CHAPTER 2 GEOLOGY. Page No.

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1 CHAPTER 2 GEOLOGY Page No. 2.1 Introduction Selection of the Study Area Geographical Location Topography Geology Granites and Gneisses Porphyritic Granite Pegmatite, Aplites and Quartz Veins Gabbros Epidiorite Lithology Stratigraphy Structural Features Rift, Grain and Hardway Sheeting Joints Fractures Lineaments and Faults Strike and Dip Regional Setting Dolerite Dykes References 46

2 GEOLOGY CHAPTER Introduction The Indian Peninsular shield is infested by a large number of dyke swarms. The geological investigations of an area form an important basis for various geophysical surveys to have a comprehensive picture under study. A classification of hard consolidated rocks like granites and dykes according to their mineral composition. Granites are also characterized by horizontal joints (Sheeting) which are parallel to the surface. Granites are deeply weathered either by mechanical or chemical processes resulting in formation of a thick covered mantle of residual material commonly designated as disintegrated rock, which do not have primary porosity and permeability and hence are poor water bearing formations. Joints, fractures and other structural features can be developed Selection of the Study Area The study area, which forms part of Greater Hyderabad and Ranga Reddy District covering an area of about 2500 s.q. km is situated at about 50km north of Hyderabad, Andhra Pradesh, India and is well connected by road. The area is covered mainly by granites of Archaean age which are highly weathered and fractured. A large number of out crops are available to map the structures and fractures. Number of intrusive like dolerite dykes, Pegmatite veins and Quartz reefs/veins are common in the area. Detailed geological and hydrogeological investigations were carried out with an objective to demarcate different rock outcrops, exposures in the study area measurement of structural elements and general assessment of the hydrogeological conditions prevailing in the area. The map showing the study area is presented in Fig

3 Fig 2.1 Location map of the Study Area 29

4 2.2 Geographical Location The Mandals of Ibrahimpatnam, Keesara, Ghatkesar and Maheshwaram in Greater Hyderabad and Ranga Reddy district have been selected for the present study. These areas are continuously extended towards SSE, ESE, NE, SE, East ENE of Hyderabad city. The study area forms part of Quadrangle Map or Topo sheet No 56k. Hyderabad being the state capital and is also the headquarter of Ranga Reddy district, is very well connected with all other state capitals by air, rail and road. Two National high ways, namely NH-7 and NH-9 pass through these districts. Ibrahimpatnam, Keesra, Ghatkesar and Maheshwaram Mandals are very well connected by road. Ibrahimpatnam is on main road of Nagarjuna Sagar ring road and SSE of Hyderabad road. Keesara and Ghatkesar are situated on National high way No. 9 towards east south east. Maheshwaram is situated on National high way No.9 towards southwest. Maheshwarm is the near Shamshabad Airport, which was connected with the number of buses from Greater Hyderabad and Ranga Reddy District. Fair weather and network of macadamized roads and a few pedal path and foot tracks connecting the local villages provide accessibility to the interiors of the area Topography Topographically the study area is generally undulating or flat tracts characterize with isolated relief hillocks and hill ranges with intervening streams. Dolerite dykes, quartz reefs have developed their own prominence in the investigated area. The weathering plays major role in the development of the topographical features. Joints plains have added advantage during the weathering process on account of which smooth conical tors, rounded hills have developed into characteristic land forms in this area. The long hillock ranges are in the western part of the study area. 2.3 Geology The Indian Peninsular shield is infested by a large number of igneous dykes which constitute swarms in a few localities. These dykes which may be of different ages strike in different directions, NE-SW, ENE-WSW or NW-SE and are seen as 30

