ERCAN ALDANMAZ

168

Mineral-Chemical Constraints on the Miocene Calc-alkaline and Shoshonitic Volcanic Rocks of Western Turkey: Disequilibrium Phenocryst Assemblages as Indicators of Magma Storage and Mixing Conditions

Early to Middle Miocene (22 to 15 Ma) volcanic activity across western Turkey produced a series of lavas and pyroclastic deposits with calc-alkaline and shoshonitic affinities. The erupted magmas show a broad range of compositions from basaltic to rhyolitic (48-75 SiO2 wt%) and are composed of variable phenocryst assemblages. Petrographic and mineral-chemical characteristics suggest that the magmas underwent hydrous crystallization in deep crustal magma chambers that was dominated by plagioclase + pyroxene + pargasitic amphibole fractionation. Subsequent crystallization in shallower magma chambers followed two different trends: (1) anhydrous (pyroxene + plagioclase-dominated); and (2) hydrous (plagioclase + edenitic amphibole + pyroxene-dominated). Application of magnetite-ilmenite, hornblende-plagioclase and two-pyroxene geothermometry to the western Anatolian volcanic rocks has yielded temperature estimates in the range of 585-1086 ºC for the Early Miocene and 768-1095 ºC for the Middle Miocene rocks. Pressure estimates from pyroxene and Al-in-hornblende geobarometers are in the range of 2.1-8.6 kbar for the Early Miocene and 6.5-9.1 kbar for the Middle Miocene rocks. The presence of amphibole with clear signs of disequilibrium, and plagioclase as inclusions in pyroxenes and other phenocryst cores, suggest that magma mixing was operational during the formation of the volcanic suites. Strong compositional variations and reverse zoning patterns in single phenocrysts, as well as considerably variable pressures of crystallization, further indicate that the magmas forming the volcanic suite had a polybaric origin and are the composite products of more than one petrogenetic stage. The observed range of phenocryst assemblages and different compositional trends are likely to have originated from fractionation of magmas with different initial water contents, under variable pressures of crystallization. The repeated occurrence of magmas from different suites during a single period of activity suggests that the magmatic system comprised several conduit systems and magma reservoirs dispersed at different levels of crustal magma chambers. The results suggest that the episodic intrusion of mafic magmas provided the necessary heat and perhaps contributed to the ascent of the magma to shallow crustal depths where it reequilibrated before the onset of eruption.
Anahtar Kelimeler:

western Anatolia, magma evolution, magma mixing, compositional zoning, disequilibrium parameters, crustal magma chambers

Mineral-Chemical Constraints on the Miocene Calc-alkaline and Shoshonitic Volcanic Rocks of Western Turkey: Disequilibrium Phenocryst Assemblages as Indicators of Magma Storage and Mixing Conditions

Early to Middle Miocene (22 to 15 Ma) volcanic activity across western Turkey produced a series of lavas and pyroclastic deposits with calc-alkaline and shoshonitic affinities. The erupted magmas show a broad range of compositions from basaltic to rhyolitic (48-75 SiO2 wt%) and are composed of variable phenocryst assemblages. Petrographic and mineral-chemical characteristics suggest that the magmas underwent hydrous crystallization in deep crustal magma chambers that was dominated by plagioclase + pyroxene + pargasitic amphibole fractionation. Subsequent crystallization in shallower magma chambers followed two different trends: (1) anhydrous (pyroxene + plagioclase-dominated); and (2) hydrous (plagioclase + edenitic amphibole + pyroxene-dominated). Application of magnetite-ilmenite, hornblende-plagioclase and two-pyroxene geothermometry to the western Anatolian volcanic rocks has yielded temperature estimates in the range of 585-1086 ºC for the Early Miocene and 768-1095 ºC for the Middle Miocene rocks. Pressure estimates from pyroxene and Al-in-hornblende geobarometers are in the range of 2.1-8.6 kbar for the Early Miocene and 6.5-9.1 kbar for the Middle Miocene rocks. The presence of amphibole with clear signs of disequilibrium, and plagioclase as inclusions in pyroxenes and other phenocryst cores, suggest that magma mixing was operational during the formation of the volcanic suites. Strong compositional variations and reverse zoning patterns in single phenocrysts, as well as considerably variable pressures of crystallization, further indicate that the magmas forming the volcanic suite had a polybaric origin and are the composite products of more than one petrogenetic stage. The observed range of phenocryst assemblages and different compositional trends are likely to have originated from fractionation of magmas with different initial water contents, under variable pressures of crystallization. The repeated occurrence of magmas from different suites during a single period of activity suggests that the magmatic system comprised several conduit systems and magma reservoirs dispersed at different levels of crustal magma chambers. The results suggest that the episodic intrusion of mafic magmas provided the necessary heat and perhaps contributed to the ascent of the magma to shallow crustal depths where it reequilibrated before the onset of eruption.
