Circular features in forests seen from air have been studied for several decades at different locations around the world. Forest rings, as they are called in Canada's boreal forests, express several geochemical (pH, carbonate content) and geophysical (surface potential) anomalies on their 20-30 m wide ring edges. Although it has been proposed that microbial processes may cause these anomalies, the exact mechanisms of ring formation are still unknown. We focused on the Thorn North forest ring in Ontario, Canada to correlate the surface potential anomaly to soil gas concentrations. Field measurements showed that the surface potential drop at the ring edge center is framed by peaks in CO2 production, which is linked to O2 depletion and methane generation. Carbon isotope signatures were found to drop to lighter values (down to -20 parts per thousand), suggesting increased respiration. Higher concentrations of uronic acids bound to extracellular polymeric substances were found, indicating that the surface potential anomaly is linked to respiration. 16S rRNA gene sequencing of shallow soil did not indicate a dominant microbial group on the edges; instead, principal component analysis showed that the microbial composition was controlled by the substrate (clayey vs. sandy soil), therefore future studies should focus on deeper ground layers.

A geochemical study over the southwestern part of the South Range of the Sudbury Igneous Complex was completed to assess the suitability of surficial media (humus, B-horizon soil and C-horizon soil) for delineating geochemical anomalies associated with Ni–Cu–PGE (platinum group element) mineralization. Another objective was to test whether Na pyrophosphate can eliminate the effects of anthropogenic contamination in humus. Results of this study suggest that the natural geochemical signature of humus is strongly overprinted by anthropogenic contamination. Despite no indication of underlying or nearby mineralization, metal concentrations in humus samples by aqua regia collected downwind from smelting operations are higher compared to background, including up to 13 times higher for Pt, 12 times higher for Cu and nine times higher for Ni. The high anthropogenic background masks the geogenic signal such that it is only apparent in humus samples collected in the vicinity of known Ni–Cu–PGE deposits. Results of this study also demonstrate that anthropogenically derived atmospheric fallout also influences the upper B-horizon soil; however, lower B-horizon soil (at >20 cm depth) and C-horizon soil (both developed in till) are not affected. Glacial dispersal from Ni–Cu–PGE mineralization is apparent in C-horizon till samples analysed in this study. Compared to the background concentrations, the unaffected C-horizon till samples collected immediately down-ice of the low-sulfide, high precious metal Vermilion Cu–Ni–PGE deposit are enriched over 20 times in Pt (203 ppb), Au (81 ppm) and Cu (963 ppm), and over 30 times in Ni (1283 ppm). Supplementary material: supplementary tables and figures are available at https://doi.org/10.6084/m9.figshare.c.5691080

A till geochemistry and indicator mineral (IM) study was carried out in the South Range of the Sudbury Igneous Complex (SIC) to develop surficial mineral exploration techniques that are suitable for low sulfide, high precious metal (LSHPM) and massive sulfide Ni-Cu-PGE mineralization. Surficial exploration in this region is problematic because of heterogeneous till deposits overlain by glaciolacustrine sediments, a naturally high surficial geochemical background, and a paucity of undisturbed till for geochemical sampling due to mining-related operations. The Vermilion and Crean Hill deposits were selected for this case study because their geology and mineralogy have been extensively studied. Pathfinder elements that show a strong, positive (r2 > 0.6, n = 120) correlation with ore elements Ni, Cu, Au and PGEs (Pt, Pd, Ru, Rh, and Ir), which are derived from mineralization and present in elevated concentrations in till samples overlying mineralization are As, Bi, Co, Cr, Pb, Sb and Te. Ore minerals that survive glacial transport and post-glacial weathering and are the best indicators of Ni-Cu-PGE-Au mineralization are grains of gold, chalcopyrite, and sperrylite, predominantly recovered from the < 0.25 mm pan concentrate fraction of till. Despite challenges, this study has identified new exploration targets that warrant further investigation and demonstrates that till geochemistry and IM methods can be used to explore for Ni-Cu-PGE mineralization in established mining camps.

