Vasilopoulos, M., Molnár, F., Ranta, J.-P., & O’Brien, H. (2023). Mineralogical, lithogeochemical and sulfide trace element characteristics of the Hirvilavanmaa Au-only and the base metal-rich Naakenavaara orogenic gold deposits in the Central Lapland belt, northern Finland. Journal of Geochemical Exploration, 244, 107132. https://doi.org/10.1016/j.gexplo.2022.107132
Mineralogical, lithogeochemical and sulfide trace element characteristics of the Hirvilavanmaa Au-only and the base metal-rich Naakenavaara orogenic gold deposits in the Central Lapland belt, northern Finland
|Author:||Vasilopoulos, Mikael1; Molnár, Ferenc2; Ranta, Jukka-Pekka1;|
1Oulu Mining School, University of Oulu, P.O. Box 3000, 90014 Oulu, Finland
2Geological Survey of Finland, P.O. Box 96, FI-02151 Espoo, Finland
|Online Access:||PDF Full Text (PDF, 50 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe2022120569352
|Publish Date:|| 2022-12-05
The Hirvilavanmaa (Au-only) and Naakenavaara (Cu-Co-Au-Ni) deposits, located only 5 km apart in the Paleoproterozoic Central Lapland belt (CLB) in northern Finland, represent two types of orogenic gold mineralization that dominate the CLB: (1) Au-only and (2) Au with atypical metal association, respectively. In this study, we compare these deposits in order to pinpoint the origin of differences in their metal associations. The pyrite-rich Hirvilavanmaa and the pyrrhotite- and chalcopyrite-rich Naakenavaara deposits are hosted primarily by ultramafic metavolcanic and metasedimentary rocks respectively. Similarities in the deposits include pre-ore albitization of host rocks and ore mineralization-related carbonate and chlorite alteration and quartz‑carbonate veins. Ore-related sericite and biotite alteration is prominent only at Naakenavaara. Pyrite and chalcopyrite from the two deposits have a distinct trace element geochemistry; pyrrhotite from Naakenavaara hosts significant Co and Ni concentrations. At Hirvilavanmaa, three pyrite generations with distinct Co/Ni ratios represent the gradual evolution of ore deposition. Hirvilavanmaa can be confidently classified as an orogenic Au deposit with evidence pointing to a mafic metavolcanic rock source for the ore-forming components. At Naakenavaara, our results reveal a complex evolution involving two distinct but spatially coincident mineralizing events. The earliest base metal-rich event started as Co-rich and gradually developed into the main Cu-rich stage; two pyrite types (mean Co/Ni ratios of 12.5 and 762 respectively) are associated with these stages. Subsequently ore zones were overprinted locally by an orogenic Au event that deposited pyrite with low Co/Ni ratios (mean of 0.3). The presence of late gold deposition overprinting earlier base metal-rich ore fits with observations from other base metal‑gold deposits from northern Finland.
Journal of geochemical exploration
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
This work was financially supported by grants from the Vilho, Yrjö, and Kalle Väisälä Foundation, the K.H. Renlund Foundation and the Finnish Cultural Foundation.
© 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).