Clustering of downhole physical property measurements at the Victoria property, Sudbury for the purpose of extracting lithological information

Mahmoodi, Omid; Smith, Richard S.

doi:10.1016/j.jappgeo.2015.04.015

Cited by 8 publications

(5 citation statements)

References 15 publications

(26 reference statements)

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“…Other studies used physical properties for rock classification, for example in the Sudbury basin, Canada. Here, Mahmoodi and Smith (2015) identified homogenous physical units by density, gamma radioactivity, and magnetic susceptibility measurements. They were able to correlate most classes to lithological units.…”

Section: Discussionmentioning

confidence: 99%

Core‐Log‐Seismic Integration in Metamorphic Rocks and Its Implication for the Regional Geology: A Case Study for the ICDP Drilling Project COSC‐1, Sweden

Elger

Berndt

Kästner

et al. 2021

Geochem Geophys Geosyst

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Beyond a general scientific curiosity about the nature of the continental crust and its formation, detailed information on its lower and middle parts is a prerequisite for mineral and geothermal exploration and the assessment of earthquake hazards. For example, some of the most damaging earthquakes such as in Nepal (2015; Mw 7.8) and Sichuan (2008; Mw 7.9) occur in continental collision zones (Hubbard et al., 2016; Lin et al., 2009). Continental crust is up to 70 km thick. Thus, the lower crustal processes in active continental collision zones (e.g., formation of mafic or ultramafic cumulate rocks and emplacement of magma from the mantle) occur at too great depth to be studied directly (Arndt & Goldstein, 1989; Hacker et al., 2015), far beyond the reach of boreholes, for example, the deepest borehole on Kola peninsula was 12 km deep

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Section: Discussionmentioning

confidence: 99%

Core‐Log‐Seismic Integration in Metamorphic Rocks and Its Implication for the Regional Geology: A Case Study for the ICDP Drilling Project COSC‐1, Sweden

Elger

Berndt

Kästner

et al. 2021

Geochem Geophys Geosyst

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“…Downhole physical property measurement from six drillholes, plotted on the geological map of the Victoria property in Fig. , indicated that there is a strong contrast in the density and magnetic susceptibility between the dominant lithological units (Mahmoodi and Smith ). This suggests that Victoria is an interesting site for lithological and physical unit modelling using gravity and magnetic data inversion.…”

Section: Geological Contextmentioning

confidence: 99%

“…Analysing accurate downhole physical property measurements is a reliable tool to provide this link (Killeen ; McDowell et al . ; McDowell, Fenlon and King ; Vella and Emerson ; Mwenifumbo and Mwenifumbo ; Mahmoodi and Smith ). Then, a classifier that simulates the quantitative relationship between geological features and physical properties can be used to predict the geology (Rabaute et al .…”

Section: Introductionmentioning

confidence: 99%

“…The inversion models can potentially be used to validate and refine a geological model if a link between the physical property data and the lithological data is identified. Analysing accurate downhole physical property measurements is a reliable tool to provide this link (Killeen 1997;McDowell et al 1998;McDowell, Fenlon and King 2004;Vella and Emerson 2009;Mwenifumbo and Mwenifumbo 2012;Mahmoodi and Smith 2015). Then, a classifier that simulates the quantitative relationship between geological features and physical properties can be used to predict the geology (Rabaute et al 2003;Garcia et al 2011;Granek 2011).…”

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confidence: 99%

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Using constrained inversion of gravity and magnetic field to produce a 3D litho‐prediction model

Mahmoodi

Smith

Spicer³

2017

Geophysical Prospecting

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Geologically constrained inversion of gravity and magnetic field data of the Victoria property (located in Sudbury, Canada) was undertaken in order to update the present three‐dimensional geological model. The initial and reference model was constructed based on geological information from over 950 drillholes to constrain the inversion. In addition, downhole density and magnetic susceptibility measured in six holes were statistically analysed to derive lower and upper bounds on the physical properties attributed to the lithological units in the reference model. Constrained inversion of the ground gravity and the airborne magnetic data collected at the Victoria property were performed using GRAV3D and MAG3D, respectively. A neural network was trained to predict lithological units from the physical properties measured in six holes. Then, the trained network was applied on the three‐dimensional distribution of physical properties derived from the inversion models to produce a three‐dimensional litho‐prediction model. Some of the features evident in the lithological model are remnants of the constraints, where the data did not demand a significant change in the model from the initial constraining model (e.g., the thin pair of diabase dykes). However, some important changes away from the initial model are evident; for example, a larger body was predicted for quartz diorite, which may be related to the prospective offset dykes; a new zone was predicted as sulfide, which may represent potential mineralisation; and a geophysical subcategory of metabasalt was identified with high magnetic susceptibility and high density. The litho‐prediction model agrees with the geological expectation for the three‐dimensional structure at Victoria and is consistent with the geophysical data, which results in a more holistic understanding of the subsurface lithology.

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“…They are the key to providing physical ground truth and characterization of diverse rock types. Mahmoodi and Smith (), for example, apply fuzzy k‐means clustering on borehole susceptibility, density and gamma logs to characterize lithological zones in the Sudbury intrusive complex. These data, especially density and magnetic susceptibility when correlated to lithologies and mineralogies, are essential inputs to constrain the geophysical inversion and geological interpretation of magnetic and gravity surveys (Vallée, Farquharson, et al, ; Vallée, Morris, et al, ).…”

Section: Introductionmentioning

confidence: 99%

The Henkel Petrophysical Plot: Mineralogy and Lithology From Physical Properties

Enkin

Hamilton

Morris

2020

Geochem Geophys Geosyst

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The 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. Plain Language SummaryThe 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 three 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 behavior and control on regional geophysical mapping. Key Points: • The Henkel plot (logarithm of magnetic susceptibility versus density of rock samples) helps integrate geological and geophysical analysis • We present a quantitative mineralogical mixing model involving three components quartz-feldspar-calcite, ferromagnesian silicates, and magnetite • Major geological processes leading to petrophysical properties on different regions of the Henkel plot are easily explained

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Clustering of downhole physical property measurements at the Victoria property, Sudbury for the purpose of extracting lithological information

Cited by 8 publications

References 15 publications

Core‐Log‐Seismic Integration in Metamorphic Rocks and Its Implication for the Regional Geology: A Case Study for the ICDP Drilling Project COSC‐1, Sweden

Core‐Log‐Seismic Integration in Metamorphic Rocks and Its Implication for the Regional Geology: A Case Study for the ICDP Drilling Project COSC‐1, Sweden

Using constrained inversion of gravity and magnetic field to produce a 3D litho‐prediction model

The Henkel Petrophysical Plot: Mineralogy and Lithology From Physical Properties

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