A succession of near-orthogonal horizontal tectonic shortenings in the Paleoproterozoic Central Lapland Greenstone Belt
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ARTICLE
A succession of near-orthogonal horizontal tectonic shortenings in the Paleoproterozoic Central Lapland Greenstone Belt of Fennoscandia: constraints from the world-class Suurikuusikko gold deposit M. Sayab 1
&
F. Molnár 1 & D. Aerden 2 & T. Niiranen 3 & J. Kuva 1 & J. Välimaa 4
Received: 29 March 2019 / Accepted: 30 June 2019 # The Author(s) 2019
Abstract The relative and absolute timing of orogenic gold deposits in complex structural settings are active and challenging topics of research, especially in Precambrian greenstone belts. The Suurikuusikko gold deposit in Central Lapland Greenstone Belt is currently the largest primary gold producing deposit in Europe, located on a slight bend of the strike-slip Kiistala shear zone (KiSZ). Gold is refractory and locked inside arsenopyrite and pyrite. In this study, different structural features were investigated along the KiSZ from the recently stripped Etelä pit, which is the southern extension of the Suurikuusikko ore body. Our data source ranges from aeromagnetic to high-resolution aerial images, Xray computed tomography scans of selected rock samples and regional geological and geophysical datasets. The KiSZ has recorded five discrete deformation phases, spanning between ca. 1.92 and 1.76 Ga. The refractory gold at the Suurikuusikko deposit formed during E-W contraction related to the D1 thrusting phase. This was followed by a N-S shortening event (D2), where most of the strain was taken up by the northern and southern thrusts. Tectonic vectors then switched from N-S to NE-SW and, as a result, dextral strike-slip regime (D3) commenced along the KiSZ. This event exsolved invisible gold from the sulfides and remobilized it along with fractures. A near-orthogonal switch of the regional stress regime from NE-SW to NW-SE flipped the kinematics of the KiSZ from dextral to sinistral (D4). The last deformation phase (D5) produced widespread veining under E-W contraction and secured gold mineralization at the Iso-Kuotko gold deposit within the KiSZ. Keywords Orogenic gold . Tectonics . UAV . X-ray tomography . Greenstone belt
Introduction Editorial handling: P. Eilu Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00126-019-00910-7) contains supplementary material, which is available to authorized users. * M. Sayab [email protected] 1
Geological Survey of Finland, P.O. Box 96, FI-02151 Espoo, Finland
2
Departamento de Geodinámica and IACT-CSIC, Universidad de Granada, 18002 Granada, Spain
3
Geological Survey of Finland, P.O. Box 77, FI-96101 Rovaniemi, Finland
4
Agnico Eagle, Kittilä Mine, FI-99250 Kiistala, Finland
Research during the past two decades has shown that the localization of world-class orogenic gold deposits in metamorphic belts are intimately related to the repetitive reworking of crustal-scale compressional shears (e.g., Groves et al. 1998, 2018; Goldfarb et al. 2005; Tomkins 2013; Groves and Santosh 2016; Sayab et al. 2016). However, determining the relative and absolute timing of gold min
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