PETROLOGY of DEGCAN TRAPS of Rajamhutidry

PETROLOGY OF DEGCAN TRAPS OF RAJAmHUtiDRY. {A.P.) DISSERTATfON SUBMITTED FOR MASTER OF FHItOSOfHY IN GEOLOGY CHATTI HANUMANTHA RAO DEPARTMENT OF GEOLOGY ALiGARH MUSLIM UNIVERSITY ALIGARH (INDIA) 19 8 7 1)9-1179 ,,f ».-•^l/ DS1178 DEPARTMENT OF GEOLOGY ALIQARH MUSLIM UNIVERSITY. ALIGARH-202 001 India. 10.12.1987 Reader Dated This is to certify that the thesis entitled PETROLOGY Oi? DECCM'i TRAPii Or" AfijAHMUNDRY, submitted tor the degree of MASraR Oi;' PHILOSOPHY IN GEOUiGY is the original work of Mr. Chatti Hanumantha Rao carried out at the Aligarh M\aslim University^ .nligarhûnder my supervision and that no part of it has been submitted for any other degree or diploma. (NOMAN GHANI) CONTE NTS Acknowledgement ,,, List of figures ... List of Tables ChAPlER - I DECCAN TR^\p3 _ A GENERAL DESCRIPTION - Introduction 1 - Classitication of Deccan Traps 1 - Name 3 - GeoraoJPphology 4 - Structural features 7 -. Paleomagnetism 9 - Age and Duration of Deccan volcanism 11 ~ Alteration and weathering of Traps 12 _ The Laroeta beds. 14 CHAPTER - II LABOH-^rORY METHODS - Universal stage 16 - Method 17 _ The Fedorow method 18 - Rittmann zone method - 19 _ Fedorow Vs zone method 2o - Methods of chemical analysis 21 - Atomic absorption spectrophotometry 2 3 - Determination of FeO and ^6203 30 - Determination of H2O 30 -HAPJF.R - Hi GEOLOGY Or' RAjAHMUWDRY AREA - Introduction 33 - Geology ol the area 33 - Types oi tlows 34 - Intra trappeans and inter trnppeans 36 - Physiography and ciimate 37 - previous iitpratux"® 3y CHAPTER - IV P2TR0MINSR0L0GY OF R^^JAHMUNDRY FLOWS - Plagioclase feldspars 43 - Pyroxenes 46 - Opaque ores 47 - Secondary minerals 47 - Texture 50 CHAPTER - V MAJOR ELEMENT GEOCHEMISTRY ~ Major element distribution 51 - Differentiation index 53 - Solidification Index 54 - MgO Vs other oxides 55 - Magna classification 56 CHAPTER ~ VI TR.4CS ELEMENT GEOCHEMISTRY - Trace element distribution 60 - Nickel 61 - Chromium 62 - Cobalt 64 - Rubidium 64 - Strontium 64 - Lithium 66 - Copper 66 - Zinc 67 - Zirconium 68 CHAPTER - VII SUMMHRY AMD DISCUSSION 70 REFERENCES 71-76 * * * ** * *• ***** AC mOdLE DGEMEN13 muMm^mmm At the out set, I wish to express my profound gratitude to Mr. Neman Ghani, my supervisor, for his excellent guidence, constant support and trust throughout the course of this study, Without his keen interest and help the present dissertation would have not seen the light of the day. I am highly thankful to Prof. I.D. Pant for his encoura gement in the beginning ot my work. My sincere acknowledgements are due to Prof, and Chairman 3 ,M. Casshayap for his constant support. I am indepted to Dr. S.xM. Naqvi Scientist, N.G.R.I. Hyderabad for providing me all the facilities of chemical analysis, I also express my thanks to staff of N,G.R.I. Mr. Balaram, and Mr. Ramesh for their help in the analysis of samples. I owe my indeptedness to Dr. V,C. Takur, Director W.I.H.G. for his kind gesture in providing me the facilities to collect literature. A token of deep appreciation to Messers Z.H. Fahmi, M. Asit', Sh ih ibuddin and Shrvnim Khan who helped me most, to say the least. fhe author also owes a great deal to the encouragement and assistance of many others, friands, and colleagues. My gra titude to them will perhaps po best expressed by leaving them unndmed. Thanks to Mr. O.P, Sharma for typing the dissertation / A^ neatly within snort span of time. ,, /^ J'^ ^l/i CHArn HANUMANTHA RAO Llor OF FIGURES Fig. 1 (a, b and c) Principle and height adjustments of U-stage Fig, 2 (a and b) Trogers graphs Fig, 3 Flow chart for determination of the attitude of the biaxial indicatrix and of 2v, Fig. 4 Location Map Fig. 4a Geological Map of Sajahmundry area ifig. 5 Location Map Rajahmundry Fig, 6(1,2,3,4) Twinned plagioclase crystals Studied under U-stage (Reinhard method) Fig, 7 (5, 6,7, b) Twinned plagioclase crystals Studied under U-stage (Reinhard method) Fig, 8 (9,lU,ll,12) Twinned plagioclase crystals Studied under U-stage ^Reinhard metl"iod) Fig. 9(1,2,3,4) Twinned plagioclase crystals Studied under U-stage(Rittmann method) Fig, lo Fedoroff - NiKitin Stereogram I'ig, 11 Extinction angle curvps for Plagioclase . Fig, 12 Extinction angle curves for Plagioclase, Fig, 13 NaÔ + K2O /Si02 diagram Fig, 14 SiO^/xNorm (j + Or + Ab) diagram Fig. 15 D.I./various oxides diagrcun Fig. 1ba The solidification Index/various oxides diagram Fig, 16 &£ 16a iîgO/various oxides diagram Fig. 17 MgO/various oxides diagram Fig, lb A F M diagram showing tholeiite trend Fig. 19 K20-Na2 0-CaO diagram Fig, 2u Al202/Na20 + K2O diagram Fig, 21 Al202/Nonnative plagioclase diagram Fig. 22 Al-Fe+Ti - Mg cation percent Ternary diagram Fig. 2 3 (a,b,£i c) Variation of Si02,FeO and Ti02 with Feo/MgO Fig. 24 Ti02/Si02 diagram J='ig. 2 5 {a,t, c and d) Al_3i