Slate Samples Research Articles

Optical microscope and SEM evaluation of roofing slate fissility and durability

The fissility and durability of representative samples of commercial roofing slates from ten deposits in the NW of Spain have been evaluated using transmitted and reflectedlight optical microscopy, scanning electron microscopy, chemical testing and geomechanical procedures. The dominant sulphides in the different slate samples are pyrite and pyrrhotite, the weathering potential of which can be highly variable. The dominant carbonate mineral is ankerite, which explains the low reactivity of these slates in acidic media. The minimum commercial plate thickness varies between 3.5 and 5 mm, depending on the microtexture of the rock. The methodology used in this paper is proposed in order to eliminate the subjectivity of input data that are used in current methods of evaluation and modelling of slate deposits, thus producing an improvement in the profitability of mining operations and a reduction in waste materials.

Passivation techniques to prevent corrosion of iron sulphides in roofing slates

The aim of the present study was to evaluate the efficacy of different methods of sulphide microencapsulation in terms of inhibiting sulphide oxidation in roofing slate. For this, a preliminary test was carried out with ground pyrite and the methods that provided the best results were applied to samples of roofing slate. Protection against oxidation was measured by the amount of iron released after enforced oxidation with H 2O 2 in the tests with pyrite, and by thermal cycle alteration, SO 2 and saline spray tests (EN 12326-2:2000 and EN 14147:2004) in the tests with the slate samples. The results indicate that treatments with potassium phosphate and potassium silicate, proposed for controlling acid mine drainage, were the most effective at protecting pyrite against oxidation, and that these methods are also effective when applied to slate.

Similar quartz crystallographic textures in rocks of continental earth’s crust (by neutron diffraction data): I. Quartz textures in monomineral rocks

The types of quartz textures found in a large collection of multiphase rocks from different regions of the earth are analyzed. Crystallographic textures of granulite, amphibolite, slate, and gneiss samples are measured, classified, and compared with the similar textures of monomineral rocks.

Thermal evolution of a slate

The thermal evolution of a slate rock sample (Berja, Almeria, Spain) has been studied. The phase minerals identified in this sample were mica (illite), chlorite (clinochlore) and quartz as major components, with minor microcline, iron oxide and a mixed-layer or interstratified phase (montmorillonite-chlorite). This slate is highly silico-aluminous (48.33 mass% silica, 22.04 mass% alumina), and ca. 20 mass% of other elements, mainly Fe2O3 (8.35 mass%), alkaline-earths and alkaline oxides. Two main endothermic DTA effects, centered at 640 and 730°C, were observed. The more important contribution of total mass loss (7.15 mass%) was found between 500–900°C, with two DTG peaks detected at 630 and 725°C. All these effects were associated to the dehydroxylation of structural OH groups of 2:1 layered silicates mixed in the slate. The dehydroxylation of the layered silicates evidenced by dilatometry, produced a rapid increase of expansion between 600–800°C. The thermal evolution of the slate upper 800°C indicated the first sintering effects associated to shrinkage, which is also favoured by its low particle size (average 23 μm) and the presence of a liquid or vitreous phase as increasing the heating temperature. The application of thermal diffractometry to the slate sample allowed to study the formation of dehydroxylated crystalline phases from the layered silicates after heating. At 1000°C, β-quartz, dehydroxylated illite, iron oxide, relicts of microcline and the vitreous phase were present in the sample. All these results are interesting to know the thermal behaviour of a complex mineral mixture as identified in the slate.

Trace metals in bulk freefall and roof intercepted rainwater at Ile-Ife, Southwest Nigeria