5 persistent linear ridges extending for several kilometers with width varying between 3 to 60 meters Granites and Gneisses The granitic rocks of the world are the subject of intense investigation regarding their origin and as read as put it There are granites and granites. The study of Precambrian shield granites present many problems as they are subjected to many phases of deformation, metamorphism and igneous activity. The granites of Hyderabad belong to the Precambrian shield type and consist of many rock types from syenites to Alaskites. Precambrian rocks, such as Granite, Adamellite, Tonalite, Amphibolites, Hornblende biotite schist occupy a major part of the area. These formations were subjected to tectonic and green schist facies metamorphism. Except for portion in the western part of the district to understand its geological significance most of the area is occupied by granites. Based on mineral composition they were further classified as alkali feldspar granite, Magmatite granite gneiss, Adamellite, Granodiorite, Tonalite and Trondjimite. Granites and gneissic complexes, occupy vast expenses of Peninsular India. Granitic rocks of the Hyderabad form part of the Peninsular Gneissic Complex. Pink and Grey granites are the major rock types occurring in and around Greater Hyderabad. Dolerite dykes, basic enclaves, aplites, pegmatite, quartz veins, migmatites and alaskite traverse these granites. At places alaskites and leucogranites are emplaced within the pink and grey granites (Krishna, 2004). Mineralogy, textures, structure and major intrusive of these areas are The major units are: 1). Grey series: coarse porphyritic grey granites, biotite granites and pyroxene granite. 2). Pink series: coarse porphyritic pink granite, fine to medium grained pink granite, coarse porphyrite pink alaskite, fine grained pink alaskite, white alasklite. 3). Dykes and veins: Dolerite dykes (both fine and coarse grained) Quartz veins and epidote veins 31

6 4). Enclaves: Fine grained 5). Migmatitic zone: Inter mingling zones of pink and grey granites. Investigated study area. Fig. 2.2 Fig. 2.2 Geology Map of the Study Area and it covers the cluster of Mandals i.e. Ibrahimpatnam, Keesara, Ghatkesar and Maheshwaram Greater Hyderabad and Ranga Reddy district. Almost all the Mandals are covered with Peninsular granites. The Granites of Hyderabad have been extensively studied during last three decades by a number of researchers, (Balakrishna, 1964; Janardhan Rao, 1965 and Sitaramayya, 1968). The rock types covered in the area are classified as grey and pink granites and they are intruded by younger formation i.e. dolerite dyke, quartz, epidote and Pegmatite veins. 32

7 Raja (1959) attempted systematic studies on the petrography of the granites occurring in and around the twin cities of Hyderabad & Secunderabad. According to him, soda metasomatism of pre-existing hornblende biotite schist gave rise to grey granites. The parental rock occurs as enclaves and the pink granites were derived from the granites by potash metasomatism. Rao (1963) suggested that there might not be any age difference between grey granites and pink granites. He opined that the difference in the colour of the two granites could be due to the difference is the parental material, which was subjected to process of granitization. Rao (1965) opined that both grey and pink granites are metasomatic in origin. The grey granites were formed by granitization of parental metasediments like quartz mica schists and related rocks. The pink granites were supposed to have formed along shear zones in grey granites by potash metasomatism. There are several researchers who have expressed different opinions regarding their origin. Geological Survey of India, Hyderabad has concluded that the granites of Hyderabad are of magmatic origin. Balakrishna, (1964) studied in detail the Petrology and Petrogenesis of these granites. They came to the opinion that the granites have formed due to metasomatism of the country rock. According to (Balakrishna, 1964) granitc rocks predominate the peninsular complex and are represented in the city of Hyderabad. He studied the granitic rocks of Hyderabad with special reference to tectonics, petrography and textural features. He noticed two types of granites, pink and grey, and said that it has been found difficult to demarcate them separately. On the basis of his studies he concluded that the pink could be a derivative from the grey series of granites and gneisses. He also concluded that the pyroxene bearing granites seem to have all characteristics of the conventional charnokites and they appear to be a sort of basis front formed due to late stage of potash feldspar. He further said that, the pink granites are found to be rich in perthite and myrmekitic structure and are seen in all types of granites particularly in hybrid or magmatic zone. He also studied the elastic constants pointed out that the pink granites are younger than the grey granites. Janardhan Rao and Sitaramayya, (1968) has extensively studied the Geological features like structures, the petrology and geochemistry of granites of 33

