Reactivity Of Carbon Research Articles

Effects of supports on hydrogen production and carbon deposition of Fe-based oxygen carriers in chemical looping hydrogen generation

Chemical looping hydrogen generation (CLHG) can produce high purity hydrogen from fuel gases with inherent separation of CO2. However, the performance of oxygen carrier in CLHG varies with the support materials. In this paper, the reactivity, carbon deposition, redox stability, hydrogen yield and purity, and sintering behavior of the Fe-based oxygen carriers were analyzed to investigate the effects of supports, i.e. Al2O3, SiO2, MgAl2O4, ZrO2 and YSZ (yttrium-stabilized zirconia). The results showed that the properties of the oxygen carriers, e.g. carbon deposition, reactivity and stability, mainly depended on the support and its interaction with iron oxides. The reactivity and hydrogen yield for the oxygen carriers investigated followed the order: Fe2O3/MgAl2O4 > Fe2O3/ZrO2 > Fe2O3/YSZ > Fe2O3/Al2O3 > Fe2O3/SiO2, and the order of hydrogen purity was identical with that of hydrogen yield as a result of carbon deposition. Furthermore, the hydrogen purity of the Fe-based oxygen carriers supported by MgAl2O4, ZrO2, or YSZ could reach above 99.5% and Fe2O3/YSZ showed the lowest carbon deposition. The oxygen carriers, Fe2O3/MgAl2O4 and Fe2O3/SiO2, were selected to be characterized by SEM images and XRD patterns before and after the redox cycles.

Photochromic 1,2-bis(2′-methyl-5′-(carboxylic acid)-3′-thienyl) perfluorocyclopentene and its Co(II) coordination polymer

Crystallization from methanol of 1,2-bis(2′-methyl-5′-(carboxylic acid)-3′-thienyl)perfluorocyclopentene (BM-5-CATP, H2L) afforded a new single crystal (H2LMeOH) characterized by single crystal X-ray diffraction analysis, whose structure is different from those of the known crystals crystallized from ethanol, acetone/hexane or acetonitrile. There are two independent molecules with different conformations in one asymmetric unit of H2L. One is a photo-active anti-parallel conformation in which the reactive C atoms are separated by 3.90Å whereas the other is a photo-inactive parallel conformation in which the reactive C-C distance is 4.42Å. The packing characteristics of the two structures derived from methanol and ethanol were compared and analyzed in detail helped by the corresponding computational analyses. The photo-isomerizations of H2LMeOH in tetrahydrofuran and in solid state occur reversibly upon alternate irradiation with ultraviolet (λ=254nm) and visible light (λ>550nm).Reaction of CoCl2·6H2O with BM-5-CATP in methanol afforded a new complex [CoL(MeOH)4](MeOH) (1). Complex 1 is revealed by X-ray crystal diffraction as a 1D zigzag chain, where BM-5-CATP serves as bis-monodentate ligand bridging Co(II) centers in syn-anti fashion. The two thienyl rings in 1 adopt anti-parallel fashions and the distances of 3.80Å between two reactive carbons is short enough for the occurrence of photocyclizations. As expect, complex 1 displayed effective photo-isomerization in crystalline phase with color interconversion between pink and purple, indicating weak suppression of photochromism from metal coordination and extensive H bonds as well as Van de Waals contacts. The λmax of 1 (580nm) in closed form shifted to longer wavelength compared with that of free ligand (576nm).

