General Weathering Research Articles

Coal Tar Distillate (Creosote)—The First and Still Great Choice to Preserve Utility Poles

Abstract Creosote, a coal tar distillate product, has been used to preserve wooden utility poles for well over 100 years. Such use began in the late 1800s and continues to this day. Creosote’s efficacy in protecting wood from decay, termite attach, and general weathering has been demonstrated by actual performance of poles in utility service and in documented field and laboratory testing. The American Wood Protection Association has standardized and long recognized the efficacy of creosote preservation. With production of pentachlorophenol ending after 2022, preservation may easily convert to creosote preservative. Creosote preservative also is an environmentally sound choice in that used poles can be used as fuel and otherwise, creosote degrades biologically. Wood is sustainable as new trees are grown to replace poles while the poles are sequestered carbon. Utility service life of creosote preserved wooden poles typically lasts for 70 to over 100 years with inspection and maintenance. Utilities can expect new creosote preserved poles to last into the next century.

The Influence of Fresh and Weathered Rock Foliation on the Stability of the Monte Seco Tunnel

The Monte Seco tunnel (MST) is one of several old unlined tunnels constructed for Brazilian railways in the 1950s, and the MST still receives intense train traffic (primarily for iron ore transportation). The MST was constructed in a fractured gneissic rock mass, which has potential instability problems associated with gravity-driven block falls (at low stress confinements) defined by three fracture sets and the metamorphic foliation. Previous geological and geotechnical surveys at the MST site have included basic geomechanical classifications from outcrops and drill core specimens, detailed terrestrial laser scanning (TLS) mapping of foliation and fracture planes, geoelectrical imaging and laboratory tests. These surveys discovered two sections of the tunnel (referred to herein as MS1 and MS2) with major potential for instability problems (i.e., poor rock mass qualities). In this paper, the 3D discrete element method (DEM) was used to assess the potential stability problems in these sections with particular interest on the role of the rock foliation strength on the current stability state of these sections. Three instability indicators were developed and monitored during and after the DEM simulations: the total failed block volume (FBV), the average displacement of the tunnel face (AD), and the percentage of slipping contacts near the tunnel face (SC). The weathering effects were considered in two different scenarios: the occurrence of isolated weathered foliation planes (WFPs) and the general weathering advance through potentially weathered regions. In the latter scenario, the percentage of weathered contacts (WC) increased progressively. The overall results indicated that fresh foliation planes ensured the current tunnel stability due to the moderate mica content (Ma) in such geological structures. Thus, underestimating the strength of foliation planes causes unrealistic instability conditions in the tunnel. However, the weathering advance on fractures and foliation planes can trigger important instability problems over time.

Weathering of Bi-bearing tennantite

The tennantite-tetrahedrite solid-solution series [called fahlore; (Cu,Ag)6Cu4(Fe,Zn,Cu,Hg,Cd)2(Sb,As,Bi,Te)4(S,Se)13] is widespread in many geological environments. Since it incorporates heavy metals and toxic elements, a better understanding of its weathering behaviour and details of its weathering process is important to evaluate environmental risks (emerging mainly from the mobilization of As-Sb-Bi) and local and global metal fluxes in stream waters and oceans. In this study, weathering of Bi-rich members of this mineral group was investigated using microscopy, EMPA, SEM, TEM, LA-ICP-MS, Raman, μXRD, and MLA.Observations reveal a succession of four distinct stages of weathering: During stage 1, irregular tubes within fahlore show an assemblage of nm- to μm-sized roméite group minerals, tripuhyite, crystalline Cu-oxides and Cu-sulfides. Stage 1 textures and secondary sulfides indicate a low redox-potential and a low fluid/rock ratio, typical of cementation zones. Mass balance calculations show that during this stage all Zn and the majority of As and S are released to the weathering fluids. Bismuth is immobile in this stage and Sb and Fe are immobile, if Bi is sufficiently available from fahlore, but both are partly released, if the fahlore did not contain sufficient Bi. During stage 2, amorphous and nano-crystalline arsenates replace fahlore as weathering fronts. Such assemblages indicate a higher redox-potential than in stage 1, typical for oxidation zones. Mass balance calculations reveal that Zn, Sb, S and partially Cu are lost. Arsenic and Bi are immobile. Stage 3 occurs only locally, dissolving former weathering stages and/or precipitating amorphous Cu-arsenates/silicates reflecting processes in micro-compartments, not characteristic for the general weathering process. Stage 4 is characterized by the formation of crystalline Bi-, Cu-, Ba-, Ca- or Al-bearing arsenates and Cu-carbonates, spatially independent of the precursor fahlore. Copper and As originate from older weathering assemblages, whereas many other elements are derived externally (Ca, Ba, Al). This stage reflects the increasing importance of the local host rock and gangue mineralogy, as it is typical in near-surface environments of oxidation zones or on mine dumps, where elements are highly mobile and a high fluid/rock ratio prevails (gossan mineralization).The temporal evolution of fahlore weathering textures reflects the transition from fresh ore to cementation zone, oxidation zone and gossan assemblages in one hand specimen. Thus, one fahlore grain can record the uplift and erosion and the increasing fluid/rock interaction of a weathered ore deposit with time. Tube-like textures similar to the ones observed in stage 1 have been reported from other weathering environments and from a variety of element, oxide, arsenide, and sulfide phases. They also were produced during experimental work in ilmenite. This is clear evidence, that the diffusive process during the first contact with alteration fluids is a basic physical process and that it is not only valid for fahlore.The importance of Bi to stabilize Sb-bearing supergene phases (and thereby for the immobilization of toxic Sb) shown in the present work, may stimulate further investigations on the environmental immobilization of toxic elements by “companion metals” during weathering processes.

