TY - JOUR
T1 - Minimizing and quantifying mis-indexing in electron backscatter diffraction (EBSD) determinations of antigorite crystal directions
AU - Nagaya, Takayoshi
AU - Wallis, Simon R.
AU - Seto, Yusuke
AU - Miyake, Akira
AU - Soda, Yusuke
AU - Uehara, Seiichiro
AU - Matsumoto, Megumi
N1 - Funding Information:
We thank D. Mainprice for providing the software to analyze the CPO data. We also thank the members of the Structural Petrology group of Nagoya University and the Geomaterial and Energy group of Tohoku University for discussions and comments on this study. This work was supported by JSPS grants-in-aid Nos. 24244079, 26287139, 13J00199 and 16J01480.
PY - 2017/2/1
Y1 - 2017/2/1
N2 - Antigorite is common in hydrated mantle domains and commonly shows strong alignment either due to deformation or growth in a preferred orientation. The alignment of antigorite imparts a strong anisotropy to the host rock affecting physical properties. A quantitative analysis of how antigorite affects these properties requires a reliable measurement of the crystallographic preferred orientation of antigorite, and EBSD analysis is the most widely used technique. Potential problems include (i) mis-indexing, which can add significant uncertainties to the results; and (ii) sample preparation, which may affect the measured CPO in particular for automated mapping. Combining results derived from X-ray goniometry, EBSD and U-stage techniques with FIB-TEM analysis leads to the following conclusions concerning these two issues. (i) There is a significant issue with mis-indexing a- and b-axes due to rotational similarities about the c-axis. Similar problems may also affect the c-axes measurements but this is less significant than the a- and b-axes when data are filtered using lower MAD values. Filtering using MAD values of <0.7° can significantly change the resulting CPO. (ii) Sample preparation can also affect the measured CPO: sections prepared parallel to the foliation show only minor differences with MAD values of <2.0°. Mis-indexing problems can be minimized by using an MAD value of <0.7° and analysing thin sections cut parallel to the foliation.
AB - Antigorite is common in hydrated mantle domains and commonly shows strong alignment either due to deformation or growth in a preferred orientation. The alignment of antigorite imparts a strong anisotropy to the host rock affecting physical properties. A quantitative analysis of how antigorite affects these properties requires a reliable measurement of the crystallographic preferred orientation of antigorite, and EBSD analysis is the most widely used technique. Potential problems include (i) mis-indexing, which can add significant uncertainties to the results; and (ii) sample preparation, which may affect the measured CPO in particular for automated mapping. Combining results derived from X-ray goniometry, EBSD and U-stage techniques with FIB-TEM analysis leads to the following conclusions concerning these two issues. (i) There is a significant issue with mis-indexing a- and b-axes due to rotational similarities about the c-axis. Similar problems may also affect the c-axes measurements but this is less significant than the a- and b-axes when data are filtered using lower MAD values. Filtering using MAD values of <0.7° can significantly change the resulting CPO. (ii) Sample preparation can also affect the measured CPO: sections prepared parallel to the foliation show only minor differences with MAD values of <2.0°. Mis-indexing problems can be minimized by using an MAD value of <0.7° and analysing thin sections cut parallel to the foliation.
UR - http://www.scopus.com/inward/record.url?scp=85008965855&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85008965855&partnerID=8YFLogxK
U2 - 10.1016/j.jsg.2016.12.006
DO - 10.1016/j.jsg.2016.12.006
M3 - Article
AN - SCOPUS:85008965855
VL - 95
SP - 127
EP - 141
JO - Journal of Structural Geology
JF - Journal of Structural Geology
SN - 0191-8141
ER -