Diamond sources beneath the Hall Peninsula, Baffin Island, Nunavut: A preliminary assessment based on Chidliak diamonds

Abstract

Diamonds from the Chidliak kimberlite field, located on the Hall Peninsula of Baffin Island, are the focus of this study. Morphology, carbon and nitrogen isotopic compositions, and nitrogen characteristics of Chidliak diamonds are used to constrain diamond sources, and conditions of diamond formation and preservation. Strong variations in δ13C and nitrogen content across growth layers indicate that at least two diamond growth events occurred, interrupted by resorption. Diamond mantle residence temperatures range from ~980 to 1350°C, equivalent to a depth range of ~150-200 km. Stable isotopic analyses indicate that diamond formation occurred principally from fluids or melts with a dominant mantle signature (modes in δ13C of -6‰ and δ15N of -3‰), but contribution of a subducted crustal component is also apparent (13C depleted and 15N enriched samples). Combined with observations of overall high nitrogen contents (≤3830 atomic ppm), Chidliak diamond characteristics suggest derivation (partially or completely) from eclogitic mantle sources.