8 Ghatkesar area near Hyderabad and opined that the pink alakites and basic dykes are of anatectic origin. Janardhan Rao, (1965) has studied the origin of Hyderabad granites. Janardhan rao, (1965) is of opinion that these granites could ever passed through a magmatic stage. The parallelism of the structural elements of the granites with the Dharwar meta-sediments, the textural characters between the major mineral constituents, the enormous heterogeneity in the composition of the granites in a very small area, all go against magmatic origin. He also opines that all the granitic rocks and their associated pegmatite and quartz reefs are metasomatic origin and also says pink granites are associated with shear zones in grey granites. Age of this granite, 2490± 115 m.y. is very close to closepet granites (Crawford, 1969). Studied peninsular granites and gneisses and the ages of many of the granites in peninsula are similar. According to (Baleequddin Hussain, 1968), Grey granites are due to the soda metamorphism. The pink granites were formed during the stage of potash metamorphim. The pink granites follow certain shear zones in the masses of grey granites. He also indicated parallelism in the structural elements like foliation, lineation, basic enclaves and dykes and the NNW-SSE trend is parallel to the Dharwarian trend. He is of the opinion that the granites of Hyderabad are of metasomatic origin derived from a parent rock of hornblende-biotite- schists type and suggest that the granites might have passed through a magmatic stage. Work done by (Raghava Rao, 1974), and (Satyanarayana, 1983) in different part of Hyderabad area, together concluded that the granites are formed due to metasomatic processes. These rock types in this region is characteristic of the Archaean granite terrain. Due to similar rock type mineralogy of both are described together. The rocks of the areas in grain size from medium to coarse grained. Feldspar is the predominant mineral and occurs as phenocrysts. These rocks are essentially composed of quartz, potash feldspar, plagioclase hornblend and biotite and accessory minerals as magmatite, epidote and sphene. Few specks of pyrite and chalcopyrite are noticed in the rock samples of the area. Gnaneshwar (1986) concluded in his litho geochemical surveys of Hyderabad granites that porphyritic granites, white alaskite and pink alaskite are potentially the 34

9 ore-bearing rock types. The porphyritic granites contain higher amount of U, Th and Mo. In the vicinity of pink alaskite and these elements were mobilized and emplaced in fracture systems at higher structural levels. The geological Survey of India (2006) have investigated this area and suggested that these granite rocks are of magmatic origin and pink series are intrusive into grey series. A very large area of the investigation is underlain by Peninsular gneissic complex of Archaeans age, consisting of pink and grey granites, granitic, magmatites, Pegmatites, quartz veins and dolerite dykes, occurring in the forms of domes, scaprs, massive columnar blocks and tor scattered over a partly undulating country Porphyritic Granite These are the dominant rock type of pink and grey colour in this area. Grey porphyritic granite is predominating in the area of investigation. They are mainly comprised of microcline perthite, plagioclase and biotite. At some places hornblend occurs in addition to biotite. Magmatite, sphene, zircon and pyrite are the important accessories in these granites. The variation in texture and composition is attributed due to the assimilation of the pre-exisiting rocks of porphyritic granite. Band of composite gneiss occurring at places in the porphyritic granite might have formed earlier than the porphyritic granite though injection of granitic fluids along the foliation planes of the pre-existing schist and reaction with them. The structure of the porphyritic granite is generally massive, but where it is composite in character it shows foliation. The foliation is derived from the preexisiting schist s which are granitised. This has a NW-SE strike and vertical dips. The porphyritic granite is traversed by many joints. They generally belong to NE-SW and NW-SE set, and the dip of the joints is vertical. Apart from these are sheet joints, curved and low dipping in the porphyritic granite Pegmatite, Aplites and Quartz Veins Porphyritic granites are traversed by numerous veins of pegmatites with different trends. The common trends are NE-SW, NNE-SSW, NNW-SSE and NW- SE. They are found in white, grey, pink and milk white colours. Feldspar is generally 35

10 microcline perthite. Apart from feldspar and quartz the other constituents are biotite, magnetite, muscovite, sphene and zircon. Among the sulphides are pyrite, chalcopyrite and molybdinite. The molybdinite bearing pegmatites traversing the porphyritic granites are older than the medium grained granites (Kittu, 1968). Aplites which are exposed in a few places occur either as narrow veins or small lenses. The trend of the quartz veins is NE-SW. These veins are found in the porphyritic granite and at some places quartz veins passes into pegmatites. Generally they are entirely made up of quartz. The pegmatites contain mostly feldspar and quartz and quartz veins traversing these granites occasionally contain pyrite, chalcopyrite and malachite. These are minor intrusive & traversing the host rocks granites. They are a few centimeters to few meters wide and run over a few hundreds of meters of distance Gabbros Gabbro is a coarse-grained, dark-colored, intrusive igneous rock. It is usually black or dark green in color and composed mainly of the minerals plagioclase and augite. It is the most abundant rock in the deep oceanic crust. Gabbro is composed mainly of calcium-rich plagioclase feldspar and clinopyroxene (augite). Minor amounts of olivine and orthopyroxene might also be present in the rock. This mineral composition usually gives gabbro a black to very dark green color. A minor amount of light-colored mineral grains may be present. Unlike many other igneous rocks, gabbro usually contains very little quartz Epidiorite Epidiorite dykes are noticed in this area. They are mostly in NE-SW direction they are generally composed of amphibolites and andesine. Hornblende generally occurs as pseudo-morph of pyroxene. The feldspar is very much altered. Flourite, Epidote, Calcite, Feldspar, Quartz and Jaspar veins are travelling the porphyritic granites, numerous veins of epidote, calcite, feldspar; quartz and jasper are 36

