Natural Resources Research

, Volume 26, Issue 4, pp 571–584 | Cite as

Optimizing a Knowledge-driven Prospectivity Model for Gold Deposits Within Peräpohja Belt, Northern Finland

  • V. Nykänen
  • T. Niiranen
  • F. Molnár
  • I. Lahti
  • K. Korhonen
  • N. Cook
  • P. Skyttä
Original Paper

Abstract

This paper combines knowledge- and data-driven prospectivity mapping approaches by using the receiver operating characteristics (ROC) spatial statistical technique to optimize the process of rescaling input datasets and the process of data integration when using a fuzzy logic prospectivity mapping method. The methodology is tested in an active mineral exploration terrain within the Paleoproterozoic Peräpohja Belt (PB) in the Northern Fennoscandian Shield, Finland. The PB comprises a greenschist to amphibolite facies, complexly deformed supracrustal sequence of variable quartzites, mafic volcanic rocks and volcaniclastic rocks, carbonate rocks, black shales, mica schists and graywackes. These formations were deposited on Archean basement and 2.44 Ga layered intrusions, during the multiple rifting of the Archean basement (2.44–1.92 Ga). Younger intrusive units in the PB comprise 2.20–2.13 Ga gabbroic sills or dikes and 1.98 Ga A-type granites. Metamorphism and complex deformation of the PB took place during the Svecofennian orogeny (1.9–1.8 Ga) and were followed by intrusions of post-orogenic granitoids (1.81–1.77 Ga). The recent mineral exploration activities have indicated several gold-bearing mineral occurrences within the PB. The Rompas Au-U mineralization is hosted within deformed and metamorphosed calc-silicate veins enclosed within mafic volcanic rocks and contains uranium-bearing zones without gold and very high-grade (>10,000 g/t Au) gold pockets with uraninite and uraninite-pyrobitumen nodules. In the vicinity of the Rompas, a magnesium skarn hosted disseminated-stockwork gold mineralization was also recognized at the Palokas-Rajapalot prospect. The exploration criteria translated into a fuzzy logic prospectivity model included data derived from regional till geochemistry (Fe, Cu, Co, Ni, Au, Te, K), high-resolution airborne geophysics (magnetic field total intensity, electromagnetic, gamma radiation), ground gravity and regional bedrock map (structures). The current exploration licenses and exploration drilling sites for gold were used to validate the knowledge-driven mineral prospectivity model.

Keywords

Prospectivity Fuzzy logic Receiver operating characteristics Gold Uranium Paleoproterozoic Rompas Peräpohja Belt Finland 

Notes

Acknowledgments

Parts of this work were supported by the Academy of Finland project No. 281670, Mineral Systems and Mineral Prospectivity Mapping in Finnish Lapland and Tekes project No. 2631/31/2015. The constructive comments of Mark Gettings and an anonymous reviewer helped to improve the manuscript significantly.

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Copyright information

© International Association for Mathematical Geosciences 2017

Authors and Affiliations

  1. 1.Geological Survey of FinlandRovaniemiFinland
  2. 2.Geological Survey of FinlandEspooFinland
  3. 3.Mawson Resources LtdVancouverCanada
  4. 4.Department of Geography and GeologyUniverstiy of TurkuTurkuFinland

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