Summary
Of twelve flows at Pavagadh Hill, the two three-phenocryst-basalt flows with Mg#∼0.70 and Ni/MgO∼33 are the most primitive and perhaps as primitive as any basalts in the Deccan province. Scatter on variation diagrams and the occurrence of primitive flows at two different levels in the volcanic sequence implies that most rocks are probably not, strictly speaking, comagmatic. Nevertheless, mass balance calculations indicate a generalized differentiation scheme from primitive basalt to hawaiite that involved removal of olivine, augite, plagioclase and Fe-Ti oxides in the proportions 40:33:22:5 with ∼ 50% of the magma remaining. Crustal assimilation had a minimal effect on evolution of the basalts but rhyolites at the top of the volcanic sequence may have been produced by crustal melting following prolonged heat release from alkali basalt pooled along fault zones in the continental crust. Major element based calculations indicate that the most primitive basalts were generated by 7 to 10% melting of mantle peridotite. These low percentages of melting, typical of alkali basalts, are consistent with the steep slopes on chondrite-normalized REE diagrams. Low heavy REE concentrations point to residual garnet in the source region. Incompatible element concentrations (e.g. Rb, Ba, Zr, La) in Pavagadh basalts exceed those in Deccan tholeiitic basalts but are substantially lower than those reported for some other Deccan alkali basalts. Obviously Pavagadh basalts do not reflect the lowest percentages of melting and greatest amount of source region metasomatic enrichment attained in the Deccan province. Deccan tholeiitic and alkali basalts are largely characterized by low La/Nb ratios and high La/Ba ratios similar to those in oceanic island basalts. This indicates minimal involvement of the subcontinental lithospheric mantle in their petrogenesis. Comparison with continental mafic magma provinces where a subcontinental lithospheric mantle imprint is common indicates long periods of extension and/or melting of mantle lithosphere still hot from pre-extension subduction are more likely to produce magmas bearing the lithospheric imprint.
Zusammenfassung
Im Gebiet von Pavagadh Hill, Indien, treten 12 Spät-Deccan und rhyolithische alkalibasaltische Ergüsse und Intrusiva auf. Variationsdiagramme zeigen, daß die Abfolge nicht komagmatisch ist. Zusammen mit Berechnungen der Massenbilanz unterstützen sie vielmehr ein Zwei-Stadienmodell für die Entstehung von Hawaiiten aus sehr primitiven (i.e. Mg#=Mg/(Mg+.(0.9*Fetotat)) at.%∼0.70) Basalten. Olivin und Augit dominierten die frühe Fraktionierung während Augit vorherrschte als der Magmaanteil von 65% auf 50% sank. Die Entfernung von Plagioklas spielte bei der Differentiation nur eine geringe Rolle. Niedrige Th/Nb (∼0,2), Rb/Sr(<0,12) und K/NbVerhältnisse geben keine Hinweise auf signifikante Assimilation von Krustenmaterial. Die Seltene-Erd-Verteilungsmuster (SEE), niedrige Gehalte an schweren SEE sowie die Hauptelementspektren der Alkalibasalte weisen auf eine granatführende Ursprungsregion und auf einen Aufschmelzungsgrad von nur 7% bis 10% hin. Es gibt jedoch auch stärker alkalische (höhere Rb, Zr etc.) Deccanbasalte (i.e. Rajpipla). Die Assoziation von Deccanalkalibasalten, Rhyolithen und Störungszonen zeigt, daß letztere die Extraktion von Magma aus dem Mantel erleichterten und dazu führten, daß Magma aus Magmenkammern Krustenschmelzen (Rhyolithe) produzierte. Deccanbasalte tendieren zu hohen La/Ba und niedrigen La/Nb-Verhältnissen; dies weist auf eine asthenosphärische Herkunft hin, selbst wenn die Gesteine verhältnismäßig spät gebildet wurden (i.e. Pavagadh). Längere Perioden von Krustenextension oder von Subduktion, die der Extension vorhergeht, führt offensichtlich zur Entstehung von Magmen mit einer lithosphärischen Komponente.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Alexander PO (1980) The Pavagarh rhyolites. J Geol Soc India 21: 453–457
