 4 Map showing iron ore deposits o£ Orissa Figure H»l Histogram showing frequency distribution o£ Si02 Figure H*2 N N M a AljOj Figuire H-3 It n a a CaO Figure K->4 n n tt n a ^«2°3 ti n R a Figure H«>5 » liajO Figure H-.6 H n a KgO Figure H-7 M a a MnO Figure M If u a H-8 ^2^5 Figure H-9 n M a a MgO Figure H-10 H H a H TiOj Figure H-11 H It a a HgO^- Figure 0*1 tti d SiO^ contents Figure G-2 H n a Figure G-3 « m " ^2° a Figttre G-4 tt d a N a Figure 0»5 N " MnO a
Figure 0-6 « M a Figure G-7 N « • MgO a Figiire G-8 « m " TiOj a Figure G*9 •I " CaO a Figure 0-10 n -H^O^ a CBAPTER - X
INTRODUCTIOH
The iron and atmml industry is a key industry of national importance, the development of various industrial activities in the country is linked with its development. In an under developed country any scheme for industrialisation presupposes the development of the iron and steel industry* Iron is known to have been used in Egypt from the Middle Pre-historic times (7»000*6,000 B.C.) end its use is well authenticated from at least the 4th Dynasty onwards. Sir Flinders Petrie, the well known archaeologist, was of the opinion that all such iron was of meteoric origin and that manufactured iron did not come into general use until after the assyrian invasion of Egypt in 666 B.C., for the largest group tools found in this country at Thebes or as of the age (Jour. Iron & Steel Inst., 1925, vol. 112, pp. 182), Eminent metallurgist have held that iron and steel were amongst the earliest metals manufactured by ii»n and that the ancient people of India, China, Egypt and Mesopotamia knew how to make iron (Day, 1887). Several instances of ancient iron are given by Ooodale and Speer (1920)and by Swank (1892). Glorious was the past o£ this basic Industry In India. The country was a leader In the production o£ carbon and steel In the world. The development of the modern Industry in the country has been rather delayed, India lags for behind the leading countries of the world in the production of Iron and steel. The raw material and power resources of the country, the vast labour force, and advancen^nt in science and technology, all augur well for the development of the country. The major ixron ore producing countries in the world are the U.S.S.R., Brazil, India, U.S.A., Canada and Australia. The principal deposits in the U.s.s.R. and in the vicinity of Black Sea (the Kerch, Krlvol Roy and Kursk deposits) and Oral Kaseaakhastan (Mt. Magnituaya and Svevdlovsk deposits). India has around 60% of world's high grade ore reserves. The total reserves of iron ore are estimated to be around 8,050 million tonnes. These would last for about 100 years at an assumed rate of about 84 million tonnes which is twice the present rate of production. Of the three types of deposits (magnetitlc, hematitic and limonitlc), the hematltic variety consisting about B0% of the total reserves is of considerable iii^>ortance because of its high grade quality. About 43% of the Indian reserves are situated in Bihar and Orissa (Table-I).
The hill ranges covering the parts of Singhbhum district (Bihar) and Keonjhar, Bonai, Mayurbhanj and Cattuck 3
districts (Orissa) fomi the major mining region. Important mining centres of this region are Oaa« Hoaimindi^ 6oruniahisani# Bolani« Barsua« BarajanxSa# Tomka# Daiteri and Kiriburu (Fig. 4) The deposits o£ Bihar and Orissa l:»long to the Precambrian iron ore series and the ore is within the banded iron formations occurring as massive ore with iron content around 60% (concentrated hy leaching)» blue duat ore (extremely friable and micaceous hematitic powder) and weathered ore*
PHYSIOGRAPHY OF THE AREA
The Orissa state is divisible into four regions* The KTorthern Plateau* The Central River Basin* The Eastern Ghats hill ranges and the coastal plains• The Northern Plateau covering the districts of Mayturbhanj, Keonjhar* Sundergarh and part of Ohenkanal* is an undulating country having a general slope froai north to south. The area of investigation viz.* Thakurani Hill lies in district Keonjhar. Thakurani Hill mass consists of three main ridges Which rise about 3003 ft. from mean seal level. The hill mass consists banded hematite-quertzite whereas the rich hematite is exposed mainly on the top of the ridges. The rocks dip generally to the northwest at high angles* but much contorted and folded. Good hematite is exposed at eastern ridge but at places foiand to be lateritised. The hematite is often covered d
with consolidated ore. The slopes of tM ridge are largely covered with hematite and other debris. At the south and of this ridge the hematite seems to pass laterally into banded hematite-quartsite. The actual passage of one to the other is not seen, owing to the covered nature of the ground, but on following along the strike of the hematite beds« often a few yards of covered ground, banded hematite- quartsite occurs. Western ridge is mainly covered with thick forest and soil but contains a band of hematite which is iimll seen towards the southern end of the ridge* The eastern end western slopes of this ridge shows good exposures of banded hematite<-guartasite • At the southern ei^ of the middle ridge, rich laminated and massive steel grey hematite are well exposed but lower down the slopes is banded hematite-quartsite. According to Percival (1934} the rocks seem to be bent into an anticlinal fold, but the dip is very variable. The hematite seem to become lateritic at the north end of the ridge.
LOCATIOH & ACCESSIBILITY OF THE AREA
The Thakurani Hill (22^06* t 85**26») selected for the present investigation is located at about 12 miles south-east of Barbil (22*^07• i 85**24»), district Keonjhar, Orissa and is included in the one inch topographic sheet no. 73 F/8 of Survey of India. :)
The area is approachable from Jamshedpur by train as well as by bus via Jamda (Fig. X)»
CLIMATE
The climate o£ the area is tropical with high sismmer temperature and heavy rainfall. The laaxiimira tenqperattire during sumoaer period touches about 40®C* in the month o£ April and ?4ay* During winter months sometimes the temperature falls below 15^C«
TOPOGRAPHY
The area in which the iron ore bodies occur consists mainly of a mass of hills and ridges largely covered with reserved and protected forests of sal trees. The small valleys between the hills usually have a goc»l layer of soil* which is often cultivated but the hilly area is rather sparsely inhabited. The hills rise about l«OdO to X«500 feet from ground level. To the north east of the iron ore area stenches the granitic plain of Singhbhum, The iron ores are located at Thakurani Hillland the main iron ore range, running in a south-southwest direction,
DRAINAGE
The general drainage of the area is to the northeast and the principal rivers being tiie Karo^the KOira and the Baitami, i)
SCOPE & PURPOSE OF IMVESTIGATIOK
The area undertaken for the present study lies in Orissa state and foctoing parts of iron ore series* Iron ores occurs as bedded deposits Which is rich in hematite* Till todete no comprehensive work has been undertaken as regards to the geochemistry of these deposits* It is therefore, the author has the systematic collection of all the lithological units including the hematite bands in or^ier to determine the geochemical variation, if any# between the various lithological units. Such a study together with the studies of iron ores under reflected light might reveal the possible source of iron concentration besides suggesting a geochemical classifica tion of the ores for their specific econcmic uses based on their chemical quality* It may also throw some light on the metallogeny of these deposits*
PREVIOUS INVESTIGATIONS
Bose, P*N* (1904) of Geological Survey of India discovered iron ore at Gorumahisani in Mayurbhanj state* This was brought to the notice of Mr* Jamsetji Ktauserwanji Tata who caused the deposit to be further investigated by Messers* Perrin end l-teld, CM* <1915) of Hew York* This deposit on which the great firm of the Tata Iron and Steel Cos^any was founded* has since lost its position as tho premier source of supply to the steel worki in favour of the {loaimmdi deposit in South Singhbhtim, Sonbolle« R* {1907)« a prospector, first discovered the Singht^tium iron ore deposits, viz., KK}tu Burn and Fansira Burn. Earlier accounts of these ores were given by Weld,CM. (1915) and Parsons, E. (1922) before the geological problems were clearly appreciated, Jones, H.C. (1923) described in detail the iron ores of Singhbhmn, Keonjhar and adjoining areas. Again, Jones and Krishnan, M.S. (1924*25) worked together in BansacB state and then in the year 1925*26 and 1926*27 in the Keonjhar state with the help of the new maps produced by the Survey of India.
Nairayana Xyer worked with Jones during 1923*24 and 1924*25 on the iron ores of Singhfahiira and Orissa deposits. During his work Rairayana in 1924-25 and 1926*27 mapped most of the granitic area with its dykes. Hobson, G.V. (1927) completed the mapping of eastern Singhbhuun that was left blank during the work of Jones and Krishnan (1924*25). Dunn, J.A. (1929) comprised both tlw iron ore series in the older metamorphics of Singhl^um area. He noticed at Gurumahisani that the iron ores banded hematite-quartzites and apparently also phyllitic rocks, have been metamorphosed to a magnetite-cutnmingtonite grunerite rock, which is according to imnn (1929) possible, but unlikely, that curamingtonlte grunerite has developed in these rocks as a a
result o£ regional metamorphism. Percival* F*G. (1931), was the first who made a cosigjrehenslve study of the iron ores of Hfoaimmdi and suggested sedimentary origin for banded hematite- quartzites because they tsrere precipitated from igneous thermal solutions poured out on the sea bottom. Dunn (1936, 1941) while working on the iron ores of the eastern Singhbhum and adjoining areas described the minerographic characters of the ores v/hlch was published in Hemoir by Geological Survey of India, He observed that magnetite was not the primary iron minerals, it has been a product of nffitamorphisra. Krishnan (19S4) vrarked in detail over ths iron ores of Singhbhum and Keonjhar areas describing the three major groups vi2#, Gangpur, Iron Ore and Kolhen v;hich was published by Geological Survey of India in its Bulletin*
Chakraborty, K*L« (1958) stated that Ciumoingtonite- magnetite rocks occurring in Badampahar are ascribed to the thermal metainorphism caused by the intrusion of mafic igneous rocks. According to caiosh, P.K.i Prasad, U#? and Ghosh, R.B. (1963) the different facies of the banded iron formations throughout the Singhbhurai-Keonjher-Bonai belt and Badampahar areas in the east, can best be explained on the assumption that they were formed in a barred basin or basins,
Sikka (1963) mad© a study over banded hematite- quartssites of Bihar, Orissa and Hadhya Pradesh and has grouped the iron fornmtions of these areas into Bonai and Bose deposits which according to him, formed the shores of the Satpura geosyncline* Acharya# S. (1964) working at the stratigraphy of the banded iron formations of the Daiteri-Tomka area* observed that the lower contacts of the banded iron formations are not sharp. He considered the banded cherts as irt>n formations tnough they do not contain any iron, because of their stratigraphic and physical continuity. Earlier work by Prasada Raoj G«H»S«V,7 Murthy, IT.G.K* and Deekshitulu, M,H* (1964} on stratigraphic relations of Precainbrian iron formations and associated sedimentary sequences in parts of Keonjhar, Outtack, Dhenkanal end Sundergarh districts, shoiaeA that lava# sandstones, and grits around the shale banded hematite jasper forrruattions of Keonjhar-Bonai (Iron Ore Stage of t5unn) constitute a separate older sequence and hfs revealed two older sequences containing banded iron forimtions, Chakraborty and Tarx>n (1968) reported the presence of quart2-cuinntingtonite«-granurite-magnetite with a«K>site ani quarts-actinolite-soisite magnetite developed in Orissa at the contact of banded iron formation and gabbro.