Samples of bulk freefall and roof-intercepted rainwater collected over five roof types (viz: Iron–Zinc sheets, Aluminum sheets, Asbestos sheets, Slate tiles, and Thatch) at Ile-Ife (SW Nigeria) were analysed for nine trace metals (aluminum, cadmium, chromium, copper, iron, lead, manganese, nickel, and zinc) using atomic absorption spectrophotometry (AAS). The mass concentrations and percent detection of the trace metals were generally higher in roof-intercepted samples than in the freefall samples. The ranking order of the mean concentrations of the metals in freefall samples (Al > Cr > Fe > Zn > Pb > Mn > Ni > Cu > Cd) is indicative of an atmospheric environment greatly influenced by heavy vehicular emissions and remobilized suspended particulate matter of soil origin. Mean metal enrichment of samples over the different roofs was in the order of Iron–Zinc > Aluminum > Thatch > Asbestos > Slate roof. Each roof sample type (except Slate samples) was characterized by relatively high enrichment of one or two metals. These include the high enrichment of zinc and iron in Iron–Zinc roof samples, cadmium and manganese in Aluminum roof samples, copper and manganese in Thatch roof samples and cadmium in Asbestos roof samples. The metal concentrations of roof-intercepted rainwater were lower than those of neighboring surface water, packaged table water, and vegetation-intercepted rainwater in the same environment. The metal levels in all the rainwater sources occurred within the allowable guide levels for most public and domestic applications.

Diagenesis and low-temperature metamorphism of Mt. Medvednica, Croatia: Mineral assemblages and phyllosilicate characteristics

New mineral paragenetic, illite Kübler index, chlorite “crystallinity”, apparent crystallite thickness, lattice strain, and K-white mica geobarometric data proved that the Eoalpine (Paleozoic-Mesozoic) metamorphic complex was affected by medium-pressure, high-temperature anchizonal regional metamorphism, whereas the Jurassic ophiolitic mélange and the Late Cretaceous-Paleocene sedimentary sequence of Mt. Medvednica were diagenetically altered. Mineral chemical investigations carried out on phyllosilicate flakes found in various microstructural positions revealed complete mineral chemical homogenization of chlorite and K-white mica of selected slate samples from the Eoalpine (Paleozoic-Mesozoic) metamorphic complex. One possible explanation of this feature is an Alpine (Cretaceous) regional metamorphic event with polyphase deformational history. Variscan low-temperature metamorphism overprinted by an Alpine (Cretaceous) event, with temperatures at least as high as those of the Variscan one, may be an alternative, although more complicated explanation. However, no isotope geochronological evidence supports this assumption. At present only one metamorphic event can be detected. Its physical conditions were ca. 350-400 °C on the basis of illite Kübler index and chlorite Al(IV) empirical thermometers and 3-4 kbar using K-white mica b cell dimension measurements.

Expandability of anchizonal illite and chlorite: Significance for crystallinity development in the transition from diagenesis to metamorphism

In mixed-layer illite/smectite containing >80% illite, the presence of an expandable component and changes in its abundance are difficult or impossible to detect with the X-ray diffraction (XRD) method using conventional polar interstratification compounds, e.g., solvation with ethylene glycol. Although high-grade diagenetic and very low-grade metamorphic (VLGM) samples do not expand in response to ethylene glycol treatment, the illite crystallinity (IC) improves significantly with increasing diagenetic/metamorphic grade. Improvement of IC in anchizonal to epizonal samples previously was thought to be related primarily to increase in crystallite thickness and decrease in the number of stacking faults. The present study reexamines the contribution of expandable components to IC in shale and slate samples from the Gaspe Peninsula for both the <2 μm and <0.1 μm size fractions in the high-grade diagenetic and VLGM zone. As tools, we have used XRD patterns and high-resolution transmission electron microscopy (HRTEM) lattice-fringe images of samples treated with n- alkylammonium cations. These studies reveal the presence of expandable components including R1- and R3-ordered structures and “expandable illite.” Expandable 2:1 clay minerals decrease in abundance with increasing metamorphic grade. The improvement of IC with grade is due to the decrease in expandable layers and also to the decrease in the number of lattice defects and an increase in crystallite size. Stacking faults may be the main source of lattice distortion only when phyllosilicates consist of thick non-expandable layer silicates. During late diagenesis, the chlorites become ordered and are stabilized. They are the dominant phyllosilicate minerals present together with illites in the illite-chlorite facies of the anchizone. Lattice fringe images and XRD patterns document the presence of a short-range, corrensite-like R1 ordered phase and thick chlorite packets.

