The first data on petrology, geochemistry and mineralogy, unexplored, and the recently discovered occurrences of alkaline magmatism Kandalakshsky district
Akimenko MI, Kogarko NN., Sorohtina NV
Vernadsky Institute, Moscow, email@example.com
This work is devoted to the study of recently identified new occurrences of alkaline magmatism in Kandalakshsky district, represented by rare species of alkaline rocks of agpaitic series - malignites.
Geology. Dike of malignite locate in the south-western part of the Kola Peninsula, in the Kandalaksha district. In the middle reaches of the river Kanda. The strike of the dike east, north-east. Contacts with the host rocks clear. The host rocks are metamorphic of Archean (AR2 mt), Proterozoic igneous complexes acid composition (γ2PR1), and igneous massif of ultrabasic Sorkayokskoy Group (νσРR1).
According to the drilling alkaline rocks can be traced in the range of 4.0 - 93.9 m dike parameters: stretch east, the length of about 1.0 km, the width in terms of an average of 160 m drop to the north at an angle of 600-90 ° .
Mineralogy. The rock generally consist of mafic alkaline minerals, which makes up 70 vol. The main rock minerals are arfvedsonite, aenigmatite, lamprophyllite, barytolamprophyllite, astrophyllite, nepheline, feldspar. Minor mineral are shcherbakovite, aegirine-augite. Ore minerals are ilmenite, goethite. Of the group of secondary minerals are sodalite, natrolite.
Feldspar and nepheline usually form a mass of fine-grained leucocratic practically inseparable, occupying the interstices between the grains of mafic minerals.
Arfvedsonite represented by two generations which closely related to each other. Arfvedsonite I forms elongate major grain brown in color, with slight bluish tinge, longitudinal cross-section less frequently have a hexagonal shape (Fig. 1). Arfvedsonite - I forms an elongated, sometimes needle-like grains of blue-green color with an uneven color, with negative elongation. It develops in the earlier arfvedsonite.
Lamprophyllite represented by two species (Fig. 1, 2). Lamprophyllite I forms a yellow prismatic crystals in the interstices between the grains of amphibole. Lamprophyllite II (barytolamprophyllite) forms a scaly shapeless mass of yellow color in the interstices between the grains and I arfvedsonite lamprophyllite. According to their optical properties lamprophyllite II is different from the early lamprophyllite.
Astrophyllite forms a yellow-orange fine-scaled, micaceous mass units less needle-like crystals in the interstices between the grains of amphibole and lamprophyllite .
Aenigmatite (fig. 2) forms large tabular crystals with perfect cleavage and a very high relief. Aenigmatite often surrounded by a rim of light, yellow-orange astrophyllite and often replaced by lamprophyllite.
Geochemistry. Agpaite coefficient values (according to Table 3) in the test unit malignites greater (mean 1.2).
Table 1. Chemical composition of maligmite (wt.%)
Conclusions. The studied rocks are rare species of nepheline syenite - malignite. It can be assumed that they are analogues of nepheline syenite, as described earlier in the largest alkaline massifs of the Kola alkaline province: the Khibini and Lovozero . Malignite rocks arise as a result of derivative the same tectonic and magmatic activity of Paleozoic age.
Gerasimovsky VI, Volkov VP, Kogarko N. Polyakov, I., Saprykina T., Balashov, Yu A, Geochemistry of the Lovozero alkaline massif, M. 1966.