ABSTRACT We report new isotopic data for H2 and CH4 gases and Sr for groundwater collected from Jurassic Kirkland Lake kimberlites in northern Ontario, Canada. Groundwaters interacting with kimberlites have elevated pH (up to 12.4), are reducing (Eh as low as the H2-H2O couple), are dominated by OH− alkalinity, and have non-radiogenic (mantle) 87Sr/86Sr values (∼0.706–0.707). Most significantly, the highest pH groundwaters have low Mg, high K/Mg, and are associated with abundant reduced gases (H2 ± CH4). Open system conditions favor higher dissolved inorganic carbon and CH4 production, whereas under closed system conditions low DIC, elevated OH− alkalinity, and H2 production are enhanced. Hydrogen gas is isotopically depleted (δ2HH2 = −771 to −801‰), which, combined with δ2HH2O, yields geothermometry temperatures of serpentinization of 5–25 °C. Deviation of H2-rich groundwaters (by up to 10‰) from the meteoric water line is consistent with Rayleigh fractionation during reduction of water to H2. Methane is characterized by δ13CCH4 = −35.8 to −68‰ and δ2HCH4 = −434‰. The origin of CH4 is inconclusive and there is evidence to support both biogenic and abiogenic origins. The modeled groundwater–kimberlite reactions and production of elevated concentrations of H2 gas suggest uses for diamond-production tailings, as a source of H2 for fuel cells and as a carbon sink.

The Attawapiskat cluster of kimberlites in northern Ontario, Canada was chosen as a study site to evaluate geochemical anomalies in surface media associated with kimberlites. Kimberlites contain abundant ultramafic minerals and during weathering should impart electrochemically reducing conditions to surrounding surficial materials, both groundwater and sediments (Hamilton et al., 2004; Sader et al., 2007). The purpose of the study was to evaluate the processes of metal dispersion in wetlands overlying glacial and glaciomarine deposits, thereby assessing the validity of using geochemical techniques to discriminate kimberlites from other geophysical targets in similar terrain. Kimberlites in the Attawapiskat cluster are Jurassic in age (~170 Ma) and were emplaced through Ordovician and Silurian strata (Webb et al., 2004). They are overlain by glacial sediments which are capped by marine clays of the post-glacial Tyrrell Sea (~ 4000 – 12000 years BP). One to four meters of peat overlie kimberlites in this region (Fraser et al., 2005).

Regional geochemical characterization of groundwaters in a bedrock aquifer in the Ottawa – St. Lawrence Lowlands of eastern Ontario has identified an iodine (I) anomaly, with values regularly exceeding 150 μg/L and a maximum observed concentration of 10 812 μg/L. The spatial distribution, enrichment mechanisms, and sources of I and organic matter were investigated using geochemical and isotopic data. High-I groundwaters (>150 μg/L) are prevalent in Na–Cl-type groundwaters at low bedrock elevations in areas overlain by thick layers of glacial sediments. I is thought to be linked to massive muds in the glacial sediments overlying the aquifer, deposited during the postglacial incursion of the Champlain Sea 12–10 ka BP. Principal component analysis of I and 18 other chemical parameters revealed correlations among I, salinity, and indicators of microbial oxidation of organic matter, suggesting that the intrusion of saline pore waters affected by decomposition of organic matter such as marine phytoplankton in the massive muds is the dominant process controlling I enrichment in groundwater. 129I/127I ratios in the pre-modern waters vary between near-marine values of 460 × 10−14 and 5 × 10−14, demonstrating that older allochthonous I derived from the surrounding Paleozoic sedimentary terrain also contributed to the I pool in the Champlain Sea basin. 14C ages and δ13C signatures for dissolved organic carbon in groundwater and disseminated organic carbon within the glaciomarine muds highlight an allochthonous source of terrestrial organic carbon predating the Champlain Sea incursion, likely transported via glacial meltwaters in tandem with I to the Champlain Sea basin.

Forest rings are 50-1600 m diameter circular structures found in boreal forests around the globe. They are believed to be chemically reducing chimney features, having an accumulation of reduced species in the middle of the ring and oxidation processes occurring at the ring's edges. It has been suggested that microorganisms could be responsible for charge transfer from the inside to the outside of the ring. To explore this, we focused on the changes in bacterial and archaeal communities in the ring edges of two forest rings, the 'Bean' and the 'Thorn North' ring, in proximity to each other in Ontario, Canada. The drier samples from the methane-sourced Bean ring were characterized by the abundance of bacteria from the classes Deltaproteobacteria and Gemmatimonadetes. Geobacter spp. and methanotrophs, such as Candidatus Methylomirabilis and Methylobacter, were highly abundant in these samples. The Thorn North ring, centred on an H2 S accumulation in groundwater, had wetter samples and its communities were dominated by the classes Alphaproteobacteria and Anaerolineae. This ring's microbial communities showed an overall higher microbial diversity supported by higher available free energy. For both rings, the species diversity was highest near the borders of the 20-30 m broad ring edges.