Precise dating of low-temperature deformation: Strain-fringe analysis by 40Ar-39Ar laser microprobe

Pyritized graptolites from the Welsh Basin (United Kingdom) slate belt acted as rigid bodies during cleavage formation, and epizonal white micas formed within the resulting. strain shadows, orthogonal to the principal stress orientation. Although the quantities of mica are small, they are a pure synkinematic mineral and have been dated by Ar-40-Ar-39 infrared laser microprobe as a means to dating cleavage. Four samples of strain-fringe mica from different hand samples yielded ages ranging from 394.4 +/- 3.1 to 397.8 +/- 1.8 Ma (2sigma), with a mean age of 396.1 +/- 1.4 Ma (2sigma). By focusing on minerals that are unequivocally synkinematic, this technique provides a novel solution to the problems of isotopically dating slaty cleavage. Previous studies have predominantly relied on dating whole-rock slate samples or separated illite grains by Ar-40-Ar-39 techniques; problems encountered included (1) separating the effects of isotopic contamination by detrital phases, (2) Ar-39 loss during the irradiation of illite mineral separates, and (3) thermally induced Ar-40 loss in nature from fine-grained minerals. By circumventing these problems, this new method provides the first unequivocal and high-precision age data for Acadian deformation in the well-characterized Welsh Basin slate belt. With such precision, the method may afford geologists the opportunity to track tectonic fronts across orogens and assess the rates of accretion processes in areas that are peripheral to sites of continent-continent collision.

40Ar/39Ar and K–Ar age constraints on the timing of regional deformation, south coast of New South Wales, Lachlan Fold Belt: Problems and implications

Four slate samples from subduction complex rocks exposed on the south coast of New South Wales, south of Batemans Bay, were analysed by K–Ar and 40Ar/39Ar step‐heating methods. One sample contains relatively abundant detrital muscovite flakes that are locally oblique to the regional cleavage in the rock, whereas the remaining samples appear to contain sparse detrital muscovite. Separates of detrital muscovite yielded plateau ages of 505 ± 3 Ma and 513 ± 3 Ma indicating that inheritance has not been eliminated by metamorphism and recrystallisation. Step‐heating analyses of whole‐rock chips from all four slate samples produced discordant apparent age spectra with ‘saddle shapes’ following young apparent ages at the lowest temperature increments. Elevated apparent ages associated with the highest temperature steps are attributed to the presence of variable quantities of detrital muscovite (<1–5%). Two whole‐rock slate samples yielded similar 40Ar/39Ar integrated ages of ca 455 Ma, which are some 15–30 million years older than K–Ar ages for the same samples. These discrepancies suggest that the slates have also been affected by recoil loss/redistribution of 39Ar, leading to anomalously old 40Ar/39Ar ages. Two other samples, from slaty tectonic mélange and intensely cleaved slate, yielded average 40Ar/39Ar integrated ages of ca 424 Ma, which are closer to associated mean K–Ar ages of 423 ± 4 Ma and 409 ± 16 Ma, respectively. Taking into account the potential influences of recoil loss/redistribution of 39Ar and inheritance, the results from the latter samples suggest a maximum age of ca 440 Ma for deformation/metamorphism. The current results indicate that recoil and inheritance problems may also have affected whole‐rock 40Ar/39Ar data reported from other regions of the Lachlan Fold Belt. Therefore, until these effects are adequately quantified, models for the evolution of the Lachlan Fold Belt, that are based on such whole‐rock 40Ar/39Ar data, should be treated with caution.