Provenance and tectonic setting of the Triassic Yidun Group, the Yidun Terrane, Tibet

The Yidun Group extends from the Shangri-La region to the south and the Changtai region to the north, and is an important component of the Triassic Yidun arc in the eastern Tibetan plateau. It is composed of the Lieyi, Qugasi, Tumugou and Lanashan Formations from the base upward. Both the Lieyi and Lanashan Formations consist dominantly of black or gray slate and sandstone, whereas the Qugasi and Tumugou Formations have variable amounts of mafic to felsic volcanic rocks and tuffs accompanied with gray slate and sandstone.Sandstone from the Yidun Group has variable CIA values from 55 to 76, indicative of mild to moderate weathering condition for the source rocks. All the sandstones define a general weathering trend nearly parallel to the A-CN boundary in the A-CN-K triangular diagram, implying limited effect of diagenetic and post-depositional K-metasomatism. Dominant detrital quartz and feldspar grains of the sandstones suggest predominantly felsic sources. Relatively high Y/Ni and low Cr/V ratios of sandstones from the Yidun Group indicate more contribution from felsic than mafic sources. Similarly, the Yidun sandstones have Co/Th and La/Sc ratios generally similar to upper continental crust (UCC) and cluster between UCC and felsic sources, indicating felsic rocks as primary sources. Granodiorite represents the average chemical composition of sources as evaluated by extending the predicted weathering trend back to the feldspar join in A-CN-K diagram.Prominently high Zr/Sc ratio or Hf concentration and Paleoproterozoic Nd modal ages (1.94–2.21 Ga) point to input of recycling components derived from old sedimentary source in a relatively stable tectonic setting.

Influence of pore system characteristics on limestone vulnerability: a laboratory study

Hyblean limestone of Oligo-Miocene age was widely used as a construction material in the architectural heritage of Eastern Sicily (Italy). Among them, the so-called Pietra Bianca di Melilli (Melilli limestone) and Calcare di Siracusa (Syracuse limestone) were prized for their attractive appearance, ease of quarrying, and workability. Syracuse limestone shows general weathering, whereas Melilli limestone is better preserved, and only differential erosion or superficial exfoliation can be detected in monuments. The cause of the different behavior of these two limestones was investigated from the petrographic and petrophysical points of view. The saturation coefficient is higher in Melilli limestone, and ultrasound measurements indicate that it is less compact than Syracuse limestone, so that Melilli limestone could deteriorate more easily than Syracuse limestone. However, pore interconnections and the size of very small pores play the main role in the durability of both materials. The “irregularity” of the Syracuse pore system and its greater number of micropores hinder water flow through the exterior, promote stress in pore structure, and favor the development of scaling, as confirmed by salt crystallization tests. In Melilli limestone, the low concentration of micropores and fast water evaporation allow solutions to reach the surface more easily, resulting in less damaging efflorescence.

