A late Neoproterozoic age for the Caledonia Mountain Pluton, a high Ti-V layered gabbro in the Caledonia (Avalon) terrane, Southern New Brunswick

Gabbro from the Caledonia Mountain Pluton in the northeastern Caledonian Highlands of southern New Brunswick yielded a U-Pb (zircon) crystallization age of 615 ± 1 Ma. The age shows that the Caledonia Mountain Pluton is co-genetic with its host metavolcanic rocks, significantly older than the Mechanic Settlement Pluton, and probably unrelated to the Lower Coverdale ferrogabbro complex. The chemical characteristics of the pluton are consistent with those of mafic volcanic rocks in the arc-generated Broad River Group, with which the pluton is likely to be co-magmatic. However, the chemical compositions of the gabbroic samples show strong evidence for modification by processes of crystal fractionation and accumulation, and most are unlikely to reflect magmatic compositions. The epsilon Nd value of +3.7 indicates that, like other igneous rocks in the Caledonia terrane, the magma that formed the Caledonia Mountain Pluton was not derived directly from depleted mantle, but had a component of older crust involved in its petrogenesis, either directly in the source area or by subsequent interaction with crustal materials. Elevated values of Ti, Fe, V, and P in the gabbro suggest that potential may exist for economic deposits, either in the Caledonia Mountain Pluton or other similar bodies in the Caledonian Highlands.