Paleoproterozoic hydrothermal reactivation in a neoarchean orogenic lode-gold deposit of the southern abitibi subprovince: U-Pb monazite geochronological evidence from the young-davidson mine, Ontario

Abstract

An important but poorly constrained issue for neoarchean orogenic lode-gold deposits of the southern Abitibi subprovince is whether they were reactivated, reworked or even enriched by younger hydrothermal fluids. The Young-Davidson mine is a lode-gold deposit that at least in part was structurally controlled. It experienced polyphase deformation and contains multiple generations of auriferous veins. Four stages of veining (V1-V4) occurred after the emplacement of the host Neoarchean syenite. V1-V3 veins formed during Neoarchean time and were responsible for the major phase of gold mineralization of the Young-Davidson deposit. Crosscutting V1-V3 veins is a distinct group of V4 planar to en echelon carbonate-quartz±hematite±epidote veins, which also cut both of the Neoarchean syenite and Paleoproterozoic Matachewan diabase dyke. Hydrothermal monazite extracted from the V4 veins gives a 235U-207Pb age of 1730±5Ma. This represents the first Paleoproterozoic age reported from Neoarchean gold deposits of the southern Abitibi subprovince. The hydrothermal activity was most likely related to the far-field 1750-1700Ma Killarnean or Yavapai magmatism and metamorphism event that ultimately reactivated the pre-existing Neoarchean structures. This Paleoproterozoic activity provides a new perspective for understanding Neoarchean lode-gold deposits of the Abitibi. © 2014 Elsevier B.V.