Sulfide textures, chalcophile element distribution, and timing of mineralization within the Crystal Lake intrusion, 1.1 Ga Midcontinent Rift

Magmatic Ni-Cu-PGE deposits of the ca. 1.1 Ga Midcontinent Rift (MCR) occur in association with a diverse range of ultramafic-mafic intrusions. High precision U-Pb dating throughout the MCR is critical for constraining the various magmatic pulses, the temporal and spatial controls on metal enrichment, and improving our general understanding of the rift's evolution. The 1099 Ma Crystal Lake layered intrusion is an olivine rich, Cr-spinel bearing, vari-textured gabbroic body, that hosts extensive low-grade Ni-Cu-PGE mineralization, and is broadly comparable to the nearby Duluth Complex. The Ni-Cu-PGE mineralization shows some similarities to other deposits such as Marathon (Coldwell Complex), Voisey's Bay and Norilsk. Segregation vesicles are common and show a close association with globular sulfides. The timing, cause and significance of degassing for ore genesis is yet to be fully explored but appears to be a feature of many Ni-Cu deposits.