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2007 Alkaline Magmatism and the Problems of Mantle Sources.Pdf 0 Alkaline magmatism, its sources and plumes Russian Academy of Sciences Siberrian Branch Vinogradov Institute of Geochemistry Dipartimento di Scienze Della Terra Università di Perugia, Italy Russian Foundation of Basic Research Alkaline magmatism, its sources and plumes ( Щелочной магматизм , его источники и плюмы ) PROCEEDING of VI International Workshop « Alkaline magmatism, its sources and plumes » Edited by Dr. N.V. Vladykin IRKUTSK NAPOLI 2007 1 UDK 552.33+552.32 Alkaline magmatism, its cources and plume Proceedings of the VII International Conference. Naples. Italy. Publishing House of the Institute of Geography SB RAS, 2007, 192 p., ISBN 978-594797-128-6. Vol.1. This book offers invited papers of the international workshop organized in Irkutsk and Naples. Alkaline rocks represent unique formations on the Earth. They are associated with large Nb, Ta, Zr, Y, TR, Cu and P deposits, gemstones of charoite, Cr-diopside, dianite. In Australia diamonds are recovered in lamproites. The complicated processes of their formation provoked scientific disputes still going on. The newly developed analytical methods and techniques provided abundant information on the composition of alkaline rocks. The data on geochemistry of isotopes confirm the evidence on the mantle - -ources of the substance of alkaline rocks. Features of mineral parageneses and origin of mantle rocks can help in interpreting the deep-seated geodynamics of the Earth. These papers view the features of alkaline, carbonatite and kimberlite magmatism. They also disclose the influence of the fluid on the thermal regime of mantle plumes. They discuss thermodynamic analysis of magnetite+titanite+ clinopyroxene equilibria in apatite-bearing intrusion of the Khibina alkaline complex, geochemistry of the dyke alkaline complex of the Kola Peninsula. They show geologic and petrologic characteristics of alkaline rocks of Italy. As to the kimberlites are concerned the papers consider variations of picroilmenite composition from many kimberlite pipes of Siberia; discuss the behavior of some minerals-indicators in kimberlites, mantle xenoliths from Nyurba pipe. The melted inclusions in olivines demonstrate mineral called rhönite and some papers give thermodynamic parameters of renite formation. The articles give grounds for distinguishing formation types of lamproites and give types of their mantle sources. ASM diagrams are suggested to be used for genetic analysis of magmatic rock series. The book might present interest to specialists involved in petrological and geochemical investigations as well as those studying deep alkaline and kimberlite magmatism, students and teaching staff of universities. Published following the decision of the Scientific Council of Vinogradov Institute of Geochemistry SB RAS Chief Editor: Prof. N.V. Vladykin Reviewers: Prof. O.M. Glazunov and Prof. V.S. Antipin Original-maket: S.S. Tsypukova, T.S. Torbeeva Consultant: Dr. Perepelov A.B. Institute of Geography SB RAS 664033, Irkutsk, Ulanbatorskaya str. 1 Published in Glazkovskaya printing House Irkutsk, Gogol str., 53. Order № 2792. Edition 100 copies. ISBN 5-94797-095-3 © Institute of Geochemistry SB RAS, 2007 © Irkutsk Geography SB RAS 2 Alkaline magmatism, its sources and plumes TABLE OF CONTENTS Foreword 4 1. Ryabchikov I.D., Kogarko L.N. Thermodynamic analysis of magnetite + titanite + clinopyroxene equilibria in apatite-bearing 5 intrusion of the Khibina alkaline complex 2. Vladykin N.V. Formation types of lamproite complex – systematics 20 and chemistry 3. Downes H., Mahotkin I.L., Beard A.D., Hegner E. Petrogenesis of alkali silicate, carbonatitic and kimberlitic magmas of the Kola Alkaline 45 Carbonatite Province 4. Peccerillo A. Mantle plume vs. subduction-related origin of volcanism 57 in Italy: A commentary 5. Ashchepkov I.V., Vladykin N.V., Pokhilenko N.P., Logvinova A.M., Palessky V.S., Afanasiev V.P., Alymova N.V., Stegnitsky 71 Yu.B., Khmel’nikova O.S., Rotman A.Y. Variations of ilmenite compositions from Yakutian Kimberlites and the problem of their origin 6. Spetsius Z.V. The nature of indicator minerals in kimberlites: a case 90 from the mantle xenoliths studying 7. Stoppa F. CO magmatism in Italy: from deep carbon to carbonatite 2 109 volcanism 8. Sand K.K., Nielsen T.F.D., Secher K. and Steenfelt A. Kimberlite and carbonatite exploration in southern West Greenland; Summary of 127 previous activities and recent work by the kimberlite research group at the Geological Survey of Denmark and Greenland 9. Sablukov S.M., Sablukova L.I., Stegnitsky Yu.B., Banzeruk V.I. Lithospheric mantle characteristics of the Nakyn field in Yakutia from 140 datas on mantle xenoliths and basalts in the Nyurbinskaya pipe 10. Sharygin V.V., Szabó C., Kóthay K., Timina T.Ju., Pet ı M., Török K., Vapnik Y., Kuzmin D.V. Rhönite in silica-undersaturated 157 alkali basalts: inferences on silicate melt inclusions in olivine phenocrysts. 