Samarium-neodymium isotopic and whole-rock chemical compositions of late Neoproterozoic and Cambrian sedimentary and metasedimentary rocks of the Caledonian Highlands, southern New Brunswick

Neoproterozoic though Cambrian clastic sedimentary and/or metasedimentary rocks occur in the Hammondvale Metamorphic Suite (> ca. 620 Ma) and Broad River (ca. 620 Ma), Coldbrook (ca. 560-542 Ma) and Saint John (ca. 540-490 Ma) groups in the Avalonian Caledonia terrane of southern New Brunswick. This study of the petrography, major and trace element chemistry and Sm-Nd isotopic composition provides new constraints on the provenance and environment of deposition of these units and hence on the tectonic evolution of this typical part of Avalonia.;Nd isotopic and whole-rock chemical data show that the Hammondvale Metamorphic Suite and metasedimentary rocks of the Broad River Group have negative &egr; Nd(T) values and were derived from recycled sedimentary and mafic igneous sources whereas the sedimentary rocks of the Coldbrook Group show generally positive &egr;Nd(T) values and likely were derived from Avalonian felsic to mafic igneous sources. Samples from the Saint John Group also have felsic to mafic igneous sources, but are characterized by negative &egr; Nd(T) values. Some metasedimentary rock samples from the Hammondvale Metamorphic Suite, Broad River Group and Saint John Group fall outside the Avalonian igneous isotopic window, whereas Coldbrook Group samples fall mainly in the Avalonian isotopic window, suggesting a substantial Avalonian crustal component for the Coldbrook Group. Sedimentary units in the Coldbrook Group were likely derived from igneous units in the Broad River and Coldbrook groups, based on their mostly positive &egr;Nd(T) values. The more negative &egr; Nd(T) values for samples from the Hammondvale Metamorphic Suite, Broad River Group and Saint John Group indicate a large, isotopically mature source, presumably outside Avalonia.