Rare-earth manifestations in the Kalmiuss deep fault of the Eastern Azov Sea Region of the Ukrainian shield

*Ukrainian State Research and Design Institute of Mining Geology, Rock Mechanics and Mine Surveying (UkrNIMI) of the National Academy of Sciences of Ukraine (NANU), Donetsk, Ukraine; **Priazovskaya Integrated Geological Party (KGP) belonging to the Public Company (KP) Yuzhgeologia, Volnovakha, Donetsk oblast, Ukraine

The Kalmiuss tectonic zone is located at the east of the Eastern Azov Sea Region (Priazovie) of the Priazovsky megablock of the Ukrainian shield. It is considered as the very old one: its age dates back to paleoproterozoic (Shatalov, 1986). It has north-east strike 30-40˚, goes through the centre of the Kalchik-Kalmiuss anticlinorium and is traced in the basement of the Dnieper-Donets avlakogene (Kalyaev, 1984).

The Kalmiuss fault controls distribution of igneous rocks and zones of hydrothermal-metasomatic rock alterations. During evolution of the Priazovsky megablock the Kalmiuss zone has activated repeatedly. Dike fields, zones of alkalization and carbonitization, fluorite-chalcedony-carbonate veins containing rare-earth mineralization have been identified along the fault by the results of depth geological mapping.

In the direction from south-west towards north-east more than dozens of rare-earth mineralizations have been identified in the Kalmiuss tectonic zone.

The most interesting one is Petrovo-Gnutovskoe deposit known as long ago as 1938 when parisite was found by V. I. Kuzmenko (Kuzmenko, 1946). The deposit is vein-like body of carbonate-chalcedony-fluorite composition with rare-earth and sulphide mineralizarion. The vein lays in intensely cataclasized quartz syenites (zone of cataclasis of the Kalmiuss zone). Primary ores contain calcite, fluorite, chalcedony, parisite and fluocerite. Of subordinate importance are pyrite, haematite, chalcopyrite, galenite, sphalerite, argentite, and quartz. Composition of rare-earth elements (REE) ranges 0.10 – 6.99 %.

Mineralization	Confinedness	Ore mineralization	Composition of REE, %
Petrovo-Gnutovskoe deposit	Intensely cataclasized quartz syenites	Vein-like body of carbonate-chalcedony-fluorite composition	0.10 – 6.99
Pishchevikskoe (Levoberezhnoe)	Zone of intensely brecciated diorites and granodiorites with widely manifested processes of metasomatosis and lenses of carbonate-chalcedony and carbonate-chalcedony-ochric compositions	Carbonate-chalcedony and carbonate-chalcedony-ochric substance with fluorite and parisite dotty and nest impregnations
28	Zone of cataclasis and crushing of pyroxene-amphibole quartz syenites		0.53
31	Zone of intensely brecciated pyroxene-amphibole quartz syenites and low-temperature metasomatosis		0.1
29	Quartz syenites	Quartz-calcite vein with fluorite and parisite dotty and nest impregnations	0.04-0.48
27	Zone of cataclasis, crushing and low-temperature metasomatosis of pyroxene-amphibole quartz syenites		0.2
26	Quartz syenites	Fluorite- chalcedony vein with parisite and fluorite dotty and nest impregnations	0.16-7.0
25	Zone of cataclasis, crushing and alkaline metasomatosis of pyroxene-amphibole quartz syenites	Thin egyrine-riebeckite streaks (sometimes with fluorite)	0.07-0.1
24	Zone of cataclasis, brecciation and alkaline metasomatosis of quartz syenites		0.1
23	Tectonic zone (cataclasis, mylonitization)		Се – 0.5 Y- 0.03
Novolaspinskoe	Zone of intensely brecciated pyroxene-amphibole quartz syenites and low-temperature metasomatosis	Vein of haematite-micro-wedge-shaped metasomatite	0.25
Anadolskoe	Granosyenites	Vein-like body and a row of smaller veins and zones of similar mineralization composed mainly of orthite, fluorite, britholite and fluorine-carbonate	19.32

A common for all of them is presence of hydro-thermal rare-earth mineralization of yttrium-cerium group and confinedness to zones of crushing and alkaline metasomatosis. As for zones of alkalization and veins with fluorite-rare-earth mineralizarion, alkalization structures are more widely dispersed in space than ore-bearing structures.

Genesis of this mineralization can be considered from the view point of confinedness of single-type mineralization, only high-temperature one, to sub-alkaline magmatic south-kalchik (Azov deposit) and oktyabrsky syenite-nephelin complexes.

The Kalmiuss tectonic zone being zone of deep faults was an entrance channel for flows of mantle fluids that initiated sub-alkaline magmatism. Most probably, now it represents the roots of deep tectonic zone which has been eroded for a long period of Pre-Cambrian existence.

Kalyaev G.I., Glevassky Ye.B., Dimitrov G.Kh. Paleotectonics and structure of Earth crust of Precambrian iron-ore province of Ukraine. Kiev: Naukova dumka, 1984. 240 p. (in Russian).

Kuzmenko V.I. Petrovsko-Gnutovskoe parasite deposit // Sovetskaya geologiya. 1946. No. 2. P. 49-61 (in Russian).

Shatalov N.N. Dikes of the Azov Sea Region (Priazovie). Kiev: Naukova dumka, 1986. 192 p. (in Russian).