{"id":97,"date":"2018-02-16T10:18:51","date_gmt":"2018-02-16T08:18:51","guid":{"rendered":"http:\/\/minsysfin.gtk.fi\/?page_id=97"},"modified":"2020-06-15T15:17:18","modified_gmt":"2020-06-15T12:17:18","slug":"suurikuusikko","status":"publish","type":"page","link":"https:\/\/minsysfin.gtk.fi\/index.php\/suurikuusikko\/","title":{"rendered":"Suurikuusikko, Paleoproterozoic Central Lapland greenstone belt"},"content":{"rendered":"
\"CLGB<\/a><\/span>
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Five discrete, near-orthogonal deformation events occurred during the tectonic evolution of the CLGB. The early D1 thrusting phase (ca. 1.92\u20131.91 Ga) and associated bend in the thrust splay provided the first-order structural control on the localization of the deposit. Albitization is the most intense, pre-ore alteration. Distal alteration zones are characterized by chlorite.<\/p>\n

The main lodes are controlled by the N-S trending major shear zones smaller orebodies are also located along contacts of lithological units with contrasting competence. The lodes plunge to the north and known to about 1 km depth. They consists of disseminations of sulphides and carbonate (Fe-dolomite) veins. Age of mineralization at Suurikuusikko is estimated ca. 1916 \u00b1 19 Ma based on Re-Os dating of auriferous arsenopyrite.<\/p>\n<\/div>\"Micropicts\"<\/a><\/span>\"Au<\/a><\/span>

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(Last update: 20.05.2020)<\/span><\/p>\n<\/div>

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The Paleoproterozoic Central Lapland greenstone\u00a0belt of northern Finland hosts a number of orogenic gold deposits mostly along two crustal-scale shear zones, the NNE-SSW\u2013trending Kiistala shear zone and WNW-ESE\u2013striking Sirkka shear zone. The Kittil\u00e4 mine at the Suurikuusikko deposit is currently the largest gold-producing mine in Europe, with total reserves of 30.5 million tons of ore grading 4.49 g\/t.<\/p>\n

The deposit is located along the Kiistala shear zone and is hosted by ca. 2.0 Ga Kittil\u00e4 Group consisting of mafic volcanic rocks and smaller proportions of a metasedimentary (greywacke and carbonaceous graphitic phyllite) package which was intruded by 1.91 Ga felsic porphyry dikes. These rocks suffered deformation and greenschist facies metamorphism during the Svecofennian orogeny (1.92-1.77 Ga).<\/p>\n<\/div>\"Suurikuusikko\"<\/a><\/span>

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The majority of gold at Suurikuusikko is refractory in arsenopyrite (73.2%) and pyrite (22.7%), with 4.1% as free gold. Other sulphide minerals are rare accessories. The trace element and sulphur isotope characteristics of pyrite from the high grade ore zones is significantly different from the low grade\/barren zones. This finding suggests that paired trace element and sulphur isotope data are useful for defining vectors to ore.<\/p>\n<\/div>

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