0 Russian Academy of Sciences Vinogradov Institute of Geochemistry Siberian Branch Russian Foundation of Basic Research Alkaline magmatism and the problems of mantle sources (Щелочной магматизм и проблемы мантийных источников ) PROCEEDING of International Workshop «Alkaline magmatism and the problems of mantle sources» Edited by Dr. N.V. Vladykin IRKUTSK 2001 1 The Organiziring Committee: academician: V.I. Kovalenko L.N. Kogarko N.L. Dobretsov F.A. Letnikov I.D. Rjabchikov Corresponding member: M.I. Kuzmin I.V. Gordienko Dr. N.V.Vladykin Editor – in-chief N.V. Vladykin 20-30 august 2001 Irkutsk Russia 2 TABLE OF CONTENTS 1. Kogarko L.N. Alkaline magmatism in the history of the Earth 5 2. Vladykin N.V. The Aldan Province of K-alkaline rocks and carbonatites: problems of magmatism, genesis and deep sources 17 3. Kryvdik S.G. Alkaline magmatism of the Ukrainian shield 42 4. Perepelov A.B., Volynets O.N., Anoshin G.N., Puzankov Yu.M., Antipin V.S., Kablukov A.V. Western Kamchatka alkali-potassic basaltoid volcanism: geological and geochemical review 53 5. Morikiyo T., Miyazaki T., Kagami H., Vladykin N. V., Chernysheva E. A., Panina L.I., Podgornych N. M. Sr, Nd, C and O isotope characteristics of Siberian carbonatites 71 6. Sharygin V.V. Lamproites: a review of magmatic inclusions in minerals 88 7. Mitchell R.H. The classification of melilitite clan 120 8. Mahotkin I.L., Podkuiko Yu.A., Zhuravlev D.Z. Early paleozoic kimberlite- melnoite magmatism of thePri-Polar Urals and the geodynamic formation model 157 9. Ashchepkov I.V., Vladykin N.V., Gerasimov P.A., Saprykin A.I., Khmelnikova O.S., Anoshin G.N. Petrology and mineralogy of disintegrated mantle inclusions of kimberlite- like diatrems from the Aldan shield (Chompolo field): mantle reconstructions 168 10. Nivin V.A., Ikorsky S.V., Kamensky I.L. Noble gas (He, Ar) isotope evidence for sources of devonian alkaline magmatism and ore formation related within the Kola province (NW Russia) 185 11. Miyazaki T., Kagami H., Mohan V.R., Shuto K., Morikiyo T. Evolution of South Indian enriched lithospheric mantle: evidence from the Yelagiri and evattur alkaline plutonsin Tamil Nadu, South India 197 12. Ashchepkov I.V., Travin S.V., Andre L., Khmelnikova O.S. Cenozoic flood basalt volcanism, mantle xenoliths and melting regions in the lithospheric mantle of the Baikal rift and other regions of Central Asia 213 13. Asavin A.M. Geochemistry of the rare lithophile elements, Zr, Hf, Nb, Ta, Th, U, and variations in their ratios during fractionation of alkali-basalt series in oceanic islands 225 14. Gornova M.A., Solovjeva L.V., Glazunov O.M., Belozerova O.Yu. Formation of Precambrian lithosphere mantle - geochemical analysis of coarse- grained peridotites from kimberlites, Siberian craton 233 15. Kuzmin M.I., Yarmolyuk V.V., Kovalenko V.I., Ivanov V.G. Evolution of the central asian "hot" field in the phanerozoic and some problems of plume tectonics 252 16. Viladkar S.G. Carbonatites of India: an overviev 267 3 Foreword Alkaline rocks are unique formation on the Earth. They have been of particular interest for researchers. Large Nb, Ta, Zr, Y, TR, Cu, P deposits, gem stones of charoite, Cr-diospide, dianite are associated with alkaline rocks. The Australian lamproites are connected with diamonds. The complicated processes of their formation provoked multi-year scientific disputes, which are still the case. The new methods of investigations provided much information on the composition of alkaline rocks. The data on geochemistry of isotopes confrim the mantle sources of the substance of alkaline rocks. The new stage of the plume tectonics deepened the interest of scientists to the alkaline rocks from the viewpoint of plate tectonics. The deep-seated Earth’s geodynamics can be interpreted using these data. The given proceeding contains the invited reports of the International Workshop “Alkaline magmatism and the problems of the mantle source”, held at the Institute of Geochemistry, SB RAS, Irkutsk city. The papers consider the features of the alkaline magmatism on the Earth’s history. A detailed characteristics of the alkaline magmtism of different provinces of the world (Aldan, Ukraine shields, eastern Kamchatka, Kola Peninsula, Ural, India) is given in this proceedings. The classification of mallite rocks and determination of PT- conditions of the crystallization of lamproites are provided using the data on the homogenization of melted inclusions. The papers consider the features of the genesis of kimberlites from the Urals and Siberia, alkaline basalts of the Baikal Rift and oceanic islands, Transbaikalia and Mongolia. The isotope characteristics of carbonatites of many Siberian massifs are presented. We hope that the similar meetings of scientists to discuss the genetic problems of the alkaline magmatism will be continued. The reports are translated into English by the authors. The Chairman of the Organizing Committee Dr. N. V. Vladykin 4 L. N. Kogarko Alkaline magmatism in the history of the Earth L. N. Kogarko