Keywords:

western Anatolia, magma evolution, magma mixing, compositional zoning, disequilibrium parameters, crustal magma chambers,

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  • ALDANMAZ, E., P
  • , J.A., THIRLWALL, M.F. & MITCHELL, J.G. 2000.
  • Petrogenetic evolution of Late Cenozoic, post-collision volcanism
  • in western Anatolia, Turkey. Journal of Volcanology and
  • Geothermal Research 102, 67–95.
  • ALDANMAZ, E. 2002. Mantle source characteristics of alkali basalts and basanites in an extensional intracontinental plate setting, western Anatolia, Turkey: implication for multi-stage melting. International Geology Review 44, 440–457.
  • ALDANMAZ, E., GOURGAUD, A. & KAYMAKÇı, N. 2005. Constraints on the composition and thermal structure of the upper mantle beneath NW Turkey: evidence from mantle xenoliths and alkali primary melts. Journal of Geodynamics 39, 277–316.
  • ALDANMAZ, E, KÖPRÜBAşı, N., GÜRER, Ö.F., KAYMAKÇı, N. & GOURGAUD, A. 2006. Geochemical constraints on the Cenozoic, OIB-type alkaline volcanic rocks of NW Turkey: implications for mantle sources and melting processes. Lithos 86, 50–76.
  • ALLEN, S.R. & CAS, R.A.F. 1998. Rhyolitic fallout and pyroclastic density current deposits from a phreatoplinian eruption in the eastern Aegean Sea. Journal of Volcanology and Geothermal Research 86, 219–251.
  • ANDERSEN, D.J. & LINDSLEY, D.H. 1988. Internally consistent solution models for Fe-Mg-Mn-Ti oxides: Fe-Ti oxides. American Mineralogist 73, 714–726.
  • ANDERSEN, D.J., LINDSLEY, D.H. & DAVIDSON, P.M. 1993. QUILF: a Pascal program to assess equilibria among Fe-Mg-Mn-Ti oxides, pyroxenes, olivine and quartz. Computers and Geosciences 19, 1333–1350.
  • BACON, C.R. & HIRSCHMANN, M.M. 1988. Mg/Mn partitioning as a test for equilibrium between coexisting Fe-Ti oxides. American Mineralogist 73, 57–61.
  • BAKER, D.R. & EGGLER, D.H. 1987. Compositions of anhydrous and hydrous melts coexisting with plagioclase, augite, and olivine or low-Ca pyroxene from 1 atm to 8 kbar: application to the Aleutian volcanic center of Atka. American Mineralogist 72, 12–28.
  • BARCLAY, J. & CARMICHAEL, I.S.E. 2004. A hornblende basalt from western Mexico: water-saturated phase relations constrain a pressure-temperature window of eruptibility. Journal of Petrology 45, 485–506.
  • BERMAN, R.G. 1988. Internally-consistent themodynamic data for minerals in the system Na2O-K2O-CaO-MgO-FeO-Fe2O3-Al2O3- SiO2-TiO2-H2O-CO2. Journal of Petrology 29, 445–522.
  • BORSI, S., FERRARA, G., INNOCENTI, F. & MAZUOLI, R. 1972. Geochronology and petrology of recent volcanics in the eastern Aegean Sea. Bulletin Volcanologique 36, 473–96.
  • BOWER, S.M. & WOODS, A.W. 1997. Control of magma volatile content and chamber depth on the mass erupted during explosive volcanic eruptions. Journal of Geophysical Research 102, 10273–10290.
  • BOZKURT, E. 2001. Neotectonics of Turkey – a synthesis. Geodinamica Acta 14, 3–30.
  • BOZKURT, E. & MITTWEDE, S.K. 2005. Introduction: evolution of continental extensional tectonics of western Turkey. Geodinamica Acta 18, 153–165.
  • COUCH, S., SPARKS, R.S.J. & CARROLL, M.R. 2001. Mineral disequilibrium in lavas explained by convective self-mixing in open magma chambers. Nature 411, 1037–1039.
  • DAVIDSON, J.P., TEPLEY, F.J. & KNESEL, K.M. 1998. Crystal isotope stratigraphy: a method for constraining magma differentiation pathways. EOS 79, 185–189.