Environmental geochemistry of a mega beach nourishment in the Netherlands: Monitoring freshening and oxidation processes

As coastal lowlands are prone to sea water flooding, sea-level rise might globally increase this risk. To protect its coastline, the Netherlands adds an average of 12 million m3 of sand annually, but more is needed to cope with the expected consequences of global warming. In 2011 a novel approach for coastal protection was applied near The Hague, consisting of a mega beach nourishment of 21.5 million m3 of sand: the Sand Engine – an artificial sand spit rising to 6 m above mean sea level. It uniquely combines coastal engineering construction with environmental, ecological and social considerations. To construct the Sand Engine, material was used from the seafloor, which changed the materials environment from anaerobic to aerobic, triggering two main hydrogeochemical processes: pyrite oxidation and groundwater freshening. The objective of this study was to assess the sediment geochemistry of the Sand Engine and understand the hydrogeochemistry with respect to pyrite oxidation and freshening. When sufficient buffer capacity is lacking, the mobility of metals and metalloids originated from the mineral pyrite, can cause local impacts on ecology and environment. Geochemical and multivariate statistical analyses were performed on 174 sediment samples from the Sand Engine and from material collected from the seafloor prior to its construction, as well as on 86 samples of pore water collected from the Sand Engine. First, a cluster analysis was performed, using model-based (Mclust) and variable clustering. Second, a robust factor analyses (RFA) was used to explain the variation between the groups and discover relationships between elements and/or soil properties within the groups. We distinguished three clusters of sediment samples and two clusters of pore water samples. Sediment cluster 1 was comprised exclusively of surface samples from the Sand Engine; it was differentiated from the other two clusters by its geochemistry, sorting processes and weathering. Sediment clusters 2 consisted of shallow samples from the Sand Engine, as well as deeper autochthone material from the sand pit. Sediment cluster 3 contained deeper samples from the Sand Engine and also shallow autochthone material from the sand pit. Sediment clusters 2 and 3 show differences in carbonate content and, especially, in reactive iron, confirming that in the sand pit area a Holocene marine layer overlies Pleistocene fluvial sand. For the pore water samples, two clusters were estimated: a saline water cluster and a fresh water cluster. Thus the Sand Engine contains source material from two different geological layers, which vary in their reactive iron concentration and carbonate minerals. Pyrite oxidation is seen with depth, resulting in iron oxides and an increase in alkalinity because of calcite dissolution. With the development of the Sand Engine source material is expected to show a decrease in pyrite oxidation, because of low amount of available sulphide minerals. Carbonate dissolution due to pyrite oxidation will then decrease as well. Additional calcite dissolution is caused by freshening processes. With the amount of CaCO3 present in the sand, the Sand Engine contains calcareous-rich sand where acidic conditions are not likely to occur during its life span and therefore create no local environmental risks for acidification. At the surface of the mega beach nourishment, sorting processes are causing locally enrichment of iron oxides and associated elements, as well as a decrease in the stability of heavy minerals like rutile.

Oxidations of chromene-annulated chlorins.

A chromene-annulated chlorin is a meso-pentafluorophenyl-2,3-dihydroxychlorin in which one of the hydroxy groups is linked to the ortho-position of a flanking meso-aryl group, thereby forming an annulated chromene moiety; the second hydroxy group is unprotected. This report illustrates the oxidation chemistry of the chromene-annulated chlorin under a number of different oxidation conditions. In some reactions, chromene annulation is retained and the non-protected alcohol is oxidized, generating chlorin-like chromophores carrying pyrroline β-carbons in oxidation states between those found in typical porphyrins and chlorins. Other products have lost the chromene moiety. The reactivity of the pyrroline carbon with respect to undergoing radical chemistry is shown with the formation of a number of products following a Swern oxidation, including the formation of two directly linked pyrroline-pyrroline and pyrroline-pyrrole chlorin dimers. This work contributes to the further understanding of the chemistry of chlorins. Selected compounds possess functionalities at their periphery susceptible to nucleophilic attack by MeOH, suggesting their use as chemosensors.

Reactive Transport Modeling of Arsenic Mobilization in Groundwater of the Red River Floodplain, Vietnam

The arsenic content in groundwater of the Red River floodplain decreases with the burial age of the aquifer sediment over a 6000 year period. This decrease is caused by diminishing reactivities of both sedimentary organic carbon, Fe-oxides as well as CaCO3. Here we present a 1-D reactive transport model developed in PHREEQC-3 that quantifies the resulting changes in groundwater bulk chemistry as well as arsenic content over the last six millennia.

