Spatial correlation of deformation and mineral reaction in experimentally deformed plagioclase–olivine aggregates |
| |
| Authors: | AA de Ronde R Heilbronner H Stünitz J Tullis |
| |
| Institution: | aDepartment of Earth Sciences, Basel University, Bernoullistrasse 32, 4056 Basel, Switzerland;bDepartment of Geological Sciences, Brown University, 324 Brook Street, Box 1846, Providence, RI 02912, USA |
| |
| Abstract: | Shear deformation of hot pressed plagioclase–olivine aggregates was studied in the presence and absence of mineral reaction. Experiments were performed at 900 °C, 1500 MPa, and a constant shear strain rate of 5×10−5 s−1 in a solid medium apparatus. Whether the mineral reaction between plagioclase and olivine takes place or not is controlled by choosing the appropriate plagioclase composition; labradorite (An60) does not react, anorthite (An92) does. Labradorite–olivine aggregates deformed without reaction are very strong and show strain hardening throughout the experiment. Syndeformational reaction between olivine and anorthite causes a pronounced strain weakening. The reaction produces fine-grained opx–cpx–spinel aggregates, which accommodate a large fraction of the finite strain. Deformation and reaction are localised within a 0.5-mm-wide sample. Three representative samples were analysed for their fabric anisotropy R* and shape-preferred orientation α* (fabric angle with the shear plane) using the autocorrelation function (ACF). Fabric anisotropy can be calibrated to quantify strain variations across the sheared samples. In the deformed and reacted anorthite–olivine aggregate, there is a strong correlation between reaction progress and strain; regions of large shear strain correspond to regions of maximum reaction progress. Within the sample, the derived strain rate variations range up to almost one order of magnitude. |
| |
| Keywords: | Reaction weakening Plagioclase Olivine Autocorrelation function Strain localisation and partitioning |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