First 40 Ar/ 39 Ar age constraints for the Caledonian evolution of the Trans–European Suture Zone in NE Germany

From three Rügen boreholes (G14, Rügen 5, Loissin 1) across the Caledonian deformation front four Lower Palaeozoic slate samples and three detrital muscovite concentrates from associated sandstones have been analysed by 40 Ar/ 39 Ar analysis. Microprobe analysis of the detrital muscovites show homogeneous, but distinct chemical compositions for each concentrate. Particulate organic matter reflectance and illite crystallinity indicate that all the analysed whole–rock samples have experienced anchizonal metamorphic conditions. 40 Ar/ 39 Ar analysis of the samples from the G14 and Loissin 1 wells give almost identical results. Muscovite concentrates define plateau ages of c. 830 Ma and show an isotopic rejuvenation of low–temperature increments around 440 Ma. Whole–rock slate samples give plateau ages of c. 440 Ma and c. 427 Ma. Isotopic rejuvenation in the low–temperature increments prior to 350 Ma in the Loissin 1 sample can be attributed to the Permo–Carbonifereous volcanism which is known from this borehole. In contrast, samples from the borehole Rügen 5 show a different isotope pattern. A muscovite concentrate defines a plateau age of 609 Ma. Two whole rock slate samples give internally discordant but identical 40 Ar/ 39 Ar spectra with consistent isotopic rejuvenation from high– to low–temperature increments from 510 Ma to 420 Ma. While for the G14 and Loissin 1 sandstone samples a Baltica–derived provenance can be assumed, greywackes of Rügen 5 indicate a Cadomian–influenced Perigondwanan detrital source. According to the results of whole–rock slate samples the main Caledonian tectonothermal event in NE–Germany occurred around the Ordovician–Silurian boundary or in the early Silurian (450–425 Ma). From these data the Rügen Palaeozoic appears as an allochthonous Caledonian nappe complex which has been thrust much further onto the Baltic shield than previously thought.

Detrital and metamorphic 40Ar/39Ar ages from muscovite and whole-rock samples, Meguma Supergroup, southern Nova Scotia

40Ar/39Ar dates from eight muscovite separates and two whole-rock samples of slate, siltstone, and sandstone provide detrital, metamorphic, and post-metamorphic overprinting ages for the low-grade metamorphic rocks of the Meguma Supergroup in the Mahone Bay region of southern Nova Scotia. Variably reset detrital muscovite ages of 600-550 Ma agree with previously obtained U-Pb dates from detrital zircon. Separates of foliation-parallel muscovite yield precise 40Ar/39Ar ages of 395-388 Ma. Petrographic and metamorphic data indicate that these are metamorphic mica growth ages. The range overlaps with the younger limit of previously reported whole-rock ages (410-380 Ma), but is more tightly constrained. An apparent inconsistency between previous 40Ar/39Ar whole-rock ages as old as 410 Ma and regional deformation that affected sedimentary rocks as young as 385 Ma has been resolved by the younger ages reported here and by recent adjustments to the early Paleozoic time scale which suggest that the Lochkovian to Emsian Torbrook Group was deposited between 419 and 394 Ma. A muscovite plateau age of 376 Ma from one sample may be related to late-stage flexural slip deformation in the Ovens gold district.

Mineralogy and microstructure of roofing slate: thermo-optical behaviour and fissility

The mineralogy and microstructure, which affect the slaty cleavage, are linked with the strong preferred orientation of phyllosilicates and this enables the rock to be split into large, thin, flat sheets. Roofing slate samples with different commercial fissilities have been analyzed by radioluminescence (RL), thermoluminescence (3DTL), by X-ray diffraction (XRD), by scanning electron microscopy (SEM) using the back-scattered mode (BSEI) and by electron microprobe (EMP). They are made up of white micas, chlorite, quartz, detrital feldspars, ilmenite, pyrite, rutile apatite and tourmaline. Texturally, all consist of silt-sized clasts of detrital quartz, feldspars, chlorite-mica stacks, muscovite and ilmenite in a recrystalline, lepidoblastic matrix of white micas and chlorite with quartz lenses, all showing a very strong preferred orientation. The luminescence emission centers are a low broad blue band around the 400 nm spectra positions linked with alkali losses and formation of [AlO 4 ]o defects; a peak at 473 nm interpreted as a the first thermal step (150-300oC) of a non-isothermal dehydroxylation of the slate phyllosilicates; and a 568 nm peak which agrees with Mn 2+ point defects in aluminosilicate lattices. The studies on the slaty cleavage could be significant because Spain is the largest producer of roofing slate tiles in the world (87% of world production).