Groundwaters with total dissolved solids up to 9.5 g/l occur at depths of <50 m in the Paleozoic strata of the Niagara Peninsula. Major ions and trace elements are 1.5–40 times higher than in the same strata elsewhere in Ontario. The δ 18 O and δ 2 H values ( ; ) of groundwater suggest that meteoric precipitation is the primary source with a small portion recharged during Pleistocene glaciation. Tritium (up to 17.42 TU) and coliform bacteria (up to 600 counts/100 ml) data indicate groundwater is generally recently recharged and undergoes a series of modifications that progressively increase salinity. Elemental concentrations and δ 34 S of dissolved sulphate indicate that the salinization is due to multiple processes: (1) road salt inputs into shallow groundwater, (2) upward flow of basinal brines that mix with meteoric groundwater, (3) gypsum and anhydrite dissolution, and (4) sulphide oxidation of minor metallic sulphide minerals. Comparison with water from flowing abandoned gas wells suggests some are acting as conduits allowing upward flow of deeper (Appalachian Basin) brines. The distribution of brine-impacted wells suggests natural vertical pathways also contribute to upward transport and mixing of brine. Supplementary material: The full set of δ 34 S SO 4 in sulphate data are available at: https://doi.org/10.6084/m9.figshare.c.4012885

Forest rings are large circular features common in boreal forests in Ontario, Canada, characterized by ring-shaped topographic depressions in carbonate-rich soil. This paper documents the compositional variation of soil and of the peat that commonly fills the depression, along transects across two representative rings: one centred on an accumulation of CH 4 in glacial sediments and the other on H 2 S in both glacial sediments and bedrock. Clayey mineral soil at the ring edge (annulus) shows low pH, oxidation-reduction potential (ORP), Ca and carbonate, and high Al, Fe and Mn by both aqua regia digestion and a 0.25M hydroxylamine hydrochloride leach (0.25M NH 2 OH.HCl at 60 ° C). Antithetic responses occur in the overlying peat, including elevated carbonate and pH over the areas with low pH, ORP and carbonate in the mineral soil. The observed relationships suggest vertical migration of carbonate species from mineral soil into peat at the annulus, and lateral migration from the annulus to adjacent areas in the mineral soil. The geochemical data support the hypothesis that forest rings are the surface expression of reduced chimneys, similar to those observed over metallic mineral deposits, despite both these sites being known to be barren. Strongly negative ORP values in shallow soils in the annulus suggest autotrophic microbiological activity contributes to the sharp change in redox conditions at the ring boundaries. The similar geochemical responses at forest rings and soils over mineral deposits show that these features can be used to understand the variation in redox, pH, metals and soil hydrocarbons over mineral deposits and to help differentiate ore-related from secondary geochemical features due to the presence of a reduced chimney.

Baseline groundwater geochemical mapping of inorganic and isotopic parameters across 44,000 km 2 of southwestern Ontario (Canada) has delineated a discreet zone of natural gas in the bedrock aquifer coincident with an 8,000-km 2 exposure of Middle Devonian shale. This study describes the ambient geochemical conditions in these shales in the context of other strata, including Ordovician shales, and discusses shale-related natural and anthropogenic processes contributing to hydrogeochemical conditions in the aquifer. The three Devonian shales—the Kettle Point Formation (Antrim equivalent), Hamilton Group and Marcellus Formation—have higher DOC, DIC, HCO 3 , CO 2(aq) , pH and iodide, and much higher CH 4(aq). The two Ordovician shales—the Queenston and Georgian-Bay/Blue Mountain Formations—are higher in Ca, Mg, SO 4 and H 2 S. In the Devonian shale region, isotopic zones of Pleistocene-aged groundwater have halved in size since first identified in the 1980s; potentiometric data implicate regional groundwater extraction in the shrinkage. Isotopically younger waters invading the aquifer show rapid increases in CH 4(aq) , pH and iodide with depth and rapid decrease in oxidized carbon species including CO 2 , HCO 3 and DIC, suggesting contemporary methanogenesis. Pumping in the Devonian shale contact aquifer may stimulate methanogenesis by lowering TDS, removing products and replacing reactants, including bicarbonate, derived from overlying glacial sedimentary aquifers.