  • DEWEY, J.F., HEMPTON, M.R., KIDD, W.S.F., ŞARO⁄LU, F. & ŞENGÖR, A.M.C. 1986. Shortening of continental lithosphere: the neo-tectonics of eastern Anatolia – a young collision zone. In: COWARD, M.P. & RIES, A.C. (eds), Collision Tectonics. Geological Society, London, Special Publications 19, 3–36.
  • DUNGAN, M.A. & RHODES, J.M. 1978. Residual glasses and melt inclusions in basalts from DSDP Legs 45 and 46: evidence for magma mixing. Contributions to Mineralogy and Petrology 67, 417–431.
  • ERCAN, T., SATıR, M., KREUZER, H., TÜRKECAN, A., GÜNAY, E., ÇEVİKBAş, A., ATEş, M. & CAN, B. 1984. Batı Anadolu Senozoyik volkanitlerine ait yeni kimyasal, izotopik ve radyometrik verilerin yorumu [Interpretation of new chemical, isotopic and radiometric data on Cenozoic volcanics of western Anatolia]. Geological Society of Turkey Bulletin 28, 121–136 [in Turkish, with English abstract].
  • ERCAN, T., SATıR, M., STEINITZ, G., DORA, A., SARıFAKıO⁄LU, E., ADIS, C., WALTER, H.J. & YıLDıRıM, T. 1995. Biga Yarımadası ile Gökçeada, Bozcaada ve Tavşan adalarındaki (KB Anadolu) Tersiyer volkanizmasının özellikleri [Characteristics of the Tertiary volcanism of the Biga Peninsula, Gökçeada, Bozcaada and Tavşanadası, western Anatolia]. Mineral Research and Exploration Institute of Turkey (MTA) Bulletin 117, 55–86 [in Turkish, with English abstract].
  • ERKÜL, F., HELVACı, C. & SÖZBİLİR, H. 2005. Stratigraphy and geochronology of the Early Miocene volcanic units in the Bigadiç borate basin, western Turkey. Turkish Journal of Earth Sciences 14, 227–253.
  • FODEN, J.D. & GREEN, D.H. 1992. Possible role of amphibole in the origin of andesite: some experimental and natural evidence. Contributions to Mineralogy and Petrology 109, 479–493.
  • GAMBLE, R.P. & TAYLOR, L.A. 1980. Crystal/liquid partitioning augite: effects of cooling rate. Earth and Planetary Science Letters 47, 21–33.
  • GAETANI, G.A., GROVE, T.L. & BRYAN, W.B. 1993. The influence of water on the petrogenesis of subduction-related igneous rocks. Nature 365, 332–334.
  • GILL, J.B. 1981. Orogenic Andesites and Plate Tectonics. Springer, Berlin.
  • GINIBRE, C., WORNER, G. & KRONZ, A. 2002. Minor- and trace-element zoning in plagioclase: implications for magma chamber processes at Parinacota volcano, northern Chile. Contributions to Mineralogy and Petrology 143, 300–315.
  • GREEN, T.H. 1982. Anatexis of mafic crust and high pressure crystallisation of andesite. In: THORPE, R.S. (ed), Orogenic Andesites. Wiley, Chichester, U.K., 465–487.
  • GRUNDER, A.L. & MAHOOD, G.A. 1988. Physical and chemical models of zoned silicic magmas: the Loma Seca Tuff and Calabozos Caldera, South Andes. Journal of Petrology 29, 831–867.
  • GÜLEÇ, N. 1991. Crust–mantle interaction in western Turkey:
  • implications from Sr and Nd isotope geochemistry of Tertiary and Quaternary volcanics. Geological Magazine 128, 417–435.
  • HAWTHORNE, F.C. 1981. Crystal chemistry of amphiboles, In: VEBLEN, D.R. (ed), Amphiboles and Other Hydrous Pyroboles-Mineralogy. Chelsea, Michigan, USA, 1–95.
  • HELZ, R.T. 1973. Phase relations of basalts in their melting ranges at pH2O = 5 kb as a function of oxygen fugacity, Part I. Mafic phases. Journal of Petrology 14, 249–302.
  • HEUBNER, J.S. & SATO, M. 1970. The oxygen fugacity-temperature relationships of manganese oxides and nickel oxide buffers. American Mineralogist 55, 934–952.
  • HIBBARD, M.J. 1981. The magma mixing origin of mantled feldspars. Contributions to Mineralogy and Petrology 76, 158–170.
  • HILDRETH, W. & MOORBART, S. 1988. Crustal contributions to arc magmatism in the Andes of southern Chile. Contributions to Mineralogy and Petrology 98, 455–489.