While Iyengar, S.V.P, and Banerjee, P,K. (1971) observed that Noanmndi iron forn ation and manganese bearing shales, are younger than the Gorumahisani-Sukinda iron forrretions because the latter is seen to pass below the horse-shoe«shaped Moaniundl sync line whose western lii^ is overturned. 10
Mt2khopadhyaya» A» and Chanda* S*K* (1972) studied the silica diagpnesis in the banded hematite jasper and bedded chert associated with the Iron Ore Qrotip of Jarada-Koire valley, Orisse* and £ound that spheralites are syngenstie in origin* possibly originating from precipitation as a colloidal gel, Reczrystallisation tends to oblterate the spherulitlc structures and leaves as shadowy palin^sest of the original spherulite marked only by a circular outline of iron oxide. Pichaimithu, S.C» (1974) while working on banded iron formations of Orissa said that the deposits of the Singhbhuas- Keonjhar-'Bonai belt suggest deposition in a deeper part of the basin or in a different basin, as it primarily contains fine sediments deposited as chetnical precipitates*
METHODOI,0GY
All spectrophotoraetric measureraents were made with a Beckman DU-2 Spectrophotonwter by developing coloured ions of the respective elements, all of ndiich were made in the range 400-700 mja* The revised method of Shapiro and Brannock (1956) for analysis of silicate rocks was adopted. The chemical analysis data are shown in Table-V,
PREPARATION OF SAHPt^ S0LOTI0W5
The major part of the analysis is made on two solutions, which are designated solution A and Solution B» V
Solution A is used in the determination of siO^ and AijOj* Xt is prepared by fuaing 0«1 grara of the seiQpIe p3\ii6.ee HaOH in a nickel crucible* In thia way deccxnposition is obtaine<2 very quickly and at a comparatively low temperature. Two reference standard solutions end e reference blank solution are prepared sicailtaneoualy with solution A» The reference blank solution is prepared in the saxm way as solution A €»ajept that sacaple pov?der is ondtted, solution B is used in the deterainetions of TiOg, total
iron, r-mO, ^2^5' ^'^^* ^^' ^2^ ^^ ^^* ^° prepare this solution* a 0*5 gram sample poiirder is digested overnight with m and HgSO^ in a large covered platinum crucible on a steam bath, HP is then cmmoved iy^f heating until copious fumes of SO. are given off* and the residue is dissolved in water and made to volusiip* To Biiniiaise contaiaination fr<»« glass, the aliquots of solution B was stored in plastic bottles. CoEHiblned water CHgO^) is determined by taking 0.5 gram of the seniJle po%^«r in a six inch long tube of hard glass, closed at the one end with a bulb blown there. The weighed cample is transferred inside the bulb by tmens of a thin strip of glaxed papers. The sample is heated to red he©t for half an hour end the loss of ignition Is weighed. The difference give the weight of total water* For each sample a fresh tube is used. 12
ACKIIOWLEDGEHENT
Hie author wishes to expxress his deep sense of gratitude and appreciation to Mr. M.H.A. Sajid, for his valuable guidance and constant encouragenMint all through the accomplishment of this work. The author place on record his indebtedness to Prof. S.H. Rasul (Ex*C3iairman)« my ex-supervisor, for his constructive criticism and valuable advice during completion of this dissertation. The author is also grateful to Prof. V.K. srivastava. Chairman, Department of Geology, A.M.U., Aligarh, for providing necessary facilities and taking keen interest in this work. To Mr. Syed Hamid Hasan Khan, Xiecturer, Computer Centre, A.M.U., Aligarh, the author owes special thanks for his valuable help during the computer programming. The author is particularly grateful to his friend Mr. Rayaz Ahmad who never failed to help at every stage. The author is grateful to Mr. NOman Ghani, Dr. L.A.K. Rao and Mr. Mohd. Ajmal with whom many fruitful sessions of discussion arranged. Ihe author appreciate the valuable help readily received from Mr* Shahid Farooque during photography of ore samples. Many thanks are due to Mr. S, Mohd, Hasan, Habeeb Ahmad, Zakir Husain, Nazar Ali Khan for the help they extended in their respective fields* 13
The author wishes to express his deep a^reclatlon to the Orissa Mining Corporation Ltd* and to Mr. S,A. Rahlm for providing all sorts of facilities during the field work at Barbll, district Keonjhar* The author avails of this opportunity to acknowledge the blessings and good wishes received frcmi his mother and last but not least the author Is also thankful for the nK>ral strength and support which he received from his wife. In the end, the author has the pleasure to acknowle»dge the U.G.C. Fellowship, 14
CHAPTFR - II
STRATIGRAP-IICAL AND STRUCTURAL SET-UP
STRATIGRAPHY
The geological history of Orlssa commencea with the fornation of the granulitic rocks of the Eastern Ghats Group, These are probably the oldest rocks having acted as the baaeir.ent for the deposition of Iron Ore Group sediments as seen in the Dharwar and Brahmani valley tracts (Sarkar, 1972). The most imoortatt group of iron ore deposit in India occurs in south Singhbhum and adjoining districts of Keonjhar and Bonei between the latitudes 21°40*?^and 22°20'NF and lonciitttdee 85°5«E and 85°32»E. Banded iron formations constitute an important member of the Iron Ore Group which is niore than 2700 m.y, in age according to Sarkar, Saha and Miller (1969), While the name •Dharwar* was coined by Foote (1B86) to designate the schistose rocks in •Central Deccan and southward as far as the northwestern corner of the wilgiri massif, while Fermor (1909) generelised the use of the term pnd applied it to all sedimentery schists lying below the Epachaen unconformity, Dunn (1929) accepted this view and employed it to comparise both the Iron Ore Series and the older metamorphics of the 15
Singhbhum areas. According to Krlshnan (1935) the Iron Ore Series, the Gangour Series, and the Older Metamorphic Series form the Upper, Middle, and Lower sections respectively o€ the Dharwars, Later, Permor (1936) came to the conclusion that the important masses of hematite quartzite end hematitic ore that occur in the iron ore series seems to provide the deciding factor in favour of the Iron Ore Series being equivalents of the Dharvars in South India, The presence of banded iron formation was thus used to decide whether a sedimentary sequence should be considered as Dharvar or not. Later, Dunn (1940) rejected this mode of correlation on the ground that in •Rajputana, Central Provinces and Chota tfegpur, there are several systems of schists of which any one system may or may not be the equivalent. He discussed this problem and suggested that the term 'Oharvrar* should not be used to designate the schistose rocks outside the type area in K^rnataka, since all these unfossiliferous deposits can not be considered as synchronous or even homotaxial.
Besides the iron formations, the Iron Ore Group includes a sequence of lava, shale, and sandstone. Although the stratigraphical relationship of the iron formation with lava is not consistent throughout south Singhbhum and adjoining terrains, the lava is nowhere directly in contact with the banded hematite Jasper but a shale is always between them (Sarkar ftnd Roy, 1966) the iron ore groups lb
overlies unconforraably the Older Metamorphlcs ( 3200 m.y,) and separated by an unconformity, underlies the Dhanjori Formation (1600-1700 m.y.). The earliest attempt at working out the stratigraphy was made by Jones in 1923 (Table-II, No. 1) and followed by Krishnan in 1937 (Table-II, Mo. 2). Gangpur, Iron Ore, Kolhan were recognised as three major groups. The Singhbhum-Keonjhar- Bonai belt of Bihar and Orissa (Fig. 3 ) contains chiefly banded hematite jasper rocks, while banded hematite quartzites are exposed in Thakurani Hill (Fig. 2) and Tomka areas in Orissa. Considerable work was done in the field to establish stratigraphy by Dunn (1929, 1937, 1940), (Table-II, No. 3), and Dunn and Dey (1942). The Iron Ore Series of north and east Singhbhum was divided into a lower Chaibasa stage and an upper iron ore stage. The iron ore formation which consists of banded hematite jasper, basic igneous rocks, phyllites and tuffs, was supposed to be present on either side of the Copper Belt Thrust - a well marked thrust zone 200 km, long which separates the low grade metamorphics of the south from the high grade rocks of the north. Earlier, intensive structural and stratigraphic studies have been made in this region by Sarkar and Saha (1959, 1962, 1963, 1964, 1966), and Sarkar, Saha and Miller (1967, 1969), Three distinct orogenic cycles were recognised by them in this region, viz., the Older Metamorphic Orogenic Cycle (3200 m.y.) and the Singhbhum OrOgenic Cycle (850 m.y.). They observed that the banded hematite-jasper in Singhbhum north Keonjhar and north riayurbhv nj must be older because the end of iron ore orogeny is placed at 2700 m.y, Sarkar (1972) considers that the Iron Ore Group sediments, pyroclastics, and volcanics were deposited on the eroded Older Metaroornhlcs and associated granites mainly under unstable shelf conditions, While Percival (1931)« (Table-li, Ho, 4). Correlated the iron ore stage rocks on either side of the thrust, and found striking lithological differences, especially in the absence of the banded hematite-jaspers in the north though they are prominent in the iron ore series in the south,
A detailed study by Prasada Rao, Murthy, and Deckshitulu (1964) besides establishing that the lavas, sandstones, and grits around the shale-banded hematite- Jasper formations of Keonjhar-Bonai (iron ore stage of Dunn) constitute a separate older sequence, has further revealed two older sequences containing banded iron formation. The Goxrumahisani-Sukinda belt, which comprises banded hematite quartzite, banded magnetite quartzite, quartzites, and phyllites is intruded by the Singhbhum granite. The Noamundi iron formation consisting of shales, banded hematite Jaspers, and manganese bearing shales, is considered to be younger than the Gorumahisani-Sukinda iron formation because the latter is seen to pass below the horse-shoe shaped Noamundi syncline whose western limb is overturned (Iyengar and Banerjee, 1971). The main difference between these two formations are manganiferous whereas such J8
manganese bearing members are not present in the Gorumahisani sequence. The manganese ore deposits occurring in the Iron Ore Group rocks of the Bonai-Keonjhar belt have been described by riurthy and Ghosh (1971). The lower contacts of the banded iron formf>tions are not sharp at Daiteri-Tomka area, however, the banding starts in the lower quartzite itself signifying the rhythmic change in the geochemical conditions of precipitation (Pichamuthu, 1974). The change-over from the lower quartzite to iron formation, however, is completed within a few feet and laterally also within a short distance of a few feet, the ore minerals change over to jasper or chert, and therefore, the banded cherts though they do not contain any iron, have to be considered as iron formations because of their stratigraphic end physical continuity (Acharya, 1964).