11 noticed with less than a centimeter in width. In few cases pyrite, chalcopyrite, biotite and sphence are present. Epidote veins traverse the epidiorite, pegmatites and quartz veins. The veins in general have NE-SW strike and steep dips. The structure of the porphyritic granite is generally massive, but where it is composite in character it shows foliation. The foliation is derived from the preexisiting schist s which are granitised. This has a NW-SE strike and vertical dips. The porphyritic granite is traversed by many joints. They generally belong to NE-SW and NW-SE set, and the dip of the joints is vertical. Apart from these are sheet joints, curved and low dipping in the porphyritic granite. 2.4 Lithology Peninsular rocks, a major part of the area are covered by Pink and Grey granites. The variations in the granites, the country rocks, are quite apparent through the two major types, pink and grey are being recognized, each one of them show several minor variations. These variations are mainly due to mineralogical composition textural difference, coarse to medium grained, fabric, and enclosers. The enclosers may be schistose pockets which are referred xenoliths. These xenoliths are considered to be remanents of pre-existing rock masses. Besides xenoliths, aplites, pegmatites epidote veins and quartz veins are also responsible for lithological variations. On a large scale the enclosers are formed from a dolerite cutting across the lineation and foliation of the granite. The size of dolerite dykes both in width and length is variable. Some of the dykes traverse this granite for kilometers together with definite trends. Some times these dykes show enclave pattern indicating that they are followed the joints plains. Branching, piching and swelling nature is a characteristic feature of some of these dykes. All these variations exert considerable influence on weathering and consequent evolution of land forms. The major contrast is found that the grey granites are not generally prone to weathering while pink masses are less resistant. Consequently one finds large terrain being covered with black soils. Most probably some of these are derived from dolerite dykes. As such the importance of lithology is to be recognized in the development of soils and evolution of land form which has an explicit control on occurrence. 37

12 Apart from these rocks the younger intrusive of dolerite dykes, quartz, Pegmatite veins, Basalts are present. Geologically the area consists of Predominantly Peninsular suite of rocks. Based on mineral composition, they were further classified as alkali feldspar granite, migmatite granite gneiss, adamellite, granodiorite, tonalite and trondjhemite. A few patches of amphibolites and pyroxene granulites are also seen around the Hyderabad. All these rock formations are traversed by NE-SE and N-S trending dolerite dykes. The area experienced volcanism at the time of eruption of the Deccan Traps. The Deccan Traps and intertrapean beds are seen in the western part of the study area. 2.5 Stratigraphy The investigated area is occupied mainly granite rocks of Archaean age comprising grey and pink with medium to coarse grained texture cover a major portion of the study area. In palaeomagnetic study, Proterozoic to Archaean age acid intrusive pegmatite, quartz reef/veins and migmatites occur in the study area. The granites were also intruded by Paleocene to Cretaceous age dolerite dykes and basalts and represented in geology map of the area. The stratigraphic succession is given below: Basic dykes Basic enclaves/quartz reefs Peninsular gneissic complex Dykes Porphyritic type Fine grained type Leucocratic type Mesocratic type Melanocratic type Pink granites Fine grained Medium grained 38