The effect of CeO2–ZrO2 structural differences on the origin and reactivity of carbon formed during methane dry reforming over NiCo/CeO2–ZrO2 catalysts studied by transient techniques

The kinetic rate of inactive and active carbon formation in DRM over CeZrO2-supported NiCo alloy particles depends on the support's oxygen mobility.

Measurement of Li-Ion Battery Electrolyte Stability by Electrochemical Calorimetry

Recent work describing the use of high precision coulometry combined with isothermal heat flow calorimetry has shown promise in studying electrolyte reactivity in Li-ion batteries. In this paper we describe what we term an “integration/subtraction” technique for determining the electrolyte reactivity as a function of cell voltage in Li-ion full pouch cells. We apply this method to the characterization of a base electrolyte blend of ethylene carbonate and ethyl methyl carbonate (EC/EMC 3/7 w/w) with 1 M LiPF6. We then show how the parasitic thermal power and coulombic efficiency are affected by the addition of the reactive carbonates vinylene carbonate and 1-fluoro-ethylene carbonate to the base electrolyte. We show how this method can discriminate the effectiveness of additives used in Li-ion cells as a function of cell voltage and cycle life.

Mechanisms of inorganic carbon-14 attenuation in contaminated groundwater: Effect of solution pH on isotopic exchange and carbonate precipitation reactions

Radioactive 14C is a significant contaminant associated with nuclear fuels and wastes that is potentially highly mobile in the environment as dissolved inorganic carbonate species. This study investigated the mechanisms by which dissolved inorganic 14C is retained in surface and groundwater environments via precipitation and isotopic exchange reactions. Precipitation of calcite in the presence and absence of nucleation sites is considered along with isotopic exchange with both atmospheric CO2 and solid carbonates. Precipitation occurs at calcite supersaturation values of SICAL > 1.5 in the absence of nucleation sites and SICAL > 0–0.5 in the presence of nucleation sites, suggesting that precipitation of 14C-bearing carbonates is much more likely in subsurface environments where nucleation sites are abundant. The maximum 14C removal in solid isotopic exchange experiments occurred after approximately 2 weeks equilibration. In these experiments the amount of 14C removed from solution was proportional to the amount of calcite surface area present, and removal from solution was equivalent to rapid equalisation of the isotope ratio in an 8–10 Å active surface layer. Although the reactivity of natural carbonates may be lower than the calcite samples used in this study, these results suggest isotopic exchange with solids will be an important 14C retardation mechanism in subsurface environments containing only modest TIC concentrations. These results suggest that if inorganic 14C is released into sub-surface environments, both precipitation and solid phase isotopic exchange can result in non-conservative 14C-DIC transport and 14C contamination may persist in groundwater for decades following accidental releases. In contrast, in experiments open to atmosphere with pH values below 9.3, complete loss of dissolved inorganic 14C was very rapid and occurred with timescales of 10's of hours. 14C loss was due to a rapid exchange of dissolved 14C species with 12CO2 (g) and the kinetics of 14C removal increased as pH values were lowered (i.e. atmospheric isotopic exchange was first order with respect to the concentration of carbonic acid present). Thus these results suggest that release of inorganic 14C to surface waters with pH values <9.3 would result in rapid exchange with 12CO2 (g) and 14C would not persist in the aqueous environment, whereas 14C-DIC released to saturated subsurface environments may persist close to the release site for decades due to precipitation and solid phase exchange reactions preventing/retarding transport with the groundwater.

