B. Emmel

Postcollisional High-Grade Metamorphism, Orogenic Collapse, and Differential Cooling of the East African Orogen of Northeast Mozambique

The postcollisional tectonic development of northeast Mozambique and subsequent cooling from high-temperature metamorphism is delineated with an extensive new set of U-Pb titanite, 40Ar/39Ar hornblende, and 40Ar/39Ar mica analyses. The complex data suggest a polyphase metamorphic history from the late Neoproterozoic to the Ordovician within the East African–Antarctic Orogen (EAAO), with marked differences between the major constituent blocks. In all the data sets, samples from the basement south of the Lúrio Belt show generally younger ages than those from the north, resulting from a late metamorphic event and slow cooling between ca. 520 and 440 Ma. The ages north and south of the Lúrio Belt are consistently offset by ca. 30–70 Ma, a difference that is maintained and even appears to increase during cooling from very high temperatures to ca. 350°C. Based on the first-order assumption that all the ages are cooling ages, cooling rates in the south are estimated at ca. 7°–8°C/Ma, while those north of the Lúrio Belt are faster at ca. 16°C/Ma. The data are consistent with previous geochronological, petrographic, and field data and suggest a late high-temperature/low-pressure metamorphic event that affected only the basement rocks south of the Lúrio Belt and portions of the latter. This late metamorphism and subsequent delayed, slower cooling agree well with a model of elevated heat flow following lithosphere delamination in the southern part of the orogen, which also explains the observed widespread granitoid magmatism, migmatization, and renewed deformation in the southern basement.

Combined titanite and apatite fission-track data from Gjelsvikfjella, East Antarctica – another piece of a concealed intracontinental Permo-Triassic Gondwana rift basin?

Abstract Titanite and apatite fission-track ages from Gjelsvikfjella and the eastern Mühlig–Hofmann Mountains, East Antarctica, range between 516±50 and 323±30 Ma and 366±16 and 186±9 Ma, respectively. The thermochronological data set indicates differential cooling of two tectonic blocks (Hochlinfjellet–Festninga and Risemedet). Inverse modelled time–temperature paths suggest that the Hochlinfjellet–Festninga block cooled at first below 60 °C during the mid-Palaeozoic, whereas the Risemedet block cooled during the earliest Triassic. Differential cooling is most probably related to physical separation along active faults, which is associated with Gondwana-wide intracontinental rifting. This tectonic activity shaped the landscape in the study area along structures running perpendicular to the continental margin of Dronning Maud Land. A rift locus was possibly located along the Penck–Jutul graben west of the study area. In contrast to other parts of Dronning Maud Land, Jurassic magmatism and initial break-up between East Africa and East Antarctica did not influence the apatite FT data. Modelled apatite fission-track data indicate the onset of final cooling since the Early Cretaceous, suggesting post-Cretaceous unroofing of the palaeosurfaces in eastern Dronning Maud Land.

CO2 Storage Capacity Estimates for a Norwegian and a Swedish Aquifer Using Different Approaches – From Theoretical Volumes, Basin Modelling to Reservoir Models

Open dipping aquifers might offer a unique possibility to store huge quantities of carbon dioxide. Many different modelling approaches have been used to quantify possible storage capacities often giving very diverse results. In this study, we applied three different methods to calculate and model theoretical volumes, structural trapping volumes using a basin modelling tool and capacities obtained from dynamic reservoir simulations. We tested end-member scenarios for different critical parameters. The results for two stratigraphic confined open/semi-closed dipping saline aquifers, the Garn Formation (Norwegian Sea, Norway) and the Faludden sandstone (Baltic Sea, Sweden) show broad variations. For the Garn Formation CO2 storage capacities vary from 2.0 to 8.4 Gt. Taking into accounts all results, we estimated a representative storage capacity ranging between 2.0 and 3.5 Gt. In the case of the Faludden sandstone the different modelled scenarios give a spread from 10 to 836 Mt and a representative capacity of 250–435 Mt was defined. We will show and discuss how the different estimates are calculated, how they are related to each other and finally exclude unreliable results. Furthermore we compare our results with published data from the same areas. This will demonstrate the complexity and difficulty of a direct comparison of geological CO2 storage estimates and pinpoint to the need for a general strategy to compare modelling results for geological CO2 storage estimates.