Precambrian geodynamics and ore formation : the Fennoscandian Shield

• Main Authors: Weihed, Pär, Arndt, Nicholas, Billström, Kjell, Duchesne, Jean-Clair, Eilu, Pasi, Martinsson, Olof, Papunen, Heikki, Lahtinene, Raimo
• Format: Conference Object
• Language: English
• Published: Luleå tekniska universitet, Geovetenskap och miljöteknik 2006
• Subjects: Geology; Geologi; Fennoscandian
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-27631

The complex geodynamic evolution of the Fennoscandian Shield from 2.06 to 1.78 Ga involved rapid accretion of island arcs and several microcontinent-continent collisions in a complex array of orogens. With a few exceptions, all major ore deposits formed in specific tectonic settings between 2.06 and 1.78 Ga and thus a strong geodynamic control on ore deposit formation is suggested.All orogenic gold deposits formed syn- to post-peak metamorphism and their timing reflects the orogenic younging of the shield towards the SW and west.The ca. 2.5 to 2.4 Ga Ni-Cu±PGE deposits formed in basins formed during rifting of the Archaean craton at ca. 2.5 to 2.4 Ga, while Svecokarelian ca. 1.89 to 1.88 Ga Ni-Cu deposits are related to mafic-ultramafic rocks intruded along linear belts at the accretionary margins of microcratons.All major VMS deposits in the Fennoscandian Shield formed between 1.97 and 1.88 Ga, in extensional settings, prior to basin inversion and accretion. This occurred in primitive, bimodal arc complexes during extension, in strongly extensional intra-arc regions that developed on continental or mature arc crust or in intra-continental, or continental margin back-arc, extensional regions developed on older continental crust.Of the iron oxide-copper-gold deposits the oldest deposits formed in continental arcs or magmatic arcs inboard of the active subduction zone. Younger mineralization took place during cratonization distal to the subduction zone.Finally, the large volumes of anorthositic magmas formed a major concentration of Ti under granulite facies conditions, about 40 million years after the last regional deformation of the Sveconorwegian Orogeny. Godkänd; 2006; 20111007 (andbra)