Abstract

Bedded barite deposits can be divided into two types based on stratigraphic succession, tectonic setting, and geochemistry. The first, herein termed the "continental margin type," has abundant chert in the host sediments, is deposited in small ocean basins lying between a subduction zone and a passive continental margin, and has a geochemical signature that suggests an appreciable influence of oceanic crust. The barite is deposited on or adjacent to the passive margin side of the basin. Subduction leads to consumption of the ocean floor of the basin, collision of the volcanic arc with the passive margin, and thrusting of the barite-bearing sedimentary sequence onto the stable platform. This group of deposits lacks economic accumulations of Pb and Zn. Examples are the Fancy Hill and Chamberlain Creek deposits in the Ouachita Mountains of Arkansas and the East Northumberland Canyon deposit in central Nevada. The second type, for which we propose the term "cratonic rift type," is hosted by coarse clastics of turbidity current origin and is deposited in intracratonic rifts with strong local relief; the host rocks have a chemistry suggesting entirely continental affinities. Volcanic rocks, where present, tend to be alkalic basalts. Most barite deposits of this type are accompanied by economic accumulations of Pb and Zn. Examples include the Meggen and Rammelsberg deposits in Germany and the Anvil and Howard's Pass deposits in the Selwyn basin of western Canada.The barite deposits of south China can be assigned tentatively to these two types. Those of the Qinling district were deposited in a chert-dominated section on oceanic crust in a closing, remnant-ocean basin, placing them in the continental margin type. Those of the Jiangnan region are chemically more like the cratonic rift-type deposits and seem to reflect a similar tectonic setting. If this assignment is correct, the Jiangnan area should be considered prospective for Pb and Zn mineralization near the barite deposits.

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