13 Grey granites 2.6 Structural Features Coarse grained Gneissic type The investigated area is mainly occupied with hard rock formations. In such cases which are devoid of any primary porosity, secondary structures like faults, joints, cleavage fractures, lineation, and foliation serve as channel ways for the circulation of palaeomagnetism and dykes. Hence, the study of these features is essential for proper understanding of the occurrence and behavior of dykes in these formations. First, many exposed granitic bodies display three sets of joints disposed at right angles to each other or mutually. These are together referred to as orthogonal system and they effectively divided the mass Granites. Even though granites are quite massive and impermeable in their original unmodified state; they are generally rendered pervious with the development of joints and fractures. In the investigated area the regional structures and fracture pattern control the topography. The trend of the main structural features is NNW-SSE and the alignment of bed rock exposures in the study area mainly follows the same trend. National Remote Sensing Agency (1978) employed the satellite imaginary techniques to unravel the lineament pattern over the granite-gneiss terrain of Andhra Pradesh. Their studies indicate lineaments in almost all directions of A.P. However, the intensity and direction vary from area to area. The most important directions are as follows: a). NNE to SSW b). WNW to ESE c). ENE to WSW d). NW to SE and e). NE to SW The two trends NNW-SSE and E-W are best displayed in the study area 39

14 The granitic rocks of the area possess certain characteristic structures in great perfection. 2.7 Rift, Grain and Hardway These planes approximately at right angles to one another along which granite falls most easily under tension. The rift is due to the peculiar property of quartz and is approximately horizontal in most of the granites in the investigated area. The grain is usually in the direction to the rift and may be determined by tectonic cracks or other features. The joints trend to be more consistent in altitudes than the cleavage. When there are systems, they are equally spaced. The fractures planes give rise to a structure of cuboidal blocks. However in many instances the jointing is much less regular. This features is commonly seen in most of the outcrop areas. 2.8 Sheeting This is the most important structure, particularly well developed at shallow depth and usually observed in the outcrops of Ibrahimpatnam, Ghatkesar and Maheshwaram and other areas. Sheeting is kind of horizontal feature. Though it shows curved aspect on domal hills and resembles exfoliation shells. It will be nearly horizontal at ground level. All types of granites are sheeted Joints The concept of joints are studied & explained by different researchers in several types. The simplest of all classification is based on the criteria of degree of openness (Babuskin, 1972). Joints can be classified as 1). Hidden joints, these are not seen by naked eye, 2). Closed joints, these are seen by naked eye, 3). Open joints with the walls clearly separated. According to (Balk, 1937) classified joints into 1). Cross joints, 2). Longitudinal joints and 3). Diagonal joints. Based on the origin (Babuskin, 1972) classified the joints 1). Tectonic 2). Weathered 3). Separater 4). Drained 5). Gravitational. 40

15 The joints directions can be explained & obtained by various surface and as sub-surface geophysical methods. Among the surface geophysical methods vertical electrical resistivity method is used for delineating major joint directions and fractures occurring up to a depth Fractures These may be called closely spaced joints developed due to tectonic forces. Intense shearing often produces potential fracture zone which would constitute highly productive aquifers Lineaments and Faults The area reveals several lineaments and faults identified running different strikes. The lineaments and faults in the study area show NE-SW, NW-SE and N-S trend is mainly associated with these lineaments and faults. Fig.2.3 Fig. 2.3 Structural Features Map of Study Area 41

16 The outcrops of the rock units have been demarcated by trekking the area. Rocky outcrops of granites in the study area are well exposed in the central, north eastern and south western part. Detached boulders of pink and grey granite are seen all over the place due to intense fracturing Strike and Dip Strike and dip refer to the orientation or attitude of a geologic feature. The strike line of a bed, fault or other planar feature is a line representing the intersection of that feature with a horizontal plane. Strike (or strike angle) can be given as either a quadrant compass bearing the strike line (N25 E for example) or in terms of east or west of true north or south. The dip gives the steepest angle of descent of a titled bed or feature relative to a horizontal plane and is given by the number with degrees (0-90 ) as well as a letter (NS-EW) with direction in which the bed is dipping. 2.9 Regional Setting These areas are covered under the investigations come under hard rock terrains as far as palaeomagnetic study investigations are concerned. The chief rock types are plutonic complex consisting of peninsular granites and gneiss of the Archaean age. Which form a part of the vast Precambrian Peninsular shield. Subsequently Balakrishna, (1964) suggested that the pink granite could be metasomatic derivatives of the grey series of granite and gneiss. Janardhan Rao, (1965) has argued against magmatic origin of these granites based on the parallelism of the structural elements in the granites with Dharwarian metasediments and certain mineralogical and textured relationships. The different rock types occurring in this area have been broadly classified (Sitaramayya, 1968) into three groups. First two groups belong to granites while the third group comprises the dolerite dykes. Among the first two groups, grey and pink series have been identified. 42