Application of Inverse Gas Chromatography to the Study of the Surface Properties of Slates

AbstractInverse gas chromatography (IGC) at zero surface coverage was used for determining the surface characteristics of a slate sample. Previously this sample had been characterized by means of X-ray diffraction (XRD), chemical analysis, infrared (IR) spectroscopy and nitrogen adsorption. Quartz, muscovite and chlorite were the minerals foming the slate. A well-defined mesoporous structure with pores of 15 Å of interlayer distance was observed. Chemical analysis and IR spectroscopy corroborated the X-ray results. The surface characteristics of the slate were defined in relation to nonspecific and specific interactions with organic molecules. In accordance with the nonspecific interactions, the London component (γSD) of the surface free energy gave an estimation of the surface energy of the slate sample. The obtained values for γSD were 140.0, 124.8, 108.2 and 96.8 mN m-1 at 100, 110, 120 and 130 °C, respectively. These values were characteristic of an inorganic sample of high surface energy. The values of the thermodynamic variables—differential heat of adsorption, free energy and entropy of adsorption—were in accordance with these results. At the same time, specific interactions were characterized by the ηπ parameter and the acid-base (KA, KB) indices. The positive value of ηπ (0.09 kJ mol-1) indicated the presence of Lewis acidic sites on the slate surface. The value of KA (acid index) of 1.17 was higher than the value of KB (base index) of 0.37; this result confirmed the acidic nature of the studied slate's surface.

A rectorite-pyrophyllite-chlorite-illite assemblage in pelitic rocks from Colombia

AbstractIn samples of slate from the Fomeque Formation near Bogota, Colombia, pyrophyllite was found to occur together with mixed-layered illite-smectite, chlorite and illite. Other minerals were quartz, K-feldspar, dolomite and pyrite. X-ray diffraction patterns revealed that the mixed-layer represents an R1 ordered rectorite with 80–90% illite layers. The microfabric is developed as a closely spaced cleavage in the phyllosilicate-rich rocks, and grades into a fracture cleavage with coarsening of the grain size. No cleavage was observed in the interbedded siltstones. It is suggested that the microfrabrics developed in these rocks correspond to high diagenetic to anchizonal conditions. The illite crystallinity from the slate has been measured on glycolated samples and ranges from 0.47 to 0.55°Δ2θ with a mean of 0.52°Δ2θ Based on the stability of R1 ordered rectorite, the illite crystallinity and the microfabric development, it is proposed that the rocks have been subjected to a temperature of ∼200°C at low pressure. At this temperature, pyrophyllite can only be stabilized at the expense of kaolinite and quartz if aH2O ≪ 1.

The drilling of slate tiles by a Nd:YAG laser

We have undertaken a series of experiments to investigate the feasibility of using a Nd:YAG laser to drill slate tiles. Slate is used primarily as a roof building material after it is split into thin flat layers. The traditional fixation system of slate tiles in Europe consists of clamping the slate pieces by means of metallic clamps and overlapping the different tiles in order to form an impervious roof. An alternative to this clamping technique, is the use of nails to fix the slate tiles to a wooden frame. This method improves the fixation of the slate tiles and reduces the costs related to roof repair by extending the period between maintenance. However, the use of nails requires the production of holes in the slate pieces, which is currently achieved by a mechanical route that results in large holes and an extended manufacturing time. The aim of this work is to explore the capabilities of a pulsed Nd:YAG laser to drill tiny holes in slate tiles in order to produce a better quality drilled slate tile in a reduced time. Shallow holes were produced in slate samples using a 1 kW Nd:YAG pulsed laser focused onto the slate surface by an 80 mm fused silica lens. The results obtained in this study shows the enormous potential of Nd:YAG lasers in the production of slate tiles.