Chemical trends in a perhumid soil catena on the Turrialba volcano (Costa Rica)

The variation in chemical composition of soil samples (XRFS data) from a soil catena of 14 soil profiles on the northern slope and foot slope of the andesitic Turrialba volcano (3300 m) has been analysed to test the two hypotheses, which underlie our interpretation that this catena is a weathering sequence. The first hypothesis is that all parent material is chemically homogeneous and the second hypothesis is that development of chemical variation is the net result of progression of weathering and of diversity of weathering, which both depend on altitude via gradients in temperature and precipitation. The aim of this purely chemical approach is to find out if trace elements are significant “tracers” for different weathering paths leading to different amorphous or crystalline products, for example imogolite, allophane, halloysite, gibbsite, and ferrihydrite. The results show that volcanic ash is sufficiently homogeneous to detect the well-known dominance of a general weathering trend with relative depletion of mobile elements (Mg, K, Si, etc.) and relative enrichment of less-mobile elements (Ti, Fe, Al, Ce, Cr, V, Zr, etc.). The least-mobile elements were Ti, V, and Zr. From their contents, a Weathering Index for all samples has been derived that describes 95% of their total variance (hypothesis 1). In addition to this general trend, Ti, V, and Zr showed systematic deviations that could be defined as a chemical differentiation factor. In combination with the general weathering trend, this explained 99% of the total variation of Ti, V, and Zr (hypothesis 2). The contents of other (major, minor, and trace) elements used can only partially be described by the Ti–V–Zr-derived Weathering Index and Chemical Differentiation. The level of explanation decreases roughly with increasing mobility of the chemical element in the system. Triangular plots of element ratios suggest that contents of mobile elements are influenced by too many weathering processes. Trace elements did not show a more specific Chemical Differentiation than major and minor oxides. The leaching pattern of Mg indicates the presence of three different processes: (1) short-term preferential leaching of basic cations at high altitude, (2) subsequent allophane formation between 660 and 1220 m altitude, and (3) long-term loss of basic oxides (and not of silica) upon ageing of fluvio-volcanic sediments in the foot plain below 240 m. Fe shows anomalous depletion (redistribution) due to oxidation and reduction, and Al shows extra depletion in two of the allophanic profiles.

Geomorphology and stone conservation: sandstone decay in Stoke‐on‐Trent

Identifying stone decay forms is an essential first step in stone conservation. In this study a visually based geomorphological approach was used to provide a rapid assessment of the general weathering characteristics displayed by building sandstones in Stoke‐on‐Trent. Stone decay was found to be largely caused by the mechanical disruption of the sandstone and its occurrence was extremely variable in both space and time. The study demonstrates the close interrelationship between stone properties, environmental conditions, morphology of weathering features, and building characteristics. It is important that these close and dynamic interrelationships are recognised when seeking to explain or predict stone behaviour for management purposes.

Clay mineral assemblages in weathered basalt profiles from central and southern Portugal: climatic significance

Mineralogical and chemical changes during weathering of basalts from central and southern Portugal were studied. Both regions have a temperate Mediterranean type climate, the Algarve being more arid. The areas concerned are the Lisbon (72 Ma) and the Runa Volcanic Complexes (100–70 Ma), and Rio Maior (160–130 Ma) in central Portugal, and Budens (170–180 Ma) in the south. The basalts are generally rich in olivine phenocrysts. Clay minerals are in general well crystallised and comprise smectites, associated with 1:1 minerals (principally halloysite), illite and palygorskite. Kaolin minerals prevail in topographic highs, whilst smectites predominate in lower areas. Smectites were analysed from the <2 μm fraction and from weathered microsites on olivine crystals. Both approaches identified dioctaedral smectites. Smectites from the south (Budens) have higher Na contents and lower Mg concentrations than those from central Portugal. This, together with different climatic or microclimatic conditions, may explain the smectite–analcime association in the first case, and smectite–palygorskite in the second. Smectites can thus generate one or the other of these minerals. In weathered microsites on olivine crystals, iron oxides were noted as well as the possible replacement of smectites and Fe oxides by calcite. The general weathering features appear to be similar to those found on basalts in other temperate climates, i.e. the formation of secondary minerals with a predominance of smectites or 1:1 minerals according to geomorphic location. However, the degree of aridity may affect the stability of smectites, which seem to evolve either to palygorskite or to analcime.

