Abstracts Travel
Program Organizing committee

The first petrological data about Kontay differentiated sub-alkaline intrusion, Polar Siberia, Russia.

Zaitsev V.A.

Vernadsky institute for geochemistry and analytical chemistry, RAS


Kontay intrusion located 40 km SW from Guli massif (Maimecha-Kotui province, Polar Siberia, Russia). Samples from drill hole up to 1231 m were studied. Intrusion is build up of layered sequence strongly differentiated from subalkaline gabbro in the lower part to the monzonites and granosyenites in the upper part.

Rock-forming minerals are clinopyroxen (ortopyroxen was found in one sample), phlogopite-annite, containing 2-5% TiO2, magnesiohorblendite (Na0.3K0.1-0.2)(Ca1.6-1.8Na0.2-0.4)(Mg2.1-2.2Fe2+1.9-2.1Fe3+0.6-0.8Ti0.1Mn0.1)[Si7Al0.7-0.9Fe3+0.1-0.3…., plagioclase An57-An26, anorthoclase and quartz. Accessory minerals are apatite, titanite, ilmenite and titanomagnetite and sulphides.

There are two group of clinopyroxen compositions, both are diopside-hedenbergite. The high-titanium pyroxene (1-1.2% TiO2 2-2.5% Al2O3 0.2-0.3 % MnO, 0,3-0,35% Na2O) present only in the lower part of intrusion. Low-titanium pyroxene present overall, Mg# decrease from 0.7 to 0.63, concentration of Al2O3 increase from 0.7 to 1.3, TiO2 increase from 0.4 to 0.6, MnO from 0.4 to 0.7 and Na2O decreace from 0.32 to 0.28 wt%.

Secondary minerals are chlorite, albite, prenite, and fluor and alumina rich titanite. The alteration temperature was estimated as 200-400°C. 

These observations seem to indicate that Kontay intrusion is notably different from the alkaline-ultramafic intrusions of Maimecha-Kotui province and, probably, belong to gabbro-syenite formation. This may question as is Kontay intrusion result of the same plume manifestation as alkaline-ultamafic intrusions of Maimecha-Kotui province and Siberian traps?