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associated with the closing stages of tectono-magmatic cycles, it is reasonable to suggest that the reported ages represent the closing stages of a tectono-magmatic event in Pal ghat Gap, presumably related to isothermal depression during crustal uplift associated with the retrogressive event. This inturn would suggest that the tectonic framework for the formation of the Palghat Gap was this period. 16 initiated during
CHAPTER I INTRODUCTION Palghat Gap is a prominent geomorphic feature in the landscape of South India (Fig.1). This low level landform . having a width of about 30 km and a length of over 80 km in an east -west direction and bordered by the Nilgiris to the north and the Anaimalai massif to the south, constitutes the only major break in the Western Ghats. The Gap proper has a subdued profile (Fig.2 a & b) with an average elevation of 60 m in the western part and 120 m in the eastern part, with we I I defined scarp faces towards southern and northern flanks. Origin of this interesting geomorphic feature is s t i I I a controversy with the present day discussions centering around apparently conflicting hypotheses: (1) Fluviatile action model of Jacob and Narayanaswamy (1954) attributed the origin of the Gap to a large easterly flowing and a probable westerly flowing drainage systems with their source very close to the Palghat region. Absence of strike trends and other structural features indicative of faulting were taken as supporting evidences in favour of a fluviatile origin. {2l Supported by the geomorphological and structural evidences in favour of uplift of the Nilgiris flanking the Palghat Gap to the north, through large - scale faulting and 17
Page 1 and 2: GEOLOGY, METAMORPHISM AND TECTONIC
Page 3: Acknowledgement Abstract Chapter I
Page 6: Field investigations indicate that
Page 9 and 10: mineralogy of K-feldspar (46 modal
Page 12 and 13: granulite terrains. Enrichment of a
Page 14: Amphiboles of both the calc granuli
Page 19: through syn to post-thickening magm
Page 23 and 24: Fig.2(a) A view of a part of the Pa
Page 25: Narayanaswamy,1954), paucity of myl
Page 28: of movement. Aeromagnetic data of R
Page 34: Bounded by the Western Ghats, the K
Page 39 and 40: Fig.5 Coarsening of sillimanite in
Page 43: and a proven vertical extent of mor
Page 47 and 48: F1g.12 Hornblende - biotite gneiss
Page 49 and 50: of 0.75 m, along NE-SW trending fra
Page 52: direction of fracture planes. Withi
Page 57 and 58: Fig.21 Rootless isoclinal folds (F
Page 59 and 60: Fig.23 Isoclinal folds axial plane.
Page 62: Pig . 27 Concordant pegmatite belon
Page 67 and 68: The tectonic framework of the area
Page 69: inclusions of plagioclase as wel I
Page 72:
the reaction:- G.rossularite + Sill
Page 77 and 78:
TABLE:- 1 MICROPROBE ANALYSES OF SI
Page 79 and 80:
Fig.43 .Fig.40
Page 81 and 82:
Fi g.44 Fig.45 Fig.46 Fig . 47
Page 83 and 84:
where biotite is almost completely
Page 85:
.Fig. 48 Fig.49 Fig.SO Fig . Sl
Page 90 and 91:
Fig.52 Fig.53 Fig.54 Fig.55 B6
Page 93 and 94:
Fig. 56 Fig. 57 Fig. 58 Fig. 59 Cal
Page 97 and 98:
Magnetite is present ubiquitously a
Page 99:
Fig.60 Fig.61 Fig.62 Fig.63 • O.S
Page 103 and 104:
Fig. 64 Fig. 65 Fig. 66 Fig. 67 Bri
Page 105:
Biotite gneiss is typically a coars
Page 109 and 110:
Fig.6B Fig.69 Fig.lO Fig.71 l e::..
