Petrologic and stable isotopic studies of the metamorphosed zinc-iron-manganese deposit at Sterling Hill, New Jersey

Sterling Hill is a metamorphosed sequence of zinc-, iron- and manganese-rich strata surrounded by the Franklin marble. Ore layers contain willemite, franklinite, zincite and calcite; other layers which were not mined contain calc-silicates and calcite.;Generally, oxygen isotopic and chemical compositions of individual minerals vary from lithologic layer to lithologic layer and are uniform within layers which suggests that mineral compositions reflect the bulk compositions of the rocks. Willemite and zincite are stable at high ;Models for the protolith are presented in which bulk oxygen isotopic and chemical compositions are assumed to reflect protolith values modified by metamorphic devolatilization. Data from marbles interbedded with ore layers suggest either (1) exchange with meteoric water at Earth's surface temperatures, or (2) exchange with a more ;The formation of the protolith is inferred to have taken place on the seafloor or in shallowly buried sediments which were well-irrigated by seawater. The closest modern analogs for Sterling Hill, and by analogy the nearby Franklin Furnace deposit, are the sulfide-free strata in metalliferous sediments beneath the Red Sea brine pools. There are, however, significant differences between the two occurrences.;The Reading Prong - Hudson Highlands contains stratiform magnetite deposits in addition to the zinc-iron-manganese deposits. The association of base metal and iron deposits and the distribution of the deposits in 10 km-scale clusters suggest that all the deposits may have had a similar origin on or beneath the Proterozoic seafloor, and that hydrothermal activity may have been localized by second-order basins. Other Grenville terranes show the same associations and similar regional distributions. The other terranes also contain sulfide-bearing deposits which suggests that depositional sites spanned a range of redox conditions.