Abstract
The hornblende-biotite gneisses of Central Kerala which cover approximately 490km2 exhibit schlieric and nebulitic structures, tending towards a homophanous nature and are classified here as diatexites. Mafic protoliths and restite biotite, each representing the refractory residuum of two independent partial melting episodes are widely present in the gneisses. The general mineral assemblage of the gneisses comprise quartz, K-feldspar, oligoclase, biotite and hornblende. Chemically, they are dominantly adamellitic and the behaviour of major and trace elements is consistent with a magmatic parentage. Based on petrochemical criteria, a two-stage evolution model is proposed here, which involves (i) partial melting of mafic granulites under high Archean geothermal gradients and generation of tonalite/trondhjemite through amphibole and plagioclase fractionation and (ii) partial melting and subsequent quartz-alkali feldspar fractionation of the tonalite/trondhjemite under amphibolite facies conditions with synchronous K-enrichment resulting in the diatectic adamellites.
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References
Arth J G and Hanson G N 1972Contrib. Mineral. Petrol. 37 161
Arth J G and Barker F 1976Geology 4 534
Barker F and Arth J G 1976Geology 4 596
Bridgwater D and Collerson K D 1976Contrib Mineral. Petrol. 54 43
Collerson K D and Bridgwater D 1979 in Trondhjemites, dacites and related rocks (ed.) F Barker (Amsterdam: Elsevier) p. 205
Condie K C 1981Archean greenstone belts (Amsterdam: Elsevier) 434 p
Condie K C and Hunter D R 1976Earth Planet. Sci. Lett. 29 389
Condie K C and Lo, H H 1971Geochim. Cosmochim. Acta 35 1079
Eade K E and Fahrig W F 1971Bull. Geol. Surv. Canada 179 51
Fyfe W S 1973Philos. Trans. R. Soc. London A273 457
Halloway J R 1971Geol. Soc. Am. Bull. 82 233
Hanson G N 1978Earth planet. Sci. Lett. 38 26
Harpum J R 1963Rec. Geol. Surv. Tanganyika 10 87
Iyer A G V and Kutty N T R 1978 in Archaean geochemistry B F Windley and S M Naqvi (eds) (Amsterdam: Elsevier) p. 269
Janardhan A S, Srikantappa C and Ramachandra H M 1978 in Archaean geochemistry (eds) B F Windley and S M Naqvi (Amsterdam: Elsevier) p. 127
Mahadevan T M 1964Proc. Int. Geol. Cong. 22 Sess. III 88
Mehnert K R, 1968Migmatites and the origin of granitic rocks (Amsterdam: Elsevier) 393 p
Nair N G K and Santosh M 1983aProc Indian Acad. Sci. (Earth Planet. Sci.) 92 129
Nair N G K and Santosh M 1983bJ. Geol. Soc. India (in press)
Naqvi S M 1977Bull. Geophys. Res. 15 17
O’Conner J T 1965U. S. Geol. Surv. Prof. pap 525-B
Rao P S 1976 Seminar on Geology and Geomorphology Kerala (Abstr) Geol. Surv. India
Santosh M 1981 Geology and tectonics of Periyar-Thodupuzha drainage basins, Kerala Report D.O.E. project-I (unpub.) Centre for Earth Science Studies 11p
Santosh M and Nair N G K 1983aJ. Geol. Soc. India 24 291
Santosh M and Nair N G K 1983bProc. Indian Acad. Sci. (Earth Planet. Sci.) 92 297
Santosh M and Rajan P K 1982 Geology of Periyar-Thodupuzha drainage basins Kerala, Report D.O.E. Project-I (unpub.) Centre for Earth Science Studies. 16p
Santosh M Rajan P K and Nair N G K 1983Bull. Indian Geol. Assoc. 16 33
Winkler H G F 1974Petrogenesis of metamorphic rocks (New York: Springer-Verlag) 334 p
Wyllie P J 1977Tectonophysics 43 41
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Rajan, P.K., Santosh, M. & Ramachandran, K.K. Geochemistry and petrogenetic evolution of the diatexites of Central Kerala, India. Proc. Indian Acad. Sci. (Earth Planet Sci.) 93, 57–69 (1984). https://doi.org/10.1007/BF02863384
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DOI: https://doi.org/10.1007/BF02863384