Natural gas reservoirs in organic-rich shales in the Appalachian and Michigan basins in the United States are currently being produced via hydraulic fracturing. Stratigraphically-equivalent shales occur in the Canadian portion of the basins in southwestern Ontario with anecdotal evidence of gas shows, yet there has been no commercial shale gas production to date. To provide baseline data in the case of future environmental issues related to hydraulic fracturing and shale gas production, such as leakage of natural gas, saline water, and/or hydraulic fracturing fluids, and to evaluate hydrogeochemical controls on natural gas accumulations in shallow groundwater in general, this study investigates the origin and distribution of natural gas and brine in shallow aquifers across southwestern Ontario. An extensive geochemical database of major ion and trace metal chemistry and methane concentrations of 1010 groundwater samples from shallow, domestic wells in bedrock and overburden aquifers throughout southwestern Ontario was utilized. In addition, select wells (n = 36) were resampled for detailed dissolved gas composition, delta C-13 of CH4, C-2, C-3, and CO2, and delta D of CH4. Dissolved gases in groundwater from bedrock and overburden wells were composed primarily of CH4 (29.7-98.6 mol% of total gas volume), N-2 (0.8-66.2 mol%), Ar + O-2 (0.2-3.4 mol%), and CO2 (0-1.2 mol%). Ethane was detected, but only in low concentrations (<0.041 mol%), and no other higher chain hydrocarbons were present, except for one well in overburden overlying the Dundee Formation, which contained 0.81 mol% ethane and 0.21 mol% propane. The highest methane concentrations (30 to > 100 in situ % saturation) were found in bedrock wells completed in the Upper Devonian Kettle Point Formation, Middle Devonian Hamilton Group and Dundee Formation, and in surficial aquifers overlying these organic-rich shale-bearing formations, indicating that bedrock geology is the primary control on methane occurrences. A few (n = 40) samples showed Na-Cl-Br evidence of brine mixing with dilute groundwater, however only one of these samples contained high (>60 in situ % saturation) CH4. The relatively low delta C-13 values of CH4 (-89.9% to -57.3%), covariance of delta D values of CH4 and H2O, positive correlation between delta C-13 values of CH4 and CO2, and lack of higher chain hydrocarbons (C3+) in all but one dissolved gas sample indicates that the methane in groundwater throughout the study area is primarily microbial in origin. The presence or absence of alternative electron acceptors (e. g. dissolved oxygen, Fe, NO3, SO4), in addition to organic substrates, controls the occurrence of microbial CH4 in shallow aquifers. Microbial methane has likely been accumulating in the study area, since at least the Late Pleistocene to the present, as indicated by the co-variance and range of delta D values of CH4 (-314% to -263%) and associated groundwater (-19% to -6% delta D-H2O). (C) 2014 Elsevier Ltd. All rights reserved.

Shallow groundwaters were collected over and near buried kimberlites in the Attawapiskat River region of the James Bay Lowlands, Ontario, Canada in order to study the impact kimberlites have on CO2–CH4 systematics. Groundwaters collected from boreholes in kimberlites and limestone, and from groundwaters in overlying Tyrell Sea sediment (TSS) were analyzed for δ13CDIC, δ2HH2O, δ18OH2O, dissolved inorganic carbon (DIC), and metal concentrations. Methane gas samples from borehole and TSS groundwaters were analyzed for concentration, δ13CCH4, and δ2HCH4. The CH4 concentrations and Δ13CDIC–CH4 (isotope separation) values indicate biological carbonate reduction in TSS groundwaters overlying kimberlites. Whereas, Δ13CDIC–CH4 values from TSS groundwaters over limestone and from boreholes within limestone and kimberlite indicate the biological consumption of methane (oxidation). The δ2HH2O values from TSS over kimberlites are consistent with the variation in Δ13CDIC–CH4, as they are less negative compared to where they should fall on the local meteoric water line, suggesting that methanogens are using lighter δ2HH2O values to produce CH4. Biological DIC reduction requires H+ ions from H2O to form CH4. There is evidence in the water geochemistry to support the isotopic results, as the ratio of methane to calculated Fe3+ (as amorphous Fe hydroxide), SO42−, and O2(aq) is largest in the majority of TSS groundwaters over kimberlites (where Δ13CDIC–CH4 values indicate CH4 production). Low temperature serpentinization of olivine in kimberlite is not considered for CH4 production, as redox conditions in kimberlite groundwaters do not support abiogenic methane production. The findings here suggest that kimberlites are indirectly influencing the CO2–CH4 system by consuming oxidized ions in the overlying TSS, thereby creating a favorable environment for methane producing bacteria. In contrast, isotopes and geochemistry suggest methane oxidation in areas overlying limestone. The broader implication of this study is that variable lithology underlying sediment cover may impact biological methane production or consumption.