11. Anfilogov V.N. The hardenessing of the ASM diagram for genetic 183 analyses of the magmatic rock series 3 FOREWORD The fact is well accepted that alkaline rocks represent unique formations on the Earth. They have been long attractive for research because large Nb, Ta, Zr, Y, TR, Cu and P deposits, gemstones of charoite, Cr-diopside, dianite are associated with them. For instance, in Australia diamonds are recovered in lamproites. The complicated processes of their formation provoked scientific disputes still going on. The newly developed analytical methods and techniques provided abundant information on the composition of alkaline rocks. The data on geochemistry of isotopes confirm the evidence on the mantle sources of the substance of alkaline rocks. The new concepts of plume tectonics are applied by scientists when studying alkaline rocks as the deep-seated geodynamics of the Earth is interpreted based on these data. These problems were discussed at the international workshops held in 2001 at the Institute of Geochemistry in Irkutsk; in 2002 at the Far-East Geological Institute, Vladivostok; in 2003 at the Institute of Tectonics and Geophysics in Khabarovsk, in 2004 at Geological Institute in Ulan-Ude, in 2005 at the Institute of Volcanology and Seismology in Petropavlovsk-Kamchatski and 2006 at TsNIGRI of the Stock Company “ALROSA” (Mirnyi). This book offers invited papers of the international workshop organized in Irkutsk and Naples under the title “Alkaline magmatism, its sources and plumes”. These papers view the features of alkaline, carbonatite and kimberlite magmatism. They also disclose the influence of the fluid on the thermal regime of mantle plumes. They discuss thermodynamic analysis of magnetite+titanite+ clinopyroxene equilibria in apatite-bearing intrusion of the Khibina alkaline complex, geochemistry of the dyke alkaline complex of the Kola Peninsula. They show geologic and petrologic characteristics of alkaline rocks of Italy. As to the kimberlites are concerned the papers consider variations of picroilmenite composition from many kimberlite pipes of Siberia; discuss the behavior of some minerals-indicators in kimberlites, mantle xenoliths from Nyurba pipe. The melted inclusions in olivines demonstrate mineral called rhönite and some papers give thermodynamic parameters of renite formation. The articles give grounds for distinguishing formation types of lamproites and give types of their mantle sources. ASM diagrams are suggested to be used for genetic analysis of magmatic rock series. The book might present interest to specialists involved in petrological and geochemical investigations as well as those studying deep alkaline and kimberlite magmatism. Chairman of Organizing Committee, Chief Editor Dr. N.V. Vladykin 4 Alkaline magmatism, its sources and plumes UDK 550,42+552 Thermodynamic analysis of magnetite + titanite + clinopyroxene equilibria in apatite-bearing intrusion of the Khibina alkaline complex Ryabchikov I.D. 1, Kogarko L.N. 2 1Institute for Geology of Ore Deposits, Russian Academy of Sciences, Moscow, Russia. 2Vernadsky Institute of Geochemistry, Russian Academy of Sciences, Moscow, Russia. ABSTRACT Most titanomagnetite in the Khibina alkaline igneous complex, sampled through 500 m of a vertical cross-section, is represented by Ti-rich varieties. The ulvöspinel component is most commonly around 55 mol %, rarely reaching up to 80 mol %. We calculated an fO2 -T diagram for magnetite + ilmenite + titanite + clinopyroxene + nepheline + alkali feldspar and magnetite + titanite + clinopyroxene + nepheline + alkali feldspar phase assemblages at a hedenbergite activity of 0.2. The diagram shows that magnetites with 55 mol % of ulvöspinel crystallized at oxygen fugacities just slightly below the quartz-fayalite-magnetite buffer. More Ti-rich varieties crystallized at higher temperatures and slightly lower QMF values, whereas more Ti-poor magnetites crystallized at or below about 650 oC. Under the redox conditions estimated for the apatite-bearing intrusion of the Khibina complex (close to the QFM buffer), substantial quantities of methane may only form during cooling below 400 oC in equilibrium with magma. However, even at higher orthomagmatic temperatures and redox conditions corresponding to ∆QMF=0, the hydrogen content in the early magmatic stage is not negligible. This hydrogen present in the gas phase at magmatic temperatures may migrate to colder parts of a solidifying magma chamber and trigger Fischer-Tropsch-type reactions there. We propose therefore, that methane in peralkaline systems may form in three distinct stages: orthomagmatic and
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