Processes of Formation and Distribution of Pb-, Zn-, Cd-, and Cu-Bearing Minerals in the Tyne Basin, Northeast England: Implications for Metal-Contaminated River Systems

Historic mining has produced widespread Pb, Zn, Cd, and Cu contamination in the fluvial deposits of the Tyne River Basin, northeast England. Detailed mineralogical analysis of contemporary overbank river sediment, mining-age alluvium, and mine-waste tips and of suspended solids in river waters has defined a general weathering reaction paragenesis of Pb-, Zn-, Cd-, and Cu-bearing minerals: sulfides → carbonate, silicate, phosphate, and sulfate weathering products → iron and manganese oxyhydroxides. Textural and chemical evidence suggests that the sulfides alter to carbonates in high pH/pCO2, limestone-dominated source terrains. These minerals and other contaminant metal-rich minerals such as silicates and manganese oxyhydroxides decline and disappear downstream in lower pH shale/sandstone-dominated environments. The concomitant decrease in total Pb, Zn, Cd, and Cu sediment contents in the Tyne and possibly other metal contaminated rivers may be related to these essentially chemical weathering and dispersi...

Reassessment of Polynov's Ion Mobility Series

AbstractPolynov (1937) calculated the relative mobilities of important elements in landscapes: Cl &gt; SO4 &gt; Ca &gt; Na &gt; Mg &gt; K &gt; Si &gt; Fe &gt; Al. This series depicts a general weathering sequence that is essential to understanding many aspects of soil genesis and soil geography. It is argued on tbeoretical grounds that Ca and Na are out of proper sequence in Polynov's series. Polynov estimated ion mobilities by comparing the average content of elements in igneous rock to the average content of the same elements in river waters. However, an estimated 80% of the rocks at the earth's surface, which supply most of the leachate to rivers, are sedimentary. Accordingly, Polynov's mobility series was recalculated after adjusting rock chemical composition for the dominance of sedimentary rock types at the earth's surface. By using the elemental composition of igneous rocks in his calculations, Polynov greatly overestimated the amount of Na relative to Ca in rocks providing leachate to rivers. As a result, he significantly underestimated the mobility of Na relative to Ca. It is recommended that Polynov's ion mobility series be modified to the following: Cl &gt; SO4 &gt; Na &gt; Ca &gt; Mg &gt; K &gt; Si &gt; Fe &gt; Al. This study showed that Na is much more mobile (relative mobility 18.0) than Ca (8.1), Mg (5.4), or K (3.5). Therefore, it is recommended that Na be placed in a distinct mobility phase (II) second in relative mobility to Cl and SO4 (I).

Weathering Statics Problem and First-Arrival Time Surfaces: ABSTRACT

Where organized by shot and receiver coordinates, the collection of picks of the first arrivals forms a jagged surface. It is thus crucial that the properties of the time surface of first arrivals be studied for various situations. It is particularly useful to End_Page 1685------------------------------ analyze two projections of the time surface: one to a constant shot plane and one to a constant receiver plane. For each fixed shot or receiver, there is a distribution of time picks. Comparisons with real data distributions show a good match to theory as the time surface is manipulated. The study of these projections enables us to derive criteria for estimating the accuracy, precision, and consistency of any solution to the statics problem for the simple model of a linear refractor and high frequency statics. In this case the specific criteria are: (1) the expected value of each distribution is constant along each axis, (2) the variance of each distribution is zero along both shot and receiver axes, and (3) the shot and receiver statics are equal. In addition, several basic types of anomalies can be recognized by their effects upon the first-arrival time surface. These basic types are: (1) geometric variation in the refractor, (2) velocity variation in the weathering, and (3) velocity variations in the subweathering. The combination of these three is a complete description of the general weathering statics problem. The effects of these anomalies may be studied via the shot and receiver projections. Type (1) can lead to a blurring of the first-arrival time distribution. Type (2) can lead to a lens shape within the first-arrival projections. The lens is formed by a splitting of the left-hand and right-hand shots. Since the lens is composed of both time-rise and time-fall segments, it will be split under certain circumstances. Type (3) can appear as a change in the trend of the projections and a discrepancy between shot and receiver statics. End_of_Article - Last_Page 1686------------

A gibbsitic soil derived from the weathering of an ultrabasic rock on the island of Rhum

Synopsis The mineralogy of a soil derived from the weathering of an ultrabasic rock near the summit area of Askival on the Island of Rhum was investigated by optical, X-ray diffraction and differential thermal techniques. The fine sand fraction is dominated by olivine and anorthitic plagioclase felspar whilst the clay fraction contains gibbsite and chlorite. General weathering reactions in the soil are discussed and the origin of the gibbsite is considered in detail.