Gekoppelte Simulation von crack-seal Kluftfüllungen

• Antragstellerinnen / Antragsteller: Professorin Dr. Britta Nestler; Professor Dr. Klaus Reicherter, seit 9/2019
• Fachliche Zuordnung: Paläontologie ; Mechanische Eigenschaften von metallischen Werkstoffen und ihre mikrostrukturellen Ursachen
• Förderung: Förderung von 2018 bis 2023
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 391503625

• Erstellungsjahr: 2023

Zusammenfassung der Projektergebnisse

The first part of this work provides a detailed description and interpretation of the development of different vein microstructures that are common in micritic carbonate rocks. Microtextural observations from natural samples with numerical modeling of syntaxial crystal growth in fractures are compared. For example, wide-blocky vein morphologies form in fluid-filled open fractures by rapid epitaxial growth on a few grains along the fracture surface, such as freshly broken cleavage planes of calcite, whereas growth on wall-rock grain boundaries is slow due to the presence of inert second phases, such as clays, organics or dust particles that covers the growth surfaces. Therefore, the morphology and mineralogy of an initial fracture surface has major implications on vein sealing rates and resulting crystal morphologies. Depending on the fracture type (intergranular, transgranular or mixed type) and the fracture aperture, different crystal morphologies are observed, such as equidimensional-stretched/ blocky (in small veins), elongated-blocky/ elongated-stretched, and wide blocky. The simulated vein microstructures show many similarities with natural veins in limestone and overall are in agreement with previous numerical studies. Additionally, a systematic phase-field study on the formation of multi-crack-seal veins in quartz microstructures is presented. The results reveal that with small fracture apertures little growth competition between the fractured grains occurs, which is resulting in no crystallographic preferred orientation (CPO) inside the vein. With an increasing aperture increment growth competition is possible and leads to larger crystal width with a CPO inside the vein. Furthermore, when a oblique opening trajectory is applied sheared crystals form which show into the direction of minimal principal stress (similar as in antitaxial veins). Moreover, natural microstructures with serrated grain boundaries (radiators-fin structures) in thick veins and their transition to delocalized fracturing with thin vein bundles are recreated in the phase-field simulations and extended by probabilistic simulations. The simulated structures show many similarities with natural veins in quartz microstructures and give valuable insight in the crack-seal mechanism. An extension of the phase-field model is presented which incorporates a supersaturation dependent driving force by including the concentration equation and Navier-Stokes equations into the modeling approach. This results in locally different crystal growth velocities in the case of potash alum in a flow channel, where the supersaturation decreases along the flow direction due to a depletion of the fluid. The studies with potash alum give a sound agreement with experimental data, however, this approach might be limited to mesoscopic length scale and crystal systems with high solubilities and fast crystallization rates. The presented simulations demonstrate the capability of the phase-field method to model crystal growth in veins, considering a large number of variables that are expected to influence vein formation in nature. The results obtained during the course of the project are published in various renowned journals as individual and joint papers, presented at international conferences, and led to doctoral and master theses. Further, the findings also revealed many interesting future directions of research.

Projektbezogene Publikationen (Auswahl)

• The role of fracture wall cementation on the vein spacing in microporous carbonates in the Lilstock area, UK”, EGU General Assembly, Vienna, 07.-12.04.2019
  Liene Spruzeniece & Janos Urai
  
• “Multiphase-field Simulation a Study of Brittle Anisotropic Crack Propagation in Sandstones”, 8th GACM Colloquium on Computational Mechanics, Kassel, 28.-30.08.2019
  M. Späth, N. Prajapati, C. Herrmann, D. Schneider, M. Selzer & B. Nestler
  
• “Phase-field Investigation of Epitaxial Vein Growth with Lateral Flow”, AGU Fall Meeting 2019, San Fransisco, 09.-13.12.2019
  M. Späth, M. Selzer & B. Nestler
  
• Formation of wide-blocky calcite veins by extreme growth competition. Journal of the Geological Society, 178(2).
  Spruženiece, Liene; Späth, Michael; Urai, Janos L.; Ukar, Estibalitz; Selzer, Michael; Nestler, Britta & Schwedt, Alexander
  
• Kinematics of Crystal Growth in Single‐Seal Syntaxial Veins in Limestone ‐ A Phase‐Field Study. Journal of Geophysical Research: Solid Earth, 126(10).
  Späth, Michael; Spruženiece, Liene; Urai, Janos L.; Selzer, Michael; Arndt, Max & Nestler, Britta
  
• Wide-blocky veins explained by dependency of crystal growth rate on fracture surface type: Insights from phase-field modeling. Geology, 49(6), 641-646.
  Spruženiece, Liene; Späth, Michael; Urai, Janos L.; Ukar, Estibalitz; Selzer, Michael & Nestler, Britta
  
• “Self-sealing mechanisms of fractured rock”, Biota z Bazant Conference, Northwestern University (remote participation), 01.-03.06.2021
  M. Späth, L. Spruženiece,, M. Selzer, B. Nestler & J. Urai
  
• “Vein growth in z a limestone: microstructures and models”, TSK-Online-Seminarreihe, 16.06.2021
  L. Spruženiece, M. Späth, J. L. Urai, E. Ukar, M. Selzer, A. Schwedt, M. Arndt & B. Nestler
  
• Formation of radiator structures in quartz veins - Phase-field modeling of multi-crack sealing. Journal of Structural Geology, 158, 104576.
  Späth, Michael; Urai, Janos L. & Nestler, Britta
  
• Incomplete Crack Sealing Causes Localization of Fracturing in Hydrothermal Quartz Veins. Geophysical Research Letters, 49(15).
  Späth, Michael; Urai, Janos L. & Nestler, Britta