Gasification characteristics of different rank coals at H2O and CO2 atmospheres

Gasification characteristics of Shenhua bituminous (SH) and Baorixile lignite coal (BRXL) were investigated using both a thermogravimetric analyzer and tubular furnace. Coal samples were pyrolized in a tubular furnace at five different temperatures (800–1000°C in 50° increments), at two heating rates, 10°C/min and 1000°C/min. The resultant chars were gasified isothermally at (i) each of these five temperatures under a constant atmosphere (40% H2O(g) + 60% CO2) and (ii) at 1000°C while varying the atmosphere from pure H2O(g) to pure CO2 by increasing the CO2 component stepwise in 20 vol.% increments. Carbon conversion, reactivity index, and average specific gasification rate were calculated and fit to a mixed reaction model. It was found that both the gasification temperature and atmosphere composition greatly impacted gasification characteristics, and the temperature effect was more pronounced in a heterogeneous atmosphere. The char produced with a high heating rate pyrolysis process promoted gasification reactivity likely a result of the more open pore structure. The gasification reactivity was lowest under a pure CO2 gasification atmosphere and increased continuously with the H2O partial pressure. SH and BRXL char samples achieved peak gasification reactivity under atmospheres with 60% and 80% H2O(g), respectively. Also, a synergistic effect was observed for heterogeneous CO2/H2O gasification atmosphere and not all the gasification reactions obeyed a first-order reaction model. The results of this work indicate that there is an optimal gasification atmosphere and temperature combination, specific to the coal sample, for efficiently converting char to gasification products.

Controls on Nitrous Oxide Emissions from the Hyporheic Zones of Streams.

The magnitude and mechanisms of nitrous oxide (N2O) release from rivers and streams are actively debated. The complex interactions of hydrodynamic and biogeochemical controls on emissions of this important greenhouse gas preclude prediction of when and where N2O emissions will be significant. We present observations from column and large-scale flume experiments supporting an integrative model of N2O emissions from stream sediments. Our results show a distinct, replicable, pattern of nitrous oxide generation and consumption dictated by subsurface (hyporheic) residence times and biological nitrogen reduction rates. Within this model, N2O emission from stream sediments requires subsurface residence times (and microbially mediated reduction rates) be sufficiently long (and fast reacting) to produce N2O by nitrate reduction but also sufficiently short (or slow reacting) to limit N2O conversion to dinitrogen gas. Most subsurface exchange will not result in N2O emissions; only specific, intermediate, residence times (reaction rates) will both produce and release N2O to the stream. We also confirm previous observations that elevated nitrate and declining organic carbon reactivity increase N2O production, highlighting the importance of associated reaction rates in controlling N2O accumulation. Combined, these observations help constrain when N2O release will occur, providing a predictive link between stream geomorphology, hydrodynamics, and N2O emissions.

High-Pressure Reactivity of Triptycene Probed by Raman Spectroscopy.

The high-pressure reactivity of caged olefinic carbons and polyatomic aromatic hydrocarbons (PAHs) are of interest because of their ability to produce unique C-H networks with varying geometries and bonding environments. Here, we have selected triptycene to explore the creation of pores via high-pressure polymerization. Triptycene has internal free volume on a molecular scale that arises due to its paddle wheel-like structure, formed via fusion of three benzene rings via sp3-hybridized bridgehead carbon sites. At 25 GPa and 298 K, triptycene polymerizes to yield an amorphous hydrogenated carbon, with FTIR indicating an sp3 C-H content of approximately 40%. Vibrational spectroscopy conclusively demonstrates that triptycene polymerizes via cycloaddition reactions at the aromatic sites via a ring opening mechanism. The bridgehead carbons remain intact after polymerization, indicating the rigid backbone of the triptycene precursor is retained in the polymer, as well as molecular-level (∼1-3 Å) internal free volume. High resolution transmission electron microscopy, combined with dark field imaging, indicates the presence of ∼10 nm voids in the polymer, which we attribute to either polymeric clustering or a hierarchical tertiary porous network. Creation of a polymerized network that retains internal voids via high-pressure polymerization is attributed to the presence and retention of the bridgehead carbons.

