The Ghansura Felsic Dome (GFD) occurring in the Bathani volcano-sedimentary sequence was intruded by mafic magma during its evolution leading to magma mixing. In addition to the mafic and felsic rocks, a porphyritic intermediate rock occurs in the GFD. The study of this rock may significantly contribute toward understanding the magmatic evolution of the Ghansura dome. The porphyritic rock preserves several textures indicating its hybrid nature, i.e. that it is a product of mafic-felsic magma mixing. Here, we aim to explain the origin of the intermediate rock with the help of textural features and mineral compositions. Monomineralic aggregates or glomerocrysts of plagioclase give the rock its characteristic porphyritic appearance. The fact that the plagioclase crystals constituting the glomerocrysts are joined along prominent euhedral crystal faces suggests the role of synneusis in the formation of the glomerocrysts. The compositions of the glomerocryst plagioclases are similar to those of plagioclases in the mafic rocks. The results from this study indicate that the porphyritic intermediate rock formed by the mixing of a crystal-rich mafic magma and a crystal-poor felsic melt.
If the inline PDF is not rendering correctly, you can download the PDF file here.
Acharyya S.K. (2003). The nature of Mesoproterozoic central Indian tectonic zone with exhumed and reworked older granulites. Gondwana Research 6 197-214. DOI: 10.1016/S1342-937X(05)70970-9.
Ahmad M. & Paul A.Q. (2013). Investigation of Volcano-Sedimentary Sequence and Associated Rocks to Identify Gold and Base Metal Mineralization at Gere-Kewti Area of Gaya District Bihar (G4). Unpublished Report Geological Society of India Bangalore.
Bachmann O. & Bergantz G.W. (2004). On the origin of crystal-poor rhyolites: extracted from batholithic crystal mushes. Journal of Petrology 45 1565-1582. DOI: 10.1093/petrology/egh019.
Baxter S. & Feely M. (2002). Magma mixing and mingling textures in granitoids: examples from the Galway Granite Connemara Ireland. Mineralogy and Petrology 76 63-74. DOI: 10.1007/s007100200032.
Brothers R.N. (1964). Petrofabric analyses of Rhum and Skaergaard layered rocks. Journal of Petrology 6 255-274. DOI: 10.1093/petrology/5.2.255.
Brown G.M. (1956). The layered ultrabasic rocks of Rhum Inner Hebrides. Philosophical Transactions of the Royal Society London Ser. B 240 1-53. DOI: 10.1098/rstb.1956.0011.
Castro A. De la Rosa J.D. & Stephens W.E. (1990). Magma mixing in the subvolcanic environment: petrology of the Gerena interaction zone near Seville Spain. Contributions to Mineralogy and Petrology 105 9-26. DOI: 10.1007/BF00306405.
Charreteur G. & Tegner C. (2013). Magmatic emulsion texture formed by mixing during extrusion Raudafell composite complex Breiddalur volcano eastern Iceland. Bulletin of Volcanology 75 721. DOI: 10.1007/s00445-013-0721-6.
Chatterjee N. & Ghosh N.C. (2011). Extensive early neoproterozoic highgrade metamorphism in North Chotanagpur Gneissic Complex of the central Indian tectonic zone. Gondwana Research 20 362-379. DOI: 10.1016/j.gr.2010.12.003.
Clague D.A. Moore J.G. Dixon J.E. & Friesen W.B. (1995). Petrology of submarine lavas from Kilaueas Puna Ridge Hawaii. Journal of Petrology 36 299-349. DOI: 10.1093/petrology/36.2.299.
DePaolo D.J. (1981). Trace-element and isotopic effects of combined wallrock assimilation and fractional crystallization. Earth and Planetary Science Letters 53 189-202. DOI: 10.1016/0012-821X(81)90153-9.
Dowty E. (1980). Synneusis reconsidered. Contributions to Mineralogy and Petrology 74 75-84. DOI: 10.1007/BF00375491.
Eichelberger J.C. (1975). Origin of andesite and dacite; evidence of magma mixing at Glass Mountain in California and the other Circum-Pacific volcanoes. Geological Society of America Bulletin 86 1381-1391. DOI: 10.1130/0016-7606(1975)86<1381:OOAADE>2.0.CO;2.
Faure G. (1986). Principles of Isotope Geology. Chichester: J. Wiley & Sons.
