Gays River Research Articles

The Gays River mine tailing revegetation study

The Gays River (NS) lead-zinc mine ceased operations in 1982. Seven ha of calcereous mine tailings were left which required stabilization. The tailings, variable in physical composition with depth, were devoid of organic matter, N and P. A potting experiment using the tailings, with and without fertilizer, established 6 plant species which could potentially revegetate the tailing site. Experimental plots (24) were established on the tailings in May 1983 using the same 6 species and 2 indigenous species (alder ( Alnus rugosa) and bulbrush ( Scirpus americanus Pers.)). The plots were maintained through June 1985; plant yield and tissue analysis for macro- and micronutrients followed each cutting or sampling data. The final recommendations for reclamation were to drill in alfalfa ( Medicago sativa L.) and red clover ( Trifolium pratense L.) seeds, cut and fertilize annually with 800 kg ha -1 of 12-24-24 or transplant couchgrass ( Agropyron repens) and fertilize periodically with 12-24-24.

Isotopic constraints on the genesis of Zn-Pb mineralization at Gays River, Nova Scotia, Canada

The Gays River Zn-Pb deposit is hosted in a Carboniferous carbonate bank on the southern marginal platform of the major (>8 km deep) Fundy-Magdalen basin. Fluid inclusion homogenization temperatures (130 degrees -215 degrees C) and structural control of the mineralization (determined in our previous study of the immediate mine area) suggest affinities with both Mississippi Valley-type and Irish-type deposits. New isotopic work, extending to within a 2-km radius of the mine area, significantly constrains genetic hypotheses for the deposit. Preliminary hydrogen isotope measurements of inclusion fluids, together with calculated oxygen isotope compositions, suggest that the mineralizing fluids were basinal brines (delta D = -39ppm; delta 18 O = +3.3ppm). Strontium isotope composition of ore-stage calcite ( 87 Sr/ 86 Sr = 0.7117) indicates that components of the strontium and calcium had a source considerably more radiogenic than Mississippian carbonate or evaporite ( 87 Sr/ 86 Sr = 0.7085-0.7090). These and limited lead isotope data suggest that the fluids had a strontium and metal source in Cambro-Ordovician basement rocks or their immediate clastic derivatives.Sulfur, probably derived from the voluminous Mississippian evaporites (delta 34 S = 14 + or - 1ppm) was probably carried as sulfate (in a fluid with neutral pH) to the depositional site where complete (nonbiogenic?) reduction (at [asymp] 200 degrees C) occurred. This is supported by the lack of extensive dissolution and brecciation and the close similarity of the delta 34 S (sub Sigma S) value for the mineralizing fluids and the delta 34 S value of the evaporites. The carbon budget of the ore-forming fluids was dominated by oxidized carbon from a carbonate source with delta 13 C value near 2 per mil, locally influenced by organic carbon with low delta 13 C values which is abundant in the Gays River carbonate bank.A basinal brine expulsion model is favored. The hot mineralizing fluid must have originated at a >4-km depth and interacted with elastic, carbonate, and evaporite sedimentary rocks on its way to the depositional site. The likely age for this mineralizing event is approximately 300 m.y.

The organic geochemistry of two mississippi valley-type lead-zinc deposits

The organic matter associated with two Mississippi Valley-type deposits (Gays River, Nova Scotia, and Shullsburg, southwestern Wisconsin) has been characterized by petrographic, isotopic, spectrophotometric, gas chromatographic, and mass spectral methods. Comparisons were made of distributions of organic species identified from unmineralized and mineralized samples. The primary variations in the distributions of organic species isolated from the two deposits reflect variations in host-rock paleoecology, facies, and geologic age. Secondary effects were microbial degradation, thermal maturation, and mineralization. Mineralization in both deposits caused an increase in the concentrations of low molecular weight hydrocarbons.The genetic model tested in this study presumed that mineralizing brines evolved from sedimentary basins and migrated to the ore host rocks. This model implies that an epigenetic generation of organic matter should occur in the deposits. In the Gays River deposit, the probable aquifer for the mineralizing solutions contained an organic distribution markedly different from the indigenous organic matter in the host reef and can be interpreted as a second, epigenetic organic fraction added to the deposit. Evidence was not observed for an epigenetic organic generation in the Shullsburg deposit. The thermal maturity of the organic matter in the Wisconsin district supports a previous estimate of 0.25 m.y. to form a major orebody in the district.

Improving the characteristics of fine dolomitic-limestone tailings by agglomeration with selected materials

There are about 1.8 Mt (2 million st) of discarded dolomitic-limestone tailings from the Gays River lead/zinc mining operation in Nova Scotia currently stockpiled in a tailings pond at the mill site. Neutralization effectiveness similar to an agricultural grade limestone and low contents of residual metals make the tailings a potential source of soil conditioner material for the local market. However, the fine particle size, 98% passing 147 µm (about 100 mesh), and a moisture content of 20% make their handling, shipping, and application to soils difficult. The tailings were agglomerated into small hard pellets with various amounts of soil nutrients, moisture content less than 13%, and pH values ranging from 6.5 to 8.7.

