Prof. Dr. Helga de Wall

No publications found.

• Störungsflächenanalyse an Bohrkern- und Aufschlussdaten, Gebiet Obernsees, Fränkisches Becken und in situ-Spannungsanalyse (RACOS® Methode)

  (Third Party Funds Single)

  Term: 1. February 2018 - 31. December 2019
  Funding source: andere Förderorganisation
  Abstract

  Im Rahmen von Untersuchungen zur Struktur des Untergrundes im Zielgebiet des GAB-Forschungsprojektes „Petrotherm“ wurden neben den schon bekannten NW-SE verlaufenden Störungen im Fränkischen Becken auch N-S verlaufende Störungen als bedeutende Lineamente beschrieben. Die Kinematik dieser Strukturen im Paläo- und im in situ Spannungsfeld und damit ihr Reaktivierungspotential sind bislang nicht ausreichend untersucht. In diesem Kurzprojekt (12 Monate) soll eine detaillierte Datenerhebung zum Störungs- und Kluftsystem in einem kleinräumigen Gebiet um die Bohrung Obernsees durchgeführt werden, um das strukturelle Inventar zu erfassen. Mittels der RACOS^®-Methode soll an einem Bohrkern aus der Bohrung Obernsees eine Bestimmung der herrschenden in situ-Spannungen durchgeführt werden.

  Diese Methodenkombination wurde im Projekt „Petrotherm“ bislang nicht angewendet, wären aber für eine Bewertung des Reaktivierungspotentials von Störungsflächen im Fränkischen Becken und seines Untergrundes von Bedeutung. Mit diesem Kurzprojekt soll daher die Machbarkeit und Nützlichkeit für die Thematik „Ermittlung von Spannungszuständen im Zielgebiet und das Bruchverhaltens ausgewählter Gesteinstypen“ des Gesamtprojektes getestet und die Datenbasis zu dieser Thematik verdichtet werden.

  →More information

• Masterstudiengang "GeoThermie/GeoEnergie"

  (Third Party Funds Group – Sub project)

  Overall project: Geothermie-Allianz Bayern (GAB)
  Term: 1. January 2016 - 31. December 2021
  Funding source: Bayerisches Staatsministerium für Bildung und Kultus, Wissenschaft und Kunst (ab 10/2013)
  URL: https://www.geoenergy.nat.fau.de/studium/
  Abstract

  In Bayern gibt es bisher keinen Studiengang, der auf Geothermie/Geoenergieressourcen fokussiert ist und relevante Lehrinhalte ganzheitlich - von der Aufsuchung und Erschließung bis zur energetischen Nutzung und Speicherung der Ressource - an Studierende vermittelt. Die an den beiden Standorten TU München und FAU Erlangen vorhandenen Lehr- und Forschungskompetenzen sollen durch die Einrichtung eines in der Verantwortung der FAU liegenden interdisziplinären Master-Studiengangs "GeoThermie/GeoEnergie" zusammengeführt und und inhaltlich ergänzt werden. Dies erfordert einen personellen Ausbau der Fachrichtungen I) Seismische Interpretation & Untergrund-Modellierung und II) Reservoirgeologie & Geohydraulik.
  Für den Master-Studiengang "GeoThermie/GeoEnergie" wird ein interdisziplinärer Ansatz angestrebt:
  Neben der geowissenschaftlichen Komponente soll auch die technische Erschließung
  und energietechnische Nutzung von geothermischen Reservoiren, ergänzt durch energiewirtschaftliche
  und berg-/umweltrechtliche Aspekte behandelt werden. Somit kann den Studierenden
  sowohl das angestrebte ganzheitliche Systemverständnis als auch das einem modernen
  Anforderungsprofil der Energiewirtschaft entsprechende Methodenspektrum vermittelt werden.
  Die den Studierenden vermittelten Methoden sind jedoch keinesfalls nur auf Anwendungen in
  der Geothermie beschränkt, sondern auch auf sehr viele andere, das Verständnis des tieferen
  geologischen Untergrunds betreffende Fragestellungen (z.B. Gas-, Fluid- und
  Wärmespeicherung) direkt übertragbar.

  →More information

• Understanding the Neoproterozoic geodynamics of NW India: clues from tectonomagmatic studies of the Cryogenian Sindreth Basin at the eastern Malani Igneous Province

  (Third Party Funds Single)

  Term: 1. January 2015 - 1. August 2017
  Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
  Abstract

