Alkaline Rocks and Carbonatites of the World

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

Pokrovo-Kireevo

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Occurrence number: 
171-00-014
Country: 
Ukraine
Location: 
Longitude: 38.27, Latitude: 47.63
Carbonatite: 
No

Pokrovo-Kireevo is a collective name for alkaline and subalkaline intrusive, dyke and effusive rocks encountered in the area of intersection of the Ukrainian shield along the Azov Sea coast with the Donetz coal basin near the village of Kumachovo (formerly Pokrovo-Kireevo). Intrusive rocks are represented by gabbro, pyroxenite, peridotite, malignite and nepheline and pseudoleucite syenites; effusive and dyke rocks by subalkaline and nepheline basalts, limburgite, augitite and bergalite (Buturlinov et al., 1973). The relationship between the intrusive and effusive rocks is not clear. Quartz-bearing rocks of the normal and alkaline series, such as liparites and grorudites, also occur in the area but their geological status is uncertain. The best known intrusion is oval in shape and lies within Precambrian granosyenites and Devonian basalts; it occupies an area of about 10 km2 and has a zonal structure. The periphery is composed of pyroxenites and associated rocks rich in ore minerals, while gabbroic rocks of the central zone range from plagioclase pyroxenite to leucocratic gabbro. Malignites and juvites occupy a similar or smaller area and between these rocks a gradual transition is observed. Poikilitic textures are a salient feature of the juvites and malignites within which coarse segregations of K-feldspar contain numerous inclusions of fine-grained nepheline. Nepheline is also found included in pyroxene, biotite and calcic rinkolite. Large crystals of pyroxene in malignite are zoned from pinkish-brown titanaugite in the centre to green aegirine-ferrosalite at the periphery. Smaller grains of pyroxene are optically homogeneous and of aegirine-hedenbergite composition. Hence, the alkaline rocks of the Pokrovo-Kireevo massif, like those of Oktyabr'skii and Malotersyanskii, are spatially and apparently genetically linked with subalkaline gabbroic rocks and alkaline basalts, an association that seems to be supported by the pyroxenes. Pokrovo-Kireevo shows a similar agpaitic trend of development to the other complexes, from subalkaline gabbroids and basalts to hyperalkaline malignite-juvites in which agpaitic minerals such as calcic rinkolite occur. A description of a drilled specimen of bergalite is given by Gladkikh (1973).

Economic: 
Titanomagnetite is the most abundant ore mineral of the Pokrovo-Kireevo massif forming about 35% in the ore-rich pyroxenites. The amount of apatite is widely variable but in some rocks reaches 20-30%. High concentrations of Ta, Nb, Be, Pb, Zr, Hg and F are associated with the later magmatic phases (Buturlinov et al., 1973).
Age: 
According to geological data and absolute age determinations by the K-Ar method the complex was formed between 408+_20 and 326+_12 Ma (Buturlinov et al., 1973).
References: 

BUTURLINOV, N.V., GONSHAKOVA, V.I. and ZARITSKY, A.I. 1973. The Devonian alkaline-basic alkaline-basaltoid complex of the conjunction zone of the Donbass with the Preazov part of the Ukrainian shield. In: Bazit-giperbazitovii magmatizm i mineralogiya yuga Vostochno-Evropeiskoi platformy. 171-263. Nedra, Moscow.
*GLADKIKH, V.S. 1973. Bergalite of the Pokrovo-Kireyevskaya structure. Doklady Earth Science Sections. American Geological Institute, 203: 166-8.

Map: 
Fig. 2_49. Pokrovo-Kireevo (after Krivdik and Tkachuk, 1990, Fig. 15).
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith