Residence and partitioning of REE and selected trace elements in amphibolite-facies metabasites: An example from the St. Anthony complex, northern Newfoundland.

摘要

Metabasites from the metamorphic sole of the Hare Bay Allochthon, northern Newfoundland, exhibit a narrow metamorphic field gradient from greenschist---through epidote-amphibolite to amphibolite-facies. The metamorphic facies are defined from the distribution of the following mineral assemblages (all with quartz and titanite): chlorite-epidote-plagioclase-Ca amphibole (greenschist), Ca amphibole-plagioclase-epidote (epidote amphibolite), and Ca amphibole-plagioclase (plagioclase amphibolite). The assemblage Ca amphibole-plagioclase-garnet-biotite-apatite (biotite amphibolite) equilibrated in a K2O-enriched shear-zone. Representative samples from each metamorphic facies were analyzed for rare earth elements (REE) and a suite of trace elements (Sc, V, Cr, Ni, Cu, Zn, Sr, Rb, Y, Zr, Nb) in bulk rocks and the major minerals Ca amphibole, plagioclase, epidote, titanite and garnet, by solution ICP-MS and laser-ablation microprobe (LAM)-ICP-MS respectively. Major-element concentrations of bulk rocks and minerals were determined by XRF and electron probe microanalysis (EPMA) respectively. (Abstract shortened by UMI.)