Characteristics of REE and other trace elements in response to successive and superimposed metasomatism within a portion of the South Mountain Batholith, Nova Scotia, Canada

Abstract

Successive and superimposed periods of late- to post-magmatic metasomatism have resulted in mineralogical and textural modification within (leuco) monzogranitic rocks of the Big Indian Lake Polyphase Intrusive Suite (BIPIS). The alteration and associated mineralization exhibit a transition from an early pervasive style to a later fracture-controlled style, and can be defined by diagnostic REE and other trace-element behavior. While the anomalous behavior of some elements (MnO, Ta, U, K/Rb, HREE) is attributed to metasomatic-hydrothermal activity, the compatible behavior of B, F, Li, W and Rb appears to have been governed by predominately magmatic processes. All elements including Al can be mobilized during repeated fluid-rock interaction. The behavior of REE during evolution of the BIPIS indicates that they also were affected by both magmatic (LREE depletion, Eu depletion) and metasomatic (HREE, LREE enrichment, Eu enrichment/depletion) processes. The remobilization and subsequent redeposition of trace elements is dependent upon the nature and stability of the metasomatic mineral assemblages. In this respect, a metasomatized granitic rock could reflect a REE pattern similar to that of an unaltered equivalent.