Isocyanate-Free Route to Poly(carbohydrate–urethane) Thermosets and 100% Bio-Based Coatings Derived from Glycerol Feedstock

Glycerol serves as the exclusive bio feedstock for the preparation of high purity sorbitol tricarbonate (STC) as new intermediate for poly(carbohydrate–urethane) thermosets and 100% bio-based non-isocyanate polyhydroxyurethane (NIPU) coatings. In this process, glycerol-based acrolein is dimerized, carbonated, and oxidized, thus producing the highly reactive diepoxy functional ethylene carbonate (DOC), which by facile chemical CO2 fixation yields high purity STC. Opposite to most state-of-the-art multifunctional five-membered cyclic carbonates and regardless of the feedstock used for its manufacture, STC enables amine curing at ambient temperature even in the absence of catalysts. According to FT-IR and NMR spectroscopic analyses of the amine/carbonate reaction kinetics, the internal cyclic carbonate group is 3 times more reactive with respect to the two terminal carbonate groups. This is attributed to the electron-withdrawing effect of terminal cyclic carbonates. Curing STC with a blend of bio-based flexi...

The steam gasification of coal with molten blast furnace slag as heat carrier and catalyst: Kinetic study

In this study, we carried out a kinetic investigation to analyze the steam gasification of FS (Fu Shun) coal. The effect of reaction temperature (1573 K–1673 K) was studied, and the coal/slag ratios were in the range of 1:0–1:2. The reaction temperature and coal/slag ratio affected the carbon conversion and reactivity index of FS coal gasification. With reaction temperature increasing, the time for carbon conversion completing decreased. But the effect of temperature was non-significant, when it was above 1623 K. The reactivity index of coal at 1673 K was about 1.6 times faster than that at 1573 K, when the coal/slag ratio was 1:0. The BFS (blast furnace slag) acted as not only a heat carrier but also an effective catalyst in steam gasification. Compared with the steam gasification of “pure” FS coal, both carbon conversion and reactivity index of gasification were enhanced by BFS. Meanwhile, the Diffusion model (D1 model) and Shrinking core model (R2 model) were proved as the most appropriate model to describe the steam gasification without and with BFS as heat carrier, respectively. The kinetic parameters applicable to the established model with different coal/slag ratios were obtained. Under these conditions, the valid range of activation energy for gasification reaction was 20 kJ·mol−1–64 kJ·mol−1.

A model for the evolution in water chemistry of an arsenic contaminated aquifer over the last 6000 years, Red River floodplain, Vietnam

Aquifers on the Red River flood plain with burial ages ranging from 500 to 6000years show, with increasing age, the following changes in solute concentrations; a decrease in arsenic, increase in Fe(II) and decreases in both pH, Ca and bicarbonate. These changes were interpreted in terms of a reaction network comprising the kinetics of organic carbon degradation, the reduction kinetics of As containing Fe-oxides, the sorption of arsenic, the kinetics of siderite precipitation and dissolution, as well as of the dissolution of CaCO3. The arsenic released from the Fe-oxide is preferentially partitioned into the water phase, and partially sorbed, while the released Fe(II) is precipitated as siderite. The reaction network involved in arsenic mobilization was analyzed by 1-D reactive transport modeling. The results reveal complex interactions between the kinetics of organic matter degradation and the kinetics and thermodynamic energy released by Fe-oxide reduction. The energy released by Fe-oxide reduction is strongly pH dependent and both methanogenesis and carbonate precipitation and dissolution have important influences on the pH. Overall it is the rate of organic carbon degradation that determines the total electron flow. However, the kinetics of Fe-oxide reduction determines the distribution of this flow of electrons between methanogenesis, which is by far the main pathway, and Fe-oxide reduction. Modeling the groundwater arsenic content over a 6000year period in a 20m thick aquifer shows an increase in As during the first 1200years where it reaches a maximum of about 600μg/L. During this initial period the release of arsenic from Fe-oxides actually decreases but the adsorption of arsenic onto the sediment delays the build-up in the groundwater arsenic concentration. After 1200years the groundwater arsenic content slowly decreases controlled both by desorption and continued further, but diminishing, release from Fe-oxide being reduced. After 6000years the arsenic content has decreased to 33μg/L. The modeling enables a quantitative description of how the aquifer properties, the reactivity of organic carbon and Fe-oxides, the number of sorption sites and the buffering mechanisms change over a 6000year period and how the combined effect of these interacting processes controls the groundwater arsenic content.