Page 112 and 113:
Fig. 72 Fig. 73 Fig. 74 Fig. 75 Sie
Page 114 and 115:
Opaques constitute 0 to 6 modal per
Page 116 and 117:
(X= yel lowish green, Y= brownish g
Page 119 and 120:
11 1.7 PEGMAT I TE Pegmatites are u
Page 121 and 122:
Fig.BO Fig.Bl Fig .B2 UI
Page 125 and 126:
Average values of CaO/MgO ratios fo
Page 127:
proportion in the first two varieti
Page 135 and 136:
TABLE. 6 COMPOS I T ION OF KHONDAL
Page 138:
wt % of type I I varieties. Oxidati
Page 150:
.£.=1-5-2-3 fm c -=1-0-1-5 fm - -
Page 153:
assemb I ages (Goldsmith & Newton,
Page 157 and 158:
TABLE.9 ( c ) NIGGLI PARAMETERS ---
Page 159:
Fig.93 a). In the AlkFM diagram on
Page 162:
elements, CaO, t FeO , TiOZ and MgO
Page 171 and 172:
Rb depleted and Sr enriched nature
Page 173:
TABLE 11.a MAJOR ELEMENT ANALYSES O
Page 178:
their genesis. Amphibolites interla
Page 187:
granites, compared to hornblende-pr
Page 191:
low « 3.Z wt %), with slightly hig
Page 199:
Enrichment of almandine towards rim
Page 205:
!Table.1S). On the basis of their i
Page 212:
2C7 tempera'ture of the former. Com
Page 216 and 217:
cordierite-bearing rocks fall close
Page 219:
TABLE.l9 HICROPROBE ANALYSES OF CLI
Page 227 and 228:
The static involving changes fluid
Page 229 and 230:
to minerals with the largest grain
Page 232:
227 b. Garnet-Cordierite:- Holdaway
Page 237:
thermometric calculations is:- = [-
Page 240:
235 formulae of Raheim & Green (197
Page 243 and 244:
238 100-300 C C compared to other s
Page 245 and 246:
specified P-T conditions. However,
Page 247:
al ka I i feldspar upon cool ing. r
Page 254 and 255:
pressure-dependent equilibria: CaAI
Page 256 and 257:
Cpx and ()(CaMgSi 0 2 = 2 6 pyroxen
Page 258:
253 Bhattacharya & Sen (1985) provi
Page 268 and 269:
TABLE.21 contd ... 4000 GAR CORE-BT
Page 270:
265 TABLE.21 (b) GARNET-CORDIERITE
Page 278 and 279:
TABLE.24 b CROSSINGS OF GPAQ P-T LI
Page 281:
TABLE.25 (contd •.• ) Temperatu
Page 288:
283 which yield data on the process
Page 292:
Fig.124 H 2 0-rich inclusions Ca )
Page 297:
292 carbonic inclusion densities se
Page 309:
low density C02 rich fluids in rift
Page 313 and 314:
J08 sequences, the success in datin
Page 315:
deformation stage, would represent
Page 323:
318 ear lies t recognisable planar
Page 328 and 329:
323 to effect the quasi-isochemical
Page 330 and 331:
The rapid extension of continental
Page 333 and 334:
flanks (2) development of fissile m
Page 335 and 336:
330 extracted with Hydrochloric aci
Page 337:
Estimation of CaO and MgO 332 Twen"
Page 340:
spectrometer while measuring the co
Page 343 and 344:
13. Balasundaram, M. S . ( 1953) .
Page 345:
340 34. Boyd, F.R. and England, J.L
Page 349:
77. Fonarev,V.I. and Konilov, A.N.
Page 353 and 354:
119. Heier, K.S. (1962) amphibolite
Page 355 and 356:
141. Hutcheon, I., Froese. E, Gordo
Page 357 and 358:
162. Krauskopf, K.S. (1979) Introdu
Page 359:
185. MacDonald, G.A. (1968) Composi
Page 362 and 363:
218. Newton, R.C., Charlu, T.V. and
Page 366 and 367:
261. Raith. H.. Raase. P .. Ackerma
Page 371 and 372:
313. Srikantappa. C.and Prakash Nar
Page 373 and 374:
335. Urey, H.C. (1947). the thermod
Page 375:
357. Wood, B. J . ( 1976) . The par
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