Abstract Zinc-lead-silver massivle sulfide and barite deposits hosted in dark, fine-grained clastic sedimentary rocks are economically important resources in Alaska and major producers worldwide. Alaska contains several identified belts of such deposits, the best known and largest of which is the Noatak district in the western and central Brooks Range. Most Alaskan occurrences contain either barite (Gargaryah, Cutaway basin) or base metal sulfides (Lik-Su, Drenchwater); Red Dog contains both. Knowu Zn-Pb-Ag deposits in Alaska occur mainly in Carboniferous strata, although the host rocks for other prospects are Late(?) Proterozoic to Triassic(?) in age. Many of the barite-only deposits are also hosted in Carboniferous rock, including some in facies that are not known to host sulfides. Other barite-only deposits are Cambrian(?), Silurian(?), Devomian(?). Permian, and Triassic in age. Deposits in the Cutaway basin of the north-central Brooks Range and in the Lime Hills quadrangle, southwestern Alaska, contain significant reserves of high-grade barite. The Red Dog mine is one of the few deposits where both barite and sulfides are abundant. The deposit formed under in a long-lived hydrothermal system, probably controlled by extensional faulting. The dominantly stratiform Zn-Pb-Ag massive sulfide deposits as well as some barite deposits formed by syngenetic to early diagenetic proeesses at and near the sea floor in highly restricted basins of at least modemte depth, with condensed, often highly siliceous sedimentation. Several deposits replaced primary siliceous or calcareous sedimentary layers, including fossils; others apparently formed from fluids vented directly to the sea floor. Dewatering of mixed carbonate and clastic basins of Proterozoic(?) to Paleozoic age along syntectonic faults is the most commonly proposted mechanism for formation of shale-hosted Zn-Pb-Ag and barite deposits, but the genesis of most Alaskan occurrences is still poorly known. Some barite lenses may have formed during oxygenation of a previously anoxic water column, without requiring a discrete hydrothermal system. The sedimentologic, diagenetic, and tectonic history of possible host basins and/or fluid-source basins and the chemistry and migration pathways of mineralizing fluids have not been defined for Alaskan deposits. Restricted basins of Carboniferous age in northwestern Alaska are interpreted to reflect widespread small-seale extensional faulting along the continental margin in Early to Middle Mississippian time. Extensional basin formation could reflect an incipient continental rift, a transtensional wrench environment, or a rift behind a continental collision zone. Sedimentation of chert and shale at very low depositional rates was subsequently restored, and diagenetic barite was precipitated in regioually extensive post-Mississippian condensed sequences. Dark, fine-grained clastic rocks are common in Late Proterozoic, Palezoic, and some Mesozoic Sedimentary-rock sequences in Alaska and formed in a variety of continental and marine tectonic and sedimentary setting. Most are prospective for additional Zn-Pb-Ag and barite deposits.