Day Five Field Guide: Cu-Au Deposits in the Gällivare Area
Published:January 01, 2000
Olof Martinsson, Christina Wanhainen, 2000. "Day Five Field Guide: Cu-Au Deposits in the Gällivare Area", Svecofennian Ore-Forming Environments: Volcanic-Associated Zn-Cu-Au-Ag, Intrusion-Associated Cu-Au, Sediment-Hosted Pb-Zn, and Magnetite-Apatite Deposits in Northern Sweden of Northern Sweden, Rodney L. Allen, Olof Martinsson, Pär Weihed
Download citation file:
The Gällivare area was first recognized for its iron deposits in the eighteenth century. When the railway from Luleå was built in 1888 to exploit the large iron resources, it initiated extensive exploration activities for other deposits in the surrounding areas. In 1898 copper ore was discovered at Nau-tanen and within a few years a number of Cu mineralizations had been found northeast and east of Gällivare. The Nautanen Copper Ore company was founded in 1900 and mining started in 1902 but lasted only until 1907 (Geijer, 1918). Some other small Cu mines (Likavaara, Ferrum) were active during the same period in the Nautanen area, and a prospector was working a small gold mine (Fridhem). The Aitik deposit was discovered in 1932 by drilling on geophysical targets in an area where a rich ore boulder and a mineralized outcrop had been found. Further drilling was carried out in 1960 through 1965, and this delineated a low-grade but large Cu deposit suitable for large-scale open pit mining (Malmqvist and Parasnis, 1972; Zweifel, 1976). Mining started in 1968 with an annual production of 2 Mt of ore, which has successively increased to c. 18 Mt in 2004.
Most of the Cu deposits in the Gällivare area are hosted by volcaniclastic sediments varying in composition from aren-ites to pelites. These sediments are intruded by synorogenic diorites and late orogenic to postorogenic granites and pegmatites. The ore deposits occur within or close to the Nauta-nen Deformation zone, which
Figures & Tables
Svecofennian Ore-Forming Environments: Volcanic-Associated Zn-Cu-Au-Ag, Intrusion-Associated Cu-Au, Sediment-Hosted Pb-Zn, and Magnetite-Apatite Deposits in Northern Sweden of Northern Sweden
The Fennoscandian or Baltic Shield (both names occur in the literature) occupies the northern part of Europe. Pre-cambrian areas are exposed in Norway, Sweden, Finland, and Russia and their continuation beneath the platform cover sequences to the east and south have been better understood through studies within the European “Euro-probe” project. The craton of which the exposed Fenno-scandian Shield forms a part is bordered to the west by the Caledonian orogenic belt. Precambrian rocks of the same craton outcrop again in the Ukrainian Shield and the Voronezh Massif (cf. Gee and Zeyen, 1996).
The Fennoscandian Shield is composed of Archean to Neoproterozoic rocks (Fig. 1). It is beyond the scope of this guidebook to describe all the different settings in detail, but adjoining areas that both predate and postdate the Svecofennian rocks that are the main interest of this field trip will be briefly described. The term Svecokarelian is used for the orogeny that occurred between 1900 and 1800 Ma (i.e., emphasizing deformation and metamorphism as defining the orogeny), while the term Svecofennian is used for the supracrustal rocks that were emplaced during c. 1.95 Ga to 1.85 Ga. To the reader unfamiliar with literature on the Fennoscandian Shield it is important to remember that these terms are not used consistently in the literature.
The pre-Svecokarelian crustal growth can be subdivided into Archean and Paleoproterozoic. During the Archean, greenstone belts and tonalite-trondhjemite-granodiorite (TTG) terranes formed, while crustal growth during the Paleoproterozoic involved rifting of the Archean basement with the formation of rift-fill sequences of sedimentary and igneous rocks, and addition of juvenile Paleoproterozoic crust by accretionary processes along the margin of the Archean continent.
The oldest known rocks in the Shield are c. 3.1 Ga in age and were generated during the Saamian Orogeny (3.1—2.9 Ga). Rocks of the age 3.2 to 2.7 Ga are present in the Archean nuclei of the shield and are composed of tonalitic gneisses and migmatites. The oldest documented magmatic and metamorphic event took place at c. 2.84 Ga (Nurmi and Sorjonen-Ward, 1996). Rift-related greenstones, subductiongenerated calc-alkaline volcanic rocks and tonalitictrondhjemitic igneous rocks were formed during the Lopian Orogeny (2.9—2.6 Ga). These greenstone belts form a prominent part of the Finnish and Russian bedrock, but are minor in Sweden. The Hattu schist belt in the southwestern part of the Archean of Finland seems to record a collisional arc setting