R. J. Roberts W.S. Snyder G.L. Lahusen J.E. Motica R. O. Rye 1984 <p><span>The massive ore contains two major generations of pyrite, a fine and a coarse grained, both of which show a striking variety of textures involving quartz. Framboidal pyrite in the argillite host rock has delta&nbsp;</span>³⁴<span>&nbsp;S values of approximately -24 per mil indicating the presence of a euxinic environment. The delta&nbsp;</span>³⁴<span>&nbsp;S values of fine-grained pyrite in the massive ore range from degrees 6.4 to + or -2.0 per mil; those of coarse-grained pyrite range from -3.5 to + or -5.5 per mil. A significant portion of the isotopically light sulfur for the early, fine-grained hydrothermal pyrite in the massive lens was probably derived from framboidal biogenic pyrite in interflow sediments of the underlying greenstone pillow lavas. Microcrystalline quartz in massive ore, hanging-wall jasper, footwall hydrothermal chert and coarse quartz from hanging-wall and footwall stringer zones have delta&nbsp;</span>¹⁸<span>&nbsp;O values between 15.6 and 19.6 per mil; one sample of vein hematite has a value of 4.4 per mil. The combined sulfur and oxygen isotope and textural data indicate that much of the material in the massive lens originally precipitated as fine-grained pyrite or as a precursor iron sulfide along with some silica from a hydrothermal plume similar to those recently observed at the East Pacific Rise spreading center at lat 21 degrees N. The primary material underwent recrystallization, mineralization, and late-stage quartz deposition in the presence of later fluids which had distinctly different sulfur isotope compositions.</span></p> application/pdf 10.2113/gsecongeo.79.1.124 en Society of Economic Geologists Textural and stable isotope studies of the Big Mike cupriferous volcanogenic massive sulfide deposit, Pershing County, Nevada article