17 The grey granites are fine to medium grained, dark coloured and appear homogeneous from a distance. However, on close observation, they show small clusters of mafic minerals, pyroxene and biotite. These clusters are arranged in parallel planes and constitute the lineation causing pronounced gneissic banding. The quartz grains in these rocks have light brown colour. They have greasy appearance. Feldspar crystals are light brown colour and plagioclase grains are semi opheic with white or light or light green colour. Sometimes these rocks show patches of porphyroblasts of potash feldspar. The gneissic bonding shows dominant trend of N50 W. These rocks are traversed by aplitic veins and dykes of width ranging from a few centimeters to 100 meters. Many epidote veins come across these granites. The pink granites are usually fine to medium grained but coarse grained porphyritic varieties are not uncommon. These are characterized by a very low mafic mineral content and have pink colour. The minerals are quartz and potash feldspars. Minor amounts of plagioclase, biotite, magmatite and zircon are present. Usually these rocks occur as ridges sometimes rising to a high top, more than 80m. They are having consistent structural trends, the important trend is N W followed by the N-S N60-70 E. These rocks sometimes are characterized by pronounced foliation due to the parallel arrangement of quartz grains. These rocks exhibit a characteristic weathering which is controlled by closely placed joints in more than one set. Many narrow quartz veins also traverse these rocks. These rocks are to be considered younger to the grey series of rocks but to dolerite dykes. It is considered that the emplacement of basic dykes followed weak structural planes in the country rocks. Both the pink and grey granites are traversed by quartz and pegmatite veins. Intrusive bodies were more in to pink granites than in grey granites. The demarcation between pink and grey granites is difficult. In pink granite itself there are several distinct types. Some of them are brick red in colour, others are bright pink and still others show all shades of pink red and reddish brown. 43

18 3.0 Dolerite Dykes Dolerite is coarse grained variety of basalt, if present in the dorm of a dyke (discordant igneous body), it is called a dolerite dyke. Dolerite is the medium grained, intrusive, equivalent of a basalt (link to basalts). It usually occurs as dykes. Being intruded into country rocks at shallow levels, the magma has more time to cool than if extruded. Dolerites may be porphyritic, containing phenocrysts of plagioclase, olivine and even quartz (an olivine analcite dolerite is known as a crinanite). Dolerite dykes, like many other magmatic intrusions, develop by rapid hydraulic fracturing via the propagation of a fluid-filled open fissure, resulting in a massive magmatic intrusion with a neat and transgressive contact with the country rock. This fracturing mechanism is in contrast to the slow mode of hydraulic fracturing responsible for breccia-intrusions (kimberlite). For the intrusion to develop the magma pressure at the tip of the fissure must overcome the tensile strength of the surrounding rock. Dykes can develop vertically upwards or laterally along-strike over very long distances, as long as the magma pressure at the tip of the fissure is maintained. The intrusion of dolerite and basaltic dykes are therefore never accompanied by brecciation, deformation or shearing of the host-rock, at least during their propagation. The main gabbroic body is intruded by a member of dolerite dykes running North- South. It is composed of clinopyroxene, Plagioclase, Hornblende, Orthopyroxene and Ilmenite. Hornblend occurs as large Poikilitic grain and constitutes around 60% of the rock. Both gabbro and associated dolerite dykes (Aditimaddal et al., 2012). The Shillong Plateau occupies a unique position in the Precambrian history of the Indian plate both geodynamically and seismically. The Precambrian framework of Meghalaya and tectonics of NE India were given by (Mazumber, 1986) and (Acharya, 2005). In the central and northwestern shilling plateau a number of Mesozoic dolerite/basalt and ultra basics have intruded the basement rocks in NW-SE. Greenstone are also exposed in NE-SW direction within the gneisses (Nivarani Devi and Sarma, 2006). Palaeomagnetic and geochemical data of the Proterozoic Khasi greenstone dykes to understand the evolutionary history of the Shillong basin vis-à-vis the Shillong plateau (Mallikharjuna Rao et al., 2009). 44

