Research Group Rojas-Agramonte Isotope Geology and Petrology
Isotope geology interprets isotopic signals to reconstruct geological processes. These signals result from the physical and chemical separation of isotopes or from radioactive processes. Radiometric dating makes it possible to assign an absolute age to geological events.
This method is based on the radioactive decay of a parent isotope into a daughter isotope, whereby an age can be calculated with the help of the half-life (time interval after which half of the initial amount of parent isotopes has decayed).
Depending on the geological environment from which the rock originates, which minerals can be found in it and which isotope systems are used, the chronological sequence of important geological events can be reconstructed from this, such as magmatic or metamorphic crystallization, the erosion and cooling of rocks, volcanic eruptions or the deposition and diagenesis of sediments.
Beyond dating, isotope geology is crucial for understanding the chemical evolution of Earth’s mantle and crust. By analyzing radiogenic isotopes (e.g., Sr-Nd-Pb-Hf) and stable isotopes (e.g., O, C, B, Li), geologists can trace material recycling in subduction zones, mantle heterogeneities, and the geochemical evolution of oceanic and continental lithosphere. Research in this field has provided insights into deep-Earth processes, the lifetime of mantle plumes, and even the presence of ancient zircons in unexpected oceanic settings providing insights into global-scale geodynamic processes.
The current lines of research of our working group focus on the geochemical and temporal evolution of magmatic systems (e.g. hotspot-related oceanic islands, intra-oceanic convergent margins; IOCMs), as well as the provenance of sediments along active margins. We also investigate the presence of ancient zircons in oceanic settings and their role in mantle heterogeneities. To achieve this, resistant minerals containing the radioactive element uranium (U) are examined, such as zircon, titanite, baddeleyite or monazite. Our approach integrates ion probe (SIMS = secondary ion mass spectrometry), LA-ICP-MS isotopic analyses (U-Pb/Hf/O/REE) with petrochronology, and whole-rock geochemistry, to refine our understanding of magmatic systems, mantle dynamics, subduction processes, and sedimentary transport in active margins.