Natural building stones     

Jennifer M. McKinley 《Geology Today》2011,27(3):114-118

Natural stone due to its durable properties has been the choice of building materials since the very beginning of civilization. However, once stone is taken from its natural environment it begins to change to reach a state of equilibrium with its new environment. The polluted urban environment is a particularly hostile environment for natural stone and the effect on natural stone buildings, especially of historical or cultural significance, is a major cause for concern. Ongoing research into weathering studies is essential to provide a greater understanding of the processes that trigger stone decay and to ensure the implementation of successful stone conservation and replacement strategies.  相似文献   

The use of soil geochemistry to map tectonic assemblages: Case study based on the Tellus Survey, Northern Ireland     

McKinley  J.M.  Grunsky  E.C.  Mueller  U.A. 《《地质学报》英文版》2018,92(Z1):158-158

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River-induced flow dynamics in long-screen wells and impact on aqueous samples     

Vermeul VR  McKinley JP  Newcomer DR  Mackley RD  Zachara JM 《Ground water》2011,49(4):515-524

Previously published field investigations and modeling studies have demonstrated the potential for sample bias associated with vertical wellbore flow in conventional monitoring wells constructed with long-screened intervals. This article builds on the existing body of literature by (1) demonstrating the utility of continuous (i.e., hourly measurements for ～1 month) ambient wellbore flow monitoring and (2) presenting results from a field experiment where relatively large wellbore flows (up to 4 L/min) were induced by aquifer hydrodynamics associated with a fluctuating river boundary located approximately 250 m from the test well. The observed vertical wellbore flows were strongly correlated with fluctuations in river stage, alternating between upward and downward flow throughout the monitoring period in response to changes in river stage. Continuous monitoring of ambient wellbore flows using an electromagnetic borehole flowmeter allowed these effects to be evaluated in concert with continuously monitored river-stage elevations (hourly) and aqueous uranium concentrations (daily) in a long-screen well and an adjacent multilevel well cluster. This study demonstrates that when contaminant concentrations within the aquifer vary significantly over the depth interval interrogated, river-induced vertical wellbore flow can result in variations in measured concentration that nearly encompass the full range of variation in aquifer contaminant concentration with depth.  相似文献   

Magmatic and structural controls on porphyry-style Cu–Au–Mo mineralization at Kemess South,Toodoggone District of British Columbia,Canada     

Paul Duuring  Stephen M. Rowins  Bradley S. M. McKinley  Jenni M. Dickinson  Larry J. Diakow  Young-Seog Kim  Robert A. Creaser 《Mineralium Deposita》2009,44(4):435-462

Kemess South is the only Cu–Au–Mo mine in the Toodoggone district and a major Cu and Au producer in British Columbia. Porphyry-style Cu–Au–Mo mineralization is mainly hosted by the tabular, SW-plunging, 199.6 ± 0.6-Ma Maple Leaf granodiorite, which intrudes tightly folded, SW-dipping, Permian Asitka Group siltstone and limestone and homogeneous Triassic Takla Group basalt. Southwest-dipping 194.0 ± 0.4-Ma Toodoggone Formation conglomerate, volcaniclastic, and epiclastic rocks overlie the granodiorite and Asitka Group rocks. Minor Cu–Au–Mo mineralization is hosted by the immediate Takla Group basalt country rock, whereas low-tonnage high-grade Cu zones occur beneath a 30-m-thick leached capping in supergene-altered granodiorite and in exotic positions in overlying Toodoggone Formation conglomerate. Granodiorite has an intrusive contact with mineralized and altered Takla Group basalt but displays a sheared contact with unmineralized and less altered Asitka Group siltstone. The North Block fault is a deposit-scale, E-striking, steeply S-dipping normal fault that juxtaposes the granodiorite/basalt ore body against unmineralized Asitka Group rocks. Younger NW- and NE-striking normal–dextral faults cut all rock types, orebodies, and the North Block fault with displacements of up to 100 m and result in the graben-and-horst-style block faulting of the stratigraphy and ore body. Both basalt and granodiorite host comparable vein sequence and alteration histories, with minor variations in hydrothermal mineral assemblages caused by differing protolith chemistry. Early potassic alteration (and associated early-stage Cu ± Au ± Mo mineralization) is partly replaced by phyllic and intermediate argillic alteration associated with main-stage Cu–Au–Mo mineralization. Two main-stage veins have Re–Os molybdenite ages of 201.3 ± 1.2 and 201.1 ± 1.2 Ma. These mineralization ages overlap the 199.6 ± 0.6-Ma U–Pb zircon crystallization age for the Maple Leaf granodiorite. Late-stage pyrite-rich stringer veins and related phyllic alteration assemblages are cut by anhydrite-rich, carbonate-rich, and chlorite veins. Fluids and metals associated with early-, main-, and late-stage veins were probably derived principally from the same deep magma chamber as the Maple Leaf granodiorite. These magmatic-derived fluids interacted with Asitka and Takla Group country rocks and possibly with meteoric and metamorphic fluids prior to mineralization.  相似文献   