Gogoi B. Saikia A. & Ahmad M. (2017). Titanite-centered ocellar texture: A petrological tool to unravel the mechanism enhancing magma mixing. Periodico di Mineralogia 86 245-273.
Gogoi B. Saikia A. & Ahmad M. (2018a) Field evidence mineral chemical and geochemical constraints on mafic-felsic magma interactions in a vertically zoned magma chamber from the Chotanagpur Granite Gneiss Complex of Eastern India. Chemie der Erde 78(1) 78-102. DOI: 10.1016/j.chemer.2017.11.003.
Gogoi B. Saikia A. Ahmad M. & Ahmad T. (2018b). Evaluation of magma mixing in the subvolcanic rocks of Ghansura Felsic Dome of Chotanagpur Granite Gneiss Complex eastern India. Mineralogy and Petrology 112 393-413. DOI: 10.1007/s00710-017-0540-0.
Gogoi B. & Saikia A. (2018). Role of viscous folding in magma mixing. Chemical Geology501 26-34. DOI: 10.1016/j.chemgeo.2018.09.035.
Grove T.L. Kinzler R.J. Baker M.B. Donelly-Nollan J.M. & Lesher C.E. (1988). Assimilation of granite by basaltic magma at Burnt Lava Flow Medicine Lake Volcano Northern California decoupling of heat and mass-transfer. Contributions to Mineralogy and Petrology 99 320-343.
Hawkesworth C.J. Blake S. Evans P. Hughes R. Macdonald R. Thomas L.E. Turner S.P. & Zellmer G. (2000). Time scales of crystal fractionation in magma chambers. Integrating physical isotopic and geochemical perspectives. Journal of Petrology 41 991-1006. DOI: 10.1093/petrology/41.7.991.
Hibbard M.J. (1991). Textural anatomy of twelve magma-mixed granitoid systems. In J. Didier & B. Barbarin (Eds.) Enclaves and granite petrology (pp. 431-444). Elsevier Amsterdam.
Hildreth W. & Wilson C.J.N. (2007). Compositional zoning of the Bishop Tuff. Journal of Petrology 48 951-999. DOI: 10.1093/petrology/egm007.
Hogan J.P. (1993). Monomineralic Glomerocrysts: Textural Evidence for Mineral Resorption During Crystallization of Igneous Rocks. The Journal of Geology 101 531-540.
Huppert H.E. Turner J.S. Stephen R. & Sparks J. (1982). Replenished magma chambers; effects of compositional zonation and input rates. Earth and Planetary Science Letters 57 345-357. DOI: 10.1016/0012-821X(82)90155-8.
Ikeda S. Toriumi M. Yoshida H. & Shimizu I. (2002). Experimental study of the textural development of igneous rocks in the late stage of crystallization: the importance of interfacial energies under non-equilibrium conditions. Contributions to Mineralogy and Petrology 142 397-415. DOI: 10.1007/s004100100300.
Jerram D.A. Cheadle M.J. & Philpotts A.R. (2003). Quantifying the Building Blocks of Igneous Rocks: Are Clustered Crystal Frameworks the Foundation? Journal of Petrology 44 2033-2051. DOI: 10.1093/petrology/egg069.
Koyaguchi T. (1986). Textural and compositional evidence for magma mixing and its mechanism Abu volcano group Southwestern Japan. Contributions to Mineralogy and Petrology 93 33-45. DOI: 10.1007/BF00963583.
Larsen E.S. Irving J. Gonyer F. & Larsen E.S.III. (1938). Petrologic results of study of the minerals from the Tertiary volcanic rocks of the San Juan region Colorado. American Mineralogist 23 227-257.
Luhr J.F. & Carmichael I.S.E. (1980). The Colima volcanic complex Mexico I. Post caldera andesites from Volcan Colima. Contributions to Mineralogy and Petrology 71 343-372. DOI: 10.1007/BF00374707.
Marsh B.D. (1998). On the interpretation of crystal size distributions in magmatic systems. Journal of Petrology 39 553-599. DOI: 10.1093/petroj/39.4.553.
Martin V.M. Holness M.B. & Pyle D.M. (2006). Textural analysis of magmatic enclaves from the Kameni Islands Santorini Greece. Journal of Volcanology and Geothermal Research 154 89-102. DOI: 10.1016/j.jvolgeores.2005.09.021.