Alexander PO (1981) Age and duration of Deccan volcanism: K-Ar evidence. In:Subba Rao KV, Sukheswala RN (eds) Deccan volcanism and related basalt provinces in other parts of the world. Geological Society of India, Memoir No 3, pp 244–259
Basaltic Volcanism Study Project (1981) Basaltic volcanism on the terrestrial planets. Pergamon Press, New York, 1286 pp
Basu AR, Renne PR, DasGupta DK, Teichmann F, Poreda RJ (1993) Early and late alkali igneous pulses and a high-3 He plume origin for the deccan flood basalts. Science 261: 902–906
Bean JE, Hooper PR (1988) A note on the picrite basalts of the Western Ghats, Deccan traps, India. In:Subbaro KV (ed) Deccan flood basalts. Geological Society of India, Memoir 10, pp 117–133
Bryan WB, Finger LW, Chayes F (1969) Estimating proportions in petrographic mixing equations by least-squares approximation. Science 163: 926–927
Bose MK (1972) Deccan basalts. Lithos 5: 131–145
Carswell DA (1980) Mantle derived lherzolite nodules associated with kimberlite, carbonatite and basalt magmatism: a review. Lithos 13: 121–138
Chatterjee SC (1961) Petrology of Pavagarh Hill, Gujarat. J Geol Soc India 2: 61–67
Chen C-H (1988) Estimation of the degree of partial melting by (Na2O+K2O) and (Al2O3/ SiO2) of basic magmas. Chem Geol 71: 355–364
Clague DA, Dalrymple GB (1987) The Hawaiian-Emperor volcanic chain, part l. Geologic evolution. In:Decker RW, Wright TL, Stauffer PH (eds) Volcanism in Hawaii, vol 1. U.S. Geological Survey Professional Paper 1350, pp 5–54
Condie KC, Viljoen MJ, Kable EDI (1977) Effects of alteration on element distribution in Archean tholeiites from Barberton Greenstone Belt, South Africa. Contrib Mineral Petrol 64: 75–89
Cox KG, Bell JD (1982) A crystal fractionation model for the basaltic rocks of the New Georgia Group, British Solomon Islands. Contrib Mineral Petrol 37: 1–13
Cox KG, Hawkesworth CJ (1985) Geochemical stratigraphy of the Deccan traps at Mahabaleshwar, Western Ghats, India, with implications for open system magmatic processes. J Petrol 26: 355–377
Cox KG, Devey CW (1987) Fractionation processes in Deccan traps magmas: comments on the paper by G. Sen - Mineralogy and petrogenesis of the Deccan trap lava flows around Mahabaleshwar, India. J Petrol 28: 235–238
Cullers RL, Ramakrishnan S, Berendsen P, uGriffin T (1985) Geochemistry and petrogenesis of lamproites, Late Cretaceous age, Woodson Country, Kansas, U.S.A. Geochim Cosmochim Acta 49: 1383–1402
De Paolo DJ (1981) Trace element and isotopic effects of combined wallrock assimilation and fractional crystallisation. Earth Planet Sci Lett 53: 189–202
Devey CW, Cox KG (1987) Relationships between crustal contamination and crystallisation in continental flood basalt magmas with special reference to the Deccan Traps of the Western Ghats, India. Earth Planet Sci Lett 84: 59–68
Dostal JB, Dupuy C (1984) Geochemistry of the North Mountain Basalts (Nova Scotia, Canada). Chem Geol 45: 245–261
Duncan RA, Pyle DG (1988) Rapid eruption of the Deccan flood basalts, Western India. In:Subbaro KV (ed) Deccan flood basalts. Geological Society India, Memoir 10, pp 1–9
Evans JL (1978) An alkalic volcanic suite of the Labrador Trough, Labrador. Thesis, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
