Neutron diffraction was used to investigate the crystallographic preferential orientation and structure parameters of samples of metagabro mylonite collected from the eastern part of the metagabbro sheet at the Stare Mesto belt, Bohemia Massif, Czech Republic.
Two specimen types were prepared and investigated: a powder specimen used to refine the lattice parameters of the constituting minerals, and spherical samples (50±0.1 mm in diameter) for texture analysis. The experiments were performed on the KSN-2 neutron diffractometer and collected data were processed by software package GSAS [1].
Data recorded with powder specimens prepared by milling the sampled rocks were used to refine the structure parameters of plagioclase (labradorite structure, triclinic space group C-1) and amphibole (monoclinic space group C2/m). For both mineral phases, the values of lattice parameters obtained from measurements with powder specimen agree with the expected model (Table 1) [2].
Activation of (001)[010] and (001)[-170] slip systems occur for plagioclase plastic deformation of ultramylonite. For the amphibole rich sample activation of (-201)[010] slip system is assumed.
Dominant slip system (100)[001] typical for amphibole was found only for ultramylonite sample.
|
|
plagioclase |
amphibole |
|
a [nm] |
8.154(3) |
9.837(4) |
|
b [nm] |
12.82(5) |
18.01(3) |
|
c [nm] |
7.104(2) |
5.296(6) |
|
α [°] |
93.55(6) |
90 |
|
β [°] |
116.18(7) |
105.00(5) |
|
γ [°] |
89.77(5) |
90 |