Hostname: page-component-78c5997874-lj6df Total loading time: 0 Render date: 2024-11-19T11:11:34.514Z Has data issue: false hasContentIssue false
  • English
  • Français

Inherited Fabric in an Omphacite Symplectite: Reconstruction of Plastic Deformation under Ultra-High Pressure Conditions

Published online by Cambridge University Press:  13 May 2013

Florian Heidelbach  and
Michael P. Terry
Florian Heidelbach*
Affiliation:
Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany
Michael P. Terry
Affiliation:
Department of Geology and Geological Engineering, South Dakota School of Mines and Technology, 501 E. St. Joseph St., Rapid City, SD 57701, USA
*
*Corresponding author. E-mail: [email protected]
Get access

Abstract

We investigated an eclogitic gneiss from the Western Gneiss Region in Norway, which underwent subduction as part of Baltica lithosphere beneath Laurentia during the Scandian orogeny. Petrologic data indicate that the eclogite was deformed plastically at about 4 GPa and 800°C producing a strong macroscopic foliation and lineation. Whereas garnet remained largely stable during the retrograde uplift, omphacite was transformed statically into a symplectite consisting of lamellar diopside and plagioclase with more equant grains of hornblende and orthopyroxene. Measurements of the crystallographic preferred orientation with electron backscatter diffraction show that diopside and hornblende, as well as orthopyroxene, have a systematic orientation relationship with the macroscopic fabric, as well as the (presumed) orientation of the host omphacite. The orientation relationship between the chain silicates is very sharp with the crystallographic forms {100}, {010}, and ⟨001⟩ being parallel. Their bulk texture shows a maximum of ⟨001⟩ parallel to the lineation and girdles of {010} and {110} perpendicular to the lineation with maxima subparallel to the foliation corresponding to an L-type texture of the original omphacite and indicating constrictional strain with an additional component of pure shear/simple shear component.

Keywords

symplectiteelectron backscatter diffractiontopotaxytexturesdeformationhigh pressure
Type
EBSD Special Section
Information
Microscopy and Microanalysis , Volume 19 , Issue 4 , August 2013 , pp. 942 - 949
Copyright
Copyright © Microscopy Society of America 2013 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Angel, R.J., Sochalski-Kolbus, L.M. & Tribaudino, M. (2012). Tilts and tetrahedra: The origin of the anisotropy of feldspars. Am Mineral 97, 765–778.CrossRefGoogle Scholar
Bascou, J., Barruol, G., Vauchez, A., Mainprice, D. & Egydio-Silva, M. (2001). EBSD-measured lattice-preferred orientations and seismic properties of eclogites. Tectonophysics 342, 61–80.Google Scholar
Bestmann, M., Habler, G., Heidelbach, F. & Thöni, M. (2008). Dynamic recrystallization of garnet and related diffusion processes. J Struct Geol 30, 777–790.CrossRefGoogle Scholar
Brenker, F.E., Prior, D.J. & Müller, W.F. (2002). Cation ordering in omphacite and effect on deformation mechanism and lattice preferred orientation (LPO). J Struct Geol 24, 1991–2005.Google Scholar
Brodie, K.H. (1995). The development of orientated symplectites during deformation. J Metamorph Geol 13, 499–508.Google Scholar
Godard, G. & van Roermund, H.L.M. (1995). Deformation-induced clinopyroxene fabrics from eclogites. J Struct Geol 17, 1425–1443.CrossRefGoogle Scholar
Groppo, C., Lombardo, B., Rolfo, F. & Pertusati, P. (2007). Clockwise exhumation path of granulitized eclogites from the Ama Drime range (Eastern Himalayas). J Metamorph Geol 25, 51–75.Google Scholar
Kleinschrodt, R. & Duyster, J. (2002). HT-deformation of garnet: An EBSD study on granulites from Sri Lanka, India and the Ivrea zone. J Struct Geol 24, 1829–1844.CrossRefGoogle Scholar
Krogh Ravna, E.J. & Terry, M.P. (2004). Geothermobarometry of UHP and HP eclogites and schists—An evaluation of equilibria among garnet-clinopyroxene-kyanite-phengite-coesite/quartz. J Metamorph Geol 22, 579–592.CrossRefGoogle Scholar
McNamara, D.D., Wheeler, J., Pearce, M. & Prior, D.J. (2012). Fabrics produced mimetically during static metamorphism in retrogressed eclogites from the Zermatt-Saas zone, Western Italian Alps. J Struct Geol 44, 167–178.Google Scholar
Müller, W.F., Brenker, F.E., Barnert, E.B. & Franz, G. (2004). Chain multiplicity faults in deformed omphacite from eclogite. Eur J Mineral 16, 37–48.CrossRefGoogle Scholar
Obata, M. & Ozawa, K. (2011). Topotaxic relationships between spinel and pyroxene in kelyphite after garnet in mantle-derived peridotites and their implications to reaction mechanism and kinetics. Miner Petrol 101, 217–224.Google Scholar
O'Brien, P.J. & Rötzler, J. (2003). High-pressure granulites: Formation, recovery of peak conditions and implications for tectonics. J Metamorph Geol 21, 1–18.CrossRefGoogle Scholar
O'Conner, B.C. & Terry, M.P. (2002). P-T conditions and microstructural analysis of UHP metamorphic rocks during exhumation, Fjørtoft, Western Gneiss Region, Norway. Geological Society of America Meeting, vol. 37, p. 53. Google Scholar
Odashima, N., Morishita, T., Ozawa, K., Nagahara, H., Tsuchiyama, A. & Nagashima, R. (2008). Formation and deformation mechanisms of pyroxene-spinel symplectite in an ascending mantle, the Horoman peridotite complex, Japan: An EBSD (electron backscatter diffraction) study. J Miner Petrol Sci 103, 1–15.CrossRefGoogle Scholar
Terry, M.P., Heidelbach, F., Couvy, H., Bromiley, G.D. & Krogh, T. (2005). PT-history from the Kvalvika mantle peridotite, Norway: Implications for crust-mantle interactions, and conditions and timing for olivine c-slip during continental subduction. Geological Society of America Annual Meeting, Paper No. 171-13, Salt Lake City, UT, USA. Google Scholar
Terry, M.P. & Robinson, P. (2004). Geometry of eclogite-facies structural features: Implications for production and exhumation of ultrahigh-pressure and high-pressure rocks, Western Gneiss Region, Norway. Tectonics 23, TC2001, doi: 10.1029/2002TC001401. Google Scholar
Terry, M.P., Robinson, P. & Krogh Ravna, E.J. (2000). Kyanite eclogite thermobarometry and evidence for thrusting of UHP over HP metamorphic rocks, Nordøyane, Western Gneiss Region, Norway. Am Mineral 85, 1637–1650.CrossRefGoogle Scholar