19 In the present work of palaeomagnetism, we have selected prominently visible 20 dykes in and around the Greater Hyderabad and Ranga Reddy District and they are shown in the Fig. 2.4 Fig. 2.4 Map showing the Dykes in the Study Area 45

20 REFERENCES 1. Acharyya. S.K., (2005). Geology and Tectonics of NE India. Jour. Geophys., V. XXXVI, No. 1, pp Aditi Mandal, Arijit Roy, Mayukhee Debnath, and Shankar Prasad Paul, (2012). Petrology, geochemistry of hornblende gabbro and associated dolerite dyke of Paharpur, Puruliya, West Bengal: implication for Petrogenetic Process and tectonic setting. J. Earth Syst. Sci.121, No. 3, pp Babuskin, V.D., (1972). Prognz Vodopritikov Ve gorni virabotki Vodozaboli, Padyomlin Vod Ve Treshinovathde Zakarstovannin Paradan (Nedra) (in Russian). 4. Balakrishna, S., (1964). Some studies on granites of Hyderabad from Proceedings of the Seminar on Peninsular Geology, Geology Department, Osmania University, Hyderabad, pp Baleequddin Hussain, (1968). A note on the textural features of granites of Hyderabad and their bearing on petrogeneisis. Bull. Geo. Soc. India. Vol. 5, pp Balk, R., (1937). Structural behavior of igneous rocks. Geol. Soc. Am. Mem. 5, pp Crawford, A. R. (1969). Reconnaissance Rb Sr dating of the Precambrian rocks of Southern Peninsular India, Jour. Geo. Soc. Ind., Vol. 10, No.2, pp Gnaneshwar. P., (1986). Lithogeochemical surveys in Hyderabad granites. Ph.D. thesis Osmania University, p Janardhan Rao, Y.J., (1965). The origin of Hyderabad granites. A new interpretation. Jour. Ind. Geo. Sci. Assn. vol. 5, pp

21 10. Janardhan Rao, Y.J., and Sitaramaiah, S., (1968). The Pink alaskites of Ghatkesar area, Hyderabad district, A.P. Jour. Osmania University (Science) Golden Jubilee, Vol. pp Kittu. N., ( ). Progress report for the field season ( ). Investigation for molybdenite in parts of karimnagar district. A.P. G.S.I. 12. Kittu. N. and Krishnamurthy. A., ( ). Progress report for the field season ( ). Investigation for molybdenite in parts of karimnagar district. A.P. G.S.I. 13. Krishna, B., (2004). Geochemistry of Ground water and Soils of Jedimetla Industrial Area, Ranga Reddy District, Andhra Pradesh, Ph.D. Thesis, Osmania University, Hyderabad. 14. Mallikharjuna Rao. J., Poornachandra Rao G.V.S., and Sarma K.P., (2009). Precambrian Mafic Magmatism of Shillong Plateau, Meghalaya and their Evolutionary History. Journal of Geological Society of India, Vol. 73. pp Mazumber. S.K., (1986). The Precambrian framework of part of the Khasi Hills. Meghalaya Ree. Geo. Sur. India, V. 117, pt.2, pp Nivarani Devi and Sarma, K.P., (2006). Tectonostigraphic study of conglomerates of Shillong Basin of Meghalaya. Jour. Geol. Soc. India, V. 68, pp Raghava Rao, M., (1974). Studies on the structure, petrology and engineering properties of the rocks around Bhongir, Nalgonda district., A.P. Ph.D. thesis, Osmania University. 18. Raja, N., (1959). Studies on granites of Hyderabad. Ph.D. thesis Osmania University, Hyderabad. 19. Rao,Y.J., (1963). The Pink and Grey granites of Hyderabad and the problem of their age relationship, Proc. Symp. On stratigraaphy. Age and correlation of the Archaean Provinces of India. 47

22 20. Rao, Y.J., (1965). The origin of Hyderabad granites a new interpretation. Jour. Ind. GeoSci. Assn., Vol.5, pp Satayanarana, B., (1983). Petrological studies and their bearing on the origin of Hyderabad granites. Jour. Ind. Acad. Geoscience., Vol. 26. pp Sitaramayya, S., (1968). Structure, Petrology and Geochemistry of Granites of Ghatkesar, A.P., India, Ph.D. Thesis, Osmania.University, Hyderabad. 48