ChemInform Abstract: Advances in the Chemistry of Organozinc Reagents

AbstractReview: [43 refs.

Experimental disinfection by-product formation potential following rainfall events

Spring rainfall events can have deleterious impacts on raw and drinking water quality for water treatment plants that use surface waters. This study compares the influence of land use and climate on DBP precursors in two catchments supplying the region around the City of Québec, Canada, and assesses the variability of Disinfection By-Product (DBP) concentration and speciation following rainfall events. DBPs (trihalomethanes (THMs) and haloacetic acids (HAAs)) and their precursors in raw waters (pH, turbidity, specific ultraviolet absorbance (SUVA), total and dissolved organic carbon, bromides and chlorine dose) were monitored. Various experimental chlorination tests, DBP formation potential (DBPFP) and Simulated Distribution Systems (SDS), were also performed.Differences in pre-rainfall (baseflow) water quality were noted according to the different watershed land uses. Raw water quality patterns showed modifications between baseflow and rainfall periods, with a degradation of raw water quality according to turbidity and SUVA in both water sources. Rainfall events were also shown to alter organic matter reactivity with an increase in THM formation potential for both sites. A less noticeable impact on HAA formation potential was observed. However, no clear differences in DBPFP tests were observed between the sites. SDS tests showed that rainfall events lead to considerable rises in organic carbon reactivity of filtered waters, even after primary treatment, with a 2-fold increase in THM and HAA concentrations following rainfall for waters representing the end of one main distribution system (20 h contact time). These increases are linked mainly to a rise in non-brominated DBPs such as chloroform, trichloroacetic acid and dichloroacetic acid. This study confirms the importance of strictly controlling OM levels during drinking water treatment to ensure safe drinking water quality throughout the distribution system.

Улучшение свойств серого чугуна кремнийдиоксид и углеродными наноструктурами

Increasing requirements in terms of performance in modern industry forced to use materials that can operate at higher loads. For metallurgical industry production increasingly require the casting of gray cast iron (GI) high marks. Improving the properties of cast iron and steel is achieved only through the effective doping and modification, allowing to eliminate defects, to grind grain. Currently, the industry uses over 500 existing types of modifiers, most of them are multicomponent. Amount of various additives vary from 2 to 15 components. Very often the main component of additives is silicon – effective graphitizer and deoxidizer. Additives remaining components serve to enhance the effect of modification, increase “survivability” of modifiers, and to change the shape of inclusions of graphite in the iron. Frequently alloying additives are rare earth metals, and other components, considerably raising the price of the final product. At present, the highly competitive component requires an efficiency modifiers, considering the economic component. For this purpose, this paper investigated the effect of nano-additives with high chemical reactivity of carbon and silicon. The theoretical aspects of the modification and the main difficulties that do not fit into the framework of the theory of nucleation are explored. Cast iron modification process made by three different formulations of modifiers, including: Composition 1 – Replaced 50 % of standard metallurgical graphite particulate graphitic carbon with a content of 0.20 % by weight. carbon multiwalled nanotubes. Composition 2 – nanograins silica (89-90 %) + amorphous carbon in different concentrations. Composition 3 – blend compositions 1 and 2 in the proportion of 30 to 70 %. Smelting of gray iron took place in standard mode according to the current smelting technology instruction. Casting the melt in two ways: 1) Fill the melt on top of the modifier 2) “sandwich” process. Evaluation of modifier performed using test strength at break the modified samples. Modifiers all formulations showed a temporary increase in resistance (HB). The tested samples were subjected to the study by scanning electron microscopy (SEM). The theoretical justification of efficiency of dispersed mixed modifiers

