The Implications of Mafic Enclaves on Magmatic Differentiation and Pluton Emplacement: Geochronological and Geochemical Insights from the Bergell Intrusion, N. Italy

Abstract

Mafic enclaves from the Bergell Intrusion, N. Italy are analyzed with a critical lens in order to better understand magmatic differentiation and pluton emplacement. Magmatic processes involved in pluton generation remain contested even after over a century of ongoing debate centered on the development of continental crusts. This study attempted to characterize the role of magma mixing in the creation of granitoid plutons through mafic enclaves, which are mesoscale inclusions of a more mafic member commonly found in plutons. U-Pb thermal ionization mass spectrometry (TIMS) was coupled with trace elemental analysis and laser ablation inductively coupled mass spectrometry (LA-ICPMS) techniques to generate a comprehensive data set. Geochronologic U-Pb ages were used to deduce a general model for enclave generation and behavior in the Bergell Intrusion, and when linked with the trace element chemistry was able further describe and date mixing events. Due to the mechanisms involved with the quenching and crystallization of enclaves, the ages of enclaves from U-Pb TIMS were by and large contemporaneous with their host rock, and thus provide an additional temporal and chemical constraint on pluton emplacement.