The nature and origin of enclaves in four peraluminous granitoid intrusions from the Meguma Zone, Nova Scotia

Abstract

Four mid-to late Devonian peraluminous granitoid intrusions in the Meguma Zone of southwestern Nova Scotia contain abundant enclaves typical of orogenic granitoid bodies. The Barrington Passage and Shelburne plutons contain an assemblage of granoblastic metasedimentary hornfelsic enclaves (49%) that have aluminosilicate porphyroblasts, and surmicaceous enclaves (51%) that consist of >70% decussate biotite with apatite and zircon inclusions. Metasedimentary enclaves predominate in the Port Mouton Pluton and the South Mountain Batholith (52%), but these intrusions also contain abundant microgranular and coarse-grained granitoid enclaves (25% and 23%, respectively) that have peraluminous mineral assemblages and tonalitic to leucomonzogranitic compositions. High concentrations of metasedimentary enclaves at the country rock contacts suggest that they probably formed as xenoliths stoped from the Meguma Group. -from Author