Research at the Geochemistry and Isotope Geology Department
Our research interests span from the formation of the Solar System to investigating the geological processes that occurred over the history of the Earth to studying the interaction between geo-, bio- and atmosphere. To achieve this we develop and apply dedicated sets of novel and established of isotope systems.
Early Earth geological processes
Understanding the physical and chemical processes that operated on the Early Earth provides the basic framework for all planetary formation and evolution models. Yet, widespread tectonic processes over geological timescales have destroyed any remnants of early terrestrial crust. This makes the investigation of early Earth processes a daunting task flawed by large uncertainties. To circumvent these problems, we apply a series of novel and sophisticated isotope systems, such as the extinct 182Hf-182W isotope system, as well as high-precision trace element data in Archean samples to investigate the geological processes that shaped the Earth more than 4 billion years ago (Prof. Matthias Willbold).
Chemical structure of the Earth´s mantle
The unique chemical and isotopic heterogeneity of the Earth´s mantle is the result of continued crustal recycling at convergent plate margins over billions of years. Identifying the type and chemical composition of recycled components is therefore crucial to our understanding of the structure and geodynamical evolution of the mantle. We employ of a series of high-precision chemical and isotopic tracers, such as radiogenic Sr, Nd, Hf and Pb isotope, stable Mo and trace element data. By this we characterise the chemical and isotopic inventory of different mantle components and draw conclusions about their origin (Prof. Matthias Willbold).
Formation of the Archaean continental crust
The continents represent the essential platform for the development and evolution of terrestrial life. Yet, the geological processes that generated the first continental crust are still highly debated. In particular, two contrasting views have emerged over the past decades: (1) assuming formation of Archaean continental crust in ancient subduction zones or (2) assuming a non-uniformitarian view of crust formation in geodynamic regime dominated by a mantle-plumes. Key here is to decipher the origin of the characteristic chemical traits of the early Archaean continental crust and compare them with those observed in modern tectonic environment. An important modern analogue of plume-related crust formation is Iceland. This unique setting allows us to investigate and understand the magmatic processes that created trace element distribution patterns that are distinctly similar to that found in rocks from subduction zones (Prof. Matthias Willbold).
Development of geoanalytical methods
Recent technical improvements in mass spectrometric techniques have open up multiple opportunities to follow new research directions in Earth and Planetary Sciences. Over the decade, we have been at the forefront of conceiving, testing and implementing new geoanalytical methods. Such customised and fit-for-purpose applications allow us to take full advantage of these new developments and to tackle these new questions (Prof. Matthias Willbold).
Speleothem-based palaeoclimate research
Speleothems are archives for palaeoclimate proxies and are dateable at very high precision back to approximately 600 ka BP using the U-Th technique. Changes of the speleothem growth rates are often related to changes in precipitation intensity, temperature or vegetation cover above the cave. Multiproxy studies on stalagmites, involving combinations of U-Th dating, stable isotopes and trace elements have enormous potential for palaeoenvironmental studies. Our work is currently focussed on speleothems from Northern Africa and the Iberian Peninsula (Dr. Dirk Hoffmann).
Speleothems and archaeology
In some cases speleothems form on the surface of archaeological finds such as bones or stone tools, or these are found within sediments that over- or underly flowstones or stalagmites. U-Th dating can be used to date the calcite and thereby provide maximum or minimum age constraints for associated archaeological finds. Using recently developed techniques, we apply this approach to constrain the age of Palaeolithic cave art sites including Altamira or Cuevas del Monte Castillo (both in Spain). Recently published results from three Spanish caves (La Pasiega, Maltravieso and Ardales) show that cave paintings are older than 65000 years and therefore were made by Neandertals (Dr. Dirk Hoffmann).
Sampling of tropospheric CO2
HarzThat's also isotope geology. In order to reconstruct the origin of atmospheric CO2, we take air samples of the 1141 m high Brocken mountain. We hope to get CO2 that is free of influence from the local biosphere. In Göttingen we have built up one of a few laboratories world wide that analyze the rare isotope 17O. The abundance of this isotope gives us unique information regarding the origin of CO2. The project is financially supported by the German Science Foundation (Prof. Andreas Pack).
Isotope analyses and mass spectrometry
Noble gas mass spectrometry allows dating of geological processes on base of the abundance of the 40-Ar isotope (Dr. Klaus Wemmer).
We use the ratios of stable oxygen, carbon and silicon isotopes to solve problems in the fields of geo- and cosmochemistry, but also atmospheric sciences. Notably that measurement of the abundance of the rare isotope 17-O opens a nev and innovative field in stable isotope research (Prof. Andreas Pack).
Experimental petrology and experimental cosmochemistry
Aerodynamic levitation in combination with laser heating allows melting of silicated and oxides without container. We study the formation of chondrules with this unique technique.
A gas mixing furnace allows to study the behavior of silicate melts in different gas atmospheres. We invstigate processes in the early stage of our solar nebular with this technique (Prof. Andreas Pack).
Geo- and cosmochemistry
We use aerodynamic levitation melting and LA-ICPMS for high-precision analyses of element ratios (e.g., Y/Ho, Zr/Hf, REE). Using elementa ratios, we want to study processes that have occurred during the formation of the fist solids in the Solar System by condensation from the gas phase (Prof. Andreas Pack).
Transcrustal magma systems
Igneous phenocrysts form during residence, degassing and cooling of magmas as they ascend through the crust. These crystals are archives that record processes of magma evolution, chemical differentiation, magma mixing, and allow reconstructing the pre-eruptive storage conditions. Distinct magmatic regimes are reflected in different rates and composition of magmas that recharge crustal magma reservoirs prior to eruption. Compositional zonation of minerals are analysed in-situ by electron microprobe and laser-ablation ICPMS in order to reconstruct the history of magmas and the processes that can trigger their eruption to the surface.
In addition, we apply different methods (diffusion modelling, direct mineral dating) to gain direct temporal information on the timing and rates of these magmatic processes: Crystal residence and magma differentiation times are reconstruct to document the volume-time-compositional evolution of magma systems. We continue to study volcanoes in Kamchatka, Central Andes, and Germany. (Prof. em. Gerhard Wörner)
Magmatism in the Central Andes
Shortening and crustal thickening and surface uplift in the Central Andes in Cenozoic times is linked to the composition and evolution of magmas that traverse the thickening crust. Uplift and erosion results in geomorphological changes that are punctuated by volcanic events. On the other hand, volcanic rocks serve as important markers of this geomorphological change that is driven by tectonic and climatic forcings. We study this complex interplay between magmatic and tectonic processes in the region of the Atacama Desert at the western margin of the Central Andes in southern Peru and northern Chile. (Prof. em. Gerhard Wörner)