The hydrological environment at the gays river mine

The Gays River zinc-lead deposit is hosted by a carbonate reef complex and overlain by the evaporites gypsum and anhydrite. Erosion at the carbonate-evaporite contact took place during the Lower Cretaceous period. This erosion led to the formation of a karst topography which was in turn overlain by lacustrian and fluvial sediments. Soil piping structures in these sediments have made mining very costly and dewatering uncertain. The history of the effort to control the water is discussed.

Geologic, fluid inclusion, and stable isotope studies of the Gays River lead-zinc deposit, Nova Scotia, Canada

The Gays River deposit is the largest carbonate-hosted lead-zinc deposit known in the Mississippian Windsor Group of Atlantic Canada. The orebody mainly occupies one flank of a porous, dolomitized carbonate bank that unconformably overlies a basement ridge of the metasedimentary lower Paleozoic Megurea Group. The orebody consists of: stratiform, disseminated sulfides as open-space fillings in primary and secondary pores of the dolomite and fault-controlled veinlike bodies of high-grade, massive sphalerite and galena. The carbonate bank is overlain by evaporite deposits of Mississippian age. Underground mapping and laboratory studies suggest four main stages of evolution for Gays River: (1) deposition of the (Visean) carbonate bank, preore evaporite deposition, pervasive dolomitization and growth of diagenetic marcasite, (2) deposition of sphalerite, galena, chalcopyrite, and calcite as a result of influx of hydrothermal metal-rich saline brines into fractures and porous dolomite, (3) postore deposition of calcite, fluorite, barite, marcasite, pyrite, and selenite, and (4) uplift, localized dedolomitization of the mineralized carbonates, and exposure by erosion in Cretaceous times. Microthermometry of fluid inclusions yields the following mean homogenization temperatures: sphalerite, 215oC; ore-stage calcite, 173oC; postore calcite, 142oC; fluorite, 142oC; and barite, 137oC. Pressure corrections should be minimal for these temperatures. No evidence of boiling was observed in the inclusions. Salinity determinations from the ice-melting temperatures of inclusions in postore fluorite and calcite yield a value of ca. 20.4 equivalent wt percent NaCI for the hydrothermal fluid during the waning stages of mineralization. Isotopic analyses indicate that anhydrite and gypsum in the overlying evaporites and barite within the orebody are enriched in heavy sulfur (t34S -- 13.1-16.5%0), suggesting a Mississippian seawater source. Ore-stage sphalerite, galena, and chalcopyrite probably derived their sulfur (b34S -- 8.0-13.65%0) from sulfates or possibly a homogenized basement source. Postore marcasite and pyrite are characterized by light, probably biogenic, sulfur (ba4S -- -9.7 to -46%0). Mineralized carbonates are significantly depleted in the heavier isotopes of oxygen and carbon with respect to their unmineralized equivalents. Preliminary lead isotope data for galena suggest that the metasedimentary basement was a source of lead. This study disputes an earlier interpretation that the stratiform lead-zinc ores are an early low-temperature diagenetic cement of the carbonate bank. The high-grade zones are not residual concentrations related to sinkholes as originally thought. Instead, both disseminated and massive ores are probably the result of the same mineralizing episode involving deeply convecting brines, or brines expelled during basin dewatering under high geothermal gradients in the late Paleozoic.

Conodont biostratigraphy of the Codroy Group (Lower Carboniferous), southwestern Newfoundland, Canada

Four stratigraphically successive conodont assemblage zones have been recognized in the Lower Carboniferous Codroy Group of southwestern Newfoundland. The Diplognathodus Zone is confined to the basal Ship Cove Limestone, and to a highly fossiliferous correlative at Aguathuna. The overlying Taphrognathus Zone occurs in carbonates in the stratigraphic interval above the sequence of massive sulphates and thick clastics. The Taphrognathus Zone, as well as the successive Cavusgnathus Zone, has been recognized on Fischells Brook, as well as in the complex section south of Codroy. The highest conodont zone, the Gnathodus Zone, has been recognized in the Crabbes–Jeffreys Limestone of the St. George's Bay area, and from south of Codroy.The discovery of conodonts of the Diplognathodus Zone in marine strata that are stratigraphie and lithologie correlatives of the Macumber and the Gays River Formations of Nova Scotia now makes it possible to microfaunally characterize the A Subzone, a macrofaunal subzone established in the Windsor Group of Nova Scotia.The Taphrognathus and Cavusgnathus Zones of the Codroy Group of Newfoundland correlate with the lower and upper B Subzone of the Lower Windsor Group of Nova Scotia, respectively. The Gnathodus Zone correlates with the C, D, and E Subzones of the Upper Windsor Group of Nova Scotia.