Chemical evolution of the Luumäki gem beryl pegmatite (SE Finland): developing vectors to economic gem beryl deposits


Granitic pegmatites are important hosts for economically important rare-element and gemstone deposits. The magmatic and hydrothermal processes responsible for enrichment of rare-elements and formation of gem bearing miarolitic pockets in granitic pegmatites are not fully understood and require further study. This project will investigate the chemical evolution of the miarolitic Luumäki gem beryl pegmatite (SE Finland) and will combine field geology, mineral chemistry, fluid inclusion studies, stable isotope geochemistry and geochemical modeling. Based on field mapping and analysis of drill cores, the geometry, mineral assemblages and zoning of the Luumäki gem beryl pegmatite (Karelia Beryl Mine) will be established. Subsequently, key minerals (feldspars, micas, beryl) will be studied for their chemical (electron-microprobe and LA-ICPMS analysis of major and trace elements) and stable isotope (oxygen and hydrogen isotopes) composition. In conjunction with data from fluid inclusion studies, the compositional zoning and time-space evolution of the Luumäki pegmatite system and the formation conditions of miarolitic pockets with gem beryl will be reconstructed. From the geochemical data for the Luumäki pegmatite and other granitic pegmatites in the area, suitable geochemical indicators will be developed that can discriminate economic gem beryl mineralization from barren granitic pegmatite systems. This will assist future prospecting activities that aim at finding new pegmatite dikes with gem beryl potential. The study will also contribute to improved understanding of the processes that govern formation of granitic pegmatites, and constrain the role of magmatic-hydrothermal fluids in development of miarolitic pockets with economic gemstone mineralization.
Gällande start-/slutdatum01/03/201330/09/2019