Modeling study for the effect of particle size on char gasification with CO2

A high temperature stage microscope to investigate the temperature effect caused by particle size on char gasification is applied in this study. Experiments were carried out with different particle sizes for raw chars and chars on molten slag surface, respectively. Heat transfer models were built for the raw char of two temperature distributions and char particle on molten slag, respectively. Results showed that reaction layer temperature of raw char decreased in the reaction dominant while char on molten slag had higher temperature. Temperature difference between two distributions increased with the initial particle size, indicating the temperature effect on large particles was obvious. Shrinking core model was applied and modified herein coupled with the modification of reaction layer temperature and reaction area. Model prediction and experimental data showed good agreements of carbon conversion and reactivity index for raw char and char on molten slag, respectively. © 2016 American Institute of Chemical Engineers AIChE J, 63: 716–724, 2017

Source, composition and reactivity of sedimentary organic carbon in the river-dominated marginal seas: A study of the eastern Yellow Sea (the northwestern Pacific)

We investigated the source, composition and reactivity of sedimentary organic carbon (OC) in a river-dominated continental marginal sea, the eastern Yellow Sea. A multi-proxy approach was applied to 9 riverbank sediments and 69 marine surface sediments, combining bulk and molecular organic parameters. The riverbank sediments (n=9) have on average low C/N ratio (4.8±0.5) and enriched δ13CTOC values (–21.5±0.6%) while the BIT index is on average 0.27. The sedimentary OC in the marine surface sediments appears to have a predominantly marine origin (on average C/N ratio=7.0±0.6 and δ13CTOC=–21.9±0.5%, n=69) with minor contribution of continental (i.e. soil- and lake/river-derived) OC (on average BIT index=0.00±0.01, n=69). However, the Δ14C values were depleted (on average –227±53%, n=8). Accordingly, our results highlight that fossil OC, potentially derived from erosion of sedimentary bedrocks in the catchment areas and/or human activities is being contributed to the sedimentary OC pool in the eastern Yellow Sea. More work is needed to better constrain the source, composition, and age of the organic material supplied to the eastern Yellow Sea, given the lack of biogeochemical data from the Korean rivers.

Structural geology of the eastern Nadaleen trend, Yukon Territory, Canada: Implications for recently discovered sedimentary rock-hosted gold

Recently discovered gold-rich mineral deposits in the eastern Nadaleen trend of northeastern Yukon Territory occur in unmetamorphosed Neoproterozoic carbonate and siliciclastic rocks and their location is partly controlled by structures. Regional deformation largely resulted from mid-Cretaceous NNE-vergent, thin-skinned fold-thrust activity. However, structures in the eastern Nadaleen trend are more complex and include strike-slip and reverse faults, and SSW-, W-, and E-plunging folds. Local structures are cospatial with regional geologic features, including (1) an E-striking structural triangle zone defined by oppositely dipping reverse faults that verge toward the eastern Nadaleen trend, (2) a transition zone between Paleozoic Ogilvie platform rocks in the north to Selwyn basin rocks in the south, and (3) a change in regional deformation character from west to east, whereby to the west, rocks in the south are more deformed than rocks in the north, whereas to the east, rocks show no obvious change in deformation style. The structural complexity within the eastern Nadaleen trend probably resulted from these regional geological features and was further complicated by local competency contrasts between rock units. The cospatial location of the regional geological features may have been caused by a pre-existing, W-trending subsurface basement structure. Reverse faults bounding the E-striking triangle zone may have acted as low permeability aquitards that directed mineralizing fluids up-dip into reactive carbonate stratigraphy in the eastern Nadaleen trend. Gold-rich mineral deposits in the eastern Nadaleen trend occur preferentially in SSW-plunging anticlines and near faults, both of which probably influenced the migration of mineralizing fluid.