Modification of fluid inclusions in quartz by deviatoric stress I: experimentally induced changes in inclusion shapes and microstructures |
| |
Authors: | Alexandre Tarantola Larryn W Diamond Holger Stünitz |
| |
Institution: | 1. Rock–Water Interaction Group, Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, 3012, Bern, Switzerland 3. UMR-G2R, Université Henri Poincaré, 54506, Vandoeuvre-lès-Nancy Cedex, France 2. Department of Geology, University of Troms?, Dramsveien 201, 9037, Troms?, Norway
|
| |
Abstract: | Fluid inclusions in quartz are known to modify their shapes and microstructures (textures) during weak plastic deformation.
However, such changes have not been experimentally demonstrated and criteria are not available to relate them to paleostress
conditions. To address these issues, quartz crystals containing natural CO2–H2O–NaCl fluid inclusions have been experimentally subjected to compressive deviatoric stresses of 90–250 MPa at 700°C and ~600 MPa
confining pressure. Strains of up to 1% cause the inclusions to develop irregular shapes and to generate microcracks in crystallographic
planes oriented subperpendicular to the major compression axis, σ
1. The uniform alignment of the microcracks imparts a planar fabric to the samples. The microcracks heal and form swarms of
tiny satellite inclusions. These new inclusions lose H2O by diffusion, thereby triggering plastic deformation of the surrounding quartz via H2O-weakening. Consequently, the quartz samples deform plastically only in domains originally rich in inclusions. This study
shows that fluid inclusions deformed by deviatoric stresses may indeed record information on paleostress orientations and
that they play a key role in facilitating crystal-plastic deformation of quartz. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|