2011

Òåçèñû ìåæäóíàðîäíîé êîíôåðåíöèè

Ðóäíûé ïîòåíöèàë ùåëî÷íîãî, êèìáåðëèòîâîãî

 è êàðáîíàòèòîâîãî ìàãìàòèçìà

Abstracts of International conference

Ore potential of alkaline, kimberlite

and carbonatite magmatism

Some mineralogical and age-specific aspects of Volynian potentially diamond-bearing formations

Yatsenko G. M., Bekesha S. M., Yatsenko I. G., Buchkovska O.A.

Geology Department, Ivan Franko National University of Lviv, Lviv, Ukraine; Yatsenko1941@list.ru

Some mineralogical and age-specific aspects of diamond-bearing formations of north – western Ukraine, particularly in Kuhotsk-Serhiv field are given. It is noted that characterized minerals found in Vendian and Riphean deposits are connected with rocks and formations of lamproite group of explosive origin of earlier Mesozoic and Cenozoic age.

In geological aspect, the north-western territory of Ukraine is a continuation of slope of Ukrainian shield with complex faulting-block structure. As far as diamond tectonics is concerned this is a territory of Proterozoic proton and partially of tecton.

The sedimentary cover consists of 3 layers: 1) Riphean (Poliska series, consisting of red color siltstone, argillite and sandstone); 2) Vendian (Volynska series – terrigenous-trappean formations of lower Vendian and Mohyliv-Podilska series – volcanic-terrigene rocks of upper Vendian; 3) Meso-Cenozoic deposits.

The perspective for detection of diamond primary deposits of kimberlite and lamproite type is Kuhotsko-Serhivske field within the Volyn region. Explosive structures and breccias, displays of alkaline basic and alkaline ultrabasic magmatism are observe here. The most known in this area is Chartoriyska explosive pipe.

In mineralogical aspect the important role belongs to fragments of rocks of so-called eruptive breccias, represented in deposits of Poliska series of Riphean and Horbashivska suite of lower Vendian. There are fragments of rocks of the Proterozoic, Riphean, Vendian, Cambrian, Silurian and Devonian period (Vlasov, Volovnik, 1975).They comprise faunally distinguished carbonaceous rocks of the Silurian which testifies to breccias formation in the Postsilurian period. The fragments of rocks are represented by tuffs, basalt, diabase, sandstone of Poliska series, granitoids and gneiss of the crystalline basement, kimberlites are described. The eclogites, peridotites, potassium basalts, orthoclase lamprophyres are distinguished. The ortophyres, trachytes and lamprophyres which are subalkaline and alkaline high potassium rocks, containing the components of mantle origin, are detected in breccias. Among the minerals potassium feldspar, pyrope, picroilmenite, chromium spinellide and moissanite are registered.

In the far southern part of the Shield’s western slope Grushkinska suite of the  Mohyliv – Podilska series correlates with Horbashivska suite. It is represented by thin red colored coarse-grained rocks, containing fragments of granitoide and scarce components of abyssal origin. The coarse-grained rocks of Grushkinska and Horbashivska suites have close to arcosic composition, they are not metamorphized, contain minerals-satellites of diamond and sometimes small diamonds. Correlation of these suites formations and their reference to the Vendian were conducted earlier by lithologic-stratigraphical methods (Aseeva et al., 1985). However, foraminifers of the Upper Cretaceous were found in them later (Diamond-bearing …, 2002).

The substance of the above-mentioned formations generated with participation of explosive activity recurrently activating up to the Cenozoic period. Therefore mixing of uneven-aged materials can be regarded conceivable, as well as different composition and different minerogenic specialization, including diamonds.

The area Perekallya – Tyhovish is one of the greatest importance within the Kuhotsk-Serhiv field. There during verification of anomalies at depth from 60 to 334 m tuffs and tuffbreccias of different composition having thickness of 2 to 215 m were found (Tarasko, 2004). Chemical analyses of the breccias is very specific; as far as the composition is concerned they are of a category from ultrabasic to medium acid rocks with MgO content from 5 to 9% and sharp domination of K₂O over Na₂O (10-15 times). On the diagram SiO₂ – (K₂O+Na₂O) for potassium rocks the compositions of pointed breccias from 8 holes are shown as compared with some types of lamproites in different parts of the world. Approximately one half of the figurative points is found within the field of lamproite type rock, alkaline row, while the second one shifts into subalkaline area. It is necessary to note that some Australian lamproites due to high silicification have the same tendency though having higher alkaline content. On the diagram the subalkaline and basaltoids branching  diverge. This fact together with geological data can be the evidence of subsequent and independent building–up of subalkaline formations to which a special mineragenic specialization is correlated related (Kvasnitsa et.al, 2009).

Among the Volyn rock minerals pink and red garnet, ilmenite, zircon, chromium spinellide are detected. The latter is characterized by a steady content of Cr₂O₃ (37-41%) and Al₂O₃ (26-30%). The clay component of breccias contains montmorillonite, saponite, antigorite, the products of ultrabasic rock transformation. Composition of the primary rocks is also verified by mixed-layer kaolinite – montmorillonite – hydromical mineral formations.

In conclusion it is necessary to say that in the given area there is no convincing evidence of existence of the diamond sources belonging to the late Pre-Cambrian period. Most probably these minerals found in the Riphean and Vendian deposits are connected with rocks and lamproite group formations of explosive origin belonging to the younger Mesozoic and Cenozoic Age.

Position of Volyn breccias composition (Perekallya-Tyhovysh area) on diagram SiO₂ – (K₂O + Na₂O) for potassium rocks

1 – fields of Australia agpaitic lamproite series rocks. Ukrainian Shield. Fields: 2 – kimberlites of Kirovograd dyke field; 3 – leucite lamproites of Russkopolyansk field ; 4 – rovenskites of Rovno field; 5 – illincites of Ilyinets field. Circled numbers: 1 – kimberlites; 2 – carbonatized kimberlites; 3 – micaceous kimberlites; 4 – lamproites; 5 – rovenskites; 6 – illincites.

References:

Aseeva Å.À., Velikanov V. A., Vinogradov V.G. New data on stratigraphy of Vendian and lower Palaeozoic in Volyno-Podoliya. Kyiv: Preprint Institute of Geological Sciences AN USSR, 1985. 56 p (in Russian).

Diamond-bearing formations and structures of the East European platform south-west outskirts. Experience of diamond minerageny / Yatsenko G. M. Gurskiy D.S., Slivko E.M. and et al. Kiev: UkrGGRI, 2002. 331 p (in Russian).

Kvasnytsya ². V., Kosovskiy Y.V., Melnichuk V.G., Mateyuk V.V. Native gold of Western Volyn // Transactions of Ukrainian Mineralogical Society. 2009. Vol. 6. P. 92-99 (in Ukrainian).

Tarasko I.V. Structural - geological, mineralogical and petrochemical peculiarities of Kuhotsk-Serhiv area breccias // Problems of diamondiferous areas in the territory of Ukraine: Data of scientific-technical meeting “Condition, prospects and directions of diamond exploration in Ukraine”. Kyiv, 19-22 May 2003. Kyiv: UkrDGRI, 2004. P. 39-45 (in Russian).

Vlasov V., Volovnyk B. Y. New data on explosive volcanism in Volyn // Tectonics and Stratigraphy. 1975. ¹ 8. P. 43-46 (in Russian).