Petrology of the Suvasvesi granitoid intrusion in northern Savonia
The first one, SUVAS-19, was graciously funded by the K.H. Renlund foundation and will partly be realized in collaboration with the Battery Minerals project operations ran by the Geological Survey of Finland in Northern Savonia. The aim of the project is to map and study the mineralogy and petrology of the ca. 1.87 Ga Suvasvesi granitoid intrusion and its relationship with nearby pegmatites intruding the Paleoproterozoic metasediment sequences of the Viinijärvi suite.
Hanna Rantanen is the MSc student who has been hired to do the field work and hopefully we will see some nice results already by the end of the year.
http://projects.gtk.fi/akku/index.html
http://khrenlund.fi/en/
Mineralogy and petrography of the Kuohenmaa orbicular quartz monzonite
Another student project will take a closer look at some orbicular rocks and especially at this stage the world-class multi-shelled example from Kuohenmaa in Kangasala. The Kuohenmaa orbicular quartz monzonite has a particularly well-developed orbicular structure consisting of a core and several alternating radial plagioclase-rich shells and tangential biotite-rich shells.
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| One of the largest samples of the Kuohenmaa orbicular quartz monzonite from the collections of the Geological Survey of Finland. The Survey was very kind to let us take detailed pictures of their samples for research purposes. The ruler used as a scale is 20 cm long. |
The petrogenesis of orbicular rocks is controversial and several theories have been suggested to explain how the orbicules were formed. The two prominent theories suggest their origin to relate either to generation of local diffusion-controlled enrichment fronts onto the orbicules crystallizing from magma or cyclic changes in crystallization pressure or temperature. In this project, major and trace element mineral chemical analyses combined with statistical petrography will be used to test the applicability and validity of existing orbicule-forming theories and, if possible, create a new hypothesis for orbicule forming process of the Kuohenmaa orbicular rock.
The student working on this topic is Minna Markkanen and she has already made some very interesting discoveries based on very basic petrographic observations. She gave a poster at the Geoscience Colloquium earlier this year on the topic and is making strong progress also on other fronts. You can read more about recent discoveries in the abstract volume of the meeting, p 42:
http://www.geologinenseura.fi/files/Abstract_Collection_v1-5th_National_Colloquium_of_Geosciences.pdf
