This comparative geochemical study of jasperoid in the northern Great Basin is based on 65 samples from 10 Carlin-type gold deposits and 22 similar but apparently barren hydrothermal systems. Multielement geochemistry coupled with oxygen isotope data indicate that hydrothermal fluids in barren and mineralized systems evolved in different ways, and that there are fundamental geochemical differences among the various gold-producing deposits of the area.Much of the variation in the jasperoid geochemical data can be explained in terms of seven abstract end-member components obtained through factor analysis. Three of these components (factors) dominate the results and are related to common products of alteration and mineralization in epithermal systems of the northern Great Basin. Element associations for these factors are: factor 1: TiO•, A12Oa, La, K20, Sr, Fe•Oa, Th; factor 2: Au, Ag, Sb, SiOn, As, Pb; and factor 3: W, B, V, Zn, Co, Au, CaO, Ni, Mn, Cu.Samples from barren systems are predominantly associated with high factor I loadings, whereas samples from mineralized systems are generally characterized by high loadings of factor 2 and/or factor 3. Factor I is related to residual, argillically altered, noncarbonate constituents in original host rocks. Factor 2 is related to hydrothermal silica (jasperoid) and is characterized by many of the so-called pathfinder elements used in Great Basin exploration. Factor 3, although characterized by a transition metal assemblage, is related to syngenetic inclusions of hydrothermal calcite within jasperoidal silica.High factor 2 loadings are associated with samples from the Windfall and Northumberland deposits but not with samples from other gold-producing systems in the study. Factor 3, on the other hand, is the dominant component in most samples from the Carlin, Gold Quarry, Maggie Creek, Pinson, and Preble deposits. It therefore appears that there are at least two geochemically discernible types of gold deposits in the northern Great Basin. These types are represented in this study by the Windfall deposit (factor 2) at one extreme and by the Gold Quarry deposit (factor 3) at the other. Other deposits, including Alligator Ridge and Tonkin Springs, are intermediate between these extremes. In this study, the hydrothermal geochemistry of the Jerritt Canyon samples is obscured by a chert-related compositional factor. Jasperoid samples from gold-producing ore deposits have filSO values ranging from 3 to 20 per mil, whereas jasperoid samples from analogous barren systems have fi•sO values ranging from 3 to 11 per mil. This indicates that at least some fluids in ore-related hydrothermal systems were relatively lsO rich compared to those in barren systems. Jasperoid samples having high •sO values invariably have high factor 3 loadings. The elemental and isotopic geochemistry ofjasperoid samples indicates that hydrothermal fluids in individual gold-producing systems of the northern Great Basin evolved in differentways. It appears that high CO• contents were a critical distinguishing ...

No abstract