RECOVERY AND CLASSIFICATION OF THIRTY NEW METEORITES FROM ROOSEVELT COUNTY,NEW MEXICO     

Edward R.D. Scott  Susan G. McKinley  Klaus Keil  Ivan E. Wilson 《Meteoritics & planetary science》1986,21(3):303-308

We report the discovery and classification of 30 new meteorites found in or close to Roosevelt County, New Mexico, including two H3 chondrites and a ureilite; the others are equilibrated ordinary chondrites. Over 160 meteorites representing at least 100 different falls have been recovered from this region, mostly from wind blowout areas. As in Antarctica, small specimens predominate and irons, achondrites and C and E chondrites are rare. Paired specimens are also very difficult to identify.  相似文献   

Dissolution of uranyl microprecipitates in subsurface sediments at Hanford Site, USA     

Chongxuan Liu  John M. Zachara  James P. McKinley  Zheming Wang 《Geochimica et cosmochimica acta》2004,68(22):4519-4537

The dissolution of uranium was investigated from contaminated sediments obtained at the US. Department of Energy (U.S. DOE) Hanford site. The uranium existed in the sediments as uranyl silicate microprecipitates in fractures, cleavages, and cavities within sediment grains. Uranium dissolution was studied in Na, Na-Ca, and NH₄ electrolytes with pH ranging from 7.0 to 9.5 under ambient CO₂ pressure. The rate and extent of uranium dissolution was influenced by uranyl mineral solubility, carbonate concentration, and mass transfer rate from intraparticle regions. Dissolved uranium concentration reached constant values within a month in electrolytes below pH 8.2, whereas concentrations continued to rise for over 200 d at pH 9.0 and above. The steady-state concentrations were consistent with the solubility of Na-boltwoodite and/or uranophane, which exhibit similar solubility under the experimental conditions. The uranium dissolution rate increased with increasing carbonate concentration, and was initially fast. It decreased with time as solubility equilibrium was attained, or dissolution kinetics or mass transfer rate from intraparticle regions became rate-limiting. Microscopic observations indicated that uranium precipitates were distributed in intragrain microfractures with variable sizes and connectivity to particle surfaces. Laser-induced fluorescence spectroscopic change of the uranyl microprecipitates was negligible during the long-term equilibration, indicating that uranyl speciation was not changed by dissolution. A kinetic model that incorporated mineral dissolution kinetics and grain-scale, fracture-matrix diffusion was developed to describe uranium release rate from the sediment. Model calculations indicated that 50-95% of the precipitated uranium was associated with fractures that were in close contact with the aqueous phase. The remainder of the uranium was deeply imbedded in particle interiors and exhibited effective diffusivities that were over three orders of magnitude lower than those in the fractures.  相似文献   

Impact of highly basic solutions on sorption of Cs to subsurface sediments from the Hanford site, USA     

C.C. Ainsworth  J.M. Zachara  K. Wagnon  S. McKinley  C. Liu  S.C. Smith  H.T. Schaef  P.L. Gassman 《Geochimica et cosmochimica acta》2005,69(20):4787-4800

The effect of caustic NaNO₃ solutions on the sorption of ¹³⁷Cs to a Hanford site micaceous subsurface sediment was investigated as a function of base exposure time (up to 168 d), temperature (10°C or 50°C), and NaOH concentration (0.1 mol/L to 3 mol/L). At 10°C and 0.1 M NaOH, the slow evolution of [Al]_aq was in stark contrast to the rapid increase and subsequent loss of [Al]_aq observed at 50°C (regardless of base concentration). Exposure to 0.1 M NaOH at 10°C for up to 168 d exhibited little if any measurable effect on sediment mineralogy, Cs⁺ sorption, or Cs⁺ selectivity; sorption was well described with a two-site ion exchange model modified to include enthalpy effects. At 50°C, dissolution of phyllosilicate minerals increased with [OH]. A zeolite (tetranatrolite; Na₂Al₂Si₃O₁₀·2H₂O) precipitated in 0.1 M NaOH after about 7 days, while an unnamed mineral phase (Na₁₄Al₁₂Si₁₃O₅₁·6H₂O) precipitated after 4 and 2 days of exposure to 1 M and 3 M NaOH solutions, respectively. Short-term (16 h) Cs⁺ sorption isotherms (10⁻⁹-10⁻² mol/L) were measured on sediment after exposure to 0.1 M NaOH for 56, 112, and 168 days at 50°C. There was a trend toward slightly lower conditional equilibrium exchange constants (Δlog _Na^CsK_c ∼ 0.25) over the entire range of surface coverage, and a slight loss of high affinity sites (15%) after 168 days of pretreatment with 0.1 M base solution. Cs⁺ sorption to sediment over longer times was also measured at 50°C in the presence of NaOH (0.1 M, 1 M, and 3 M NaOH) at Cs⁺ concentrations selected to probe a range of adsorption densities. Model simulations of Cs⁺ sorption to the sediment in the presence of 0.1 M NaOH for 112 days slightly under-predicted sorption at the lower Cs⁺ adsorption densities. At the higher adsorption densities, model simulations under-predicted sorption by 57%. This under-prediction was surmised to be the result of tetranatrolite precipitation, and subsequent slow Na → Cs exchange. At higher OH concentrations, Cs⁺ sorption in the presence of base for 112 days was unexpectedly equal to, or greater than that expected for pristine sediment. The precipitation of secondary phases, coupled with the fairly unique mica distribution and quantity across all size-fractions in the Hanford sediment, appears to mitigate the impact of base dissolution on Cs⁺ sorption.  相似文献   

