Petroiogy and Geochemfstry of AHAR RIVER GRANITE* NORTH WEST of Uoafpur
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PETROiOGY AND GEOCHEMfSTRy OF AHAR RIVER GRANITE* NORTH WEST OF UOAfPUR. RAMSTHAN DISSERTATION SUBMITTED FOR THE DEGREE OF jfMagter of ^Iiilosioplip IN GEOLOGY BY ABDUL RAHMAN DEPARTMENT OF GEOLOGY ALIGARH MUSLIM UNIVERSITY ALIGARH (INDIA) 1987 Sed in I. oirtD atai 2 SEP 1988 DS1171 -> '^ ^^' c?^ DEPARTMENT OF GEOLOGY ALIGARH MUSLIM UNIVERSITY Dr. Syed M. Zainuddin M.Sc, Ph.D.(U.S.A.;, Dated: November 17, 1987 Sigma XKU.S.A.;, F .G .S . (India J This is to certify that Mr. Abdul Rahman has completed his research work, presented in this thesis, under my supervision for the degree of Master of Philosophy of the Aligarh Muslim University, Aligarh. This work is original and has not been submitted for any degree at this or any other University. ( SYED M. ZAINUDDIN ) In the name of Allah, the Beneficent, Most Merciful The author wishes to express his deep sense of gratitude to his supervisor and guide Dr. S .M. Zainuddin, Reader, Department of Geology, Aligarh Muslim University, Aligarh for his keen interest and valuable guidance which led to the completion of this research work. His thanks are also due to Professor S.M. Casshyap, Chairman, Department of Geology, Aligarh Muslim University, Aligarh for providing laboratory and library facilities. The author is extremely grateful to Dr. V.K, Srivastava, Professor, Department of Geology, Aligarh Muslim University, Aligarh for his keen interest, help and encouragement during the course of the work. The author is also indebted to Dr. Shahid Farooq for his kind help in chemical analysis. Thanks are also due to Mr. Shamim Ahmad Khan, authors one time colleague, for his kind cooperation. Help and encouragement from authors friends and hostel roommates are also gratefully acknowledged. The author wishes to thank Mr. Zakir Husain, Librarian, for his help in the course of study, Mr. Firoz Javed for chemical analysis and Mr. Wasim Ahmad for typing of the manuscript. ABDUL RAHMAN CONTENTS Page LIST OF TABLE I LIST OF FIGURES II INTRODUCTION 1 Geography of the Area 2 Previous Work 3 GEOLOGICAL SET-UP 6 PETROLOGY OF THE GRANITE 13 Modal Composition 13 Petrography 16 GEOCHEMISTRY OF THE GRANITE 30 Geochemical Analysis 31 Major Elements 32 Classification of Granite 43 Trace Elements 47 SUMMARY AND CONCLUSION 60 LIST OF REFERENCES 6 3 Table No. Page 1 Stratigraphic succession of the 6 Precambrian formation of Rajasthan (Heron, 19 53). 2 Precambrian lithostratigraphy and n tectono-magmatic sequence of the Aravalli Super Group rocks (Anon,1981K 3 Modal composition of the Ahar River 14 Granite. 4 Chemical Analysis of the Ahar River 33 granite. II Fig. No. £^22 1 Geological map of Ahar River granite 8 northwest of Udaipur city, Rajasthan. 2 Irregular fractures in K-feldspar filled lo by thin veins of silicic material. 3 Ternary diagram of quartz-Plagioclase- 15 K-feldspar modal values for Ahar River granite. 4 Modal values for quartz-Plagioclase- 17 K-feldspar superimposed on Streckeisen's classification . 5 Fresh and unaltered polygonal quartz is grains. 5 Inclusions of quartz in microcline. 20 7 Quartz veins in microcline. 20 8 Recrystallized quartz grains. 21 9 Elongated quartz grains parallel to 21 foliation. 10(a,bJ Plagioclase grains showing bending, 23 fracturing and dislocation of twin lamellae. Ill Fig. No. Page 11 Bands of sericite filled in feldspar 25 fractures. 12 Bands of sericite and muscovite enveloping 2 5 the feldspar crystals. 13 Aggregates of quartz grains surrounded 27 by sericite. 14 Plagioclase grain showing combination of 21 albite and pericline twins. 15 Inclusions of apatite in biotite. 28 16 Plots of total alkalis vs. SiO„. 37 17 Variation diagram of major element oxides 33 as a function of the Si02 content of the Ahar River granite. 18 Plots of major element oxides against 40 Solidification index (S.I.J. 19 Plot of Na20 and K^O contents of Ahar 41 River granite. 20 K^O - Na20 - CaO plot for Ahar River granite.42 21 Plots of Ahar River granite on K^o; Na^O 46 diagram of Hine et al (1978). 22 Plots of Al^O^/^'Z&O-^l^a^O^Y.^O) (molecular 48 proportions) against SiO , after Sandra et al (1986). IV 23 Ternary diagram showing the Ahar River 49 granite composition plotted in terms of Al-Na-K, Ca and Fe+Mg after Hine et al (1978;. 24 Variation diagram of Sr, Rb and Ba as 51 a function of the SiO^ content. 25 Variation diagram of Sr and Rb vs K 0. 53 26 Variation diagram of Zn, Cr and Ni as 56 a function of the SiO^ content. 