scholarly journals Characterising Magnetic Susceptibility and Remanent Magnetisation of Magnetite and Hematite Rich Drill-Core Samples at Blötberget

2019 ◽  
Vol 2019 (1) ◽  
pp. 1-4
Author(s):  
Andreas Björk
2020 ◽  
Vol 12 (7) ◽  
pp. 1218
Author(s):  
Laura Tuşa ◽  
Mahdi Khodadadzadeh ◽  
Cecilia Contreras ◽  
Kasra Rafiezadeh Shahi ◽  
Margret Fuchs ◽  
...  

Due to the extensive drilling performed every year in exploration campaigns for the discovery and evaluation of ore deposits, drill-core mapping is becoming an essential step. While valuable mineralogical information is extracted during core logging by on-site geologists, the process is time consuming and dependent on the observer and individual background. Hyperspectral short-wave infrared (SWIR) data is used in the mining industry as a tool to complement traditional logging techniques and to provide a rapid and non-invasive analytical method for mineralogical characterization. Additionally, Scanning Electron Microscopy-based image analyses using a Mineral Liberation Analyser (SEM-MLA) provide exhaustive high-resolution mineralogical maps, but can only be performed on small areas of the drill-cores. We propose to use machine learning algorithms to combine the two data types and upscale the quantitative SEM-MLA mineralogical data to drill-core scale. This way, quasi-quantitative maps over entire drill-core samples are obtained. Our upscaling approach increases result transparency and reproducibility by employing physical-based data acquisition (hyperspectral imaging) combined with mathematical models (machine learning). The procedure is tested on 5 drill-core samples with varying training data using random forests, support vector machines and neural network regression models. The obtained mineral abundance maps are further used for the extraction of mineralogical parameters such as mineral association.


2021 ◽  
Author(s):  
Oliver Dixon ◽  
William McCarthy ◽  
Nasser Madani ◽  
Michael Petronis ◽  
Steve McRobbie ◽  
...  

<p>Copper is one of the most important critical metal resources needed to achieve carbon neutrality with a projected increase in demand of >300% over the next half century from electronics and renewables.  Porphyry deposits account for most of the global copper production, but the discovery of new reserves is ever more challenging. Machine learning presents an opportunity to cross reference new and traditionally under-utilised data sets with a view to developing quantitative predictive models of hydrothermal alteration zones to guide new, ambitious exploration programs.</p><p>The aim of this study is to demonstrate a new alteration classification scheme driven by quantitative magnetic and spectral data to feed a machine learning algorithm. The benefits of an alteration model based on quantitative data rather than subjective observations by geologists, are that there is no bias in the data collected, the arising model is quantifiable and therefore easy to model and the process be fully automated. Ultimately, this approach aids more detailed exploration and mine modelling, in turn, reducing the extraction process carbon footprint and more effectively identifying new deposits.</p><p>Presented here are magnetic susceptibility and shortwave infrared (SWIR) data collected from the KazMinerals plc. owned Aktogay Cu-Mo giant porphyry deposit, eastern Kazakhstan, which has a throughput of 30Mtpa of ore. These data are cross referenced using a newly developed machine learning algorithm. Generated autonomously, our results reveal twelve statistically and geologically significant clusters that define a new alteration classification for porphyry style mineralisation. Results are entirely non-subjective, reproducible, quantitative and modellable.</p><p>Importantly, magnetic susceptibility measurements improve the algorithm’s ability to identify clusters by between 29-36%; enhancing the sophistication of the included magnetic data promises to yield substantially better statistical results. Magnetic remanence data are therefore being complied on representative samples from each of the twelve identified clusters, including hysteresis, isothermal remanent magnetisation (IRM) acquisition, FORC measurements, natural remanent magnetisation (NRM) and anhysteretic remanent magnetisation (ARM). Through collaboration with industry partners, we aim to develop an automated means of collecting these magnetic remanence data to accompany the machine learning algorithm.</p>


1991 ◽  
Vol 28 (11) ◽  
pp. 1812-1826 ◽  
Author(s):  
James M. Hall ◽  
Charles C. Walls ◽  
Jing-Sui Yang ◽  
S. Lata Hall ◽  
Abdul Razzak Bakor

An extensive study of a segment of the Troodos, Cyprus, ophiolite using both outcrop and drill-core samples, and extending from the sediment–extrusive interface through sheeted dikes to cumulate ultramafics, has allowed a number of key questions regarding the magnetization of oceanic crust to be addressed. These include the number of strongly magnetized intervals with depth, their lateral variability and controls on their occurrence. Comparison has also been made with the section in Ocean Drilling Program (ODP) hole 504B, and a reinterpretation of its constructional setting is offered.Two strongly magnetized intervals occur in the area studied. The upper is in the extrusive sequence, extends on average from 0.2 to 0.6 km depth, and has a thickness of ~0.4 km. Here magnetization is dominated by remanence. The lower interval extends from the lowest level at which flows occur with dikes (average depth = 0.9 km) into the Sheeted Complex (average depth = 1.2 km) and has a thickness of 0.3 km. Here magnetization is dominantly induced. No other strongly magnetized intervals occur in the section. The extent of dike intrusion is closely related to the position of the lower limit of the high-remanence layer and to the occurrence of the high induced magnetization layer. In both cases the replacement of primary magnetite, which can carry a strong remanence, by magnetically soft secondary magnetite appears to be the controlling process.Comparison of the Troodos and hole 504B magnetization profiles shows close similarity in the upper, remanence-dominated magnetic interval. The absence of the deeper interval of high induced magnetization in the hole 504B profile is interpreted as meaning that sheeted dikes have not been penetrated by the drill hole.


2019 ◽  
Vol 265 ◽  
pp. 330-353 ◽  
Author(s):  
Gülüm Albut ◽  
Balz S. Kamber ◽  
Annika Brüske ◽  
Nicolas J. Beukes ◽  
Albertus J.B. Smith ◽  
...  
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