Murata K. J. & Richter D. H. (1966). The settling of olivine in Kilauean magma as shown by lavas of the 1959 eruption. American Journal of Science 264 194-203. DOI: 10.2475/ajs.264.3.194.
Perugini D. Poli G. Christofides G. & Eleftheriadis G. (2003). Magma mixing in the Sithonia Plutonic Complex Greece: evidence from mafic microgranular enclaves. Mineralogy and Petrology 78(3-4) 173-200. DOI: 10.1007/s00710-002-0225-0.
Pietranik A. & Koepke J. (2009). Interactions between dioritic and granodioritic magmas in mingling zones: plagioclase record of mixing mingling and subsolidus interactions in the Gęsiniec Intrusion NE Bohemian Massif SW Poland. Contributions to Mineralogy and Petrology 158 17-36. DOI: 10.1007/s00410-008-0368-z.
Pouchou J.L. & Pichoir F. (1987). Basic expressions of PAP computation for quantitative EPMA. Proceedings of ICXOM 11 Ontario 249-253.
Renjith M.L. (2014). Micro-textures in plagioclase from 1994-1995 eruption Barren Island Volcano: Evidence of dynamic magma plumbing system in the Andaman subduction zone. Geoscience Frontiers 5 113-126. DOI: 10.1016/j.gsf.2013.03.006.
Renjith M.L. Charan S.N. Subbarao D.V. Babu E.V.S.S.K. & Rajashekhar V.B. (2014). Grain to outcropscale frozen moments of dynamic magma mixing in the syenite magma chamber Yelagiri Alkaline Complex South India. Geoscience Frontiers 5 801-820. DOI: 10.1016/j.gsf.2013.08.006.
Saikia A. Gogoi B. Ahmad M. & Ahmad T. (2014). Geochemical constraints on the evolution of mafic and felsic rocks in the Bathani volcano-sedimentary sequence of Chotanagpur Granite Gneiss Complex. Journal of Earth System Science 123(5) 959-987. DOI: 10.1007/s12040-014-0455-7.
Sakuyama M. (1981). Petrological study of the Myoko and Kurohime volcanoes Japan: Crystallization sequence and evidence for magma mixing. Journal of Petrology 22 553-583. DOI: 10.1093/petrology/22.4.553.
Schwindinger K.R. (1999). Particle dynamics and aggregation of crystals in a magma chamber with application to Kilauea Iki olivines. Journal of Volcanology and Geothermal Research 88 209-238. DOI: 10.1016/S0377-0273(99)00009-8.
Schwindinger K.R. & Anderson A.T. Jr. (1989). Synneusis of Kilauea Iki olivines. Contributions to Mineralogy and Petrology 103 187-198. DOI: 10.1007/BF00378504.
Singer B.S. Andersen N.L. Le Mével H. & others (2014). Dynamics of a large restless rhyolitic magma system at Laguna del Maule southern Andes Chile. GSA Today 24 4-10. DOI: 10.1130/GSATG216A.1.
Sosa-Ceballos G. Gardner J.E. Siebe C. & Macías J.L. (2012). A caldera-forming eruption 14100 14C yr BP at Popocatépetl volcano México: Insights from eruption dynamics and magma mixing. Journal of Volcanology and Geothermal Research 213-214 27-40. DOI: 10.1016/j.jvolgeores.2011.11.001.
Sparks R.S. Sigurdsson H. & Wilson L. (1977). Magma mixing: a mechanism for triggering acid explosive eruptions. Nature 267 315-317. DOI: 10.1038/267315a0.
Stull R.J. (1979). Mantled feldspars and synneusis. American Mineralogist 64 514-518.
Takahashi R. & Nakagawa M. (2012). Formation of a Compositionally Reverse Zoned Magma Chamber: Petrology of the AD 1640 and 1694 Eruptions of Hokkaido-Komagatake Volcano Japan. Journal of Petrology 54 815-838. DOI: 10.1093/petrology/egs087.
Vance J.A. (1969). On synneusis. Contributions to Mineralogy and Petrology 24 7-29. DOI: 10.1007/BF00398750.
Vernon R.H. Etheridge M.A. & Wall V.J. (1988). Shape and microstructure of microgranitoid enclaves: indicators of magma mingling and flow. Lithos 22 1-11.
Vogt J.H.L. (1921). The physical chemistry of the crystallization and magmatic differentiation of igneous rocks. Journal of Geology 28 318-350.