Saturday, October 27, 2012

Gremyakha-Vyrmes, Kola peninsula. Field trip 2012.

This is short report about field trip with Vernadsky Institute, RAS to proterozoic massif Gremyakha-Vyrmes.
The massif consist of three main complexes: 1) ultramafic-mafic rocks 2) foidolites 3) alkali granites and syenogranites [Polkanov et al., 1967]. Interpretation of sequence is complicated because of late tectonic and metamorphic processes that are occurred here intensive.
To view the location on the map click here. It is wonderful, you can see faults in granite complex form satellite.
Our object of study were alkaline rocks, particularly alkaline granites. Some authors do not recognize alkaline granite as the product of the same source as for ultramafic and basic alkaline complexes. They consider granites and layered ultramafic-alkaline pluton separately. It is difficult to belive because of emplacement and the similar age (?) of all rocks.
I will not publish our geological schemes because of their incompleteness.
Geological scheme of Gremyakha-Vyrmes massif. Alkaline granites located on the North (elongated crosses). (Kukharenko et al., 1971)

Granites consist of two alkaline feldspars, quartz, aegirine, arfvedsonite, aenigmatite. They are distinguished from others similar granites by its age, setting and chemistry. 
In some old ditches we found uranium-molybdenum occurrence with anomaly high radiation. There is a video demonstrating this.

Materials of prospecting work in 1970's.
I should say that vegetation covers all the territory and it took a lot for observing outcrops.

Aegirinite. Alkaline metasomatic rock.
Old prospecting ditch.

Parallel cleavege. Alkaline granites.

Sometimes we had to literally wash the rocks to make clear descriptions and pictures of outcrops.

Process of washing outcrop of alkaline granites.
Pretty fresh samples with minimum signs of weathering.

Dark minerals of this granites are: 

Aenigmatite, aegirine, arfvedsonite. PPL, x100.
Aenigmatite, XPL x100

Relicts of granite in pegmatite.
Not alkaline granite but we took her with us.
Me, granites and marshes.
The view on Gremyakha lake from North to South.
 We lived in woods without any connection with world for 2 weeks. It is always great.
I found the place with weak mobile connection.

It is time to pack our equipment and go back home.
Best friend.
What a road.

Thank you for your attention.


No comments:

Post a Comment