Nusfjord Fault Rocks 2

Nusfjord Fault Rocks 2

This dataset contains the Fourier Transform Infrared (FTIR), electron backscatter diffraction (EBSD), and Scanning Transmission Electron (STEM) data of a fault rock from an anorthosite sampled from Nusfjord, Lofoten, Norway. There are a total of 594 files and the folder size is just under 22 GB.

GPS location: 33 W 432143.75 m E 7549927.62 m N

FTIR data

The following is an excerpt from Michalchuk et al., 202X in prep. describing the FTIR instrument used. See the main text of the peer-reviewed article for the locations of each FTIR transect.

"A doubly polished section of ~210 µm thickness from sample L-053 was analysed with transmission FTIR micro-spectroscopy using a Bruker(r) Tensor II FTIR system at the Institute of Geological Sciences of the University of Bern. This system is equipped with an unpolarized globular infrared source and a KBr beam-splitter, coupled to a Hyperion 3000 microscope with a dry air-purged Plexiglas sample chamber to limit H2O and CO2 variations. The focal plane array (FPA) detector is an arrangement of 64 × 64 liquid-nitrogen-cooled mercury cadmium telluride (MCT) elements on a square array with a pixel size of 2.7 µm × 2.7 µm. Point analyses use MCT, while maps use the FPA detector. A higher signal quality and an improved signal-to-noise ratio was achieved by using a 2 x 2 binning that resulted in a 5.4 × 5.4 µm pixel resolution in FPA maps. The infrared spectra were acquired with 8 cm-1 wavenumber resolution and 128 scans between 900 and 3850 cm-1. OPUS(r) version 8.5 was used for the atmospheric correction and the concave rubber band correction with 64 points and four iterations. Background measurements were made before/after XX mins for each map acquisition. Further processing of the FTIR-FPA maps was performed using SpecXY, a Matlab-based software package designed to handle, organize, and investigate spectral data (Gies et al., 2024)."

The FTIR data is labelled with L053_ at the beginning of each file. There are 6 large transects covering the damage zone adjacent to a pseudotachylyte fault. Each individual transect contains smaller maps that must be pieced together.

EBSD

The following is an excerpt from Michalchuk et al., 202X in prep. describing the EBSD instrument used. See the supplementary file of the peer-reviewed article showing each EBSD location on a SEM-CL map.

"Crystallographic orientations were collected on sample LM1726 via EBSD analysis using a Zeiss Merlin SEM coupled with an Oxford Instruments Nordlys detector at the University of Tromsø. EBSD data were collected after SEM-CL on the same microstructures. All thin sections were chemically polished with colloidal silica prior to EBSD analysis. Crystallographic patterns were acquired and processed using Aztec software (Oxford Instruments) on rectangular grids with a step size of 1 µm using an accelerating voltage of 20 kV, a 70 ° sample tilt angle, and a 24-29 mm working distance. The construction of EBSD maps and grain analysis was carried out using MTEX (version 5.10.0) (Bachmann et al., 2010; Hielscher & Schaeben, 2008). High-angle boundaries were defined as misorientations ?10°, while low-angle boundaries were defined as misorientations >2° and <10°. Grains and subgrains consisting of 5 pixels were removed. Contoured pole figures (equal-area, lower hemisphere) using the average orientation of each grain (one point per grain; 1PPG) were generated to depict crystallographic preferred orientations (CPOs). To quantify the strength of the plagioclase neoblast CPOs, J- and M-indices were calculated following the methods described by Mainprice et al. (2015) and Skemer et al. (2005), respectively. Results are presented as phase, misorientation to mean (mis2mean), KAM (kernel average misorientation using a neighbour order of n = 5), and grain orientation spread (GOS, i.e., a measure of the average internal lattice distortion of the grain) maps. Differentiating primary plagioclase from plagioclase neoblasts followed the "bent-knee" approach in Cross et al. (2017), where the GOS is plotted against the cumulative number of grains and the knee in the curve is the GOS threshold separating relict grains (plagioclase1) from neoblasts (plagioclase2). "

STEM data

The following is an excerpt from Michalchuk et al., 202X in prep. describing the STEM instrument used.

"A total of six transmission electron microscopy (TEM) foils were prepared from sample LM1726 via focused ion beam (FIB) milling at Utrecht University, using the FEI Helios® Nanolab G3 Dualbeam system, targeting key microstructures identified in SEM-CL. A 200 nm layer of platinum was deposited using the electron beam (2 kV, 0.4 nA) before the ion beam deposition of the main platinum strip. This was done to prevent surface amorphization as a preparation artefact (Ohl et al., 2020). Four foils were prepared using the “traditional” in-situ FIB lift-out technique, that is the samples were sputter-coated with a 9 nm layer of Pt/Pd, and a standardized procedure was employed to mill and lift out the cross-sectional TEM foils that were orientated perpendicular to the thin section surface (Liu et al., 2016). Two foils were prepared as “wedges” (TEM6) so that we could analyse the foil parallel to the thin section surface and correlate directly the foil with electron microscopy observations (see Li et al. (2018) for details on this preparatory technique). Subsequently, each foil was analysed with STEM and EDX using the FEI Talos® F200X, with an acquisition acceleration voltage of 200 kV and beam current of 5–10 nA, at Utrecht University microscopy center."

STEM data in this file is presented as .png image files of the TEM foils at various resolutions. There is also an overview SEM-CL map in PDF format showing the locations of each foil.