Abstract

Meso- and microscale structural analysis and the spatial distribution, morphology, and microthermometry of fluid inclusions reveal part of the fluid evolution of a multiply deformed, metamorphosed volcanic-associated massive sulfide deposit in the Scandinavian Caledonides, Norway. The ore and host rocks have suffered greenschist facies metamorphism and four deformation events. Metamorphism peaked during D 2 to D 3 and waned to subgreenschist facies by D 4 . Of the four distinct fluid inclusion types from D 2 to D 4 structural settings, primary inclusions occurring in crack-seal growth zones (type I) in D 2 vein quartz are the only preserved inclusions related to D 1 to D 3 ore remobilization and vein growth. All subsequent inclusions are secondary within healed microfracture space. Type II secondary inclusions exist in vein quartz regardless of structural setting; their formation cannot therefore predate D 4 . Both type I and type II inclusions underwent a pervasively destructive decrepitation event syn- to (more probably) post-D 4 . The leakage and/or decrepitation is attributed to internal overpressures accompanying rapid decompressive regional uplift after the D 4 event. Two populations of postdecrepitation inclusions (types III and IV) have consistent vapor to liquid ratios and yield low temperatures (T h = 137 degrees -297 degrees C) and low salinities (0-6.7 wt % NaCl equiv). They possibly record flushing by meteoric water late in the uplift history.

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