ABSTRACT Peat groundwater compositions at depths of 0.4 and 1.1 m below ground surface in the Attawapiskat region of the James Bay Lowlands are evaluated for diamond exploration applications. Samples were collected along transects that typically extended at least 200 m beyond the margins of Yankee, Zulu, and Golf kimberlites. Locations of upwelling groundwater usually occur at or near kimberlite margins based on hydrogeological measurements and variations in peat groundwater geochemical parameters (pH and EC are high, and the Eh is low relative to ombrotrophic peat groundwaters). Concentrations of the kimberlite pathfinder metals Ni, Cr, light rare earth elements (LREEs), Ba, Mg/Ca, and alkalis are commonly elevated at sample sites at or near kimberlite margins and where groundwaters are upwelling. The presence of elevated kimberlite pathfinders at these sites suggests that fractures along the boundaries between kimberlites and limestone formed during kimberlite emplacement provide dilation for upward movement of groundwater with elevated kimberlite pathfinder metals. Typically, Ni, Cr, LREE, and Ba behave similarly and thus high concentrations of these metals are found at similar locations along transects. On the other hand, locations of elevated alkalis and Mg/Ca vary. The spatial variations among pathfinder metals in peat groundwaters are possibly due to geochemical processes in the peat, such as metal binding to dissolved organic material, adsorption to insoluble organics or Fe-oxyhydroxides, and incorporation into secondary mineral precipitates, which can act to increase or decrease metal solubility. The findings of this study are readily applicable in diamond exploration in wetlands elsewhere.

The speciation and solubility of kimberlite pathfinder metals (Ni, Nd, Ba and K) in shallow peat groundwaters is investigated over the Yankee, Zulu and Golf kimberlites in the Attawapiskat region, James Bay Lowlands, Canada. The purpose of this study is to examine the relationship between dissolved organic matter (DOM) complexation with kimberlite pathfinder metals and determine the spatial distribution of those metals in shallow peat groundwaters along sampling transects over subcropping kimberlites. Nickel, Nd, Ba and K complexation with DOM and the adsorption of these metals onto ferrihydrite were calculated using Visual MINTEQ 3.0 and the NICA-Donnan database. Calculations predict almost 100% of soluble Nd, Ni and Ba form complexes with DOM at sampling sites with little to no contribution from upwelling groundwater (i.e., dissolved organic C (DOC) concentrations = 40-132 mg/L, pH = 3.9-5.5, and log ionic strength <=-3). In only the most ombrotrophic peat groundwater conditions does a majority fraction of K bind to DOM. By contrast, under conditions with large contributions from upwelling groundwaters (i.e., DOC concentrations <= 40 mg/L, pH = 5.5-6.5, and log ionic strength = -3 to -2), as little as 10% of Nd and Ni, and 0% K and Ba are predicted to complex with DOM. The modeling calculations suggest the dominant control on metal-DOM complexation, particularly with respect to Ni and Nd, is competitive effects for DOM binding sites due to elevated ionic strength where there is evidence of strong groundwater upwelling. Visual MINTEQ modeling of metal adsorption on ferrihydrite surfaces predicts that under strong upwelling conditions, Ni and Nd are scavenged from solution due to increased ferrihydrite precipitation and decreased fractions of metals complexed with DOM. Analytical geochemical data are consistent with model predictions of metal adsorption on ferrihydrite. Total dissolved Ni and Nd concentrations at sites of strong upwelling are up to five times lower than waters with little to no upwelling and log ferrihydrite saturation indices (logSl(ferr)) indicate precipitation (values up to 5) at sites of strong groundwater upwelling. Where the majority of Ni and Nd complex with DOM and ferrihydrite is highly under saturated (logSl(ferr) = -18 to -5), the concentrations of total Ni and Nd are elevated compared to other sites along sampling transects. Metal complexation with DOM effectively inhibits metal scavenging from solution via adsorption and/or from forming secondary mineral precipitates. Also, because alkaline earth metals do not compete strongly with Ni and Nd for adsorption sites on ferrihydrite surfaces, but do compete strongly for insoluble organic sites, Ni and Nd are more likely to adsorb onto ferrihydrite. (C) 2011 Elsevier Ltd. All rights reserved.

