Partial melting of rocks in the root zone of the Variscan orogenic belt (Moldanubian Zone, Bohemian Massif)
|Project Period:||1/2003 - 1/2005|
|Investor:||Czech Science Foundation|
|Programme / Project Type:||Standard Projects -|
|Field:||DD - Geochemistry (D - Scineces of Earth)|
DB - Geology and mineralogy (D - Scineces of Earth)
|Keywords:||Partial Melting, Moldanubian Zone, Petrology, Geochemistry, Sr-Nd Isotopic System|
Peraluminous granitic rocks formed by partial melting of metasedimentary lithologies are abundant in root zones of the orogenic belts worldwide. The proposed project aims to constrain the partial melting process with variable protoliths, degree of melting, P-T conditions and in distinct structural position within the Moldanubian Zone of the Bohemian Massif. Various stages of the process will be studied, starting from the presumed protoliths, through migmatites and diatexites, to likely restites and small leucocratic bodies. The main questions addressed will be potential sources for individual rock types, role of water and other volatiles (water saturated/undersaturated melts), mode of melting (equilibrium/disequilibrium melting), role of accessory phases, quantitative aspects (the restitic assemblage, the degree of partial melting, mass balance restite/melt) and timing. These goals should be achieved by a complex study of field relations, petrology, mineral chemistry, geothermobarometry, whole-rock major- and trace-element geochemistry, Sr–Nd–O isotopic compositions, geochronology as well as extensive numerical modelling. The obtained data will contribute to our current understanding of petrogenesis of broadly S-type granitic rocks. Inferred P-T-t evolution of the system (isobaric cooling vs. isothermal decompression) should be indicative of the tectonometamorphic evolution of the individual Moldanubian nappes (presence of external heat sources e.g. mafic intrusions vs. crustal thickening).