LITHOLOGY
The iron ores of the area occur in the Singhbhum- Keonjhar-Bonai belt (Fig.3 ) of iron ore series which is in Keonjhar overlying tne Older Dharwars unconformably according to Krlshnan (1937) are associated with banded hematite-quart7ite and shales, which an of typical sedimentary aspect and almost un-metarnorphosed, and vrere considered to be possibly of Post-Dharwer age (Jones, 1923), 13
Banded Hematite-Quartgite
The hematite-quartzlte is often very highly folded and contorted and faulted on a small scale. These structures are s\ibjected to compression during the course of composition and partly to the result of slumping of the material during the process of leaching of the silica and enrichment by ferric hydroxide through the agency of circulating ground waters (iCrishnan, 1937). The small scale folding and puckering often seen in the formations are due, as pointed out by Spencer and Perclval (1952), to compression while the material was still soft enough to accomodate itself to features as well as slump structures were impressed on them after final consolidation during period of folding and enrichment by ground water. At end near the surface the material has generally been converted into massive hematite. The depth to which enrlchmc?nt too't^ place must have been controlled by former topography Mixed ore end banded hetnatito-quartzite Is mainly exposed in the southwestern part of the area while a small patch of this, is located In the west north of the area covered by dumped material end soil. The banded hematite-Jasper contains varying proportions of iron oxide and silica. Owing to their greater hardness they stand up as prominent ridges and cliffs on weathered surfaces, the hematite bands often stand up while the jasper bands form depressions owing their being partly leached out. The bands vary in colour fro>Ti grey or white to lavender, red and brown to black. They may shov/ intense cumpling and contortion and minute faulting and dislocation. The silica in the jasper band is sometimes of chalcedonic nature and sometimes micro- crystalline. The individual layer varies in thickness in different exposures from almost the thinness of a knife's edge to as much as one inch or more, vjhile the average is about one-tenth of an inch. The banding is not always very regular. Owing to the fact that it is highly folded the apparent thickness is often deceptive. Banded Hematite Quartzite Is mainly exposed in the Kforthern West part of the area and it occupies the larger part of the Thakurani Hill (Fig. 2). Small patches of banded hematite quartzite is also found in the southern part. There is a considerable 21 literature on the origin of the similar banded hematite rocks in different parte of the world, but none of the theories put forward have been generally accepted to explain the thin alterations of silica and iron oxide. Percivel (1931) while describing the iron ores of ttoaraundi suggested that the rocks are of the result of chemical precipitation, but the conditions under which this precipitation took place is still uncertain, although it is generally assumed that the precipitation took place under marine conditions. The rocks at the present time, are undoubtedly in a different condition from that in which they were originally deposited, similar rocks in the Lake Superior area have been shovm to have cherts or sideritic shales (Wagner, 1928), Shale/Phyllite The shelee are usually soft and finely laminated in the area of investigation but in the north and north western part of the area, they often become phyllitic in character, and show an incipient cleavage which runs at a fairly high r.ngle about 67 to the bedding. The enrichment has affected not only the iron formations but also the associated shales. Such enriched shales have been found as underlying the hematite quartzite at the area of investigation where a gradual passage from shale to the ferrug^inous shale have been observed. 9 9 where conditions have been favourable. Iron has been brought In by meteoric waters, and replaced the shale material. Shales are too soft to give continuous exposures and they are usually covered with a mantle of soil. At some places quartz veins ere found in the shales and the rocks have a remarkable phyllltlc sheen, not withstanding the gently undulating nature of the beds and the normal ebsenc of close folding. Although the purple colour of many of the shale is inherent since deposition of thes8 beds, it is, in other cases, due to later staining fay iron oxide (Dunn, 1940), At times, the shale is ferruginous, and in this case, it alters extensively at the surface, end more especially at the top of the hills into laterltic material which in some cases by further alteration have resulted in hematitic iron ore bodies (Jones, 1923). The shales seldom make any surface feature, and usually occupy the low ground, except when they have been silicified or when capped by iron- ore or laterltic material which acts as a protective covering and being soft they are easily disintegrated to form a layer of soil, so that in low ground their structure and character are largely hidden by soil and debris, STRUCTURAL SET«-IJP The structural set-up of the Iron Ore Group rocks 23 is hlghl/ complicated with the deveiopment of refolds and reclined folds et places, hov/ever, the trends varies at different places. In the Bonai region the quartzites of Iron Ore Group have a subsidiary trend in a Itorth East - South West direction. While in tlie Badampahar Gurtunahisani area, a similar trend recorded by the banded iron formation and the associated metabasites veers at the Bihar state boundary in the north to assumed a Northeast-Southeast direction. It will be seen from Jone's map (1923) that the main outcrops of banded hematite-quartzite form an elongated horse shoe, open to the north and closed to the south in Bonai and Keonjhar. The western rim of this horse shoe is the iron ore range, the backbone of which is a more or lees straight and continuous zone of banded hematite-quartzite. The eastern rim is at its northern end at Noamundi mine, some eiqht miles from the iron ore ran^e, and in contrast to the western rim is represented by outcrops of bended hematite- quartzite of varying width. Smaller outcrops of banded hematite quertzite occur within the area enclosed by the horse shoe; this area consist largely of phyllites v;ith tuffs, lavas and some cherts, end in addition, occasional outliers of Kolhan rocks. On the western side of the horse shoe there is a wide area of lavas between which and the banded hematite- quartzite there is a zone of phyllites increasing in width to the north. On the eastern side of the horse shoe there is 24 a J In s wide area of lavns, with occasionally a thin zone of phyllite intervening between them and the banded- hematite-quartzite. Most of the central area v/ithin the horse shoe aopears to be occupied by phyllites Jone*sraap# however , gives an impression of the extent of these phyllites between Noamundi (22^09' j 85^28•) and Iron Ore Range as far the greater part of the area coloured as phyllite is thickly covered with alluvium, or laterite. Joints and Slickensides Jointing is sometimes very marked in the shales end is well seen in the area of investigation and they generally strike in a east-north-easterly direction and dip in north- north-west sometimes at high angle, about 68 and north to south and west-northeast to east-southeast and secondary Joints running generally to east to west. The shales generally split along the bedding planes, but towards the north of the area, cleavage is also well developed, and often runs nearly at right angles to the strike and dip of the original bedding in the shales, as is indicated by the bands of different colours in the rock. Exposures of the shales are not very good and being soft, nature, folds and slips are not often seen and the movement has taken place is evident from the slick^nsided surfeces that are occasionally exposed. Bands of cherty rocks occasionally occur in these shales* Folding and Faulting Although tnere is change of dip and strike where folds occur, these make practically no difference to the general strike and dip of the rocks as a whole. The general structure of the iron ore series in the southern part of the iron ore area is an asymmetrical synclinorium-pitching towards the north. The west arm of this syncllnorium is slightly overfolded and dip towards the west, whilst the east arm is complicated by the folding, but has a general dip of 45 in a westerly direction. This syncllnorium pitches towards the north. Hear the Singhbhum-Keonjhar boundary and towards the north, the structure becomes obscure owing to excessive folding faulting and largely to the covered nature of the ground. The structure is generally only to be made out where the banded hematite-quartzite is exposed as the shales are too soft to give continuous exposures, and they are usually covered with c mantle of soil. Faulting in the shales is often indicated by numerous slicken.ided surfacss, but is impossible to trace the faults for any distance, owing to the soft nature of the rocks, and to the covering of soil which is usually present. 'c6 CHAPTER - III IRON ORES Iron Is the most versatile of all materials so far known to n»n. No wonder. Iron provides the framework of modern civilization. It Is difficult to think about modern machines and equipments without steel. There are engines of steel and tools of steel; the machines to make the machines are also made of steel. With its myriad uses in roads# rails, bridges, tunnels, trains, n»tor-cars and trucks, steel has helped the development of the net work of transportation and communication that has fostered the growth of modern civilization. The development of modern urban civilization has been possible thanks to the intelligent utilisation of iron and steel. Beginning from the sky scrapers and giant structures in modern cities, the stoves, refrigerators, steel furnitures and a host of consumer durables are made of steel. Agricultural development has attained a new meaning today with the tractor, the harvester, equipments for irrigation and other mechanical implements. Thus, human activities in the present era are related in one way or anotiier to iron and steel. I should say that our food would be less plentiful if there was no steel for spades end hoes, our water less pure if there were no pipes. 27M Basic is the manufacture of Iron and steel to a nation's economic life. The production and consumption of iron and steel is rightly considered as a sinequanon of a country's industrial prosperity. Broadly speaking it can be said that the industrial advancement has been in keeping with the avowed objective of enabling the economy to reach as soon as possible^ the stage of self-sustaining growth, for, despite the short falls, notable progress has been achieved in the development of iron and steel, heavy engineering and other capital goods industries. IRON ORE RESERVES OF Xm: AREA India has around 60% of world's high grade ore reserves, of which about 43% of the Indian reserves are situated in Bihar and Orissa and these deposits belong to the Precambrian iron ore series. Orissa is endowed with a vast reserve and high grade ores ranks second in the country's iron ore production. The chief protores which gave rise to iron ore deposits by supergene residual enrichment are the banded hematite jasper/quartitites of Precambrian age. They are found in two distinct cycles, one in the iron ore group associated with hornblende schists and phyllites of green schist family 2B and the other In less metemorphosed rocks of the Kolra Simpllpa: group. The iron ore formations of Koira Simplipal group associated with basic lavas and shales are exposed as a major low north-plunging horse-shoe shaped synclined in the Bonai-Keonjhar belt of Sundergerh district* The reserves of iron ore, as estimated by Geological Survey of India (1974) in different areas of Keonjhar district have been shown in Table-III, The total reserves of iron ore of all grades are estimated at about 8000 million tonnes in Orissa, of which the proved reserves are 3800 million tonnes (of 59-69% Fe), ?TODE OF OCCURRF WCE At Thakurani Hill mines banded rocks are very striking, and consists of interbedded layers in varying proportions of iron oxide, silica, and combinations of the two. The chert, however, is not truely amorphous, but consists of fine interlocking grains of quartz. At times silica is red and jaspery, and this red jasper often forms a large proportion of the rock. The iron oxide is usually hematite. It is in these banded rocHs that most of the iron ore bodies occur, and all gradations between them and iron ore are found. The similarity of these banded rocks to the jaspilite described by Van Hise and Leith (1911) in their monograph on •The geology of the Lake Superior Region', was later on recognised by Jones (1934). 