27 Differentiation trends of the Ahar River 58 granite, after El-Bouseilly and El-Sokkary (197 5;. CHAPTER - I INTRODUCTION The Ahar River granite, exposed towards northwest of Udaipur city (Rajasthan^, covers an area of about 24 sq, kiris. The area lies between latitudes, 24°36'38" and 24*^47' 30" and longitudes^ 73 36' and 73°42*. The shape of the outcrop is triangular. The granite occurs within low grade Aravalli phyllites, bordered by the bands of quartzite and limestone on its western and eastern margins respectively. Heron (1953J conducted the first comprehensive study of the area,* he considered the Ahar River granite as intrusive into the Aravalli rocks of early Proterozoic age. The granite is a fine grained type (aplogranite^ and forms bosses with very irregular margins and satellite intrusions showing all the features of intrusive granite (Heron, 1953 J. Crawford (1970^ determined the radiometric age of the Ahar River granite and concluded that it as intrusive into the Aravallis. However, Roy et al (1985^, on the basis of its stratigraphic position in relation to metasediments and 2 metavolcanics, inferred that the granite constitutes the basement of the Aravallis. The relationship of the Ahar River granite with the Aravallis has been controversial. The proposed study was made to resolve this problem and also to ascertain the origin of the granite. Geography of the_Area The Ahar River granite is exposed towards the northwest of Udaipur city in Rajasthan, The area is easily accessible by road,* a metalled road from Udaipur city to Bari Lake passes through the area. Bus services are very frequent from Udaipur city upto Bari Lake. Few cart tracks and pack tracks also join the metalled road from nearby villages. It is almost a plain area which has a maximum elevation of 4000 feet above sea level. The Ahar River runs through the northeastern side of the granite body. The river is generally dry during cold and dry months of the year. The climate is semi-arid and the rainfall is low. Vegetation is generally poor and is controlled by the proximity of ground water level. Cactus, bushes and spear grasses are common. 3 Gardening and agriculture is done in low lying areas,' the source of irrigation is mainly the ground water. A low lying narrow band in the southwestern margin is densly forested. Previous work The Precambrian region of Rajasthan was first studied by Hacket (1877i who surveyed a large area of this terrain and determined the stratigraphic order of the rocks of Aravalli range. He proposed a two-fold classification of the Precambrian rocks of the area, Delhi Series and the Aravalli Series. However, his rock formation grouping has not been much accepted. Heron (1935J recognised three major granitic intrusions in the region, Bundelkhand granite (Pre Aravalli^, aplogranite (post Aravalli but pre Delhi J and Erinpura granite (Post DelhiK Heron reported that this aplogranite body is the most instructive intrusion in the Aravalli rocks . The north and northeastern border of the granite is fringed by limestone and phyllites. He reported the presence of lenticular sheets. Wisps and Knots of aplo- granites in the limestone, and abundance of limestone wedge. 4 xenolith and roof pendants in the granite, also granitic intrusion of all sizes in the limestone. He concluded that the aplogranite had intiruded into limestone. Evidence of contact metamoirphism at the limestone contact is not observed. However, silicification of limestone at the contact is common. Gangopadhyay (1961^ has reported the granite as massive and homogeneous in composition and texture. The rocks is sheared,* twinning in plagioclase is often deformed and bending, fracturing, faulting and intricate folding are present. Quartz is crushed and shows highly undulatory extinction. He has observed that the twin composition plains in feldspar grains are parallel to the conjugate shear plane. It is inferred that the twinning in plagioclase is the result of intragranular gliding along shear planes due to flattening normal to foliation which resulted in the grain elongation along the plane of schistosity. Crawford (1970^ used the term Ahar River granite for aplogranite, and determined the age 227 5 m.y. by Rb-Sr methods. Chaudhry et al (1984} analysed a series of Ahar 5 River granite samples but they did not yield acceptable isochrones. Anon (1981) grouped Udaipur, Salamber, Udaisagar and Darwal granites as Synorogenic granites and gneisses. The Ahar River granite has been correlated with pre-Aravalli basement rocks by Roy et al (1985Ji. A detailed lithological and stiructural study of the area has been carried out by many workers. However, detailed petrological and geochemical study to understand the petro- genesis of the granite has not been undertaken by earlier workers in the area. The aim of the present study is to decipher and delineate different types of granite in the area and to determine the orogin and the mode of emplacement of granite. Further, the relation of the granite with the Aravalli metasediments was studied. 6 CHAPTER - II GEOLOGICAL_S£T;UP The Aravalli region in southern Rajasthan and north eastern Guj arat, covering an area of about one hundred thousand sq.