Geological position of the Middle Alkaline Associations in Russia

K.I. Sveshnikov

Peoples” Friendship University of Russia, Moscow

 

The main problem of alkaline associations is difference between systematic subdivisions and regularities of the geological position of such subdivisions. The systematic problems (first of all of the middle alkaline associations composition) are debatable because their distinctive features remain unnsolved. The alkaline associations of North America and territory of Russia, by literary data, are connected with submeridional lineaments and in their limits with rift systems [2]. The task of the article is to obtain more distinctive features of alkaline associations and their geological position in the Russia territory.

One of the most informative petrogeochemical discriminate diagrams is “FeO – MgO – CaO” [3]. The trends of alkaline associations on this diagram may be divided for two groups. First group includes lamproitic, kimberlitic ultra-mafic, and basaltic-alkaline associations.(fig).

Fig – types of alkaline associations. 1 – the mantle composition, 2 – dunite-harzburgite intrusions, 3 – lamproitic associations, 4 – kimberlitic associations, 5 – alkaline ultramafic associations, 6 –alkaline-basaltic associations, 7 – gabbro-sienite associations, 8 – sienite associations, 9 – alkaline granitic associations

 

The trends of the first group associations are beginning near point of mantle composition. Their characteristic feature is the correlation of differentiation between MgO, CaO and FeO. The second group of associations (gabbro-syenitic, syenitic ,alkaline granitic associations) are not connected with the mantle composition, Their main characteristics are the correlation ties between CaO and FeO while the quantity of MgO is more or less constant. It may be supposed that the second group associations have crustal origin.

Geological position of alkaline associations in Russia is controlled by two sublatitudal lineaments – Moscow-Ochotsky (about 45⁰ of north l.) and Kola-Chukotka (60  70⁰ of north latitude) lineament [1]. Alkaline associations are spread to the South and North of these lineaments, the space between them is nearly amagmatic.

The first group alkaline associations are usually tied with rift systems; the second group associations which we studied in the East Siberian province, and in the South part of the East-European province, are often connected with dome vaults. They never are tied with the rifts. The same may be supposed for syenitic massives of the Kola peninsula,

[1]. Kosmic geology of the USSR / N.S.Afanasiev and others. Moscow, 1987.

[2]. Main provinces and associations of alkaline rocks.// L.S. Borodin and others. Moscow. 1974.

 [3]. K.I, Sveshnikov. Some petrochemical tendencies in alkaline magmatic associations // Donetzk, Ukr NIMI, 2009, part 2, N 5.