Neoarchean Massive Sulfide of Wutai Mountain, North China: A Black Smoker Chimney and Mound Complex Within 2.50 Ga-Old Oceanic Crust

The Wutai massive sulfide deposits are located approximately 300 km southwest of Beijing. They are associated with a mélange belt, traced for more than 40 km, within which many ophiolitic blocks are identified. The main rock types in these ophiolitic blocks include pillow lavas, amphibolite, sheeted dike, cumulatemafic and ultramafic rocks (dunites, serpentinites), and serpentinized harzburgite tectonite. The main volcanogenic massive sulfide (VMS) of Wutai forms stacked lenses and concordant sheets of massive sulfides within amphibolite, rhyolite, BIF, and metasediment. The massive sulfide dominated by pyrite typically occurs as bands or laminae within BIF, and have undergone regional folding, shearing, and flattening together with the host rock. The mechanical behavior of the sulfide during folding and flattening is variable and in some cases very unusual. In many cases sulfide bands are folded tightly, with thickening of sulfide layers in the hinge zone. In these cases, the sulfide acted as the weak layers, flowing into the fold hinges. Some pyrite appears to have mechanically penetrated into adjacent layers during folding.