Dubyna O. Geochemistry alkaline rocks from the Ukrainian shield

In alkaline and subalkaline massifs of gabbro-syenitic complexes denote clearly the enrichment in iron (Fenner's) trend. It manifests by growing iron content and alkalinity in rocks and femic minerals from early to late rocks. The latest (residual) syenites are enriched (to ore concentrations) in incompatible elements (REE, Y, Nb, Ta, Zr, Hf) but are depleted in Sr and Ba. Theses rocks have deep negative Eu-anomalies. Such features of evolution of gabbro-syenitic complexes are confirmed by mechanism of crystallization differentiation with strong feldspar fractionation. In alkaline-ultramafic complexes, unlike to gabbro-syenitic ones, this trend is absent or slightly expressed. In these complexes incoherent and rare element distribution is more complicated. They concentrate mainly in carbonatites or apofenitic albitites. The negative Eu-anomalies in REE pattens is slightly manifested or absent for all types of these rocks. The distribution of trace elements in alkali silicate rocks and carbonatites from alkaline-ultramafic complexes is explained more satisfactory by liquation of primary melts into silicate (nephelinite, phonolite) and carbonatite components. Strongly enriched in Fe femic minerals and distribution of the incoherent (high Zr, Nb, REE, Y and low Sr and Ba) elements in differently aged alkaline granitoids of USh are similar to those of syenites from gabbro-syenitic complexes. Alkaline granites with deep negative Eu-anomalies (0,06) were formed at the latest stages of anorthosite rapakivigranite pluton evolution. They are geochemicaly similar to the rare-metal syenites. The grorudites of Azov region the Eu-anomalies are not so deep (0,46-0,77) that because of lower degree of differentiation. High concentration of both compatible and incompatible elements in grorudites indicates that these rocks are genetically related to subalkaline basaltic melts of this region. Different ways of crystallization and composition of primary melts are caused various ore mineralization. In gabbro-syenitic complexes rich rare-metal mineralization is formed only in the latest and residual syenitic rocks while high content of apatite and ilmenite are connected with early gabbroids and pyroxenites. At the same time the alkaline ultramafic complex rare-metal mineralization (together with apatites) is concentrated mainly in carbonatites.