Diagenetic Controls on the Formation of the Anarraaq Clastic-Dominated Zn-Pb-Ag Deposit, Red Dog District, Alaska

Abstract The Anarraaq clastic-dominated (CD) Zn-Pb-Ag deposit (Red Dog district, Alaska, USA) has an inferred mineral resource of 19.4 Mt at 14.4% Zn, 4.2% Pb, and 73 g/t Ag is spatially associated with a separate ~1 Gt barite body. This study presents new cross sections petrographic evidence from the area. body, previously shown to have formed in shallow subsurface environment akin methane cold seep, contains multiple generations locally abundant calcite masses, which are discordant sedimentary laminae, underlain by interval massive pyrite containing framboids radiolarians. Calcite interpreted methane-driven diagenetic alteration host sediment sulfate-methane transition (SMT). sulfide two zones Zn-Pb mineralization bounded faults unknown displacement. dominant hydrothermal minerals marcasite, pyrite, sphalerite, quartz, galena. presence pseudomorphs after barite, early resembling quartz sphalerite filling voids dissolution carbonate all suggest that composition origin was similar body prior mineralization. Rhenium-osmium isochron ages Ikalukrok mudstone (339.1 ± 8.3 Ma), (333.0 7.4 (334.4 5.3 Ma) within uncertainty one another existing age (~338 for Main Red district. indicates soon sedimentation activity approximately synchronous initial Os isochrons (0.375 0.019–0.432 0.025) consistent contemporaneous seawater, indicating mantle source not involved system. highlights underappreciated but important role early, processes paragenesis some CD deposits implications exploration.