Henteleff, Harry J. MD; Barie, Philip S. MD; Hamilton, Stewart M. MD members of the Evidence-Based Reviews in Surgery Group

VOLCANIC-ASSOCIATED and sedimentary-exhalative massive sulfide deposits on land account for more than one-half of the world's total past production and current reserves of zinc and lead, 7 percent of the copper, 18 percent of the silver, and a significant amount of gold and other by-product metals (Singer, 1995). A new source of these metals is now being considered for exploitation from deep-sea massive sulfide deposits. Because the oceans cover more than 70 percent of the Earth's surface, many expect the ocean floor to host a proportionately large number of these deposits. However, there have been few attempts to estimate the global mineral potential. Significant accumulations of metals from hydrothermal vents have been documented at some locations (e.g., 91.7 Mt of 2.06% Zn, 0.46% Cu, 58.5 g/t Co, 40.95 g/t Ag, and 0.51 g/t Au in the Atlantis II Deep of the Red Sea: Mustafa et al., 1984; Nawab, 1984; Guney et al., 1988). Even more metal is contained in deep-sea manganese nodules. Current estimates in the U.S. Geological Survey (USGS) mineral commodities summaries indicate a global resource of copper in deep-sea nodules of about 700 Mt. In the Pacific "high-grade" area, an estimated 34,000 Mt of nodules contain 7,500 Mt of Mn, 340 Mt of Ni, 265 Mt of Cu, and 78 Mt of Co (Morgan, 2000; Rona, 2003). A number of countries, including China, Japan, Korea, Russia, France, and Germany, are actively exploring this area.

International Applied Geochemistry Symposium, 2009 1 Peat groundwater as a medium for surficial geochemical exploration Jamil A. Sader, Keiko Hattori, & Stewart M. Hamilton Unversity of Ottawa, Earth Sciences Department, Marion Hall, Room 121, Ottawa, Ontario, K1N 6N5, Canada (email: jamilsader@yahoo.com) Ontario Geological Survey, 933 Ramsey Lake Road, Sudbury, Ontario, P3E 6B5, Canada (e-mail: stew.hamilton@ontario.ca) ABSTRACT: Kimberlite-specific chemical responses are visible in shallow peat groundwater over Kimberlite-specific chemical responses are visible in shallow peat groundwater over kimberlites from the Attawapiskat region in the James Bay Lowlands, Canada. These chemical responses are visible due to the physical movement of deeper groundwater that has interacted with kimberlite and migrated through the Tyrell Sea sediment into shallow peat groundwater. The presence of elevated values of electrical conductivity, CaCO3 saturation index, Ca, and alkalinity indicate groundwater upwelling. Upwelling groundwaters that have high concentrations of Ni, Cr, Fe, Mg, and REEs are likely due to water-kimberlite rock interactions rather than interactions with limestone, or Tyrell Sea sediment. Some of these elements may behave more conservatively in peat groundwaters and are sometimes observed down the horizontal hydraulic gradient. This study has also determined that it is preferable to collect peat groundwater samples deeper into the saturated zone where waters are more reducing and are likely to have higher concentrations of elements. Increased depth into the saturated zone provides better groundwater geochemical resolution between locations of high element contents and lower contents along transects. More oxidized groundwaters near the surface tend produce oxyhydroxides that can adsorb to peat and lower element concentrations in peat groundwater.