Institutskolloquium

Dr. Borhan Bagherpour

Privat

Title: Permian-Triassic Mass Extinction: Insights From Paleoenvironmental Studies and Stable Isotopes In China and Iran.

Summary: The largest mass extinction of the Phanerozoic, which occurred at the Permian-Triassic Boundary (PTB), was linked to significant paleoenvironmental shifts, including perturbation in the global carbon cycle, global warming, and changes in sedimentary regimes. In this talk, I present a multi-disciplinary approach to studying these paleoenvironmental changes during the Late Permian and earliest Triassic. This research focuses on the exceptional sedimentary records from South China and Central Iran, which offer a unique opportunity to examine the effects of these changes across a variety of marine depositional environments.

The occurrence of microbial limestones on platforms and the coeval development of oxygen-depleted black shales in deeper marine settings provide insight into the prevailing environmental conditions at different depths, as well as the importance of microbial communities in the recovery. Additionally, I discuss the paleoenvironmental impacts of the Emeishan large igneous province and the factors contributing to an earlier extinction event around the end-Guadalupian (mid-Permian), which may have also contributed to the severity of the PTB extinction. Our high-resolution data suggest that volcanic activity and carbon cycle disruptions during the Late Permian had more localized effects, in contrast to the widespread environmental changes observed at the PTB in the Early Triassic.

Ms. Elena Rogmann MSc.

Privat

Title: To garnet and beyond – The fate of aluminium in the Earth’s mantle

Summary: Subduction zones transport a variety of elements, such as aluminium and alkali earth metals, into the deep Earth. These elements, particularly aluminium, are more concentrated in subducting sediment and oceanic crust (MORB) compared to the surrounding mantle, which leads to distinct mineralogical differences. In the upper mantle and mantle transition zone, aluminium is primarily stored in garnet. However, as slabs descend through to the lower mantle, garnet becomes unstable, and aluminium is hosted by other minerals.

Two key lower mantle phases, the New Aluminous Phase (NAL) and Calcium-ferrite Type Phase (CF), are the hosts of aluminium in the lower mantle. While their stabilities in simple chemical systems (NaAlSiO₄–MgAl₂O₄) are well understood (Imada et al., 2011), more realistic chemical systems have only recently been explored. This presentation will focus on how potassium—a significant component of subducting sediments—affects the stability of NAL and CF (Rogmann et al., 2024).

We performed high-pressure experiments using a laser-heated diamond anvil cell (DAC) in the KAlSiO₄–NaAlSiO₄–MgAl₂O₄ system, under pressures corresponding to the uppermost to mid-lower mantle. To constrain the elasticity of the CF phase, we conducted Brillouin scattering experiments on CF single crystals in a DAC at an array of pressures. These measurements allow us to model seismic wave velocities, which can be compared to measured seismic data of the deep Earth and can help constrain mineralogical models of the deep Earth.

We find our measurements of the elastic moduli of CF to deviate significantly from those reported in current mineral physical databases based on theoretical calculations. We also observe the onset of the spin transition in ferric iron, expected for CF between 25 and 35~GPa (Wu et al., 2017). Additionally, we find that the addition of potassium significantly broadens the stability range of NAL by more than 25 GPa. We also observe a significant potassium solubililty in CF at high pressure, which may hold the entire MORB potassium budget.

Imada, Saori, Kei Hirose, and Yasuo Ohishi. "Stabilities of NAL and Ca-ferrite-type phases on the join NaAlSiO 4-MgAl 2 O 4 at high pressure." Physics and Chemistry of Minerals 38 (2011): 557-560.

Rogmann, Elena-Marie, et al. "The effect of potassium on aluminous phase stability in the lower mantle." Contributions to Mineralogy and Petrology 179.5 (2024): 1-18.

Wu, Ye, et al. "Spin transition of ferric iron in the calcium‐ferrite type aluminous phase." Journal of Geophysical Research: Solid Earth 122.8 (2017): 5935-5944.

Title: Dates and rates of Earth surface processes revealed through trapped charge dating

Summary: The interactions between rates of Earth surface processes, climate and tectonics shape landscapes from mountains to oceans. A robust chronology is essential for understanding the timing of environmental change, its main drivers and how quickly landscapes have evolved over the recent past (i.e., the last few million years). Trapped charge dating techniques, such as electron spin resonance (ESR) and luminescence dating, provide valuable insights into Earth surface processes and landscape change over timescales of 10²-10⁶ years, offering critical information on the timing and pace of environmental change for evaluating processes that are important to society. In this talk, I will highlight the potential of trapped charge dating as a geochronological tool to constrain the timing and rates of landscape evolution, illustrated by selected geomorphological studies from around the world.

