University of Oulu

Moilanen, M., Hanski, E., Konnunaho, J. et al. Composition of iron oxides in Archean and Paleoproterozoic mafic-ultramafic hosted Ni-Cu-PGE deposits in northern Fennoscandia: application to mineral exploration. Miner Deposita 55, 1515–1534 (2020).

Composition of iron oxides in Archean and Paleoproterozoic mafic-ultramafic hosted Ni-Cu-PGE deposits in northern Fennoscandia : application to mineral exploration

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Author: Moilanen, M.1; Hanski, E.1; Konnunaho, J.2;
Organizations: 1Oulu Mining School, University of Oulu, P.O. Box 3000, FI-90014, Oulu, Finland
2Geological Survey of Finland, P.O. Box 77, FI-96101, Rovaniemi, Finland
3Geological Survey of Finland, P.O. Box 96, FI-02151, Espoo, Finland
4Mawson Oy, Ahjotie 7, 96320, Rovaniemi, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 7.9 MB)
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Language: English
Published: Springer Nature, 2020
Publish Date: 2020-05-28


Using electron probe microanalyzer (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), we analyzed major and trace element compositions of iron oxides from Ni-Cu-PGE sulfide deposits hosted by mafic-ultramafic rocks in northern Fennoscandia, mostly focusing on Finland. The main research targets were the Archean Ruossakero Ni-(Cu) deposit; Tulppio dunite and related Ni-PGE mineralization; Hietaharju, Vaara, and Tainiovaara Ni-(Cu-PGE) deposits; and Paleoproterozoic Lomalampi PGE-(Ni-Cu) deposit. In addition, some reference samples from the Pechenga (Russia), Jinchuan (China), and Kevitsa (Finland) Ni-Cu-PGE sulfide deposits, and a barren komatiite sequence in the Kovero area (Finland) were studied. Magnetite and Cr-magnetite show a wide range of trace element compositions as a result of the variation of silicate and sulfide melt compositions and their post-magmatic modification history. Most importantly, the Ni content in oxide shows a positive correlation with the Ni tenor of the sulfide phase in equilibrium with magnetite, regardless of whether the sulfide assemblage is magmatic or post-magmatic in origin. The massive sulfide samples contain an oxide phase varying in composition from Cr-magnetite to magnetite, indicating that Cr-magnetite can crystallize directly from sulfide liquid. The Mg concentration of magnetites in massive sulfide samples is lowest among the samples analyzed, and this can be regarded as a diagnostic feature of an oxide phase crystallized together with primitive Fe-rich MSS (monosulfide solid solution). Our results show that magnetite geochemistry, plotted in appropriate discrimination diagrams, together with petrographical observations could be used as an indicator of potential Ni-(Cu-PGE) mineralization.

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Series: Mineralium deposita
ISSN: 0026-4598
ISSN-E: 1432-1866
ISSN-L: 0026-4598
Volume: 55
Pages: 1515 - 1534
DOI: 10.1007/s00126-020-00953-1
Type of Publication: A1 Journal article – refereed
Field of Science: 1171 Geosciences
Funding: Open access funding provided by University of Oulu including Oulu University Hospital. This research was supported by the Academy of Finland (grant #281859), K.H. Renlund Foundation and Tauno Tönning Foundation.
Academy of Finland Grant Number: 281859
Detailed Information: 281859 (Academy of Finland Funding decision)
Dataset Reference: Electronic supplementary material The online version of this article ( contains supplementary material, which is available to authorized users.
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