Evensen NM, Hamilton PJ, O'Nions RK (1978) Rare-earth abundances in chondritic meteorites. Geochim Cosmochim Acta 42: 1199–1212
Fitton JG, James D, Kempton PD, Ormerod DS, Leeman WP (1988) The role of lithospheric mantle in the generation of late Cenozoic basic magmas in the Western United States. J Petrol [Special Lithosphere Issue]: 331–349
Fitton JG, James D, Leeman WP (1991) Basic magmatism associated with Late Cenozoic extension in the Western United States: compositional variations in space and time. J Geophys Res 96: 13693–13711
Floyd PA, Winchester JA (1978) Indentification and discrimination of altered and metamorphosed volcanic rocks using immobile elements. Chem Geol 21: 291–306
Frey FA, Bryan WB, Thompson G (1974) Atlantic ocean floor: geochemistry and petrology of basalts from Legs 2 and 3 of the Deep Sea Drilling Project. J Geophys Res 79: 5507–5527
Frey FA, Green DH, Roy SD (1978) Integrated models of basalt petrogenesis: a study of quartz tholeiites to olivine melilitites from southeastern Australia utilizing geochemical and experimental petrological data. J Petrol 19: 463–513
Gast PW (1968) Trace-element fractionation and the origin of tholeiitic and alkaline magma types. Geochim Cosmochim Acta 32: 1057–1086
Green DH (1971) Composition of basaltic magmas as indicators of conditions of origin: application to oceanic volcanism. Phil Transact Roy Soc Lond A268: 707–725
Greenough JD, Jones LM, Mossman D (1989) The Sr isotopic composition of early Jurassic mafic rocks of Atlantic Canada: implications for assimilation and injection mechanisms affecting mafic dykes. Chem Geol [Isotope Geoscience Sect] 80: 17–26
Hari KR (1991) Mineralogical and fluid inclusion studies of primary constituents of mafic and ultramafic rocks of Pavagadh Hill (Deccan Traps), Gujarat. Thesis, Vikram University, Ujjain, India, 110 p
Hari KR, Santosh M, Chatterjee AC (1991) Primary silicate melt inclusions in olivine phenocrysts from Pavagadh igneous suite, Gujarat. J Geol Soc India 37: 343–350
Hellman PL, Smith RE, Henderson P (1979) The mobility of the rare earth elements: evidence and implications from selected terrains affected by burial metamorphism. Contrib Mineral Petrol 71: 23–44
Jaques AL, Green DH (1980) Anhydrous melting of peridotite at 0–15 kb and the genesis of tholeiitic basalts. Contrib Mineral Petrol 73: 287–310
Kay RW, Gast PW (1973) The rare earth content and origin of alkali-rich basalts. J Geol 81: 653–682
Kempton PD, Fitton JG, Hawkesworth CJ, Ormerod DS (1991) Isotopic and trace element constraints on the composition and evolution of the lithosphere beneath the Southwestern United States. J Geophys Res 96: 13713–13735
Krishnamurthy P, Cox KG (1977) Picrite basalts and related lavas from the Deccan traps of Western India. Contrib Mineral Petrol 62: 53–75
Krisnamurthy P, Cox KG (1980) A potassium-rich alkalic suite from the Deccan Traps, Rajpipla, India. Contrib Mineral Petrol 73: 179–189
Krishnamurthy P, Udas GR (1981) Regional geochemical characters of the Deccan trap lavas and their genetic implications. Geological Society of India, Memoir No 3, pp 394–418
Krishnan MS (1982) Geology of India and Burma 6th ed. CBS Publishers, Delhi, 536 p
Lightfoot P, Hawkesworth C (1988) Origin of Deccan trap lavas: evidence from combined trace element and Sr-, Nd- and Pb-isotope studies. Earth Planet Sci Lett 91: 89–104
Lightfoot PC, Hawkesworth CJ, Devey CW, Rogers NW, Van Calsteren PWC (1990) Source and differentiation of Deccan trap lavas: implications of geochemical and mineral chemical variations. J Petrol 31: 1165–1200