Title: Rifting and volcanism across scales: An example from the East African Rift

Summary: The talk will take a look at close look at processes at different scales in the East African Rift System (EARS) using seismological tools. Starting in the deep mantle using shear-wave splitting, we deduce the dynamics of the African Large Low Shear Velocity Province and how these may partially drive upper mantle flow which, in turn, may facilitate rifting and further interacts with the topography of lithosphere asthenosphere boundary. We infer the influence of melt along the EARS and focus on a region at the margin of the Tanzanian craton, where carbon is advected through the Proterozoic mobile belt as evidenced by strong CO2 degassing across rift faults and the existence of Earth's only currently active carbonatite volcano Oldoinyo Lengai. We analyze the interplay between rifting and volcanism using earthquakes, focal mechanisms and attenuation imaging. This, together with the analysis and location of (deep) volcanic tremor, shows how Oldoinyo Lengai is underlain by a transcrustal magmatic plumbing system. Using acoustic and satellite-based thermal data, the talk will end with eruptions at this peculiar volcano. 

Prof. Dr. Daniel Herwartz

© RUB

Title: Corals, Evaporites, Snowballs, selected tales from triple-O isotopes

Summary: Stable isotopes are used to reconstruct paleoenvironments over Earth's history. I will demonstrate how recent advances in triple oxygen isotope analyses can help quantifying individual parameters in various fields.

Title - Calibrating rock's electrical properties to their composition and structure, based on data from the lab, the field, and the Alpine Fault and Ivrea-Verbano scientific drilling projects

Summary - Remote geophysical measurements of rock properties, reflecting distinct, commonly anisotropic arrangements of minerals and porosity, may be used to explore geo-resource distribution in Earth’s crust to tens of kilometres depth. To date, our scientific community have focussed on the geophysics of elastic wave propagation and made comparably little attempt to understand processes at depth from remote geophysical measurements of electrical properties. We aim to change the capability to make use of electrical data, by exploring the relationship of sample structures and compositions to laboratory and field-scale electrical property measurements.  The focus of this presentation will be on datasets derived from scientific drilling into the Alpine Fault (New Zealand) and the Ivrea-Verbano Zone (Italy).

Prof. Philip Ruprecht

Privat

Title: The natural laboratory of Puyehue-Cordón Caulle that links crustal scale magmatism to eruption dynamics: When and how do rhyolitic magmas blow up? 

Summary: Active volcanism requires a multi-disciplinary approach to forecast future unrest activity from both ongoing changes in the subsurface and from past activity. Thus, detailed timeseries of the heat and mass balance of the magmatic and near-surface hydrothermal system are necessary to constrain the state of the magmatic system as well as its transients through time. The Puyehue-Cordón Caulle volcanic complex is the site of three major subplinian to plinian eruptions that occurred in the last 100 years. These eruptions tapped a magmatic system that is thought to extend over more than 10 km laterally and currently deforms at rates of cm to dm per year. Furthermore, the most recent eruption in 2011-12 emplaced a very shallow intrusion only hundreds of meters below the surface adding to the multiple hazards associated with this volcanic complex.

In this presentation, I will give an overview of the many surface signals (geodetic, structural, hydrothermal) we can detect to estimate the thermal and mass budget of the system. I will also constrain through petrology the underlying magmatic system that represent an end-member of efficient single-step differentiation of basaltic mantle-derived melts to rhyolites. Mineral-scale geochemical records identify the conditions under which magmas are stored at depth and how the erupted rhyolite is formed and whether this rhyolite magma is approaching a critical state for future eruptions. Given the destructive nature of rhyolitic volcanism that is typically characterized by a long period of quiescence, the Puyehue-Cordón Caulle volcanic complex serves as a unique natural laboratory where pre-eruptive processes have and likely will be recorded on decadal timescales.

Title: Composition, structure and origin of the Moon

Summary: tba

Dr. Inês Pereira

© Universidade de Coimbra

Title: Tracing subduction zone metamorphism using rutile and titanite

Summary: Subduction zone metamorphism is a hallmark of modern plate tectonics. The metamorphic rock record indicates the absence of LT-HP metamorphic conditions, typical of subduction zones, prior to the Neoproterozoic, which has since been used as evidence for the initiation of plate tectonics at the end of the Proterozoic. Because the rock record is susceptible to preservation biases, an independent approach is needed to test this geological record. One alternative is to look at sedimentary rocks, but this presents many challenges. In this talk, I will provide experimental and petrological evidence supporting rutile and titanite as candidates for subduction zone metamorphism, and show the advances made in using their trace element chemistries as tools to discriminate their growth conditions, which are critical in searching for evidence of metamorphic gradients through time.