The Ingletonian

The Ingletonian Series comprise an alternating succession of ancient metamorphosed sediments, mainly slates and grits, which outcrop as a small inlier just to the north of Ingleton in west Yorkshire (Rayner &amp; Hemingway 1974). They are tightly folded into a series of almost vertical isoclinal folds and unconformably overlain by the Carboniferous Limestone (Fig. 1). The unconformity between the Ingletonian and the Carboniferous Limestone is one of the classic unconformities in geology and one which has often been used to illustrate the essential nature of an unconformity. The Ingletonian is equally important as a source of high quality roadstone. The purpose of this Photographic Feature is to bring together these two aspects of geology: the classical and the engineering. The fact that the Ingletonian rocks are unfossiliferous together with stratigraphical and structural considerations, led to the Series being regarded as Precambrian in age and they were officially considered so by the Geological Survey (Edwards &amp; Trotter 1954). In the 1970s, however, radiometric age determinations were made on seven samples of Ingletonian slate from Horton in Ribblesdale, 11 km east of Ingleton (O'Nions, Oxburgh, Hawkesworth &amp; Macintyre 1973). The Rb-Sr isotopic age determinations yielded an age of 505 Ma which was interpreted as being the time when the folding and development of the slatey cleavage took place. It was considered that the interval between this event and the time of sedimentation could not be more than 50 Ma, giving the age of the deposit as 555 Ma and hence putting the

On the origin of the magnetic fabric in purple Cambrian slates of North Wales

Anisotropy of magnetic susceptibility (AMS) in samples of Cambrian slate from Penrhynn, Wales, is surprisingly weak (maximum/minimum ≃- 1.1 to 1.2) in view of their large finite strain ( X/ Z ≃- 3.5 to 4.5), and their hematite-dominated magnetic mineralogy. Several lines of evidence suggest that this is a result of the presence of two or more generations of hematite. SEM observations show a somewhat bimodal size distribution of hematite particles, with modal diameters of approximately 1–3 μm and 10–20 μm. The larger grains tend to have ragged, subequant shapes, and contain titaniferous laminae; they are probably of igneous/detrital origin. The finer grains have crystallographically-controlled shapes, are Ti-free, and are probably authigenic or metamorphic. Initially, chemical leaching of deeply incised solid specimens preferentially removes the more soluble particles, and results in significant changes in AMS. Further leaching attacks the remaining grains on exposed surfaces, and the AMS ellipsoid reverts to its initial shape. Isothermal remanent magnetization (IRM) is significantly more anisotropic than low-field susceptibility; the variation of IRM anisotropy with applied field indicates relatively strong fabric development in the fine-grained hematite, but weak fabric in the coarser fraction. Grain boundaries were digitized from SEM photos in order to calculate Flinn fabric ratios by the R f − φ method. The X/ Z ratios thus obtained for quartz and fine hematite grains are 3.14 and 1.70, respectively. It is therefore clear that the hematite fabric does not reflect the total finite strain.

Tectonothermal chronology within a blueschist-eclogite complex, west-central Spitsbergen, Svalbard: Evidence from [formula omitted] and Rb[sbnd]Sr mineral ages

A high-pressure, relatively low-temperature metamorphic complex is exposed at Motalafjella, Spitsbergen. White mica concentrates from the complex record variably discordant 40Ar39Ar age spectra in which apparent ages systematically increase throughout low-temperature portions of the analyses and define intermediate- and high-temperature plateaux. Phengitic concentrates record plateau ages of c. 470 Ma whereas paragonitic concentrates yield c. 460 Ma plateaux. These ages are interpreted to date diachronous cooling through different argon closure temperatures following the high-pressure metamorphism. The slight discordance displayed in low-temperature portions of the experiments is interpreted to reflect a partial rejuvenation of intracrystalline argon systems during an c. 400–425 Ma thermal overprint associated with late Caledonian tectonothermal activity. White mica concentrates and associated whole-rocks yield RbSr mineral + whole-rock ages from 457 ± 11 Ma to 474 ± 11 Ma. These are interpreted to date post-metamorphic cooling through Sr blocking temperatures. Because similar ages are recorded by both KAr and RbSr isotopic systems, relatively rapid post-metamorphic cooling is implied. This and relatively rapid depressurization during uplift indicate that the 40Ar39Ar and RbSr mineral ages likely closely date the peak metamorphism.The high pressure complex is unconformably overlain by variably cleaved, Upper Ordovician-Lower Silurian flysch which was deformed into regional recumbent folds prior to deposition of unconformably overlying Early Devonian molasse. Two penetratively cleaved slate samples display internally discordant 40Ar39Ar whole-rock age spectra with ages increasing from c. 100 Ma to c. 470 Ma. The spectral discordance is interpreted to reflect the combined effects of: (1) a polymineralic character: (2) a detrital source similar in age to the Motalafjella complex; and (3) a partial, post-Paleozoic thermal rejuvenation of the detrital mica argon systems. No thermal overprint associated with Late Silurian cleavage formation appears to be recorded. This agrees with textural characteristics which suggest that the cleavage largely developed through pressure-solution assisted, grain-boundary sliding.

