Abstract
Detailed chemical and mineralogical data are given for three sequences of basalts and picrite basalts from bore-holes in Western India. The picrite basalts show bulk compositional variation generated by the fractionation of olivine and chromite. Evolved picrite basalt magma appears to have given rise to basalt by the fractionation of olivine+clinopyroxene, despite the presence of abundant plagioclase phenocrysts. It is suggested that a slow settling rate for plagioclase relative to clinopyroxene and olivine is sufficient to account for this feature. The high degree of equilibrium crystallisation which many of the lavas have apparently undergone is interpreted in terms of the mechanism of compensated crystal settling (Cox and Bell, 1972). Experimentally determined atmospheric pressure phase relations are used to model dyke-like magma chambers in some detail. Finally volumetric and age relationships are used to argue that the picrite basalts, despite their porphyritic nature, crystallised from ultramafic liquids containing in some cases at least 16% MgO.
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Biggar, G.M., O'Hara, M.: Temperature control and calibration in quench furnaces and some new temperature measurements in the system CaO-MgO-Al2O3-SiO2. Mineral. Mag. 37, 1–15 (1968)
Cawthorn, R.G., Strong, D.F.: The petrogenesis of komatiites and related rocks as evidence for a layered upper mantle. Earth Planet. Sci. Lett. 23, 369 (1974)
Chatterjee, S.C.: Petrochemistry of the lavas of Pawagadh hills, Gujarat. In: Advancing frontiers in Geology and Geophysics, Krishnan volume, Indian Geophysical Union, Hyderabad, India, pp. 155–170 (1964)
Clarke, D.B.: Tertiary basalts of Baffin Bay, possible primary magmas from the mantle. Contrib. Mineral. Petrol. 25, 203–224 (1970)
Coombs, D.S.: Trends and affinities of basaltic magmas and pyroxenes as illustrated on the diopside-olivine-silica diagram. Mineral. Soc. Am. Spec. Papers No. 1 (1963)
Cox, K.G.: The Karroo volcanic cycle. J. Geol. Soc. Lond. 128, 311–336 (1972)
Cox, K.G., Bell, J.D.: A crystal fractionation model for the basaltic rocks of the New Georgia Group, British Solomon Islands. Contrib. Mineral. Petrol. 37, 1–13 (1972)
Cox, K.G., Johnson, R.L., Monkman, L.J., Vail, J.R., Wood, D.N.: The geology of the Nuanetsi Igneous Province. Phil. Trans. Roy. Soc. London, Ser. A 257, 71–218 (1965)
Drever, H.I., Johnston, R.: Crystal growth of forsteritic olivine in magmas and melts. Trans. Roy. Soc. Edinburgh 63 (1957)
Fermor, L.L.: General report of the Geological Survey of India for the year 1933. Rec. Geol. Surv. Ind. 66, 18–21 (1933)
Long, J.V.P.: Electron probe microanalysis. In: Physical methods of determinative mineralogy (J. Zussman, ed.). London and New York: Academic Press 1967
Meldin, J.H., Suhr, N.H., Bodkin, J.B.: Atomic absorption analysis of silicates employing LiBO2 fusion. Atomic Absorption Newsletter No. 2, 8 (1969)
Mishra, K.K.: Petrology of the picrite-basalt flows in the Igatpuri area, Nasik District, Maharashtra. Bull. Vocanol. 35, 957–964 (1972)
O'Hara, M.J.: The bearing of phase equilibria studies on synthetic and natural system on the origin of basic and ultrabasic rocks. Earth Sci. Rev. 4, 69–133 (1968)
Pyke, D.R., Naldrett, A.J., Eckstrand, O.R.: Archaean ultramafic flows in Munro Township, Ontario. Geol. Soc. Am. Bull. 84, 955 (1973)
Reynolds, R.C.: Matrix correlation in trace element analysis by X-ray fluorescence: estimation of the mass absorption coefficient by Compton scattering. Am. Mineralogist 48, 113 (1963)
Roeder, P.L., Emslie, R.F.: Olivine-liquid equilibrium. Contrib. Mineral. Petrol. 29, 275–289 (1970)
Rose, H.J., Alder, I., Flanagan, R.J.: X-ray fluorescence analysis of the light elements in rocks and minerals. Appl. Spectry. 17, 81–85 (1963)
Ross, C.S., Foster, M.D., Myers, A.T.: Origin of dunites and of olivine-rich inclusions in basaltic rocks. Am. Mineralogist 39, 693–737 (1954)
Shapiro, L., Brannock, W.W.: Rapid analysis of silicates, carbonates and phosphate rocks. U.S. Geol. Surv. Bull. 1144-A (1962)
Sharma, C.V.: The petrology and structure of the Deccan Trap flows of Pawagadh Hill, Gujarat, India. Ph. D. Thesis, Saugar University (unpublished) (1963)
Sweatman, T.R., Long, J.V.P.: Quantitative electron probe microanalysis of rock forming minerals. J. Petrol. 10, 332–379 (1969)
Tiwari, B.D.: Magmatic differentiation of the volcanics at Pawagarh, Gujarat, India. Bull. Volcanol. 35, 1129–1177 (1972)
Vincent, E.A.: Analysis by gravimetric and volumetric methods, flame photometry, colorimetry and related techniques. In: Methods in geochemistry (A.A. Smales and L.R. Wager, eds.), pp. 33–80. New York and London: Interscience 1960
Vincent, E.A., Wright, A.B., Chevallier, R., Mathieu, S.: Heating experiments on some natural titaniferous magnetites. Mineral. Mag. 31, 624–655 (1957)
Wager, L.R., Brown, G.M.: Layered igneous rocks. Edinburgh and London: Oliver and Boyd 1968
West, W.D.: The petrography and petrogenesis of forty-eight flows of Deccan trap penetrated by borings in Western India. Trans. Nat. Inst. Sci. Ind. 4, 1–56 (1958)
Wilson, A.D.: A new method for the determination of ferrous iron in rocks and minerals. Bull. Geol. Surv. Gt. Brit. 9, 56–58 (1955)
Yoder, H.S., Jr., Tilley, C.E.: The origin of basalt magmas: an experimental study of natural and synthetic systems. J. Petrol. 3, 342–532 (1962)
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Krishnamurthy, P., Cox, K.G. Picrite basalts and related lavas from the Deccan Traps of Western India. Contr. Mineral. and Petrol. 62, 53–75 (1977). https://doi.org/10.1007/BF00371027
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DOI: https://doi.org/10.1007/BF00371027