20 These rocks range froi • pure dense quartzite on the one hand to pure massive iron ore on the other, every conceivable gradation between the two extremes being found at some point or other and often within the area and as a rule the ore bodies do not have sharply defined walls, are siliceous banded ferruginous rocks grade one into the other. Weld (1915) in his description of 'The ancient sedimentary^ iron ores of British India* says on page 452 J- "They are strikingly like the Precembrian iron ores of Brazil, In fact, one is alnK>8t tempted to apply the Brazilian term itabirite to the quartz iron ore beds, jaculinage to the laminated and micaceous ores occurring within phyllites, and canga to the surface accumulations of rubble-ore float and rich laterite". Fermor (1936) has suggested while describing similar rocks from the Jabalpur district, that these rocks should be called banded hematite-Jasper or banded hematite quartzite, Percival (1931) has used the terra banded hematite-Jasper, but the term banded hematite-guartzite has got into common usage in the iron mining areas. Owing to their hardness, and partly to the comparative insolubility of the iron constituents they resist weathering so they are usually the most conspicuous rocks in the iron ore area, end are often found fuming steep cliffs, in which the bands of materials of different colours iramediateiy attract one's attention. The bands which are often very regular, vary 30 from more partings up to several Inches In thickness« and in colour from white to lavender grey# bright red, brown black etc. The difference in colour is due to varying amount, and to the character of the iron present. The bands of hematite, although generally fairly regular, are found thicken and thin out at times. The character of the siliceous bands varies considerably some consisting mainly of chert of nearly white to brownish red colour, others compact dark grey to reddish grey, consisting of powdery hematite and magnetite in silica. When exposed at the surface, the siliceous bands may be leached away, say a quarter to half an inch, leaving the hematite bands standing out as ridges* The thin veins of hematite noted above as sometimes occurring in these rocks, are left joinning the bands of hematite when the silica is dissolved away. TYPES or IROH ORE Practically the entire ore body that occurs and is mined in the area i.e. Thekurani Hill is hematite of various types, but, of course, it is almost impossible to prevent a certain admixture of hydrated material during mining operations. Laterite which contains up to say, 45% of the iron is abundant in the area, and a small gets snapped with the ore. n In the mine quarry faces occasionally shale are Interbedded with the banded-hematite quartzite, such shales sometimes grade to ore. The hematite varies from a massive steel grey type through a porous laminated shally looking type of iron, to a fine soft powder which averages well over 65% of iron. The porous laminated tvpe at the surface is often somewhat hydrated and often has a laterltic appearance. There is usually no sharp line of division between the different types and the one seems to pass gradually into the other. The usual type of ore is massive, hard and compact and steel grey to dark and brownish black in colour. The following varieties of hematite ore may be recognised :• 1. Hard ores (steel grey to brownish, massive and laminated. 2, Moderately hard ores (laminated). 3, Blue dust (flaky, friable and powdery). 4. I !• Hard Ores (Massive Hematite^ The massive ore, which is practically pure hematite, has a steel grey colour, often with a metallic lusture, and is usually extremely fine grained, dense and compact. It has 32 a metallic ring when struck with a hananer. This ore has a specific gravity of about 5,0 and specimens have yielded up to 65% of iron. This massive ore often forms steel cliffs, which are well seen at Thakurani Hill (22°06» j 85°26»), The ore is well bedded, but is often broken into blocks by Joints planes. At the surface this type of ore oftsn has a polished appearance, and is sometimes coated with a greyish black film. It is very resistant to weathering, but along the edges of blocks a certain amount of rounding takes place owing to weathering. Solution and alteration also take place along the bedding and Joint planes and often result in the formation of thin bands of lateritic material in the solid ore. This solution and alteration of the massive ore can in some cases be seen to cause a passage into a laminated shaly looking oxre, when seen in thin section, the ore grey and metallic and often resembles magnetite, but is usually has a slightly reddish tinge under reflected light. 2, Moderately Hard Ores (Laminated Hematite) The laminated hematite varies in character, from a reddish type through a grey laminated variety, which is dense and compact, with a metallic ring under the hammer, and light almost be classed with the massive ore, to a less solid laminated variety, which is often inclined to a shaly appearance. 3 a and is often extremely porous. This shaly appearance, is usually due to thin laminae of the massive grey variety being interbanded with thin laminae of less compact ore, often of a reddish colour and usually very porous. The spaces in the porous varieties occasionally have small grains of white quartz, or white, or ferruginous shaly and kaolinic material in them. The bedding in this type of ore is usually well masked, but owing to the leaching out of much of the original material in the rock, the ore is often vary contorted and broKen up into small fragments, either by earth movements or by the weight of overlying material. Cavities sometimes occur in this type of ore. The specific gravity varies considerably, depending on the proportion of massive ore end the amount of porosity, and varies from 3,5 in the earthy varieties to about 5.0 in the solid laminated types. Owing to their porous nature these ores often become hydratad, and tend to become lateritised. As would be expected, the iron content varies considerably, but is usually well over 60% and in some of the denser typ; approaches very closely to that of the massive varieties. These seem to be no doubt that this type of ore has resulted mainly from the leaching out of silica from the banded hematite quertsite. There is also a type of laminated shaly ore which 'las resulted from the alteration of the shales. This type is rich in iron but gradually passes into the usual shales of the area. 34 3, Blue Dust (Powder Hematite) The powdery variety Is usually so fine grained and unconsolidated that it falls into powder at a touch, but it usually cont'-»ins some lumps or bands of harder ore. This powder ore can be seen in parts of most of the ore as where mining or quarrying dperations have taken place and is well exposed at some of Messrs. Bird and Company, workings at Thakureni Hill (22^06• » 85°26»), Although usually containing over 65% of iron, it is of very little use at present, and is looked on with disfavoxir by the blast furnace operations, as the material tends to choke the blast furnace or get blown out into the flues. This powder ore is at tiroes seems to pass laterally into the friable laminated ore, and when looked at in situ in a mining fare, it is difficult to imagine that it is a soft powder, but immediately it is touched, it falls to the ground as a powder. Jones (1923) believed that the 'blue dust* which is so frequently associated with the Indian ores, represents the residue after the complete removal of silica from lamirated hematite. Percival (1952) originally believ^^d that these powdery ore represented a chemical precipitate such as might be produced by the sudden chilling of magmatic solutions on their injection in the sea. 35 At some places at Thakurcml Hill (22°06» i 85°26») which were exposed faces the another there exactly similar to banded hematite quartzite, but when touched it ran down as a fine sand. Such leaching is obviously the work of recent meteoric waters. Sometimes 'blue dust' at some exposed face show perfect preservation of oil the minute structures e.g. folds of tho banded hematite quartzite; these could never have been preserved in such an incoherent material through out earth movements of any magnitude. 4. Lateritic Ores The lateritic variety occurs in large quantities through out the iron ore area, as a surface alteration product, sometimes of the iron ore itself, at other times of the ferruginous shales, end at still other times of the hematite • breccia or other rocks. Lateritisation is usually a surface feature but attention has already been drawn to the formation of laterite bands along the joints end bedding planes of the massive hematite. The laterite is usually of too poor a quality and too rich in alumina to be used as an iron - ore, though at times owing to the presence of fragments of unaltered hematite in the mass, the iron content is nearly 60%, and it becomes of economic volue, but it usually runs to between 40 and 50 percent of iron. At times the original bedding can be distinguished* and then it is known to some extent from what type of rock or ore the laterite has been derived, but at other times the lateritisation has been so complete as to obliterate all traces of the character and bedding of the original rock. nimnG WTHOD open cutraining i s practised at Thakurani Hill and also the blast hole drilling is done to break vast quantities of ore, by using large charges of liquid oxygen explosive. COM>ITIONS WARRA?^TI^^:- O^BH CUT WORK Open cut mining of minerals is justifiable technologi cally and economically when they lie immediately near the surface or at a relatively small depth. In this connection, it should be added that because of the considerable progress made by mechanisation, minerals can be carried out to advantage at ever-increasing depths. Open cut work is also possible v;hen the deposit is not exposed directly at the surface, but it is covered by consi derable amounts of overburden or country rocks* whose thickness should not exceed a certain limit. In cases like this the deposit may occur either horiszontelly or at any angle to the horlEontal. 37 The production unit of a mining enterprise extracting the mineral by the open method Is called open pit. This term Is analogous to mine, which extracts the mineral underground. It should be noted thet the term open pit often also designates an open mine workings In which' the mineral Is excavated by the open cut method. ADVANTAGES OF 0?EH CUT WOR/.If^S 1. The principal advantage is that the efficiency of labour is considerably higher in open pits, v;hHe the cost of mining Is lower. 2. Large working faces and the use of highly efficient machines for the open mining of large deposits yield considerable tonnages. The reconstruction of an active ooen pit enables to raise production more quickly. 3. Open pits may have a shorter seirvlce life than underground mines, since here it is possible to transfer the costly main items of mining and transport equipments and machines to other pits for further use. Hence, pits working even limited reserves may yield large annual tonnages. 4. Open pits need no support, filling, ventilation and artificial lighting (except at night). 38 5. Percentage recovery of the mineral is higher in open work. 6. When necessary, large size monoliths for construction ani sculptursl purposes can also be quarried. 7. Working conditions in the open, in good weather -nd not too severe climate, are better than underground mining, 8. There is less danger of accidents. However, the presence in the pits of numerous machines, the wide-flung transport netv'ork, blasting operations, the possibility of mineral and rock blocks falling from the faces are a constant source of potential accidents. 39 CfiAPTFR - IV MI?3ERAL0GY Banded rocks of the area of investigation are very striking, end consists of inter-banded layers in varying proportions of iron oxide,fciiica an ^ et others is cherty. The chert, however, is not truly amorphous, but consists of fine interlocking grrins of quartz, nt times the silica is red ©nd jarpery, and this red Jasper often forms a large proportion of the rock. Tha iron oxide is usually hematite, but soiitetimss cubes and octahedre of martite occurs, and all gradstion betw.en them and iron ore ere found. So far no mineragraphic study of the iron ortr of Thakurani mines has been made by any one the earlier workers. In coarse of the present invest!;3ation, the author, therefore, avciiled of the first opportunity to examine in detail the iron ore of Thakurani mines in K.onjhar district (22°27' t 85°35') of Orlssa state (which lies within latitude 17°48' s 23°24' and longitude 81°24' : 37°29•). The workable deposits of iron ores of Thakurani Hill occur along certain well defined ?ones. Small and scattered pockets of blue dust occur rather infrequently at some places. AS far as possible all tlie available types of iron ore samples reoreaenting lateritic, hard laminated and 40 friable were collected systematically from the different sections (benches) of the open cast mines of Thekureni Hill, While preparing the polished blocks of soft and friable specimens some difficulty were encountered because continuous cooking in Canaia balsom were required before they could be finally polished. About 20 representative samples of iron ores from the different locations have been finally selected for ore-microscopic study. Through mineragraphic study an attempt was made to identify the ore minerals and their asserablageg, state of oxidation* and finally their tsxtural relations and persgenetic sequence, MI?1ERAL0GTCAL DESCRIPTION The mineralogical description of various iron and manganesa minerals, v;hich are identified in polished sections under reflected light are given below alongwith their characteristic physical characters. Chemical formulae of the iron and manganese minerals are adopted after Deer, Howie and 7ussm.an (1962), end Hewett f^nd Fleischer (1960) resoectively. 