Robert Emo

University of Cologne | UOC · Institute of Geology and Mineralogy

Current models for the properties of Hadean-Eoarchean crust encompass a full range of possibilities, involving crust that is anywhere from thick and differentiated to thin and mafic. New data are needed to test and refine these models, and, ultimately, to determine how continents were first formed. The Rb-Sr system provides a potentially powerful p...

This study reports results from thermodynamic phase equilibrium and trace element modelling of mafic magmatic underplating and solid-liquid interaction in the lower continental crust (LCC) in intraplate settings. The arrival of underplating basalt sills into thin (∼30 km at 8 kbar) and thicker (∼45 km at 12 kbar) andesitic and basaltic LCC precurso...

Radiogenic isotopes provide an important means towards elucidating Archean crustal evolution. The global Hf and Nd isotope record of Archean crustal fragments has been instrumental to unveiling the history of ancient crustal growth and differentiation. The Rb-Sr system could provide valuable complementary constraints in this regard, as this system...

During active tectonic processes the lower continental crust plays a major role in the development and evolution of the overlying crustal column. The lower crust is heavily influenced by influx of mafic magma from the mantle and extraction of more felsic magma to the shallower crust. Evidence of such interactions are preserved in residues after mel...

The lower continental crust, representing up to 50% of the continental mass, is largely inaccessible, making its composition difficult to constrain. Previous composite models based on geophysical evidence and geochemical data of granulite terrains and xenoliths have proposed varying results, from a mafic, relatively refractory lower crust to an int...

Recent development in laser-ablation Lu-Hf dating has opened a new opportunity to rapidly obtain apatite ages that are potentially more robust to isotopic resetting compared to traditional U-Pb dating. However, the robustness of the apatite Lu-Hf system has not been systematically examined. To address this knowledge gap, we conducted four case stud...

The composition of the lower continental crust is estimated via the analysis of granulite xenoliths, granulite terrains and geophysical properties. All three proxies generally agree on the lower crust's refractory nature, dominated by mafic granulites. Estimates weighted using seismic velocity reference models yield lower Th and U concentrations an...

Current estimates for the composition of the lower continental crust show significant variation for the concentrations of the highly incompatible elements, including large uncertainties for the heat-producing elements. This has consequences for models of the formation of lower crust. For example, is lower continental crust inherently poor in incomp...

The continental crust grew and matured compositionally during the Paleo- to Neoarchean through the addition of juvenile tonalite-trondhjemite-granodiorite (TTG) crust. This change has been linked to the start of global plate tectonics, following the general interpretation that TTGs represent ancient analogs of arc magmas. However, partial melting o...

Apatite is a common accessory mineral in igneous, sedimentary and metamorphic rocks. It has potential as a provenance indicator in sedimentary systems, as it can host a wide variety of trace elements in its crystal structure and can yield thermochronological age information. However, the processes controlling the trace element and U-Pb systematics...

Earth's early crustal evolution can be studied through the geochemical analysis of Eoarchean and Hadean rocks. However, such rocks are often poorly preserved in the geological record. The Acasta Gneiss Complex (AGC), Northwest Territories, Canada, is one of the few locations where intact rocks of this age are found. Studies have suggested the invol...