  The 770 to 750 Ma Malani Igneous Suite (MIS) in NW India is regarded as one of the largest (>50.000 km2) felsic igneous provinces in the world. Its geodynamics in the context of break-up history of Rodinia and subsequent amalgamation of continental blocks to form Gondwana has been attempted in a number of recent studies but not resolved yet and contrasting models (plume-, rift-, subduction-, mantle delamination- related) have been proposed. Coeval (765 to 767 Ma) small basins (Sindreth, Punargath) situated along the eastern margin of the MIS show overlap in ages, therefore, the order of geological events cannot be established in these basins. Existing models of basin formation propose active subduction setting (either back-arc basin or accretionary sediments over a subduction zone) and implications have been discussed in the context of global crustal dynamics. Reconnaissance studies by our German-Indian research group have noted field geological evidence and collected data that clearly contradict such interpretations. Instead of an inferred ocean floor setting for the Sindreth Basin we have observed conglomerate, fanglomerate, debris flow and lake deposits derived from the nearby continental provenance, intercalated with mafic and felsic lava flows. The sequence is unmetamorphosed but shows tilting (inversion) and faulting. Our reconnaissance findings indicate a fault-related basin formation. Preliminary magnetic fabric studies point to intrusion of felsic dykes (MIS sensu stricto) into this inverted basin. These findings need to be substantiated through a detailed field and laboratory work that would allow establishing a model of basin formation and basin inversion. Magnetic fabric studies combined with measurements of natural remanent magnetization will provide constraints for deciphering the geometric interrelationship of basin inversion and the MIS. Satellite pictures will be evaluated to resolve the relationship between faulting and ascent of magma on a larger areal scale. The Sindreth Basin and its surrounding area represent a transition zone between the undeformed MIS sensu stricto in the west and corridor of coeval Cryogenian ductile deformation, anatexis and granite intrusion in the east, main target of our research in the last years. The latter region has been linked to Neoproterozoic age magmatic belts and shear zones in Madagascar and south India, thus underlining the global significance of this region.
  →More information

• Determination of ambient conditions during coseismic formation of pseudotachylyte by means of Ti-in-quartz geothermometry and Ar-Ar dating

  (Third Party Funds Single)

  Term: 1. February 2011 - 31. January 2012
  Funding source: DFG-Einzelförderung / Sachbeihilfe (EIN-SBH)
  Abstract

  Despite a wealth of data about seismic fault zones there is an ongoing discussion about the possibility of frictional melting of quartzitic rocks. In the present study we analysed fault vein bearing fault zones within quartzitic rocks within the Schneeberg Normal Fault Zone (SNFZ), Southern Tirol, Italy. Electron microscopy (scanning electron microscopy, SEM, including electron back scatter diffraction, EBSD, and cathodoluminescence, CL, analysis  in combination with transmission electron microscopy, TEM) analyses revealed that the fault veins (0.5-2 mm thick) are not ultracataclastic zones as presumed initially (see original title of the project WA 1010/11-1). Instead an extensive melting and subsequent quenching of quartz is evident. These quenched friction-induced melts along a fault during seismic slips are so-called tectonic pseudotachylytes and record paleo-earthquakes.  Pseudotachylytes are typically considered to be representative for the brittle upper crust and in association with cataclasites. However the Schneeberg NFZ quartzites show clear evidence of crystal plasticity and dynamic recrystallization resulting in ultrafine-grained (1-2 µm) aggregates along microshear zones (50-150 µm thick) in the host rock adjacent to pseudotachylyte veins. Ar-Ar dating of the Schneeberg NFZ pseudotachylyte reveal an age of 60-66 Ma and indicates that the coseismic event is younger than the greenschist facies metamorphism of the Schneeberg NFZ (76 Ma, exiting data from the literature). Thus pseudotachylyte formation should has occurred after exhumation of the Schneeberg NFZ into the brittle crust under far field ambient temperatures conditions <250-300 °C. The occurrence of such fine recrystallized quartz was also reported in other pseudotachylytes-bearing faults, but these microstructures have been overlooked in most works on pseudotachylytes (also considering that they are hardly visible with standard optical methods) and a detailed electron microscopy study including crystallographic preferred orientation analysis of the microstructure was missing. In this project we carried out a direct comparison between the deformation microfabrics of quartz in two different pseudotachylyte-bearing faults both showing the development of ultrafine-grained recrystallization aggregates: the Schneeberg NFZ quartzite and the Adamello Gole Larghe Fault Zone(GLFZ) tonalite (Southern Alps). The observations of this study suggest that the association of ultrafine recrystallization and frictional melting is a systematic feature of most pseudotachylyte-bearing faults and could yield a more complete information on the mechanics of coseismic slip. Based on thermal models we suggest that crystal plastic deformation of quartz accompanied by dramatic grain size refinement by dynamic recrystallization occurs during seismic faulting at the base of the brittle crust as a result of the high temperature transients (> 800°C) related to frictional heating in the host rock selvages of the slip surface. These localised high deformation temperatures made possible that the process of dynamic recrystallization, including recovery processes, could occur in a time lapse of a few tens of seconds.

  In order to verify these modeled quartz deformation temperatures we applied the Ti-in-quartz geothermometer by measuring the Ti content in quartz by nanoSIMS. The geochemical analysis for both pseudotachylyte-bearing samples (Schneeberg NFZ and Adamello GFZL) showed that during the seismic-related development of ultrafine-grained dynamic recrystallized quartz aggregates the pre-seismic host Ti signal is inherited. Therefore no temperature related resetting of the Ti content occurs during seismically-induced quartz recrystallization. However the steep increase of Ti in quartz in the direct vicinity (1-2 µm) of melt-related submicron-sized Ti-bearing particles gives evidence of Ti diffusion and points to short-timed high temperature transient, which is consistent with the thermal modelling of pseudotachylyte vein and its host rock margin.

   

  →More information

• Microstructural characterisation of ultracataclastic zones in quartzites by electron microscopy

  (Third Party Funds Single)

  Term: 1. June 2006 - 31. July 2009
  Funding source: Deutsche Forschungsgemeinschaft (DFG)
  →More information