41 IROM ORES As far as the mineralogy of the Iron ores is concerned hematite and martite being the dominant iron minerals of the different ore types. Goethite and limonite represent the secondary .-ninerelc formed by the conversion of the original oxiie ores to hydroxides of iron by hydration under super ficial weathering while Pseudomorph of heisie'tite after magnetite are called martite. HEMATITE (FegOg) The name hematite was first proposed by Theophrastus in 315 B.C. because of its colour rese?r±)lcnce to blood, for which the Greek v;ork 'hacme* ve. used (see Deer et al., 1962? p. 21). This is the principal mineral of the iron ore deposits of Thakurani Hill, It is extremely variable in appearance. There are all gradation fro. a hard, dense, massive steel ore through a softer, darkened hematite to a lighter red, soft, almost earthy ore. in even the steel grey dense varieties (located rt hill-top) there are gradation from massive ore to a banded material, the bands being composed of fine end coarser hematite. 42 Habit Crystalline in hexagonal form, occasionally in thin platy forms* as 'micaceous' hematlta. In Thekurani mine at aome places a fine hematite powder known as 'blue dust* is found. Simple twinninq is rare, commonly massive or infoliatad or shaly aggregates; colour - iron black to steel grey? streak - cherry red} lusture « submetallic; hardness « 5.5 to 6; brittle; cleavage - none? specific gravity - 5»0 to 4,2. Under reflected light hematite shows white to grey white vrith feint bluish tone noticed more clearly with oil immercion? moderate reflectivity? v;eak biref lectanc-' and vask but distinct enisotrooism. Etch reactions - all re,?gentf? negative, MAHTITE Kineraloglcally msrtite is hematite pseudomorphous ?fter magnetlt£ (ste Repf?, H.H., 1947; p, 488), Hematite replaced primary magnetite without leaving -ny remnant is regarded as second generation hematite (Pi, I, Pig, 3 ) «,nd further replacement of this second generation hetr.atita (marti • crystals) by geothite har, been observed (Pi, II, rig, 1). TfertitF exhibits all optical properties of normal hem'-^tite except a little higher reflectivity and well prescribed octahedral form of magnetite. 43 GQE r^ITF {o named after the philosopher Poet Goethe (1749-1332; see f>ana# 1962, p. 504)• Earlier the mineral was called *Onegit', after the place of discovery Uj&\e Onega), but since its properties were not described, the name has not survived in inineralogical literature, Habit cryscalline form - orthorhombic; ususlly in sinter- liXe; spongy, slay or pulv rulent. Etree'^ - brownish or yellow brown, lusture - ac'ementine to aubn^etallic; hardness - 4,1 to S.S; specific gravity - 4,0 to 4,4, Under reflected light gcethite occurs mostly in coiloform bandc (PI, II, Pig, 2), Sometimee streaks and anhedral patches of geethite are. ?lso found (PI. Ill, Fig. 3). It is dull grey in colour son^tim^s v^ith bluish tint. Reflecting power - low, \;hich bscomes much rsore distinct v/ith oil iiTnernion. ^^n inner reflection in sr-en in rneny gr--.lns, usu-lly orangs» rolour--^'d, but ir often deep red, r.pccif. Hy with oil irnr-erelon. Anif.otro:-ic colour eifccta ar^' vtry distinct. rtch r«cctlDns - negative to all st^sndard reagents. 44 LIMOMITF ( t FejOg.HgO?) The name of limonite is derived from the Greek •lemon* for meadow (allusion to meadow and bog iron). Brown iron ore (limonite forms only in sedimentairy cycle, first of all as a weathering product of iron-bearing sulohides, oxides, carbonates and silicates (see Ramdohr, 1950? p. 1047). Limonite occurs witn massive goethite (PI. I, Fig. II) and also as coatings in the microcavities; colour-brovm or yellowish brown; streak - yellowish brown; lusture - submetallic, silky ordull; hardness - 5,0 - 5,5; specific gravity - 3,6 to 4. Under reflected light limonite is dull brownish red in colour rnd shows excellent reddish to yellowish red internal reflection but the power of reflection is low in comparison to Geothite ^nd further it is PISO dull in internal deep red reflection in comparison to goethite. Etch reactions - negative to all stsndard rer-»gents. PYR0LU3ITI (.MnOj) Belongs to the fire grained variety while the coarsely crystalline variety are called polianite (Dunn, 1936). 4.) Habit Crystal forni - orthorhomblc but usually pseudomorphous generally forming fine matted prismatic needles; colour - iron grey or met-^llic or opaque; hardness - 2 to 2.5; often soils the fingers; specific gravity - 4.8. Undt;r reflected light colour is v/Uts, faint yellow tint, which increases in oil immersica, rather psleochroic; reflectivity • high and strongly anisotropic. Etch reactions - negative - HN0„, fCCN, FClj* KOH, HgClj. positive - HCl Bud aqua rcjgia, drop eel our £• brown, but surface UHc ffectrd. FSlLOriLLANE ( m. InO , HnO ^ • nH. C ) i'tenganese oxide und hydroxide with the addition of such eleraents as Ba, Hi, Co, K, Li, ?b (see Read, 1947; p. 473). Fermor (1909) while describing the manganese ore deposits of India regards this a3 a nangan.'te. Habit Usually amorphous, oft n botryoidel, colour - black; streak - brovmish black? lusture - submetalllcj hardness - 5 to 6; specific gravity - 4,2, 40 Under reflected light the mineral is seen to bp finely crystc'lline and found to be associated with pyrolusite, exhibiting bluish grey to greenish tinge colour with higher reflectivity than the pyrolusite and in shades of grey it is anisotropic. Etch reactions » negative - KOH, HgClj positive - HNO-, St ins light brown, fumes tarnish, HCl, st-lns brown to black. FeCl-# stains light brown. H^O, efferveflcas, no etching. While studying the iron ore samples microscopically, ic has besn found that the microleyerlng (PI. I, Pig. 1) end microfaiding (Pl. II, Fig. 2) are the most common micro- structures, present in the laminated iron ores end banded heroatite-jasper have retained csrtain sedimentary structures, particulatly the penaconttji.iporaneous deformations of iron 2.nd eilica bearing layers and other common feature is the slum iitructure of sedimentary origin resulting from the leaching of silica. iollotiving .:rfc. the textures recognised in the oresi- AI ( Replacement Texture In hypogene, replacement, as in supergene replacement, a more soluble mineral is always replaced by a less soluble mineral. Shouten, C, (1934) shovm that a single solution can set up a train of replacement. Mostly the replacement in this case is observed to proceed from the periphery of the grain minerals. At the first stage thin skin of hematite surrounded the goethite crystal (Pi. I, Fig. 2), This rim of the hematite is seen in other cases gradually penetrating towards the centre, sometimes regularly (PI. I, Fig. 2). In crystals where the replacement of magnetite by hematite is completed without any relict of reronants of magnetite (Pl, I, Fig, 3), then such crystals are referred to as pseudomorphs of hematite after magnetite. In most of tliu laai^sive ores and laminated ores the outer margins of these pseudomorphs have coalesced to give i-ise to c^ n:ore or less contiguous band of hematite (Pl. I, Fig. 3), In some cases these martite crystals have been replaced by goethite or gangue giving an impression of pseudomartite (Pl, II, Fig. 1). Replacement of hematite by goethite has taken place in the cracks and fracture planes (Pl. II, Fig. 2). Colloform Texture The term •colloform* (implying colloid or gel-texture) 4 p. is used to describe the texture of minerals that occur in a series of concentric curved or scalloped layers, in which the curvature is always convex towards the younger or face surfacf (Edward, 1966). A face surface, if present, is reniform, botryoidal, marasnillary or even stalactitic. These curved surfaces as Poydell, K.C. (1925) observed, are manifestations of surface tension effects in viscous material, and ere theretore indicative, though not by any means exclusively of colloidal origin. The iron oxides are deposited as a gel that hardens into amorphous, sometimes limonite, or dehydrates as goethite, or even hematites, under favourable conditions, Host of these minerals are of supergene origin, and are deposited from cold aqueous solutions, generally in open spaces, though the solutions from which they art deposited are capable of replacing the more or less weathered country rock (Edv;ard, 1366). Colloforti texture is exhibited by goethite and limonite. Rounded end concentric bands sometimes broken concentric bands (Pi, II, Fig. 2) or mass of goethite are commonly seen in the ores frora the zone of significrnt wecthsring (PI. II, Fig. 1). However, the colloform texture it not coravion in the iron ores even though goethite belonging to collofom-. variety shows this characteristic. 40 Granular Texture Granular texture Is less commonly the result of irmnedlate crystallisation In ore minerals than It is in mogmatic rocks or oceanic salt deposits (see Ramdhor, 1969, p. 146), Granular texture is exhibited by the ores consisting of subhedrnl to enhedral crystals of martite with some goethite occupying the intargranular spaces (Pi. I# Fig. 3 ). Granular hematite is also seen in the iron ores (Pi. II, Fig. 3 ). 'Well developed cubic crystals of martite are observed v/hich are embedded in the granular hematite as v/ell as goethite (PI. II, Fig. 3 )• Banded Texture The banded textures are very widespread and in part extreirnely fine. They con occur in a single grain end are then really *textural' profortiec, as well as in an aggregate of one or more mineral species (see Ramdhor, 1969, p, 149). Banded textur.i: are very widespread in sedimencs and almost the characteristic mcrks of dynaiaically metamorphosed ores end are deposition feature of the protore is ideally retained by the \ard and laminated iron ores consisting essentially of equigrenular groins of martite with some massive goethite (Pl. I, Fig. 3 ). The banding in these ores is quite cl ar under the reflected light. Thin trains of goethite in some ore? also serve to distinjuish banding (?1, II, Fig. 2>, however, at places bands are deformed. 50 Vein Texture Vein texture is exhibited by some of the samples where coarse grained scely hematite is cutting across the fine grained hematite and martite. At the margins of the veins replacement of hematite by goethite and limonite is seen (PI, III, Fig, 3 ), PARAGE r^JES IS To determine the paragenesis o£ en ore, it is necessary to establish for e^ach pair of minerals present v;hether they were deposited simaltaneoualy, or whether the period of deposition of one overlapped thrt of the other, or v/hcther one x^p.o ds >osited eftex^ the other (Pastin, 1931), It is evident from the texturel relation of the iron ore miiierals that hematite which constitutes the bulk of the iron ores appears to be distinctly of at least three generations. The first generation hematites apparently of primary origin, in microcrystalline and intimately intx.r-mixed with cryptocrystalline sjlica. It usually occurs aa microlryered (^1. I, Fig. i ) or banded segregations (?1. Illt Fig. 3 ), Martite re.'resents the second generation hematite because this hematite is replacing the rrjagnetite completely without leaving any remnant of the magnetite (=>1, I, Fig. 3). 51 This type of inter-layered occurrence of martlte*rich and hematite rich layers indicates that possibly both hematite and magnetite (now martite) ^fere deposited as primary minerals* The third generation of hematite is that which occurs as coarse grained patches having irregular outlines (Pl« II# Pig. 2). These later generation hematite generally show relatively higher reflectivity and brighter white appearance. They are characterised by their uniform appearance as against the gel line structure of first generation hematite* To a limited extent martite has also altered to pseudomorphically into goethite can be regarded as the first generation on the basis of talcing into consideration their textural relationship. Zt can be said that this first generation of goethite in the time of sequence. However* unlike martitization# goethitization appears to be a very UQCommon process. The first generation of goethite is at some places replaced by the hematite, however, the laar^ite associated with goethite should be later than the martite pscmdonrarph after magnetite if goethitization and martitization of magnetite are taken to be paragenetically overlapping or even contea^joraneous. The massive and colloform goethite is also recorded which are of second generation coatings of limonite, associated with goethite (PI, I, Pig, 2) suggesting that both are contemporaneous). 