Compositional diversity among Late Devonian peraluminous granitoid intrusions in the Meguma Zone of Nova Scotia, Canada

Late Devonian (385?370 Ma) granitoid intrusions in the Meguma Zone of southwestern Nova Scotia represent two geographically separate magmatic suites that show subtly different lithological, geochemical and isotopic characteristics. “Central intrusions” crop out with satellite mafic-intermediate intrusions, range in composition from granodiorite to leucogranite, contain two micas, have exclusively peraluminous compositions (molar A/CNK 1.1-1.3), variably high values for FeO_T (0.4–6.0 wt.%), Ba (5–980 ppm), Y (6–50 ppm), Pb (2–50 ppm), Ga (11–53 ppm), ⁸⁷Sr/⁸⁶Sr_i (0.7081-0.7130), δ¹⁸O (9.8–13.0) and δ³⁴S (4.5–11.9), in conjunction with low values for εNd (?1 to ?6.5). In contrast, “peripheral plutons” crop out with synplutonic mafic-intermediate intrusions, range in composition from tonalite to leucogranite, may contain minor hornblende, have dominantly peraluminous compositions (molar A/CNK 0.9-1.3), variably high concentrations of TiO₂ (0.1-1.1 wt.%), Al₂O₃ (12.0–19.7 wt.%), CaO (0.2–4.9 wt.%), Sr (7–720 ppm), Cr (3–111 ppm) and V (1–136 ppm), higher εNd values (?2.0 to 3.2), and lower values for ⁸⁷Sr/⁸⁶Sr_i (0.7040-0.7079), δ¹⁸⁸O (7.6–10.5) and δ³⁴S (0–4.6). Such regional diversity is explained by inferring that upper crustal contamination dominated the central granitoid compositions and mixing with mantle-derived mafic-intermediate magmas dominated peripheral granitoid compositions. However, additional contributions from heterogeneous lower crust cannot be excluded.