Magnetic properties of iron ores from two Ordovician deposits in Northern Portugal: Marao and Moncorvo

• Type: Article in International Scientific Journal
• Date: 2024

Authors

Dias, JM (Author) Other; Vianez, R (Author) Other; Cruz, C (Author) Other; Font, E (Author) Other; Sant'Ovaia, H (Author) FCUP; Ferreira, J (Author) Other; Guedes, A (Author) FCUP

Journal

Title: Journal Of Iberian Geology

ISSN: 1698-6180

Publisher: Springer Nature

Indexing

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Other information

Authenticus ID: P-017-CCH

DOI: 10.1007/s41513-024-00267-5

Abstract (EN): The Vila Cova do Marao Mining Field (VCMF) and the Moncorvo Iron Complex (MIC) in northern Portugal are important geo-resources of iron. Here we provide a detailed characterisation of their mineralogy through petrographic observations and magnetic properties. Petrographic observations show the VCMF ore primarily consists of quartz, magnetite, and chlorite, while the MIC ore of hematite and quartz, with rare magnetite occurrences. The magnetic susceptibility (chi) of the VCMF host rock is similar to 2470 x 10(-8) m(3)/kg, while the VCMF ore deposits have chi of similar to 20,500 x 10(-8) m(3)/kg. MIC ores show lower chi values of 520-700 x 10(-8) m(3)/kg. Isothermal Remanent Magnetisation (IRM) component unmixing of the VCMF host rock indicates that the magnetic population is represented by a single component with B-1/2 of 45-55 mT and DP values 0.30-0.35 mT, respectively, typical of magnetite. The VCMF ore is characterised by a single component with B-1/2 of 32-44 mT and DP of 0.30-0.35, typical of magnetite. The MIC ore shows two components: component 1 with B-1/2 of 50 mT and DP values of 0.31-0.37 mT, typical of magnetite, and component 2 with B-1/2 of 500 mT and DP of 0.19-0.26, typical of hematite. IRM at saturation (SIRM) of component 1 is 116-248 A/m for the host rock, 1100-2400 A/m for the VCMF samples, and 209-335 A/m for the MIC samples, providing an approximation of magnetite concentration. The Cisowski test shows the presence of strongly interacting single-domain particles (0.16 < R < 0.24) in all samples. Our data provides useful information for future iron ore resource exploration in the area.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 22