  • HOLLAND, T.J.B. & BLUNDY, J. 1994. Non-ideal interactions in calcic amphiboles and their bearing on amphibole-plagioclase thermometry. Contributions to Mineralogy and Petrology 116, 433–447.
  • HORT, M. 1998. Abrupt change in magma liquidus temperature because of volatile loss or magma mixing; effects on nucleation, crystal growth and thermal history of the magma. Journal of Petrology 39, 1063–1076.
  • HOUSH, T.B. & LUHR, J.F. 1991. Plagioclase-melt equilibria in hydrous systems. American Mineralogist 76, 477–492.
  • IRVINE, T.N. & BARAGAR, W.R.A. 1971. A guide to the chemical classification of the common volcanic rocks. Canadian Journal of Earth Sciences 8, 523–448.
  • KELLER, J. 1983. Potassic volcanism in the Mediterranean area. Journal of Volcanology and Geothermal Research 18, 321–325.
  • KONTAK, D.J., CLARK, A.H. & PEARCE, T.H. 1984. Recognition of simple and complex zoning in olivine and orthopyroxene phenocrysts using laser interference microscopy. Mineralogical Magazine 48, 547–550.
  • KÖPRÜBAşı, N. & ALDANMAZ, E. 2004. Geochemical constraints on the petrogenesis of Cenozoic I-type granitoids in Northwest Anatolia, Turkey: evidence for magma generation by lithospheric delamination in a post-collisional setting. International Geology Review 46, 705–729.
  • LEAKE, B.E., WOOLLEY, A.R., ARPS, C.E.S., BIRCH, W.D., GILBERT, M.C., GRICE, J.D., HAWTHORNE, F.C., KATO, A., KISCH, H.J., KRIVOVICHEV, V.G., LINTHOUT, K., LAIRD, J., MANDARINO, J.A., MARESCH, W.V., NICKEL, E.H., ROCK, N.M.S., SCHUMACHER, J.C., SMITH, D.C., STEPHENSON, N.C.N., UNGARETTI, L., WHITTAKER, E.J.W. & GUO, Y.Z. 1997. Nomenclature of amphiboles: report of the subcommittee on amphiboles of the International Mineralogical Association, commission on new minerals and mineral names. American Mineralogist 82, 1019–1037.
  • LEBAS, M.J., LEMAITRE, R.W., STRECKEISEN, A. & ZANETTIN, B. 1986. A chemical classification of volcanic rocks based on the total alkali- silica diagram. Journal of Petrology 27, 445–450.
  • LEPAGE, L.D. 2003. ILMAT: an Excel worksheet for ilmenite-magnetite geothermometry and geobarometry. Computers and Geosciences 29, 673–678.
  • LINDSLEY, D.H. 1983. Pyroxene thermometry. American Mineralogist 68, 477–493.
  • LINDSLEY, D.H. & ANDERSEN, D.J. 1983. A two pyroxene thermometer: Proceedings of the Thirteenth Lunar and Planetary Science Conference, Part 2. Journal of Geophysical Research 88, Supplement, A887–906.
  • LUHR, J.F. & CARMICHAEL, I.S.E. 1980. The colima volcanic complex, Mexico. I. Post-caldera andesites from Volcan Colima. Contributions to Mineralogy Petrology 71, 343–372.
  • MORIMOTO, N. 1989. Nomenclature of pyroxenes. Canadian Mineralogist 27, 143–156.
  • MORRICE, M.G. & GILL, J.B. 1986. Spatial patterns in the mineralogy of island arc magma series: Sangihe Arc. Indonesia. Journal of Volcanology and Geothermal Research 29, 311–353.
  • MYERS, J. & EUGSTER, H.P. 1983. The system Fe-Si-O: oxygen buffer calibrations to 1,500K. Contributions to Mineralogy and Petrology 82, 75–90.
  • NANEY, M.T. 1983. Phase equilibria of rock-forming ferromagnesian silicates in granitic systems. American Journal of Science 283, 993–1033.
  • NELSON, S.T. & MONTANA, A. 1992. Sieve-textured plagioclase in volcanic rocks produced by rapid decompression. American Mineralogist 77, 1242–1249. NIXON, G.T. & P
  • , T.H. 1987. Laser-interferometry of oscillatory
  • zoning in plagioclase: the record of magma mixing and phenocryst
  • recycling in calc-alkaline magma chambers, Iztaccihuat Volcano,
  • Mexico. American Mineralogist 72, 1144–1162.
