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Nanoscale imaging of Fe-rich inclusions in single-crystal zircon using X-ray ptycho-tomography

DOI: 10.1038/s41598-024-55846-4 DOI Help

Authors: Venkata S. C. Kuppili (University of Cambridge; Canadian Light Source, University of Saskatchewan) , Matthew Ball (University of Cambridge) , Darren Batey (Diamond Light Source) , Kathryn Dodds (University of Cambridge) , Silvia Cipiccia (Diamond Light Source; University College London) , Kaz Wanelik (Diamond Light Source) , Roger Fu (Harvard University) , Christoph Rau (Diamond Light Source) , Richard J. Harrison (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Scientific Reports , VOL 14

State: Published (Approved)
Published: March 2024
Diamond Proposal Number(s): 19194 , 21309

Open Access Open Access

Abstract: We apply X-ray ptycho-tomography to perform high-resolution, non-destructive, three-dimensional (3D) imaging of Fe-rich inclusions in paleomagnetically relevant materials (zircon single crystals from the Bishop Tuff ignimbrite). Correlative imaging using quantum diamond magnetic microscopy combined with X-ray fluorescence mapping was used to locate regions containing potential ferromagnetic remanence carriers. Ptycho-tomographic reconstructions with voxel sizes 85 nm and 21 nm were achievable across a field-of-view > 80 µm; voxel sizes as small as 5 nm were achievable over a limited field-of-view using local ptycho-tomography. Fe-rich inclusions 300 nm in size were clearly resolved. We estimate that particles as small as 100 nm—approaching single-domain threshold for magnetite—could be resolvable using this “dual-mode” methodology. Fe-rich inclusions (likely magnetite) are closely associated with apatite inclusions that have no visible connection to the exterior surface of the zircon (e.g., via intersecting cracks). There is no evidence of radiation damage, alteration, recrystallisation or deformation in the host zircon or apatite that could provide alternative pathways for Fe infiltration, indicating that magnetite and apatite grew separately as primary phases in the magma, that magnetite adhered to the surfaces of the apatite, and that the magnetite-coated apatite was then encapsulated as primary inclusions within the growing zircon. Rarer examples of Fe-rich inclusions entirely encapsulated by zircon are also observed. These observations support the presence of primary inclusions in relatively young and pristine zircon crystals. Combining magnetic and tomography results we deduce the presence of magnetic carriers that are in the optimal size range for carrying strong and stable paleomagnetic signals but that remain below the detection limits of even the highest-resolution X-ray tomography reconstructions. We recommend the use of focused ion beam nanotomography and/or correlative transmission electron microscopy to directly confirm the presence of primary magnetite in the sub 300 nm range as a necessary step in targeted paleomagnetic workflows.

Subject Areas: Earth Science


Instruments: I13-1-Coherence

Added On: 04/03/2024 08:50

Documents:
s41598-024-55846-4.pdf

Discipline Tags:

Earth Sciences & Environment Mineralogy Geology Geochemistry

Technical Tags:

Imaging Coherent Diffraction Imaging (CDI) Ptychography