Carbonatite Stock in the vicinity of Tul'ilukht Bay, Murmansk Oblast, Russiai

Regional Level Types
Carbonatite Stock in the vicinity of Tul'ilukht Bay	- not defined -
Murmansk Oblast	Oblast
Russia	Country

Dikes of alkaline picrites and carbonatites in the so-called Carbonatite Stock.

The carbonatite stock, an elliptical body embedded in foyaite, is located near the western shore of the north-south trending headland that limits to the east the Tul’ilukht Bay, an indentation in the western shoreline of Umbozero Lake, in which are included the extuaries of the eastward-flowing streams (Maival'taiok, Kaskasnyuniok and Tuliok) that drain the internal arc of Khibiny massif. The carbonatite stock is buried below a thick layer of fluvioglacial debris and is known thanks to a series of boreholes that have evidenced its complex petrological and mineralogical features.

The first borehole (Borehole no. 609) on the shore of Tul’ilukht Bay was drilled down to a depth of 1115.5 m and evidenced the presence in foyaite of carbonitised and biotitised rocks, various altered xenoliths, and late carbonate and biotite-carbonate veins and veinlets. Carbonate veins and veinlets, mainly composed of calcite (sometimes Mn-rich), strontianite and synchysite-(Ce), sometimes showed cavernous sectors containing minerals like dawsonite, cryolite, burbankite, zeolites, and other accessories. Biotite-carbonate veins turned out to be composed of biotite, fluorapatite, magnetite and various sulfides, such as pyrrhotite, pyrite, marcasite, chalcopyrite, sphalerite, and galena (Kirnarskiy & Kozyreva, 1974; Minakov & Dudkin, 1974; Dudkin & Minakov, 1976; Kozyreva et al., 1976; Kostyleva-Labuntsova et al., 1978). Further investigations brought to a thorough description of the so-called Carbonatite Stock (Dudkin et al., 1984). Whitin the stock, there is a host breccia containing fragments of carbonatised foyaite, ijolite, melanephelinite, tinguaite-phonolite, alkaline trachyte, and phlogopite-aegirine-apatite rocks surrounded by albite-calcite and phlogopite-calcite rocks. This is cross-cut by a dense network of late carbonatite and carbonate-zeolite veins. The carbonatite series contains eigth types of veins: the first two types are certainly igneous, whereas the others mainly contain metasomatic minerals (Zaitsev et al., 1992; Khomyakov, 1995; Zaitsev, 1996; Zaitsev, Wall et al., 1998; and other authors).

In particular, the first type of veins includes:
- phlogopite-aegirine-apatite rocks, which form veins from 50 cm to 2 m wide in foyaite and more often are found as xenoliths up to 30 cm in diametre, in carbonatite. The primary mineral assemblage consists of fluorapatite, aegirine-augite, pyrrhotite, and pyrochlore; the secondary minerals include phlogopite replacing aegirine-augite and pyrite replacing pyrrhotite.
- calcite-phlogopite-aegirine-apatite carbonatite in the form of veins 10 cm to 4 m wide. The mineral assemblage includes also pyrrhotite, pyrite, ilmenite, magnetite, pyrochlore, and chalcopyrite.
The second type comprises:
- calcite carbonatite with burbankite or carbocernaite, which forms veins 1 cm up to 6 m wide and is coarse-grained, consisting of yellow-brown burbankite or lemon-yellow carbocernaite (10-50 vol.%) with xenoliths of heavily altered ijolite, foyaite, melanephelinite, and alkaline trachyte. Carbocernaite is partially replaced by a porous aggregate of strontianite, cordylite-(Ce), synchysite-(Ce), and baryte; alteration products of burbankite include ancylite-(Ce), synchysite-(Ce), strontianite, baryte, harmotome, and edingtonite.
- ankerite-calcite carbonatite with synchysite-(Ce), which occurs as a result of metasomatic alteration of calcite carbonatite and frequently contains its relics. This medium- to coarse-grained rock, in addition to the mineral mentioned above, contains kutnohorite, parisite-(Ce), bastnäsite-(Ce), cordylite-(Ce), kukharenkoite-(Ce), mckelveyite-(Y), and strontianite.
- rhodochrosite-ankerite carbonatite with synchysite-(Ce) or cordylite-(Ce) is a brown medium- to coarse-grained rock containing parisite-(Ce), bastnäsite-(Ce), kukharenkoite-(Ce), mckelveyite-(Y), donnayite-(Y), ewaldite, strontianite, baryte, edingtonite, and harmotome.
- siderite-ankerite-natrolite veins consist of light grey medium- to coarse-grained massive aggregates of siderite, ankerite, and natrolite in association with numerous accessopry minerals, such as synchysite-(Ce), cordylite-(Ce), kukharenkoite-(Ce), cebaite-(Ce), mckelveyite-(Y), donnayite-(Y), ewaldite, strontianite, baryte, edingtonite, and harmotome.
- siderite-nordstrandite-natrolite veins contain cordylite-(Ce), mckelveyite-(Y), donnayite-(Y), ewaldite, barytocalcite, strontianite, and baryte.
- natrolite-siderite-dawsonite veins, containing also fluorite, cryolite, baryte, calcite, pyrite, analcime, edingtonite, mckelveyite-(Y), donnayite-(Y), ewaldite, strontianite, cordylite-(Ce), and baryte, occur as slender white veinlets with numerous cavities, the walls of which are encrusted by natrolite and other minerals.


The carbonatite stock is one of the five type localities for kukharenkoite-(Ce), which occurs in late carbonate and carbonate-zeolite veins. It forms greenish-yellow skeletal trillings (up to 3 mm in width) of flattened prismatic crystals (up to 2 mm long) and also equant crystals (up to 0.2 mm in diametre) in association with natrolite, siderite, orthoclase, magnetite, sphalerite, galena, baryte, strontianite, cordylite-(Ce), synchisite-(Ce), bastnäsite-(Ce), ancylite-(Ce), mckelveyite-(Y), donnayite-(Y), and ewaldite (Zaitsev et al., 1996; Pekov, 1998; Zaitsev, Wall et al., 1998; Yakovenchuk et al., 2005).

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References