Geochemistry of rutile-bearing veins at Engebøfjellet, Naustdal, Norway.

Abstract

The Engebøfjellet eclogite, located in Naustdal, Norway, contain quartz veins with large rutile (TiO2) phenocrystals. Trace element composition of rutile deposited in veins and in the eclogite matrix was analysed with the use of LA-ICP-MS. The Nb content decrease with increasing V in the rutile, and contents of these elements vary depending on depositional environment. One quartz vein associated with rutile deposition and one carbonate vein was analyzed for fluid inclusion characteristics. These inclusions show fluid salinity ranging from 2-35 wt.% with an average of 16.3 wt.% NaCl equivalents. The fluid inclusion isochores was compared with previously published data of the exhumation path of the Engebøfjellet eclogite (Braathen & Erambert., 2014). A group of inclusions have the same slope, and almost cross deformation stages D3-D5 (garnet amphibolite – greenschist facies) – leading to the interpretation that fluids was entrapped along this path. A stable isotope analysis of d13C and d18O composition was performed on three carbonate veins. The carbonate samples plotted close to the field of primary igneous carbonatites (Taylor 1967). REE trace element fractionation patterns of the host rock eclogite resembles a normal mid ocean ridge basalt.