1 / 17

Rheology of deformed Carrara marble: Insights from torsion experiments

Rheology of deformed Carrara marble: Insights from torsion experiments. 1. 2. 3. Rolf Bruijn , Claudio Delle Piane , Willemijn de Raadt. ETH, Geological Institute, Earth Sciences, Zurich, Switzerland CSIRO Earth Science and Resource Engineering, Kensington, Australia

roger
Download Presentation

Rheology of deformed Carrara marble: Insights from torsion experiments

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Rheology of deformed Carrara marble: Insights from torsion experiments 1 2 3 Rolf Bruijn , Claudio DellePiane , Willemijn de Raadt ETH, Geological Institute, Earth Sciences, Zurich, Switzerland CSIRO Earth Science and Resource Engineering, Kensington, Australia Utrecht University, Faculty of Geosciences, Utrecht, The Netherlands

  2. Single-stage deformation experiments extended to multi-stage  Effect of pre-existing strain Strain interruption and reversal: Shear zone reactivation Composite samples (2 types): Host rock/mylonite competence contrast Strain interruption and heating: Shear zone reactivation + annealing Introduction/problem Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  3. Experiments Type I: Counter-clockwise deformation followed by clockwise deformation Type II: 2-segments composite deformation After Delle Piane and Burlini, 2008 Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  4. Experiments Type III: 3-segments composite deformation After Bruijn et al., 2011 Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  5. Experiments Type IV: three-stage sample history γ = 6-9 5 hours + γ = 6-9 1st deformation annealing 2nd deformation T °C 20 Time Modified after Delle Piane and Burlini, 2008 Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  6. Experiment parameters • Focus on dislocation creep with dynamic recrystallization • Comparison with monotonic experiments (Pieri et al., 2001: Barnhoorn et al., 2004) • Type IV experiments explore effect of temperature, strain rate and switch in dominant deformation mechanism Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  7. Type I: Low-strain flow behavior • Effect of shear interruption and reversal at low strain? • Flow strength evolution barely affected • 3-6 MPa flow difference explained by fabric effects and load cell precision Modified after Delle Piane and Burlini, 2008; Bruijn et al., 2011 Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  8. Type I: High-strain flow behavior Effect of shear interruption and reversal at high strain? • Steady state flow quickly restored • 2-7 MPa flow difference explained by fabric effects and load cell precision Continued forward or reverse flow easier? Modified after Delle Piane and Burlini, 2008; Bruijn et al., 2011 Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  9. Type II & III: Stage 2 strain behavior Type II: 2-segments composite Type II stage 2 deformation Bulk strain: γ2 = 1 Segmented strain contrast Forward strain  γ2 = 1.8 First strain  γ2 = 0.2  Strain (rate) ratio ≈ 9 γ1 = 5 γ1 = 0 • Type III stage 2 deformation • Bulk strain: γ2 = 1 (left) & γ2 = 5 (right) • Segmented strain contrast • Left Right • Forward strain  γ2 = 0.7  γ2 = 7.0 • First strain  γ2 = 1.4  γ2 = 0.9 • Reversed strain  γ2 = 1.0  γ2 = 7.0 • Strain (rate) ratio ≈ 2 ≈ 8 Type III: 3-segments composite γ1 = 1 γ1 = 5 γ1 = 0 γ1 = 0 γ1 = -5 γ1 = -1 Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  10. Type I & III: Low strain fabric • Microstructures + CPO • Type II strain reversal • Grain shearing recovered • Dyn. Rx. continued • SPO removed, but CPO preserved  • Weak evidence for shear sense last deformation stage • Type III strain reversal • Recovery of “eaten” sheared grain requires less strain  • CPO + SPO are unreliable total shear sense indicator • J-index false measure for strain intensity Type I Type III After Delle Piane and Burlini, 2008 After Bruijn et al., 2011 Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  11. Type I & III: High strain fabric Type I: after strain reversal Type I: before strain reversal • Microstructure and texture after high-strain strain reversal • Continued dynamic recrystallization • Foliation indicates shear sense last deformation stage • Due to symmetry in slip system activity texture development is unaffected • Shear sense is irrelevant for recrystallization progress  product of absolute strain or work After Delle Piane and Burlini, 2008 Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  12. Type I & III: High strain fabric Type III: Top and bottom segments after second deformation stage • Fabric after high-strain shear interruption and reversal • Foliation development reflects total strain rather than absolute strain • Foliation angle can be used to estimate total strain, which is a minimum value in the case of reversed sense of shear • Crystal orientations unaffected, but J-index delayed by strain reversal After Bruijn et al., 2011 Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  13. Type IV: Strain interruption with annealing Type IV: three-stage sample history γ = 6-9 5 hours + γ = 6-9 1st deformation annealing 2nd deformation T °C 20 Time Modified after Delle Piane and Burlini, 2008 Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  14. Type IV: Texture effect Rx texture + grain refinement Weakening (A-B) = 21.5 % Only grain refinement Weakening (D-E) = 17.4 % After De Raadt et al., in prep. Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  15. Type IV: Texture effect Rx texture + grain refinement Weakening (A-B) = 7.8 % Only grain refinement Weakening (D-E) = 4.5 % After De Raadt et al., in prep. Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  16. Type IV: Texture effect Rx texture + grain refinement Weakening (A-B) = 16.4 % Only grain refinement Weakening (D-E) = 6.3 % After De Raadt et al., in prep. Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

  17. Conclusions • Strain interruption and reversal have little effect on flow strength evolution • Strain reversal at low strain slightly easier than continuation (Bauschinger effect) • Strain reversal at high strain as easy as continuation • Shearing of grains recovered by strain reversal; grain size dependent • Recrystallization unaffected by shear sense  absolute strain/work • Most deformation accommodated by weakest sample segment • Competence contrast results in one order of magnitude strain (rate) variation • Annealing preserves recrystallization texture • 33-67 % of weakening is caused by Rx texture development Complex coupling between fabric and rheology Introduction/Problem – Experiments – Flow behavior – Segmented strain – Fabric evolution – Texture effect – Conclusions

More Related