Stable isotope studies of bedded barite at East Northumberland Canyon in Toquima Range, central Nevada

Several beds of barite occur in the Slaven Chert at East Northumberland Canyon in the Toquima Range of central Nevada. Most of the barite is internally laminated but shows massive weathering. However, rosette, disseminated, conglomeratic, and concretionary varieties also occur. New fossil evidence from conodonts and brachiopods indicates a Late Devonian age for the Slaven Chert at East Northumberland Canyon. Preliminary δ³⁴S values of most disseminated and massive-laminated barite within the Slaven Chert average about 25 permil; these are within the range of values that is typical of sulfate from Late Devonian seawater and are distinctly different from δ³⁴S values of most crosscutting hydrothermal barite veins in the area. Primary δ³⁴S values of the bedded barite appear to be retained during recrystallization and hydrothermal alteration, suggesting that δ³⁴S data of bedded barites could be developed into a useful stratigraphic tool. The δ³⁴S values of rosette and concrectionary barites range from 29.1 to 56.3 permil and indicate that these varieties of barite formed in restricted microenvironments where extensive bacterial reduction of seawater sulfate occurred. The δ¹⁸O data on cherts associated with the barite beds and δ¹⁴C and δ¹⁸O data on carbonate beds within the Slaven Chert indicate that the depositional environment at tames had restricted communication with normal seawater of the open ocean.