Alkaline Rocks and Carbonatites of the World

Setup during HiTech AlkCarb: an online database of alkaline rock and carbonatite occurrences

Malotersyanskii

stripes

Occurrence number: 
171-00-009
Country: 
Ukraine
Location: 
Longitude: 35.65, Latitude: 48.33
Carbonatite: 
No

The Malotersyanskii intrusion of alkaline rocks is located on the northern slope of the Ukrainian shield adjacent to the Dnieper-Donetz basin (Timoshenko, 1975). Tectonically it is likely to be associated with the deep Orekhovo-Pavlograd fault. The massif is an assymetrical, sheared, laccolith-like intrusion which has a long axis of about 12 km and a width ranging from 2.5 to 4.5 km; the area is some 42 km2. Alkaline rocks are also encountered to the north of the massif along the Orekhovo-Pavlograd fault. Malotersyanskii is composed of subalkaline (titanaugite) gabbro and gabbro-diabase in the outer zone and alkaline syenites and foyaites in the central zone. Dyke analogues, including pegmatites, of the alkaline rocks are encountered. Enclosing granitoids in the outer contact zone are fenitized. Fenites and, more rarely, intrusive rocks of the massif include aegirine, albite, mica and carbonate as metasomatic phases. Accessory minerals occurring in the metasomatic rocks include zircon, pyrochlore-hatchettolite, bastna"site, orthite and thorite. In the opinion of Krivdik and Tkachuk (1990) the gabbroic rocks represent the earliest intrusive phase, while the alkali syenite-foyaite series of the complex was formed in the course of crystal differentiation of a single injection of magma, the composition of which was similar to that of the outer olivine-bearing alkaline syenites. Alkaline syenites and foyaites display features of cryptic layering: latent lamination has also been detected. The alkalinity and Fe:Mg values of rocks and dark coloured minerals increase from the outer contacts towards the centre of the massif. Pyroxene evolves from aegirine-bearing ferrosalite (10% acmite) to aegirine ferrosalite and aegirine-hedenbergite (48% acmite). Alkali feldspar shows an increase in orthoclase content (26 to 63%). Late veins of alkaline rocks include typical agpaitic minerals such as aenigmatite and astrophyllite. Like Oktyabr'skii (No. 13), the Malotersyanskii complex has an agpaitic trend of evolution from gabbro through alkaline syenites and foyaites to nepheline syenites of agpaitic composition.

Economic: 
Apatite and rare-earth mineralization, including pyrochlore, hatchetollite, bastna"site, orthite, thorite and zircon, are connected with albite metasomatites at the western, northern and southern margins of the complex. Nepheline syenites could be considered as potential raw materials for ceramics (Timoshenko, 1975).
Age: 
Amphiboles from nepheline syenites were dated at 1740 Ma by the K-Ar method.
References: 

KRIVDIK, S.G. and TKACHUK, V.I. 1986. Formational classification of the alkaline rocks of the Ukrainian shield. Tezisy Dokladov VII Vesesoyuznogo Petrograficheskogo Obshchestva. Novosibirsk, 85-7.
*KRIVDIK, S.G. and TKACHUK, V.I. 1989. Eudialyte-bearing agpaitic phonolites and dike nepheline syenites in the October intrusion, Ukrainian shield. Geochemistry International, 26(3): 54-60.
TIMOSHENKO, O.D. 1975. Geology, composition and perspectives of ore-formation of the Malotersyan alkaline massif (central Azov region). Thesis abstract, Kharkov, 24 pp.
TSAROVSKY, I.D. 1972. Syenite complex. In: Stratigraphy of the Ukraine SSR, Volume 1, Precambrian. Naukova Dumka, Kiev, 287-98.

Map: 
Fig. 2_46. Malotersyanskii (after Krivdik and Tkachuk, 1990, Fig. 14).
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith