Petrology and geochronology of orogen-wide calc-alkaline “I-type” plutonic complexes – arc-related magmatism or remelting of ancient continental crust?

• Applicant: Professor Dr. Stefan Jung
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 563352563

The proposed project deals with the major and trace element and radiogenic isotope (Sr, Nd, Pb) composition of a large-scale pre- to syn-tectonic batholith in Namibia; the so-called Salem granite. The batholith consists mainly of granodiorite, granite and monzogranite. Available geochemical data are incomplete but published major and trace element variations provide linear relationships against SiO2 or MgO, suggesting that the various subtypes of the batholith may have originated from a two-component mixing process. One endmember must be a mafic to intermediate lower crustal source, the other a felsic lower crustal component. Alternatively, crust-mantle interaction of a lithospheric mantle-derived melt with lower crustal rocks is a potential process. Some of the geochemical variation suggest that the various subtypes resulted from in-situ differentiation of larger isolated magma batches. Available isotope data are too scarce to quantify assimilation processes. The new results will place constraints on possible heterogeneities of the crustal structure beneath the central Damara orogen and can be used to distinguish second-order processes (e.g., fractional crystallization with or without crustal contamination, magma mixing?) from first-order processes (e.g., partial melting of diverse crustal sources, coupled crust-mantle evolution). The project aims at understanding complex crustal processes at a time during the orogenic cycle where pre-existing continental crust is re-organized and re-processed. Igneous processes associated with these re-organizations are fingerprints of the dynamic melting of diverse crustal sources and is therefore ideally suited to add knowledge on crustal dynamics.

• DFG Programme: Research Grants