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TitleRapid geochemical imaging of rocks and minerals with handheld laser induced breakdown spectroscopy (LIBS)
AuthorLawley, C J M; Somers, A M; Kjarsgaard, B AORCID logo
SourceJournal of Geochemical Exploration 106694, 2020.,
Alt SeriesNatural Resources Canada, Contribution Series 20200361
PublisherElsevier B.V.
Mediapaper; on-line; digital
File formatpdf; html
ProvinceNorthwest Territories; Nunavut
Lat/Long WENS-115.0000 -107.0000 67.1667 64.3333
SubjectsScience and Technology; geochemistry; spectroscopy; Slave Craton; machine learning
Illustrationslocation maps; tables; diagrams; graphs
ProgramTargeted Geoscience Initiative (TGI-5) Gold ore systems
Released2020 11 11
AbstractGeochemical imaging is a powerful tool for unravelling the complex geological histories of rocks and minerals. However, its applications has until recently been restricted to research applications in a lab environment due to the cost and size of conventional instrumentation, long analysis times, and extensive sample preparation for some methods. Herein we present a rapid geochemical imaging method for rocks and minerals using handheld LIBS. Analyzes were completed directly on sawed drill core surfaces for a suite of kimberlite-hosted mantle xenoliths (Jericho and Muskox kimberlite intrusions, Canada). Semi-automated LIBS spectral processing following a new open-source workflow allows stitching of multiple small-area maps (each approximately 3 x 3 mm) to produce cm-scale geochemical images of altered mantle xenolith samples. We demonstrate with open-source machine learning tools how qualitative LIBS spectral data can be converted to Feature-Of-Interest (FOI) maps to distinguish mineralogy, including differentiating primary mantle minerals from high (Cr diopside) - and low-T (kelephytic pyrope garnet) phase alteration. Our results further demonstrate that the resolution of handheld LIBS-based geochemical imaging is sufficient to map mineral overgrowths, microscale veinlets, and grain boundaries lined with hydrothermal alteration minerals. The LIBS approach is particularly sensitive for mapping the microscale distribution of elements with low atomic number (eg, Li and Na), which is challenging with other handheld technologies.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI) -5 program develops new models and methods to improve mineral exploration targeting in challenging environments. Here we present a new method for mapping the composition of rocks and minerals. The new method is rapid and requires very little sample preparation, which is important for mineral in remote areas that may not be able to access conventional research laboratories. We apply the new method to a suite of rocks from the past-producing Jericho diamond mine.

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