Fe-Mg; Ti-Fe and Ti02-MgO dia gram Fig. 2b Ni ppm/Feo/MgO diagram i'ig. 11 Si02/log Ni diagram Fig, 2b Ni/Feo/MgO diagram Fiy. 29 SiO^/Cr pfxn diagram Fig, 3U Cr ppm/FeO/MgO diagram >'iy. 31 Ni/Cr diagram Fig. 3-i(a,fc, and c) K/Rb; K/Sr; Rb/3r diagram Fig, 3 3 ftb/3r versus K and If/i/Sb diagram rig. 34 ÎC. 7/Zr ppm diagram c ilo q: , J b lCÔ//.r ppm diagram * K ** *>r *r* LIST 0F__TABLB5 1 , Division (f Deccan Trap area into subprovinces on the basis of Geomorphic features. , 2 , Various symbols of Universal stage , 3. Geological successijn of Rajahmundry area , 4. Analytical data for Major and Minor elements , 5. Normative values of various samples of Deccan basalts of Rajahmundry 6. Cation percentage of major and rainor elements of Deccan basalts of Rajahmundry 7. Comparison of Major elements in basaltic rocks of Deccan Traps, Indian ocean and Rajahmundry area «. K/Sr and Rb/Sr ratios of some selected possible basalts oi Rajai'iraundry and other Deccan Trap areas . 9. Range and average of different major oxides ratios of Rajahmundry basalts. 10. Range and average of different oxides of Rajahmundry Deccan Basalts. , 11. Trace elf^-ment analysis of Basalts of Rajahmundry in PPM. 12 . Comparison of average trace elements of basalts of the Deccan Trups. ****** Chapter - I DECCAN TRAPS . GENERAL DESCRIPTION Introduction : The Deccan Traps have drawn considerable attention and interest among the geologists owing to their vast expanse, covering about 500,000 square Kms, correspon ding to one sixth of India's land surface area. The main Deccan plateau covers parts of Maharastra, Kathaiwar and Kutch (Gujarat), Madhya Pradesh, Karnataka and Andhra Pradesh. A number of outlying patches of rocks similar in character and age are found in Belgauin (southern Karnataka), Rajahraundry (Eastern Andhra Pradesh), Amarkantak,Sirguja and jashpur in the East and Kutch in the North West, even as far as Sind (Krishnan, 1963). The traps may have occupied most of the arâs inteirvening the main mass and the outlying patches. Thus the original extent of the mass may have been over 1.5 million square kilometres, including the segment of unknown extent which foundered in the Arabian sea, west of bombay. Classification : 1—••IpiWi.iWHI—llfl - Many early workers including Krishnan (1963) and Sahasrabudhe (1952), classified the Deccan Traps into Lower, Middle and Upper, on the basis of statigrapny and Inter- trappean beds. The paleanagnetic data has also been used to 9 distinguish the Upper Traps irom the Lower Traps (SahasraJDudhe, 1962), Pal andbhimasankaran (1972, 1979), on the basis of observed directions ot remanent magnetism reconstructed paleoiatitudes. This along with the known or inferred age relationships betweeii diiterent parts, have been used by thera in the tentative grouping of the Deccan traps as follows; Group-A : Those with reversed polarity are the oldest Traps (About 70-75 m years). Group B : Those with normal polarity are the Middle Traps (a.bout 65 m years. The flows of Mahabaleswar, Bombay and Rajahmundry and the reversed flows of Llnga and jalwa. Group C ; The youngest flows are the upper most flows of Mahabalewar and Gargoti, the two upper flow of Nipani, flows ot sagar and those Pawagad hill (aboi*t 60 m years) , Group D : The two acid tuff beds on Pawaged hill (about 40 m years). These groups, according to Sukheswala (1982), correspond to systematic northward drift of India, According to him, these groups are, probably, analogous to peridds of lava extrusion suggesting that the Deccan Trap volcanism took place in at least lour pnases, Ghose Uy7b), on the basis oi chemistry, subdivided Deccan Traps into two groups - Lower Traps (Eastern and 3 Southern parts) and Upper Traps (Western coast and Narmada Valley). The Lower Traps, according to him, are character ised by tranquil eruptions of Chemically uniform quartz- nonnative tholeiite forming horizontal flows. The Upper Traps, in contrast, characterise explosive activity, foundering of the crust and deep faulting. The flows have variable dips. Saxena (1962) divided the traps into Upper and Lower, mainly, on chemical basis roughly correlating with statigx-aphical divisions of Blanford. The Upper Traps are found in Western India in places like Bombay, Pune, Katwaiwar and Kutch(!)Gujarat) and the Lower Traps in the middle and eastern regions like those of ^"êemuch, Nasik and Satpuras , The problem of grouping of flows may beconse easier if a systematic collection of samples is carried out on a large scale with proper knowledge of statigraphic columns for radio metric datin-q. Che dating done so far is on sporadic samples from distant localities, and that too of uneven quality. Perhaps a suitable tfchni ûe is yet to be devised for Cenozoic basalts (Sukhewsala, 1982).

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