The Paleoproterozoic metasupracrustal sequence of the Repparfjord Tectonic Window (RTW) within the Caledonian Nappe System in northern Norway hosts several Cu-bearing mesothermal carbonate-quartz veins. Structural analysis shows that the emplacement of the veins is geometrically and kinematically compatible with a phase of NW-SE shortening. Northwest- and southeast-dipping veins are related to brittle-ductile thrust faults, whereas sub-vertical E-W to NE-SW striking veins show a strong component of dextral strike-slip ductile shearing. It is proposed that the veins were emplaced under brittle-ductile conditions in a dextral transpressional shear corridor. Fluid overpressuring possibly led to fracturing of the host greenstones. The subsequent pressure drop led to metal precipitation. The newly-formed veins, which remained weaker than the surrounding metabasalts, localized subsequent fluid circulation and ductile strain increments. Coaxial NW-SE compression is reported for both the Paleoproterozoic Svecofennian and the Silurian Caledonian orogenies. Re-Os analysis on sulfides is in progress and will provide constraints on the age of both vein formation and associated tectonic stress regime.
Structural constraints on the formation of Cu-rich mesothermal vein deposits in the Repparfjord Tectonic Window, northern Norway
VIOLA, GIULIO;
2013
Abstract
The Paleoproterozoic metasupracrustal sequence of the Repparfjord Tectonic Window (RTW) within the Caledonian Nappe System in northern Norway hosts several Cu-bearing mesothermal carbonate-quartz veins. Structural analysis shows that the emplacement of the veins is geometrically and kinematically compatible with a phase of NW-SE shortening. Northwest- and southeast-dipping veins are related to brittle-ductile thrust faults, whereas sub-vertical E-W to NE-SW striking veins show a strong component of dextral strike-slip ductile shearing. It is proposed that the veins were emplaced under brittle-ductile conditions in a dextral transpressional shear corridor. Fluid overpressuring possibly led to fracturing of the host greenstones. The subsequent pressure drop led to metal precipitation. The newly-formed veins, which remained weaker than the surrounding metabasalts, localized subsequent fluid circulation and ductile strain increments. Coaxial NW-SE compression is reported for both the Paleoproterozoic Svecofennian and the Silurian Caledonian orogenies. Re-Os analysis on sulfides is in progress and will provide constraints on the age of both vein formation and associated tectonic stress regime.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
