Source compositions and melting temperatures of the main granitic suites from the Moldanubian Batholith
The granitoids of the Moldanubian Batholith (Moldanubian Zone of the Bohemian Massif) are represented by three main suites: Ito I/S type Weinsberg biotite granites granodiorites, S type Eisgarn two mica granites and I/S type Freistadt biotite granites granodiorites. As shown by major element data and zircon with monazite saturation thermometry, partial melting of metapelites likely produced most of the Eisgarn suite (Mrakotin/Cimer varieties) at c. 775 825 oC. Parental melts of the Weinsberg and Freistadt suites could have been generated by partial melting of a metagreywackes metabasalts mixture at c. 740 940 oC. This study confirms that the CaO/Na2O ratio could be used for source assignment of S type granite melts, whereas the CaO/(FeO MgO TiO2) ratio is more suitable for I/S type granites. The observed systematic positive shift of Al2O3/ TiO2 temperatures compared with zircon and monazite saturation temperatures in all granitoids of the Moldanubian Batholith (up to 118 oC) may be explained by accumulation of ilmenite in the S type Eisgarn suite. In the Iand I/S granite types of the Weinsberg and Freistadt suites the Al2O3/TiO2 ratio is controlled by the accumulation of ilmenite and/or titanite. Consequently, the Al2O3/TiO2 ratio may be used as a thermometer only with caution.