The influence of calcium and magnesium on the growth of the lichens Parmelia saxatilis and Xanthoria parietina on slate substrates

In South Gwynedd, Wales, U.K., the calcicole lichen Xanthoria parietina occurs not only on alkaline substrates at inland sites but also on siliceous slate rock at coastal maritime sites while the calcifuge species Parmelia saxatilis occurs only at inland sites and on slate rocks. Samples of maritime and inland slate did not differ significantly in their calcium or magnesium content. Thalli of X. parietina on pieces of slate did not survive when transplanted from maritime rocks to a site inland. Thalli of maritime X. parietina and P. saxatilis on slate were then transplanted to a site inland and were treated at intervals during 1 year either with calcium carbonate applied as a thick paste or a 0.25 mM solution of calcium chloride. Treatment of X. parietina with calcium carbonate enabled the thalli to survive and grow. However, addition of calcium carbonate to P. saxatilis resulted in low growth rates and fragmentation of the centres of the thalli. The calcium chloride solution had no statistically significant effects on the growth of either species. In addition, thalli of both species were treated either with calcium or magnesium carbonates or wetted with an alkaline buffer at intervals over 12–14 months. Thalli of X. parietina survived and grew rapidly when treated with either carbonate but the growth of the buffer-treated thalli gradually declined over the experimental period. Thalli of P. saxatilis fragmented and disappeared appeared after 8–10 months after treatment with either carbonate but normal growth occurred in the buffer treatment. Xanthoria parietina may occur on siliceous maritime rocks at the site because of the presence of calcium or magnesium in sea spray combined with the spray's alkaline pH. By contrast, P. saxatilis may be confined to siliceous rocks inland because the thalli grow poorly in the presence of calcium and magnesium.

Mineralogy of Soils Developed in Periglacial Deposits of Southwestern Canada

AbstractParent materials of glacio‐lacustrine soils, Holocene loess, glacial rock flour, and slate samples from Alberta, Saskatchewan, and Red River plain were characterized mineralogically by X‐ray diffraction (XRD) and chemical techniques. The texture became finer and the fine clay/coarse clay ratios higher (0.5 to 3.6) in progressing from the overthrust mountains, to nearby loess, then to glacio‐lacustrine materials. The clay mineral distribution illustrated lithological, geomorphological, and weathering relationships. The XRD peak broadening indicated weathering to irregularly interstratified phyllosilicate minerals in Holocene loessial materials originating from fresh rock flour carried by the Athabasca River flowing out of the mountains near Jasper. The smectite content increase (4 to 34%) and the mica content decreased (52 to 20%) from near the overthrust mountains to the glacio‐lacustrine plains overlying nonmarine and marine sediments. Mica, smectite, and chlorite (8–20%) constituted the predominant minerals in the clay fractions. Smectite was the most abundant (20–34%) mineral in the clay of the glacio‐lacustrine materials, particularly in the &lt;0.2‐µm fractions (60–85%). This was attributed mainly to glacial movement of weathered ash‐falls of Cretaceous sedimentary provenance. Some vermiculite (5–10%), kaolinite (3–11%), fine or poorly crystalline materials (4–14%), quartz (4–10%), and feldspars (1–2%) were also present. Chlorite, detrital mica, and sodic feldspar in both the clay and silt fractions indicated significant contributions for metamorphic and diagenetic source rocks to all samples, including the most distant “macro‐composite” glacio‐lacustrine samples.