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TitleThe Henkel petrophysical plot: mineralogy and lithology from physical properties
AuthorEnkin, R JORCID logo; Hamilton, T S; Morris, W A
SourceGeochemistry, Geophysics, Geosystems (G3) vol. 21, issue 1, e2019GC008818, 2020 p. 1-26, Open Access
logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20190547
PublisherAmerican Geophysical Union
Mediapaper; on-line; digital
File formatpdf; html
Subjectsigneous and metamorphic petrology; sedimentology; mineralogy; geophysics; geochemistry; economic geology; Science and Technology; Nature and Environment; petrophysics; bedrock geology; lithology; igneous rocks; sedimentary rocks; metamorphic rocks; magnetic susceptibility; rock density analyses; bulk density; geophysical interpretations; gravity interpretations; magnetic interpretations; models; modelling; mineral assemblages; mineralogical analyses; mineralization; remote sensing; satellite imagery; geochemical interpretations; mineral exploration; exploration methods; ferromagnetism; magnetite; Methodology; Classification
Illustrationsternary diagrams; plots; 3-D diagrams
ProgramTargeted Geoscience Initiative (TGI-5) Program Overview
Released2020 01 03
AbstractThe Henkel plot (logarithm of magnetic susceptibility versus density of rock samples) reveals that most rocks fall on either a 'magnetite trend' or a 'paramagnetic trend.' Interpretation of gravity and magnetic surveys is improved when the mineralogical and lithological basis of these trends is understood. We present a quantitative mineralogical mixing model, involving the components QFC (quartz-feldspar-calcite), FM (ferromagnesian silicates), and M (magnetite) and discuss the geological processes which produce or modify these mixtures. Igneous rocks mostly plot on the magnetite trend, where the FM/M ratio is about 10. The density-susceptibility mineralogical mixing model is compatible with the CIPW mineral calculation for igneous classification from chemical analyses. Sedimentary and metamorphic processes usually involve oxidation, reduction, and/or iron loss, all which are magnetite-destructive and lead to petrophysical measurements along the paramagnetic trend where FM/M > 1,000. Mineralization, with the introduction of sulfides and oxides, leads to dense rocks which do not plot along the magnetite nor paramagnetic trends. This quantitative analysis provides a method to integrate geological processes in the interpretation of geophysical surveys.
Summary(Plain Language Summary, not published)
The Henkel plot (logarithm of magnetic susceptibility versus density of rock samples) is useful for linking geophysical data and geological interpretation. Our study merges thousands of rock physical properties measurements with their corresponding rock types and minerals. Given this globally applicable database, we calibrated a model reducing these many parameters to 3 basic groups of minerals and their physical properties. This model permits users of remote sensing data to come up with equivalent rock and mineral types and a spatial view of geological processes. It also allows geochemical data on igneous rocks to predict their physical behaviour and control on regional geophysical mapping.

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