5-3 It is found that to sofne extent pyrolusite and psilo5nelr:ne are replacing goethlte and martlte (PI. Ill, Pig. 2 )• Based on the aforesaid mlnerelogical and textural studies, the paragenetlc sequence can be suOTerlssd for the iron and manganese minerals presented in Table-rv. 53 CHAPTER - V GEOCHEMISTRY Iron is aroeinber o f a family of elements which includes titanium* vanadium* chromium* manganese* cobalt and nickel (with atomic number 22 to 28} because of which there is fairly close association of these in nature* Iron is a very important and widespread nH^tal in nature* the only metal which is nusre abundant in the earth's crust being aluminium. Its atomic number is 26; atomic weight 5S«85| specific gravity 7«4 to 7«8y melting point 1530°C« The pure roetal is silver white* highly magnetic* ductile* and malleable. It closely resembles to nickel and cobalt in chemical behaviour* The core of earth is believed to be composed of an alloy of iron and nickel. It forms 5,06% of the entire lithosphere (Clarke* 1924)* S% of all igneous rocks (Washington* 1939) and anything between 13 and 90 percent of the different types of meteorites. Among the igneous rocks granite contains the least amount (about 2.490 whereas pyroxinites and homblendites contain the roast (about 8,5% to 11.7%). Iron is a constituent of all living tissues both animal and vegetable* f^l In the analysis of allicate rock8# both ferrous and ferric iron are reported, usually expressed as oxides. Ferric iron is frequently associated with aluininiui!i» and ferrous iron with magnesium. This latter association is observed in the formation of minerals with composition ar»l properties intermediate between the pure iron and pure magnesium end members. Sulphide minerals containing iron ore of considerable economic importance. These minerals occur in both igneous and sedimentary rocks* if present in more than trace amounts, can introduce difficulty in the determination of ferrous iron. Ferrous compounds are unstable in the preserve of oxygen as they are easily oxidised. Ferric salts are easily hydrolysed in natural waters. They give rise to ferric hydroxide which is precipitated readily, paxrticularly in marine surroundirgs. Org- nic colloides may also absorb ferrous compounds on their surface. Iron is quickly and completely precipitated in marine surroundings as a gel. The source of marine iron deposits may be solutions derived from weathering of rocks on land or from submarine volcanic sources containing FeCl. and FeF,* In the present study, the author has tried to find out and to establish the relationship, if any, between the iron oxides and the najor oxides respectively. The percentage of various major oxides of Wiakurani mine iron ores are given in Table-v. Further, to show the frequency distribution of the 55 various major oxides* determined by the geochemical analysis* e.g. SiOj*Al203» MQTO* CaO* TiOj* Na^O, KgO, MnO, PjOg, HjO* (total water) and Fe.O^ (total iron )i8 shown by plotting the histograms. Moreover* to establish the relationship between the various major oxides of the Thakurani mines iron ores* correlation coefficient is also determined by the computer (Table-VI). DISTRIBUTION OF KA^R OXIDES SILICA An examination of Thakurani mines izron ores shows that silica is strongly positively skewed and the maximuin frequency percent lies between 5.0 to 6.0 percent class (Fig. H«l>. Silica ranges from 5*06 to 13.04 percent (Table-VII) with a mean value of 7.70 percent while the standard deviation of silica is found to be 2.45 (Table-VIII). MAJHim Alumina is fairly low in comparison to silica in all the examined iron ore seniles which shows a strongly positive skewness and the maxiimun frequency percent lies between 4*0 to 5.0 percent class as indicated by the histogram (Fig« H«>2)« AI2O3 ranges from 3#90 to ll.lO percent (Table-VI) with a mean value of 5*63 percent and standard deviation of alumina is found to be 2,065 (Table-VIll), LIME Calcium oxide shows a tendency towards positive skewness where the maximum frequency percent lies between 11*0 to 12.0 percent as shown by the histogram (Fig. H-3)« Calcium oxide ranges from 9,69 percent to 14»91 percent (Table-VXI) with a mean value of 12*26 percent and the value of standard deviation is 2*39 (Table-VZIX). IRON FegOg (total iron) content varies in different ore bodies whereas the total hill mass consist of banded hematite* quartzite. Iron shows a unimodal distribution except in few cases where the maximiun frequency percent lies between 63*0 percent to 65.0 percent as shown by the histogram (Fig. H-4). Iron ranges from 49.63 percent to 65,93 percent (Table-VII) with a mean value of 59.99 percent end the value of standard deviation is 5.49 (Table-VIII). 0 i SODIUM Sodium oxide in the iron ores of the investigated area is fairly low and shows a tendency towards negative sHewness whereas the maxiwura frequency percent lies between 0.5 to 1«0 percent and 3*5 to 4.5 percent* classes* as indicated by the histogram CFig. H-5), NajO ranges from 0,75 percent to 4.80 percent (Table-VII) with a mean value of 3,01 percent and the value of standard deviation is found to be 1,33 (Table-VIII), POTASSIUM Potassium oxide varies in its percent distribution and it shows a tendency towards negative skewness and the maximum frequency percent lies between 2.4 to 3*6 percent and 4.2 to 4*8 percent classes as indicated by the histogram (Pig. H-6)* KjO ranges from 0,46 percent to 5#11 percent (Table-VII) with a mean value of 3*29 percent and the value of standa^ deviation is found to be 1«28 (Table«»VIIX)« Thakurani mines iron ores have fairly low percent of manganese which shows a tendency towards positive skewness and the maximum frequency percent lies between 0«3 percent to c: 8 0,6 percent as indicated 1^ the histogram (Fig. H-7). MnO ranges from 0.09 to 2,11 percent (Table-VIX) with a mean value of 0*91 percent and tbe value of standard deviation is found to be 0.56 (Table-VlII). PHOSPt«)ROUS mmmmmmmmmmmmmmmmmMmmmftm- Phosphorous is also low in iron ores of the study area which shows a tendency towards positive skewness and the taaxiimim frequency percent lias in 0,0 to 0.2 percent class as indicated by the histogram (Pig. H-8). PgOg ranges from 0.04 to 1.87 percent (Table-vil) with a mean value of 0.63 percsent and the value of standard deviation is found to be 0.54 (Table-VIII). Magnesia ia the iron ojres of the study area have very low percent and very slight positive skewness is perceptible v;hereas the maximum frequency percent lies between 0,0 to 0.3 percent and 0.6 to 0.9 percent classes as indicated by the histogram (Pig. H-9), MgO ranges from 0.19 to 2#14 percent (Table-VII) with a mean value of 0,69 percent and the value of standard deviation is found to be 0.55 (Table-VIIl). TITANHTM Titanium is found to be variable in its percent distribution and the maximum frequency percent lies between 0.4 to 0*6 percent and 0*9 to 1.0 percent classes as indicated by the histogram (Pig. H-10), TiOj ranges from 0,33 to 1,01 percent (Table-VII) with a mean value of 0,65 and the value of standard dsviatlon is found to be 0,22 (Table-VIIl), WATER Combined water (loss of ignition) shovs a very slight positive skewness and the maximum frequency percent lies between 4*0 to 4«5 percent class as indicated by the histogram (Pig. H-lD* HjO**" ranges from 3,26 to 7.56 percent (Table-VII) v^ith a mean value of 5.07 percent and the value of standard deviation is found to be 1.37 (Table->VIII), MUTUAL RELVnONSHIP OP THE SIGNIPICAOT OXIDES WITH THE Pe-O, aiLZCA VS. IRO.^ Silica has a strong negative correlation coefficient (r) « *9«930 which means both iron and silica are inversely proportional to each other ^ich means that with the increase of iron thexre is decrease in the silica content end vice-versa as indicated by the diagram (Fig, G-1), GO The oxidates connected with volcanic activity are usually attributed to submarine eruptions o£ basic lavas and copious aimdunts of hydrothexiotial solutions produced in a closed basin. When the water of the basin cooled, carbon dioxide escaped, and precipitation of calcite<-doloniite», and siderite-bearing niuds started, the sediments also contained alternating layers of silica and ferric hydroxide (Rankama and Sahaina, 1949 }• Additional iron was produced by annual wnathering* Sot^titnes ferrous carbonate are precipitated under reducing conditions, which may be later n^tamorphosed 1:^ hydrothernial solutions giving rise to jaspilites an^ ferruginous cherts* Sometimes silica was leached out and magnetite was deposited* Silicates containing essential ferrous iron are easily weathered to yield ferrous ions, generally as components of bicarbonate solutions (Ooldschmidt, 19S8)* ALUMiHA VS. mon A significant negative correlation coefficient is noticed between iron and alumina, (r) « ••0*664« The linear relationship between ix^n and aluniina is demonstrated graphically (Sig* 0*2)• In lateritic weathering under tropical and subtropical conditions, iron is collected as ferric hydroxide in the weathering residue, along with aluminium hydroxide* Ferric iron, being able to migrate in true solution only in acid (n waters« differs from aliuniniiimr which may migrate both in acid and in basic solutions, being precipitated only in the neighbour* hood of the neutral point. When an acid weathering solution is neutralised, ferric hydroxide is first precipitated, but aluminium remains in solution until a higher pH is reached* Consequently, iron and aluminium may beeoittt separated, even though the separation is not quantitative (Rankama and Sahama, 1949). SODIUM VS. IRON A vezy weak positive correlation coefficient is noticed between sodium and iron i*e«, (r) » 0»123« Both iron and sodium are directly proportional to eacii other that is with the increase of iron content there is a very slight increase in the sodium and vice-versa which is clear by the linear relationship plotted on a graph (Fig* 0*3)* Pichamuthu (1935) observed that the amphibolite layers were supposed to be remnants of mafic igneous rocks which on alteration gave rise to the bended ferruginous quartzites. Both mineralogically and chemically it bears no resemblance to an igneous rock* The presence of NTajO in these bands was explained by him (Pichamuthu, 1935) as ascribable to the sediments being derived from the rocks of spllitic affinities adjoining the iron fozonations* Some recent analyses of these mafic rocks show as rnuch as 4 to 5*5 percent of soda (fCrishna Rao and Murthy, 1971)* Similar explanations have been given for the development of soda an^jhiboles in the ferruginous quartzites of South Africa S2 (Hall, 19251 Wegner, 1928}. Both Pttacock (1928) and Hall (1930) conaidered the soda to be original and dependent upon special conditions of deposition resulting in soda rich bands in the iron stones. POTASSIUM VS. IRQgT Potassium oxide is directly proportional to iron oxide of the ore body, KjO is increasing significantly with the increase of iron. Its correlation coefficient with iron is positive (r 8 0*480)• A linear relationship is made out (Pig. G<>»4)« Potassitira in the iron ores like sodium are considered to be ofroetasoroatic origi n (Pichamuthu, 1974 )• I«ate matasoniatic development of alkali ang;}hiboles like riebeckite in the Precanibrian iron formations of Kursk Magnetic Anomaly in Russia has been reported by Glagolev (1967) due to the indroduction of alkalies post-^dating the progressive raetamorphisra* MAtlSAKESE VS.IROH Iron content shows a high degree of negative correlation with the manganese content of the ore. The value of correlation coefficient (r) « ^O^OSSe. Iron and manganese are inversely proportional to each other, with the increase in the iron 63 content o£ the ore body« there is corresponding dacrease in the manganese content* as indicated by th« graph (Fig. 0-5}• In colloidal solution containing £erric and manganic hydroxide is brought into contact with an electrolyte* the separation of the two metals« according to Behrend (1924}« starts with coagulation o£ the bulk of manganic hydroxide* while iron still remains, largely or entirely, in solution* Behrend*s laboratory experiments showed that the addition of electrolytes to solutions containing an excess of iron over manganese always caused the separation of a mixture of the hydroxides rich in manganese first, followed later by a great quantity of an iron rich mixture of the hydroxides* PHOSPHOROUS VS« IRON Positive correlation coefficient exists between phosphorous and iron* Both are directly proportional to each other* The value of correlation coefficient is determined as (r) » 0*401 and a linear graph is plotted to make it more clear (Fig. G-6)* It has been observed that acid conditions (low pH) generally pronuste the solution of iron and lakaline conditions (high pH} proRK>te the precipitation of iron. Ferric hydroxide is easily precipitated from aqueous solutions at about pH3, ferrous h^roxide is first precipitated at about pH7 (Ooldsraidt, 1958). Precipitation of ferric iron under conditions of 64 increasing pH is exenqpXified in many soils or soil horizons o£ high pHt or in weathering residues o£ rocks which have a distinctly alkaline reaction* e,g», limestoneSf anorthosite, dunites* serpentines* There is also theroetascxaatic pxrecipitatio n of linK}nite from circulating solutions in limestones and even* in the case of ferrous iron* the nntasofnatic replacement of limestone by ferrous carbonate* Secondary enrichment of phosphorous may take place in phosphate sedin^nts. Thus phosphates may become concentrated when carbonates are leached away from phosphate bearing calcareous sediments and phosphatio liuMistones (Rankama and Sahama* 1949}• FiAGNESIUM VS, IRON Magnesium oxide is inversely proportional to iron oxide and the value of correlation coefficient (r) • -O.SS?, A linear relationship was established by plotting FeO vs. MgO (Fig. 0-7)• Calcium andraangnesium a t first migrate during the leaching of the ferruginous qiiartzites* but in the contact* residual ores their concentration again increases and reaches a peak; this is because these elements are brought in by epigenetic solutions in the course of carbonatization of the ore beds (Ousel'nikov, V,N, and Volkov, G.I.