ABSTRACT The Neoarchean is generally considered to have been the final era of major crust formation and may have been characterized by the onset of modern plate tectonics. The Neoarchean may also have been the time interval during which subduction processes prevailed and became global. Evidence from individual cratons around the world suggests that this transition in geodynamic processes may have included diachronous and episodic major changes (i.e., turning points) and a more gradual evolution at the global scale, possibly largely driven by the secular cooling of the mantle and increasing stability of the lithosphere. The Superior craton, Canada, is the largest and best-preserved Archean craton in the world, making it an ideal location in which to investigate the occurrence (or absence) of turning points in the Neoarchean. This contribution examines the changes in geodynamic and magmatic processes that occurred during the Neoarchean, using geochemical data and new insights garnered from isotopic surveys from the southern part of the Superior craton. We summarize current understanding of the evolution of the youngest (southern) part of the Superior craton that led to the stabilization (cratonization) of this continental lithosphere and how this evolution aligns with local and global geodynamic processes.

Abstract The Cerro Vetas porphyry deposit is part of the Titiribi district of the Middle Cauca porphyry-epithermal belt of western Colombia. The Cerro Vetas porphyry stock consists of a premineral diorite intruded by a late-mineral quartz monzonite, with intrusion and contact breccias. These units intrude pre-Cenozoic basement metabasalts and schists, Oligocene-Miocene Amagá Formation sedimentary rocks with intercalated andesite flows. Two phases of potassic alteration are recognized, a biotite-dominant phase in the diorite, and secondary K-feldspar in the quartz-monzonite intrusion. An overprinting and grade destructive, calcic-sodic alteration (actinolite + albite ± magnetite) affects both porphyries. Biotite alteration is overprinted by weak-moderate phyllic alteration in the upper 100 m in the deposit. Below 100 m, phyllic alteration assemblages are constrained to structural zones. Mineralization is dominated by a chalcopyrite-gold-pyrite assemblage associated with biotite that is hosted in a truncated stockwork in the apical portion of the deposit with metal ratios typical of a gold-rich copper-gold porphyry. The intrusions were dated, using U-Pb in zircon laser ablation inductively coupled plasma-mass spectroscopy, to between 7.65 to 7.24 Ma, consistent with other deposits in the Middle Cauca belt. Lithologic, alteration, and stratigraphic relationships at the deposit suggest that the Cerro Vetas porphyry was emplaced at shallow depths and that the upper portion of the deposit has been eroded.