Research Group Rojas-Agramonte Solid Earth Isotope Geochemistry
The Solid Earth Isotope Geochemistry group at the Institute of Earth Sciences, Heidelberg University investigates dynamic processes shaping the Earth’s interior and its surface record, from mantle compositional heterogeneities to crust–mantle interaction, sediment recycling in subduction zones, and sedimentary provenance.
Isotope geochemistry interprets isotopic signals to reconstruct geological processes. These signals arise from the physical or chemical fractionation of isotopes, or from radioactive decay. Radiometric dating, based on the decay of parent isotopes into daughter isotopes, allows absolute ages to be assigned to geological events, such as magmatic or metamorphic crystallization, erosion and cooling of rocks, volcanic eruptions, and the deposition and diagenesis of sediments.
Depending on the mineralogy of a rock and the isotopic system used, different stages in its geological history can be dated using methods such as U-Pb geochronology in zircon, titanite, baddeleyite, or monazite. The decay rate (half-life) of radioactive isotopes forms the basis for these age calculations and helps establish the timing and duration of Earth processes across a wide range of spatial and temporal scales. Research in this field has revealed information about deep Earth dynamics, the lifetime and structure of mantle plumes, and the presence of ancient zircons in unexpected oceanic settings, offering key insights into global-scale geodynamic processes.
Beyond dating, isotope geochemistry provides insights into the chemical evolution of Earth’s mantle and crust. The analysis of radiogenic isotopes (e.g., Sr, Nd, Pb, Hf) and stable isotopes (e.g., O, C, B, Li) enables the tracing of material recycling in subduction zones, the characterization of mantle heterogeneities, and the reconstruction of the geochemical evolution of both oceanic and continental lithosphere.
The current research of the group focuses on the geochemical and temporal evolution of magmatic systems (e.g., hotspot-related oceanic islands and intra-oceanic convergent margins), as well as the provenance of sediments along active and passive margins. We also investigate ancient zircon populations in oceanic rocks and their role in reflecting mantle source variability. To achieve this, resistant uranium-bearing minerals, such as zircon, titanite, baddeleyite, and monazite, are analyzed using ion probe (SIMS) and LA-ICP-MS methods (U-Pb, Hf, O, REE), integrated with petrochronology and whole-rock geochemistry. This approach helps refine our understanding of magmatic processes, mantle dynamics, subduction systems, and sediment transport.
By combining isotopic data with petrography and field observations, the group contributes to a deeper understanding of solid Earth processes through geological time.