15 research outputs found
CPO and quantitative textural analyses within sheath folds
Acknowledgments This has been a multi-national collaboration from authors based in Europe, North America, Australia and India. Erasmus funding to GIA in 2018 enabled a visit to Catania leading to discussion and initiation of this project. The authors are grateful to Amarnath Dandapat for preparation of superpolished rock thin sections at the Department of Geology and Geophysics (IIT Kharagpur, India). Niloy Bhowmik is thanked for assistance with SEM-EBSD data generation in the Central Research Facility (IIT Kharagpur, India). E.F. thanks Sibio Carmelo for thin sections preparation at the University of Turin (Italy). Authors are grateful to ANSTO laboratory personnel for the preparation of specimens (funded proposals: P9835 with the title âSheath fold texture characterisationâ, principal scientist: E.F.; co-proposers: G.I.A. and V.L.; DB6749 with the title âTexture analysis of rocksâ, principal scientist: V.L.; co-proposer: E.F.; DB9606 with the title âA pilot experiment for texture characterisation in a sheath foldâ, principal scientist: E.F..; co-proposers: G.I.A. and V.L.). L.N. and R.G. report that this publication has been assigned the NRCan contribution number 20230109. Many thanks to Richard D. Law and an anonymous reviewer for their careful revision that substantially improved the original version of the manuscript. We also thanks Dr. T.K. Cawood from the Geological Survey of Canada for her useful comments on the drafted manuscript. The editorial handling by Fabrizio Agosta is greatly appreciated.Peer reviewedPublisher PD
Strain-rate estimation using fractal analysis of quartz grains in naturally deformed rocks
Fractal analysis of magnetite grains â implications for interpreting deformation mechanism
Kinematic evolution of the Mbakop PanâAfrican granitoids (western Cameroon domain): An integrated AMS and EBSD approach
International audienc
âIn-planeâ site-specific FIB lamella extraction from deformed magnetite and the investigation of low angle grain boundaries under TEM
In this study a modus operandi to investigate site-specific nanostructures in thin films (lamellae) excavated âin-planeâ across (sub)grain boundaries is presented. This is done by discussing the case of a magnetite grain hosted in a thin section of banded iron formation (Norway) that is prepared parallel to the kinematic reference frame (XZ section of the strain ellipsoid). SEM-EBSD analysis reveal that the magnetite grains do not develop a strong crystallographic preferred orientation, although individual grains are strained and show evidence of intracrystalline deformation in form of low angle grain boundaries (LAGB's). Two âin-planeâ lamellae using focused ion beam (FIB) technique are excavated from a magnetite grain in the kinematic reference frame, and nanostructures are studied along three LAGB's using high resolution transmission electron microscopy imaging followed by Fourier transformation (FT), inverse FT and estimation of dislocation densities. Our data establish an empirical relationship for the studied LAGBs, namely, the smaller the angle between LAGB and X-direction, the larger are the shear strain and dislocation density. This relationship is validated from numerical simulations of viscoplastic deformation and dynamic recrystallisation of polycrystalline aggregates of halite, which is also a cubic mineral analogous to magnetite. In addition to the site-specific âin-planeâ FIB lamella information, this study also shows that in a deformed mineral the different orientations of the LAGB compared to the principal strain axes show a different dislocation density. This approach of full tracking of the extension direction (X) from the macroscopic to the nano-scale could play an important role in forward modelling of microstructure evolution in future studies