Vernadskiy Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow INTRODUCTION The evolution of the Earth's magmatic regime is primarily controlled by processes of the global differentiation of the mantle, which is the largest shale of our planet. On the one hand, the postaccretionary history of the Earth was generally related to recurrent episodes of mantle melting, which produced the continental and the oceanic crust. In the course of this process, the mantle should have continuously lost the so-called "basaltic," lower melting components (such as CaO, Al 2O3, TiO 2 and rare lithophile elements) and become a strongly depleted source material, from which only highly mag-nesian melts depleted in rare elements could be derived later. However, no tendencies of this type occurred during the Earth's geologic evolution. To the contrary, more and more evidence suggests that primary mantle magmas (basalts and picrites) become progressively more enriched in Ti, LREEs, and incompatible elements with the passage of geologic time [Campbell and Griffiths, 1992]. Isotopic studies [Zindler and Hart, 1986] provide evidence for the existence of mantle reservoirs strongly enriched in trace elements; the occurrence of these reservoirs could not be explained within the guidelines of the model of continuous global mantle melting during the postaccretionary time. These facts and considerations caused the recent development of the idea of active crust-mantle interaction [Hoffmann, 1997], during which large-scale material exchange occurred and favorable conditions were created for the development of enriched reservoirs. The continental crust growth, which was definitely controlled by the intensity of partial melting in the mantle, principally decelerated in Late Archean time [Fyfe, 1978], and the volume of the crust even began to decrease, a fact suggesting that the planet entered a stationary state, in which the amount of material ascending from the mantle became equal to the amount of rocks returning to it. According to Hargraves (1976), numerous facts suggest that the material building up continents and delivered to the oceanic crust in the form of basalt magmas is counterbalanced by the consumption of the oceanic crust and its erosion products in sub-duction zones. One of the most important geochemical implications of this process is the origin of REE-enriched blocks in the mantle. Evidently, the development of alkaline magmatism during the Earth's history, a process associated with extremely high concentrations of trace elements, was related to the generation of such zones in the mantle. 5 L. N. Kogarko Synthesis of the extensive materials published earlier in the literature and our data [Wooley, 1987; Kogarko et al., 1995b; Kogarko, 1984] indicates that the first manifestations in the Earth's history of alkaline magmatism are dated at 2.5- 2.7 Ga. At present about 1500 alkaline and carbonatite intrusive and volcanic complexes are known, but no rocks older than 2700 Ma were detected (Fig. 1). The only exceptions are the syenite and alkali basalt lavas of Archean age from Kirkland, Canada [Basu et al., 1984]. However, these data call for further studies to be verified. Fig. 1. Distribution of alkaline massifs over geological time As can be seen in Fig. 1, the activity of alkaline magmatism increased continuously throughout the Earth's history. Moreover, according to Lazarenkov (1988), the thickness of the alkaline complexes also increased throughout geologic time. For example, the gross volume of young platophonolite in Kenya is more than 50000 km 3 [Logachev, 1977], i.e., much more than the integral thickness of alkaline rocks produced over other geologic epochs. The appearance of alkaline rocks at the Archean-Proterozoic boundary coincided with a number of global geologic events. This time boundary was very important in the history of the Earth: (1) Most scientists [Drummond and Defant, 1990] relate this boundary to a radical change in the geodynamic regime of our planet, when plume tectonics gave way to plate tectonics [Khain, 1994], although the role of mantle plumes remains very important up to the present. Nevertheless, many authors [Drummond, Defant, 1990; McCulluch, 1993] allow for subduction processes in the Archean, believing that the volumes of subducted material were then incomparably smaller than those sunk into the mantle over post-Archean time. 6 Alkaline magmatism and the problems of mantle sources (2) This time boundary marked the origin of the Earth's oxygen atmosphere [Walker, 1977; Holland, 1984], which was produced mainly by the activity of living beings and hydrogen dissipation to outer space. The precursory atmosphere consisted of a CH 4-H2 mixture [Rubey, 1955]. (3) The boundary between the Archean and Protero-zoic was the time of the most active continental crust growth. The effect of the oxygen-bearing atmosphere caused the origin of "oxidized" marine sediments such as jaspilite and carbonates and the oxidation of paleosoils [Holland, 1984; Cloud, 1968].