  • PANJASAWATWONG, Y., DANYUSHEVSKY, L.V., CRAWFORD, A.J. & HARRIS, K.L. 1995. An experimental study of the effects of melt composition on plagioclase–melt equilibria at 5 and 10 kbar: implications for the origin of magmatic high-An plagioclase. Contributions to Mineralogy and Petrology 118, 420–432.
  • PUTIRKA, K.D., MIKAELIAN, H., RYERSON, F. & SHAW, H. 2003. New clinopyroxene-liquid thermobarometers for mafic, evolved, and volatile-bearing lava compositions, with applications to lavas from Tibet and the Snake River Plain, Idaho. American Mineralogist 88, 1542–1554.
  • ROBERT, U., FODEN, J. & VARNE, R. 1992. The Dodecanese Province, SE Aegean: a model for tectonic control on potassic magmatism. Lithos 28, 241–260.
  • ROEDER, P.L. & EMSLIE, R.F. 1970. Olivine-liquid equilibrium. Contributions to Mineralogy and Petrology 29, 275–289.
  • RUTHERFORD, M.J., DEVINE, J.D. & BARCLAY, J. 1998. Changing magma conditions and ascent rates during the Soufriere. Hills eruption on Montserrat. GSA Today 8, 1–7.
  • SCHMIDT, W.S. 1992. Amphibole composition in tonalite as a function of pressure: an experimental calibration of the Al-in hornblende barometer. Contributions to Mineralogy and Petrology 110, 304–310.
  • ŞENGÖR, A.M.C. & YıLMAZ, Y. 1981. Tethyan evolution of Turkey: a plate tectonic approach. Tectonophysics 75, 181–241.
  • SEYİTO⁄LU, G., ANDERSON, D., NOWELL, G. & SCOTT, B. 1997. The evolution from Miocene potassic to Quaternary sodic magmatism in western Turkey: implications for enrichment processes in the lithospheric mantle. Journal of Volcanology and Geothermal Research 76, 127–147.
  • SISSON, T.W. & GROVE, T.L. 1993. Experimental investigations of the role of H2O in calc-alkaline differentiation and subduction zone magmatism. Contributions to Mineralogy and Petrology 113, 143–166.
  • SPARKS, R.S.J., BARCLAY, J., JAUPART, C., MADER, H.M. & PHILLIPS, J.C. 1994. Physical aspects of magmatic degassing I. Experimental and theoretical constraints on vesiculation. In: CARROLL, M.R. & HOLLOWAY, J.R. (eds), Volatiles in Magmas. Mineralogical Society of America, Reviews in Mineralogy 30, 413–443.
  • TEPLEY, F.J., DAVIDSON, J.P., TILLING, R.I. & Arth, J.G. 2000. Magma mixing, recharge and eruption histories recorded in plagioclase phenocrysts from El Chichón Volcano, Mexico. Contributions to Mineralogy and Petrology 41, 1397–1411.
  • TOKÇAER, M., AGOSTINI, S. & SAVAşÇıN, M.Y. 2005. Geotectonic setting and origin of the youngest Kula volcanics (western Anatolia), with a new emplacement model. Turkish Journal of Earth Sciences 14, 143–166.
  • TROLL, V.R. & SCHMINCKE, H.U. 2002. Magma mixing and crustal recycling recorded in ternary feldspar from compositionally zoned peralkaline ignimbrite ‘A’, Gran Canaria, Canary Islands. Journal of Petrology 43, 243–270.
  • TSUCHIYAMA, A. 1985. Dissolution kinetics of plagioclase in the melt system diopside-albite-anorthite, and origin of dusty plagioclase in andesites. Contributions to Mineralogy and Petrology 89, 1–16.
  • WYERS, G.P. & BARTON, M. 1987. Geochemistry of a transitional ne- trachybasalt – Q-trachyte lava series from Patmos (Dodecanese), Greece; further evidence for fractionation, mixing and assimilation. Contributions to Mineralogy and Petrology 97, 279–291.
  • YıLMAZ, Y., GENÇ, Ş.C., KARACıK, Z. & ALTUNKAYNAK, Ş. 2001. Two contrasting magmatic associations of NW Anatolia and their tectonic significance. Journal of Geodynamics 31, 243–271.
  • YÜCEL-ÖZTÜRK, Y., HELVACı, C. & SATıR, M. 2005. Genetic relations between skarn mineralization and petrogenesis of the Evciler Granitoid, Kazdağ, Çanakkale, Turkey and comparison with world skarn granitoids. Turkish Journal of Earth Sciences 14, 225–280.
Turkish Journal of Earth Sciences-Cover
  • ISSN: 1300-0985
  • Yayın Aralığı: Yılda 6 Sayı
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