Lipman PW, Prostka HJ, Christiansen RL (1972) Cenozoic volcanism and plate-tectonic evolution of the Western United States, 1. Early and Middle Cenozoic. Phil Transact Roy Soc Lond (Series A) 271: 217–248
Longerich HP, Jenner GA, Fryer BJ, Jackson SE (1990) Inductively coupled plasma-mass spectrometric analysis of geologic samples: a critical evaluation based on case studies. Chem Geol 83: 105–118
Macdonald R., Thorpe RS, Gaskarth JW, Grindrod AR (1985) Multi-component origin of Caledonian lamprophyres of northern England. Mineral Mag 49: 485–494
Mohoney J, Nicollet C, Dupuy C (1991) Madagascar basalts: tracking oceanic and continental sources. Earth Planet Sci Lett 104: 350–363
Mauger RL (1988) Geochemical evidence for sediment recycling from North Carolina (U.S.A.) minettes. Can Mineral 26: 133–141
McKenzie D, Bickle MJ (1988) The volume and composition of melt generated by extension of the lithosphere. J Petrol 29: 526–679
Pearce JA, Cann JR (1973) Tectonic setting of basic volcanic rocks determined using trace element analyses. Earth Planet Sci Lett 19: 290–300
Peng ZX, Mahoney JJ (1995) Drillhole lavas from the northwestern Deccan Traps, and the evolution of Réunion hotspot mantle. Earth Planet Sci Lett 134: 169–185
Peng ZX, Mahoney JJ, Hooper P, Harris C, Beane J (1994) A role for lower continental crust in flood basalt genesis? Isotopic and incompatible element study of the lower six formations of the western Deccan Traps. Geochim Cosmochim Acta 58: 267–288
Philpotts JA, Schnetzler CC (1970) Phenocryst-matrix partitioning coefficients for K, Rb, Sr and Ba with applications to anorthosite and basalt genesis. Geochim Cosmochim Acta 34: 307–322
Roeder PL, Emslie RF (1970) Olivine-liquid equilibrium. Contrib Mineral Petrol 59: 275289
Sen G (1986) Mineralogy and petrogenesis of the Deccan trap lava flows around Mahabaleshwar, India. J Petrol 27: 627–663
Sen G (1987) Reply to Cox and Devey. J Petrol 28: 239–240
Sinha RC, Tiwari BD (1964) Geochemistry of the volcanic rocks of Pavagadh. Proceedings, 22nd International Geological Congress, New Delhi, Section 7, pp 104–125
Sukheswala RN (1981) Deccan basalt volcanism. Geological Society of India, Memoir No 3, pp 8–18
Sun SS, Hanson GN (1975) Origin of Ross Island basanitoids and limitations upon the heterogeneity of mantle sources for alkali basalts and nephelinites. Contrib Mineral Petrol 52: 77–106
Sun S-s, McDonough WF (1989) Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In:Saundars AD, Norry MJ (eds) Magmatism in the ocean basins. Geological Society Special Publication No 42, pp 313–345
Takahashi E, Kushiro I (1983) Melting of dry peridotite at high pressures and basalt magma genesis. Am Mineral 68: 659–679
Thompson RN, Dickin AP, Gibson IL, Morrison MA (1982) Elemental fingerprints of isotopic contamination of Hebridean Palaeocene mantle-derived magmas by Archean sial. Contrib Mineral Petrol 79: 159–168
Tiwari BD (1971) Magmatic differentiation of volcanic rocks of Pavagadh Gujarat, India. Bull Volcanol 35: 1129–1177
White RS (1989) Igneous outbursts and mass extinctions. Eos 70: 1480–1491
Wyman DA, Kerrich R (1989) Archean lamprophyre dikes of the Superior Province, Canada: distribution, petrology and geochemical characteristics. J Geophys Res 94: 4667–4696
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Greenough, J.D., Hari, K.R., Chatterjee, A.C. et al. Mildly alkaline basalts from Pavagadh Hill, India: Deccan flood basalts with an asthenospheric origin. Mineralogy and Petrology 62, 223–245 (1998). https://doi.org/10.1007/BF01178030
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF01178030