Monzodioritic rocks and magma interaction in the Ahvenisto complex
This research project was initiated as far back as in 2008 as a small sub-project of my own PhD studies in Ahvenisto and the initial aim was to look a bit more closely at the enigmatic pillow
structures that occur at geographically very limited locations in the
southeastern and northwestern parts of the complex.
Figure 1. Monzodioritic pillows with granitic finger-like veins form peculiar
"net-veined complexes" in Pärnäjärvi region in the southeastern part of the Ahvenisto
complex.
In 2015 I hired Riikka Fred as a MSc student to map the monzodioritic pillows and conduct a preliminary geochemical study to assess and model the rheological relationships
between the different phases in the structures. After finishing her very successful MSc project Riikka received funding from the Doctoral School of Geosciences (2018-) to conduct a more detailed study on the geochemistry and magma evolution of the Ahvenisto monzodioritic rocks. The aim of this project is to answer many
of the open questions about the enigmatic origin of the various
interaction structures (net-veined complexes and hybrid rocks) and the evolution of the Ahvenisto complex
parental magmas.
Riikka's first paper dealing with the interaction
styles and their physicochemical controls was accepted for publication
in the Bulletin of the Geological Society of Finland in early 2019.
In the fall of 2018 Hanna-Kaisa Ruhanen was hired as a MSc student to study the mineral chemistry of the net-veined complexes and the hybrid rocks. Hanna-Kaisa will work in collaboration with Riikka to produce a comprehensive mineral chemical data set to further evaluate the magmatic evolution and P/T-conditions of magma interaction in the Ahvenisto complex.
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