Tungsten skarn mineralizations in a regional metamorphic terrain in northern Norway: a possible metamorphic ore deposit |
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| Authors: | R Berg Larsen |
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| Institution: | (1) Institute of Petrology, University of Copenhagen, Oestervoldgade 10, 1350 Copenhagen K, Denmark;(2) Present address: Geology Department, Stanford University, 94305-2115 Stanford, CA, USA |
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| Abstract: | Scheelite- and molybdenite-bearing scapolite skarn and plagioclase skarn occur as stratabound mineralizations in a terrain which has suffered regional metamorphism. Scapolite skarn formed as replacement skarns in plagioclase-bearing hornblendic gneiss whereas plagioclase skarn precipitated in fractures as vein skarn mineralizations. The genesis of these skarn deposits are closely connected to an episode of boudinage on the limbs of a large-scale dome-shaped fold. Fluid inclusion studies revealed that the ore-forming fluids were composed of CO2 with 2 to 17 mole% CH4, which formed due to decarbonation reactions during peak metamorphism at the end of the Caledonian orogenesis. Thermodynamic considerations indicate that scapolite and plagioclase formed above 550 °C and 2 Kbar pressure and were followed by precipitation of scheelite between 400 and 570 °C. |
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