105 ISSN 0869-5911, Petrology, 2008, Vol. 16, No. 2, pp. 105–135. © Pleiades Publishing, Ltd., 2008. Original Russian Text © A.A. Nosova, O.F. Kuz’menkova, N.V. Veretennikov, L.G. Petrova, L.K. Levsky, 2008, published in Petrologiya, 2008, Vol. 16, No. 2, pp. 115–147. INTRODUCTION Recent studies revealed the isotopic and geochemi- cal heterogeneity of within-plate magmatism in the rift zones and flood basalt provinces (Xu et al., 2001; Peate and Hawkesworth, 1996; Turner et al., 1999; Hawkes- worth et al., 1996; George and Rogers, 2002, and oth- ers). Basaltic melts erupted in these areas demonstrated a considerable isotopic and geochemical diversity. Within the magmatic provinces, the spatiotemporal relationships between rocks with contrasting isotopic– geochemical characteristics are intricate. This is related with the involvement of various sources in the magma generation areas (lower mantle, asthenosphere, and lithosphere) and to the character of the melt-impreg- nated lithospheric mantle. The geochemical features of the lithospheric mantle (age and the degree and geochemical style of enrichment and/or depletion) are determined by its nature (ancient craton, mobile belt, and others). Rift belts that caused the breakup of supercontinents were preferably superimposed on weakened zones, mobile belts within the latter, but also spanned adjacent Neoproterozoic Volhynia–Brest Magmatic Province in the Western East European Craton: Within-Plate Magmatism in an Ancient Suture Zone A. A. Nosova a , O. F. Kuz’menkova b , N. V. Veretennikov b , L. G. Petrova c , and L. K. Levsky d a Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Staromonetnyi per. 35, Moscow, 119017 Russia e-mail: nosova@igem.ru b Institute of Geochemistry and Geophysics, Belarussian Academy of Sciences, ul. Kuprevicha 7, Minsk, 220141 Belarus c Geological Faculty, Moscow State University, Vorob’evy gory, Moscow, 119992 Russia d Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences, nab. Makarova 2, St. Petersburg, 199034 Russia Received October 6, 2006; in final form, January 30, 2007 Abstract—The reasons for the isotopic and geochemical heterogeneity of magmatism of the Neoproterozoic large Volhynia–Brest igneous province (VBP) are considered. The province was formed at 550 Ma in response to the break up of the Rodinia supercontinent and extends along the western margin of the East European craton, being discordant to the Paleoproterozoic mobile zone that separates Sarmatia and Fennoscandia and the Meso- proterozoic Volhynia–Orsha aulacogen. The basalts of VBP show prominent spatiotemporal geochemical zon- ing. Based on petrographic, mineralogical, geochemical, and isotopic data, the following types of basalts can be distinguished: olivine-normative subalkaline basalts consisting of low-Ti (sLT, < 1.10–2.0 wt % TiO 2 ; ε Nd (550) from –6.6 to –2.7) and medium-Ti (sMT, 2.0–3.0 wt % TiO 2 , occasionally up to 3.6 wt % TiO 2 ; ε Nd (550) from –3.55 to + 0.6) varieties; normal quartz–normative basalts (tholeiites) including low-Ti (tLT, < 1.75–2.0 wt % TiO 2 ) and medium-to-high-Ti (tHT1, 2.0–3.6 wt % TiO 2 , ε Nd (550) from –1.3 to + 1.0) varieties. The hypabyssal bodies are made up of subalkaline low-Ti olivine dolerites (LT, 1.2–1.5 wt % TiO 2 ; ε Nd (550) = –5.8) and subalkaline high-Ti olivine gabbrodolerites (HT2, 3.0–4.5 wt % TiO 2 ; ε Nd (550) = –2.5). Felsic rocks of VBP are classed as volcanic rocks of normal (andesidacites, dacites, and rhyodacites) and subalkaline (tra- chyrhyodacites) series with TiO 2 0.72–0.77 wt % and ε Nd (550) of –12. The central part of VBP is underlain by a Paleoproterozoic domain formed by continent–arc accretion and contains widespread sills of HT2 dolerites and lavas of LT basalts; the northern part of the province is underlain by the juvenile Paleoproterozoic crust dominated by MT and HT1 basalts. MT and LT basalts underwent significant AFC-style upper crustal contam- ination. During their long residence in the upper crustal magmatic chambers, the basaltic melts fractionated and caused notable heating of the wall rocks and, correspondingly, nonmodal melting of the upper crustal protolith containing high-Rb phase (biotite), thus producing the most felsic rocks of the province. The basalts of VBP were derived from geochemically different sources: probably, the lithosphere and a deep-seated plume (PREMA type). The HT2 dolerites were generated mainly from a lithospheric source: by 3–4% melting of the geochemically enriched garnet lherzolite mantle. LT dolerites were obtained by partial melting of the modally metasomatized mantle containing volatile-bearing phases. The concepts of VBP formation were summarized in the model of three-stage plume–lithosphere interaction. DOI: 10.1134/S086959110802001X