* 1966}* G5 TITANIUM VS. IRON A very insigni£icant positive correlation coefficient is noticed between titanitua and iron in the area under consideration* the value of correlation coefficient (r) <• 0.0031, A linear x^lationship is established graphically (Fig. 0-8)• During weathering the titanium consequently i^mains in the rasistates. I^ie most inqportant rock making titanium minerals* particularly ilinenite ar^ rutile, are stable against weathering, and consequently they remain unchanged in the resistalMt sediments. Titanium contained in the structures of ferric minerals (Pyroxenes, amphiboles, micas, etc.) is brought into solution during the weathering* But it is prcxi^tly hydrolyzed and carried into the hydrolyzates (Rankama and Sahama, 1949). The absolute titanium amounts in the process of residual iron ore carbonatization evidently remain unchanged (Ousel*nlkov and Volkov, 1966), LI!^ vs. IRON Iron oxide shows a strong negative coefficient correlation with calcium oxide (r) <• *0.602 ii^ieh Indicates an inverse relationship. It means that with the increase of iron there is decrease in calcium or llir» content and vice- versa (Pig. G-9). 66 The occurrence of ferrous carbonate* the mineral slderite, FeCOg. aa a constituent of rock layers in sedimentary series is probably in most* if not all# cases due to secondary replacement of calcixim carbonate by solutions containing ferrous bicarbonate with exclusion of oxygen either as gas or dissolved in aquous solutions* As a result of a series of experiments, Moore and Maynard (1929) concluded that carbonated water is en effective solvent able to dissolve sufficient iron and silica firom mafic terrain to form a laxrge sedimentary iron deposit* W;^T£R vs. IRON Combined water (H^O'*') shows a significant negative correlation coefficient with the iron i«e. (r) •• ••0.447* Linear relationship indicates that with the increase in iron content there is decrease in the water content (Fig* G-IO) and vice-versa* The behaviour of iron in processes of weathering is dependent largely upon the stage of oxidetion of the iron compounds involved. In all the cases in which ferrous ions are involved further oxldrtion is likely to occur, leading to the formation of ferric ions* The increase in ionic potential from ferrous to ferric ion, according to Goldschmidt (1958) leads to hydrolytie precipitation of ferric hydroxides or oxides and thus again to an immbolization of the iron* Reduction to the ferrous state again can reproduce the ferrous ions* 67 INTER ELEMEOT REIATIONSHIP The nature of the products formed in both endogenic and exogenic reactions depends decisively on the concentrations of the participating elements* i«e* their abui^Uince* Although the local concentrations of the reacting coirpounds in nature are governed by many factors^ they depend ultimately on the abundance relationship of the elements in question* It must be added, on the other hand, that the knowledge of the abundance relationships of the elements still does not suffice to determine quantitatively the natiure of the substances formed in the reaction* The rapid increase in understanding of the ultimate composition of the atomic nucleus has resulted in the fact that now the geochemist must also consider the abundance of the nuclides which compose the various elements, in order to conqpletely understand the abundance relationships of the latter* Following are the significant inter-element relationships of the iron ores of the Thakurani mines* SODIUM VS. POTASSIUM A significant positive correlation is noticed between sodium and potassium foui»l in the iron ores of tiie area under consideration* The value of correlation coefficient is (r) » 0*663* A linear representation is made on a graph (Fig* O*!!)* Sodium in association with other elements occurs G8 in considerable amounts. The ratio of sodium to silicon in the lithosphere as a whole is probably similar to that in meteorites (Qoldschmidtf 1958}• There can be no doubt that sodium has been concentrated in the uppermost part of the lithosphere in rocks of light residual magmas* Sodium and potassium released during the weathering remain in ionic solution, whcureas, aluminium reacts with silica to form clay minerals, and also, perhaps, to form mascovite with a part of the potassitim. As the sodium is extracted from the rocks during the weathering, its absolute amount decreases in the hydrolyzate sediments which are foxrmed as a result of chemical decomposition. Potassium, on the other hand, goes first into solution but does not remain dissolvedi it is largely absorbed by, and even enriched in, clays. It has also been suggested (Rankama and Sahama, 1949) that the difference in the behaviour of sodium end potassium during the weathering is caused by the greater resistance of potash feldspar as compared with that of the plagioclase feldspar, which causes an initial accumulation of potassium* hXm VS. riAGHESIA Correlation coefficient between CaO and MgO is found to be insignificant i.e. (r) • 0.075 and linear J^lationship is shown graphically (Fig. G-12}. GB The ezthaneem«nt of calcium as against oiagn«8itxm in average igneous rocks can be explained by the fact that magnesium is eliminated by gravitational setting of early crystallizates of heavy magnesium silicates from magmas. Light minerals and lightar rocks rise towards the surface in the course of vertical displacements. Goldschmidt (1958) stated that calcium is not a typical element of very early magmatic crystallisates« but is associated rather with magmas at the transitions between the early and middle steps in the sequence of fractional crystallization whereas the distribution of magnesitun in the sedimentary sequence is fairly well known as magnesium is always included in the analyses of the major constituents of rocks. Zn most cases of iireathering the magnesium ion enters the cycle of sedimentation* in other cases it is precipitated on the spot asreagnesite* MgCO^ , or as dolomite* especially in the weathering of olivine and olivine rocks. The precipitation pf magnesium in carbonate sediments is a most interesting part of the geochemistry of this elenmnt. It is probsble that a precipitation of magnesium from sea water as carbonate is in most cases connected with a transformation of calcium carbonate into dol<»aite, but the conditions of such a transformation are not yet exactly known (Goldschmidt* 19S8). The average sedimentary rocks contains less magnesia and more lime than the igneous rock from \«hich it is desired (Leath* and Mead, 1915). Gruner (1922) noticed through his 7f] experiroents that magnesia is absorbed more rapidly than lime. Moreover* the gi^at abundance o£ ferroroagnesian minarals* whether igneous or metamorphic, suggest a closer relationship between ixron and magneai\:Bn than between iron and calcium* The concentration of certain el^nents sharply increases under conditions of epigenetic mineralization such as calcium and magnesium etc. as observed by Gusel'nikov and VolXov (1966). SILICA VS. ALUMim Coxrelation coefficient betifeen silica and aluminium is strongly positive i.e. (r> • 0.662 which indicates that relationship is directly proportional to each other. With the increase of silica there is increase in the content of alumina and vice-versa as shown by the linear representation on a graph (Fig. 0->13). During the weathering of silicate minerals silicon, like aluminium is brought into ionic solution, usually in the form of alkali silicates. If the weathering solutions becon« concentrated, silica is precipitated as an amorphous gel, e.g. in arid regions. If only a silica hydrosol is formed during the concentration of the solutions, it may migrate farther, because it is very insensitive to flocculation caused by electrolytes in solution. Rankama and Sahama (1949) found that ailica in solution may also react v/ith other substances. The solubility of silica depends upon the pH of the solution. 7 I The higher the Ph# the more silica goes into solution. If the pH decreases for Instance, by the addition of carbon dioxide, silica is precipitated. This process may sometimes lead to a notable concentration of silica. Orunder (1922) has found that the less silica, a silicate mineral contains, the greater will be the amount of cilica dissolved in the weathering solutions during the pr:isence of dilute acids, hoxiever, Goldschmldt (1937) points out that a certain portion of silicon, although sioall, might originally be contained in thexrroal waters, which are often rich, in silica. Silica is deposited from juvenile waters in geysers and hot springs as siliceous sinter (geyserite) and other spring deposits, which may often form beds of geological importance, even though they are geographically not very extensive. Other, chiefly inorganic, siliceous precipitates (chert, flint, jasper) are very common in the geological column. It might be jc^sslble that thermal waters carry a part of their silica directly to the sea, whereby the silicon content of sea water is bound to increase (Rankama and Sahama, 1949). 1*113: vs. SODIUM Calcium and sodium is found to be Inversely proportional to each other and therefore their corxrelation coefficient (r) a -0.468, is negative which shows that with increase of calcium there is decrease in the content of sodium or vice- versa in the studied iron or«s which is evident by the diagram 7;^ (Fig. G-.14). During chemical weathering* the calcium bearing minerals dec(xt^ose, and their calcium goes into solution as bicarbonate. However, sorae calcium is tenqporarily retained in the gone o£ weathering as carbonate or sulphate. According to Rankaroa and Sahama (1949) the Na t Ca ratios shows no very marked change when the igneous rocks and the shales are con^ared with each other. Therefore, it is evident that the calcium, in analogy to sodium, can not be notably absorb^ in clays, and consequently the bulk of calcium liberated during the weathering does not becoitts incorporated in the hydrolyzates. Calcium 1 liberated during weathering goes into solution as bicarbonate, Ca(HC0^}2. From this compound calcium is precipitated readily as carbonate, v^ich redissolves and finally all the calcium is transported into sea. Schloesing (1872) was the first to prove, by experiment that the solubility of calcium carbonate in vmter depends on the content of carbon diostide in the gaseous phase in equilibrium with the acqueoua phase. Wattenberg (1936) has explained the effect o carbon dioxide on the basis of the equilibrium which exists between the solid calcium carbonate and the Ca and 2— COj ions found in solution • (solid) According to Kuenen (1941), the deep sea deposits contain about 15 percent CaO, and ell sediments formed contain approximately 12.5 percent CaO. CHAPTER - VI SUMMARY 6 CONCLUSION The most Important number of the iron ore series* from an economic point of view, is the banded hematite- quart zite/ jasper* The present investigation is nminly concerned with the mineralogy and certain aspects of geochemistry t^sides the mode of occurrence of the Thakurani mines iron