V.O. Gatsenko, S.G. Kryvdik, S.V. Kushnir
M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the NAS of Ukraine
Language: Ukrainian
Geochemistry and ore formation 2019, 40: 40-47
https://doi.org/10.15407/gof.2019.40.040
The article represents results of the study of the ultramafic dyke composition. The chemical composition of the dyke was analyzed in the last century and it has attracted the attention of the reseachers by its high TiO2
content (over 9 wt. %). The dyke was observed in Andriivka open pit (the Azov area of the Ukrainian Shield, the Volnovakha region) were it cut granites of the Anadol Complex. The ultramafic dyke is made of a porphyry rock with a fine-grained full-crystalline groundmass and large phenocryst of Ca-rich pyroxene and abundant opaque minerals. The groundmass contains small microliths of Ca-rich pyroxene as well as titanite, Ti-magnetite, magnetite, albite and chlorite. Rare grains of accessory chevkinit-like mineral are also noticed. Pyroxenes composing phenocrysts and microliths have identical chemical composition Wo46-50En39-43Fs10-13, and characterized by high content of ТіО2 (up to 4.9 wt. %), Al2O3 (up to wt. 6.5 %), MgO (12.5-14.4 wt. %), Cr2O3 (up to 0.3 wt. %), low iron content (0.19-0.25). Zoning is absent. Titanite is one of the main minerals of titanium in the studied ultramafic dyke. It contain up to wt. 40 % of TiO2. Fe-Ti oxides are represented by Ti-magnetite (TiO2 11-21 wt. %) and magnetite. Ilmenite has not been found in the rock. An interesting feature of the Ti-magnetite in the studied rock dyke is the presence in the large exsolution structures of ulvospinel. High content of TiO2 and Al2O3 in Ca-rich pyroxene is indicative of igneous rocks of high alkalinity, but the studied dyke has almost a tholeiitic chemical composition (alkali content below 1 wt. %). The ultramafic dyke of the Andriivka open pit is significantly different in its composition from similar formations of the Pokrovo-Kyriyivo massif and of the Azov area.
Keywords: high titanium ultramafic dykes, ulvospinel, the Andriivka open pit, the Pokrovo-Kyriyivo massif, the Eastern Azov region.
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