Natural analogues: studies of geological processes relevant to radioactive waste disposal in deep geological repositories     

W. Russell Alexander  Heini M. Reijonen  Ian G. McKinley 《Swiss Journal of Geoscience》2015,108(1):75-100

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Spatial characterization of salt accumulation in early stage limestone weathering using probe permeametry     

O. Buj  J. Gisbert  J. M. McKinley  B. Smith 《地球表面变化过程与地形》2011,36(3):383-394

This research characterizes the weathering of natural building stone using an unsteady‐state portable probe permeameter. Variations between the permeability properties of fresh rock and the same rocks after the early stages of a salt weathering simulation are used to examine the effects of salt accumulation on spatial variations in surface rock permeability properties in two limestones from Spain. The Fraga and Tudela limestones are from the Ebro basin and are of Miocene age. Both stone types figure largely in the architectural heritage of Spain and, in common with many other building limestones, they are prone to physical damage from salt crystallization in pore spaces. To examine feedbacks associated with salt accumulation during the early stages of this weathering process, samples of the two stone types were subjected to simulated salt weathering under laboratory conditions using magnesium sulphate and sodium chloride at concentrations of 5% and 15%. Permeability mapping and statistical analysis (aspatial statistics and spatial prediction) before and after salt accumulation are used to assess changes in the spatial variability of permeability and to correlate these changes with salt movement, porosity change, potential rock deterioration and textural characteristics. Statistical analyses of small‐scale permeability measurements are used to evaluate the drivers for decay and hence aid the prediction of the weathering behaviour of the two limestones. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Microscale controls on the fate of contaminant uranium in the vadose zone, Hanford Site, Washington     

James P. McKinley  John M. Zachara  Steven C. Heald  Brian W. Kempshall 《Geochimica et cosmochimica acta》2006,70(8):1873-1887

An alkaline brine containing uranyl (UO₂²⁺) leaked to the thick unsaturated zone at the Hanford Site. We examined samples from this zone at microscopic scale to determine the mode of uranium occurrence—microprecipitates of uranyl (UO₂²⁺) silicate within lithic-clast microfractures—and constructed a conceptual model for its emplacement, which we tested using a model of reactive diffusion at that scale. The study was driven by the need to understand the heterogeneous distribution of uranium and the chemical processes that controlled it. X-ray and electron microprobe imaging showed that the uranium was associated with a minority of clasts, specifically granitic clasts occupying less than four percent of the sediment volume. XANES analysis at micron resolution showed the uranium to be hexavalent. The uranium was precipitated in microfractures as radiating clusters of uranyl silicates, and sorbed uranium was not observed on other surfaces. Compositional determinations of the 1-3 μm precipitates were difficult, but indicated a uranyl silicate. These observations suggested that uranyl was removed from pore waters by diffusion and precipitation in microfractures, where dissolved silica within the granite-equilibrated solution would cause supersaturation with respect to sodium boltwoodite. This hypothesis was tested using a reactive diffusion model operating at microscale. Conditions favoring precipitation were simulated to be transient, and driven by the compositional contrast between pore and fracture space. Pore-space conditions, including alkaline pH, were eventually imposed on the microfracture environment. However, conditions favoring precipitation were prolonged within the microfracture by reaction at the silicate mineral surface to buffer pH in a solubility limiting acidic state, and to replenish dissolved silica. During this time, uranyl was additionally removed to the fracture space by diffusion from pore space. Uranyl is effectively immobilized within the microfracture environment within the presently unsaturated Vadose Zone.  相似文献