ores, district Keonjhar (Orissa). To understand the nature of mineralisation geochemistry of the iron ores was studic»d* spectrophotometric analyses of iron ores wezre carried out to study the variations in the iron content in all these deposits as well as the major oxides. The product of alteration were critically examined to reckon the reactions that might have taken place during the course of deposition. The deposits belong to the Precambrian iron ore series and the ore is within the bandetd iron formations occurring as massive ore with iron content around 65% (concentrated by leaching), blue dust ore (extremely ^ friable and micaceous hematitic powder) and weathered ore, \ The area of investigation is a hill mass consisting of three main ridges which rise about 1000-1500 ft. from ground level and is consisting of banded hematite-quartzite whereas the rich hematite is exposed mainly on the top of the ridges. The rocks dips generally to the northwest at high angles^ but much contorted and folded* Good hematite is exposed at eastern ridge but at places found to be lateritised. The hematite is often covered with consolidated ore. The banded heraatite-quartzite is frequently seen to change into hard massive iron ore when followed laterally. It occasionally passes also into laminate'^ ore with a shaly appearance or into pockets of powdery ore which easily falls to powder if disturbed. The powdery ore is seen to contcin aggregates of martite and granular hematite, l^is powder is apparently the residue of iron ore left after the complete leaching away of the silica from the original banded hematite- quartzite. Partially altered or unaltered masses of hematite* Jasper are sometimes found amids the ore. These, however, show a certain amount of enricfunent in iron as conpared to normal type of hematite-quartzite. The ore exposed at the surface in several of the deposits is a massive, dark brown to steel grey, compact ore. It generally weathers into large blocks about a cubic yard or two in volume, this being helped by the presence of well marked joint planes. Sometimes the massive ore may show regular bedding without rraich evidence of sluiaping. The exposed surface of the such ore has generally a dark brown to black polished appearance owing probably to the presence ! •) of a film of hydroxide which has been dehydrated. This type of ore has irore than 60% of iron contents. Being very resistant to weathering, it is found strewn about on and around the outcrops* Such 'float' ore* found in association with larger deposits may often amount to many thousands of tons. The general stxructure of the iron ore deposits of Noamundi and Joda East in the southern part, an asymmetrical synclinorium pitching towards the north. The west arm is slightly over folded and dips about 70** towards west, while the east arm (Noannindl-Thakurani and Joda-Khondobond range) is complicated by folding with a general westerly dip of about 45°. The structure becomes generally obscure due to excessive folding, fsuiting and the largely covered nature of the ground. The stratigraphy of the iron ore series, like its structure, has given rise to much controversy. It is so because, in the area of the iron ore series so far geologically mapped, no sequence of rocks has been finally established. It is, however, widely accepted that the iron ore series in Singhbhum and Keonjhar consists of nwtamorphtfsed sediments made up of shales and sandstones together with considerable intorbedded volcanic matters. Mineragraphic study of the iron ores of the Thakurani mine led to the identification of hematite, martite, goethite, limonite besides pyrolusite and psilomelane minerals. From the study of the textural and micro-structures of the iron ores 76 of the study area« It la found that in most of the cases the replaceiiient of magnetite by hematite Is coi^plete without any relict reranants of magnetite, then such crystals are referred to as pseudomorphs of hematite after magnetite. In most of the massive ores and laminated ores the outer margins of these pseudomorphs have coalesced to give rise to a nwre or less contiguous band of hematite. Other In^ortant replacement textures in the ore are those resulting from goethitisation end later limonitisation of hematite. Replacement of hematite by goethite along fractures, vein# etc. have taken place and further rounded and concentric bands/masses of goethite with colloidal silica are conmionly seen in the ores from the zone of significant weathering. The chemical analysis of these iron ores indicates that the iron content ranges from 49.83% to 65.93%. Some of the low values of iron obtained are due to the high percentage of silica* present in the form of quartz. Major oxides of iron ores of Thalcurani mines were determined viz.« SiO^* ^nO«« MgO, CaO, TlOg, NajO, KjO, MnO, Pg^S* "2^* ^^ ^®2°3 ^*®*®^ iron) and an attempt has been made to establish their relationship with iron oxide. Correlation coefficient was also determined to make it more clear. It is shown by chemical analysis that iron oxide is inversely proportional to SiO.* AijOj, MgO, CaO, MnO, HgO*. In the light of the aforesaid studies follwoing conclusion may be drawn «- 7>-- < 1, That by the action of meteoric waters through supergene process of replacement and enrichment the original nature of the iron ores of Thakurani mines have been changed, 2, ^at the formation of hard friable and powdery iron ores have been taken place by the mass residual leaching of silicaf oxidation of rnagnetite to hematite and deposition of some hydroxide under certain favourable physiographic, structural and physico-chemical conditions. 3, That supergene oxidation of magnetite into hematite and their secondary enrichment with addition of colloform or massive goethite were most effective in the upper part of the deposit and as a result of which it gave rise to an upper zone of hard and enriched ores consisting domlnantly of hematite and goethite. 4, That iron has a tendency to increase and silica is to decrease vertically. 5, That in the iron ores of Thakurani mines SiOj, ^2®3* MgO, ^!nO, CaO and HjO"*" decreases with the increase in iron oxide. - _ >«• "• ' ' . * A*"'.' •%*. 8 TABLE - Z Geological distri1:mtion of Indian ores Formations {lature o£ ore Occurrences Precarobrian Basic & Ultra- Titoniferous & Bihar .» S*E, Singhbhum basin rocks vanadiferous Orissa - MayurbhanJ magnetites tlysore - South districts Granodiorite Apatite- Assam - Jaitia Hills magnetite rocks Bihar • Singfhbhum Orissa - Bonai, Keonjhar & MayurbhanJ Banded Iron Hematite :!ysore - Shimoga«C3iikmanglore, foriaations (massive, shaly etc» powdery, etc.) Madras - Sandur Bombay - Dharwar, Ratbagiri - Bastar,Chanda,Drug, «rabalpur Banded Iron Magnetite- Madras - Salem,Trichinopoly, formation quartzites Ountur (metamorphosed) ?^sore - Shimoga etc* HaP« - t^ndi Cuddapah Bijawar Hematite & - Gwalior, Indore, ferruginous Bija'./ar, etc# Gwalior quartzites Madras - Cuddapah, Vindhya Pradesh, Rewa Gondwana Barakar Iron stones & Bengal - Birbhum siderite Bihar - Aurangabad Mahadeva Iron stone •"ditto- Bengal - Raniganj coalfield shales Triassic Hematite & ICashmiz• LiiBonlte Jurassic Rajmahal Trap Iron stones Bengal - Rajmahal (interappean bed£0 Bihar - Birbhum Tertiaxrv I'liocene & Eocene Iron stones South India - Travancore, 7'telabar,etc« Assam - H.E, districts Quarternary U.P. - Kumaon Many states - derived from Laterite many formations including Deccan traos. n M Q 0 4i © " 4J 1 uM u •H «> a 4>x: 0/: 7B 1 H M I S' 0» -H Id •P OS (0 to Q> m N cx: © g H Q |g x: o © u u c (5) fl M to M © 8 •0 •0 IB H HO 03 ^ m O ta 3 jzs: 0 4i W 1 0 0} "H 0 ;<: U) •W+»'r| •H O g n 4J TABLE - III Iron Ore Reserve Keonjhar Resejrves in Average grade district million tonnes (% Fe) Thakurani Group 197 64 Boljani 489 62 Deposits north of Banspani 38 64 Joda east & ' TABLE - IV Paragenesls of the iron end associated manganese minerals of Thakuranl mines Time Hematite ZZ Martite ooethite Limonite Pyrolusite Psilomelane 82 «* o «n in ri CM * tf> v4 « » «-l CD ri «H '^ o• • • r*t o>• • • • u>• o• o• o *-< 0^ * ri CM tn c^ •4 «- CM in o in r4 m Ov CM m o «^ ^ «-l ^ v^ CO ^ 00 in in o• o• « r*•- • • • • • • f ^ CJ to c» 10 o o m o o 0> o r- >• r4 o CM CM «-i f-i ^ «* *o CM CD <* O CO in rH <* ^ in CO • • fl • cr• «n• • • • » • O* 10 m "* 0* r-t o m o o r* o t o in CO 00 o ri > o\ OJ CM o\ o S fO 0» r-t & *-l H CM CM • u>• • • « f • • e*• o^» • o •«» t-l <»> r* «-4 o rj o o to t-< o N CJ o CO »-l «-l r1 H 00 « «n » H <* CO •^ t- CM o CM so r4 r o \D o P* H <^ 00 10 \0 CO (7t r- CO O 0* (0 o> \0 "* M ^ o o CM m -¥ O fS Cl C4 O 3 0) o o o o oC M o to < 1 5 1 ? ^ ^ CM CO «o ro o «-l 'tf <^ CM C^ o •f n r- fO CM CD <«" in c^ CO CN o o o> «) r- r- <^ VO tn o •-I rH o w c^ o ** o »* in p- CM o »H o ^ ^ •-I en tn w • o• • • o• • o• o* o• • o• 83 o o o o o o o o o o tH , t 1 1 1 t 1 o <0 m ^ t-l tn ri <* tn o o ^ « o in fO NO tH CM 00 o CO in r^ yo T-l in in ON m CM tn o o o «n T-» o tn t-l Ov o H o o CM C4 -* o 't '* ^f in * CM tn o n 0* • • • • • « • • « • * o o o o O »H o 1 1 o i 1 o o o 1 C4 0^ o Ok TABLE - VII Data showing the range ofroajor oxide s of Thakurani mines. i District Keonjhar { Orissa ) Oxid« wt, % Range ( % ) SIO2 5.06 «. 13.04 3.90 •• 11.10 49.83 - 65.93 H9O 0.19 mm 2.14 CaO 9.69 4M» 14.91 TiO^ 0.33 . I.01 NagO 0.75 - 4.80 0.46 - 5.11 MnO 0.09 - 2.11 P2O5 0.04 mm 1.87 3.26 •• 7.56 85 TABLE • VIII Data showing the mean value and standard deviation o£ the major oxides of iron ores of Thakurani mines Oxides Mean value Standard Deviation AljOj 5,636 2.06515 MnO 0,918 0.56566 PjOg 0,637 0.54816 HjO 5.075 1,37227 SiOj 7,708 2.45062 NagO 3,019 1,33787 KgO 3.292 1.28107 Fe^Oj 59.998 5.49014 MgO 0.690 0,55071 CaO 12.267 2,39068 TiO, 0,654 0,22949 86 50 Si02 40 30 20^ IIMIIIUII mil iiigijlll ^ 10 r""" t c u O. 8 10 iS 12 13 14 >» u Fig.H-1 c cr 50 AI2O3 c 40 30 20 10 •f """•' •"!'"' 3 4 5 8 9 10 M^ -^2 Fig. H-2 8' 50 CaO 40 30 Ip-* 20 e • <-> JO i _.^ 1 i 1 V 1 1 I! {4 i5 c 9 10 !6 17 18 Fig. M"3 XX 50 6/ ^^2^3 40 30 r 20 JO h T i QL, x,.„ J 49 51 •K/^ >B^ 55 5? 5 9 SI ^3 C>5 S7 Fig.H-4 88 50 Na^O 40 30 20 "^ JO 4/ U ^™..,.„,™™Xn 0.5 1.0 1,5 2.0 2.5 3.0 3.5 4.0 4.5 5,0 o Ftg.H-5 c iM 50 ^^2.0 cr U. 40 30 20 h 10 .r-———-t 0 0.6 VI 1,8 2.4 3.0 3.6 4.2 4,8 .5.4 Fig. M-6 89 50 MnO 40 30 20 10 r——I u 0.0 03 O.S 0.9 1.2 t.5 8 2.1 2.4 o c c» 50 y- 40 30 20 to X--. L 0 0.2 0.4 0.6 0-S 1.0 1.2 14 l€ i.® 2-0 Fig N-8 90 MgO 40 30 20 c 40 30 20 0 0.3 ).6 0.7 0.8 0.9 t.O I.: Fig.H-IO 01 50 H^O 40 c O 30 o 20 0/ 10 r——^ } 1 1 ! 1 < 1 0 ! 1 1 3.0 3,5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7,J5 8,0 Fig.N"|i Si02 AI2O3 i 93 Na^O B P O 1 •.— « b .^ - - o 94 MnO IV M o .1. —< o» iJ» o o o* o r 1 Till T 1 1 I I « o - o o • 11 o • • • 1 '^ O b 00 o P205 0 0 0 -. mm fV» 0° A a» to a* 0 »l 1 1 "f T I 1 1 1 1 1 0 0 I 0 A 0 \ 0 • II OJ 0 0 • • • / 0 CD 0 0^^ MgO o -si Ti02 o o o — b rs» A 00 o 2j r 1 I 1 I 1 1 o a I 09 9^J 6 CaO Z? o o ( ^J H2O "23 o I o 9' CaO I fv* 2 o C»i - o Si02 tf^ 09 fU -n O r- .^l 1^ J J J J 1 J p ., ^ i o P > o M CD to o ' 98 la.o 6.0 54.0 o -re u iZ.Oh roo 8-0 0 2.0 4.0 2.0 4.0 €s,0 MgO NapO FiG G-n FlG.G-iZ ne FIG. » /<*? 1- - - • I i, BOvavo 1 ,1 .3«0iS xi mI t • o i X -i 1 d ^^ ; ? •- < Q •^ [ 2 « g; a '. i « " -' " t i i ; ^ • -A 0 S , 1 "; i > f a ' a " 3 O a ^ < * < 1 i » i M 0 O X J O » • • 1 « I'KURBONO 'woiH^/WoKAStR^ oKOOOOlH / PATHOi-V /BiCHAKHANt 9 i I PAHAR i^OANOflAHAfl''^ i ' / » ^ ^ ^PAHAR \ j\ ^\ • - I ./ TBAOAM-/ I « PUR BONTM%"* *rV|« «*liMM4<»,l«(4i MAP OF THE mON-Of^E AREA OF SlNGHBHUM-KEONJHAR - BONAI 1 f ] ;•.• t/) H REFEREHCES Acharya, S, 1964 Stratigraphy of the banded iron formations of the Daiteri«>Toinaka area» Cuttack district, Orissa, India« Rept, 22nd Session, Int. 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Sharma# R*K. 1968 Geology and Iron ore occnirrences in the Ce Satyanarayana, area bordering Drug and Bastar districts G*C« of Madhya Pradesh* Indian Minerals, v» 22, pp* 225<»226* Sikka, D.B. 19638 Banded hematite quartzites of Bihar,Orissa and Madhya Pradesh, India* Vishtfakamm, Engg* I.T. and S*R*R. Annual, pp* 19-28* Spencer* E. 1952 The structure and origin of the banded & Perclval* P.G. hematite jaspers of Singhbhum, India, Econ. Geol*, V* 47, pp* 365-383« Spirofff K« 1938 Magnetite crystals from iMteoric solutions* Econ* Geol*, V* 33, pp* 8ie*828* Van Hlse,C.R, 1911 The geology of the Lake Superior region* & Leith, C,K« U.S. Geol* Surv*, Mon* 52, p* 641* Wagner, P«A. 1928 The irxin deposits of the Union of South Africa* Mem* South Africa Geol* Surv*, V* 26, p. 72. weld, CM. 1915 The ancient sedin^ntary Iron Ores of British India* Econ* Geol., v* 10, p. 435-452. Zappfe, C. 1931 The deposition of manganese* Econ* Geol*, V* 26, p. 799«832. 1933 Catalysis and its bearing on the origin of the Lake Superior iron - bearing formations, Econ* Geol*, V, 28, pp, 751-772• Plate I FIG. 1 FIG.2 c\n. '^ Plate II FIG. 1 FIG. 2 Fir, 7 Plate III FIG. 1 FIG.2 r:\r, i