Laurence Warr

University of Greifswald · Institute for Geography and Geology

Deteriorated concrete and interstitial solutions (IS) were collected from Austrian tunnels to elucidate potential connections between de-dolomitization caused by coupled alkali carbonate reactions (ACR) and thaumasite form of sulfate attack (TSA). A conceptual reaction model for the portlandite–CSH phases–dolomite–calcium sulfate–calcite–brucite–th...

The widespread formation of interstratified glauconite-smectite (Gl-S) and illite-smectite (I-S) in modern and ancient diagenetic settings records the physicochemical conditions prevailing during clay mineral authigenesis. To date, however, significant gaps in our knowledge persist in respect to the influence of interstitial solution chemistry, tem...

Geopolymers are inorganic binders formed by adding alkaline (hydroxide) solution to silicates such as blast furnace slag, fly ash or calcined clay to dissolve Si and Al that polymerizes and precipitates while hardening. The most common clay used as geopolymer raw material is kaolin. The aim of this study was to investigate the suitability of clays...

Illitic clays, such as the interstratified illite-smectite clays, are one of the most abundant aluminosilicates on Earth's surface and are widely available for geopolymer production. Geopolymers are a group of alkali-activated materials, which are gaining increasing attention as low-CO2 binders with some advantageous properties compared to ordinary...

The presence of smectite (saponite) in fault gouge from the Central Deforming Zone of the San Andreas Fault at Parkfield, CA has been linked to low mechanical strength and aseismic slip. However, the precise relationship between clay mineral structure, fabric development, fault strength, and the stability of frictional sliding is not well understoo...

There is a current need for developing improved synthetic porous materials for better constraining the dynamic and coupled processes relevant to the geotechnical use of underground reservoirs. In this study, a low temperature preparation method for making synthetic rocks is presented that uses a geopolymer binder cured at 80 °C based on alkali-acti...

Iron impurities present in the crystal structure of kaolin minerals or in accessory species are frequently encountered in clay deposits. As knowledge of the location and states of the iron is crucial when modifying the properties of clays by activation, it is important that new deposits are well characterized in terms of the amount and location of...

The addition of calcium sulfate in the preparation of autoclaved aerated concrete (AAC) leads to improved mechanical properties but the precise mechanism is not well constrained. To study this, the hydrothermal curing process was monitored quantitatively with and without sulfate addition using ex situ and in situ X-ray diffraction. Higher concentra...

Thermally treated kaolinite is used to develop a range of alumino‐silicate‐based precursor materials but its behavior during plasma spraying has not been well‐researched. In this study, two types of kaolinite samples were investigated in the form of low defect (KGa‐1b) and high defect (KGa‐2) varieties. The extreme temperatures of the plasma stream...

Much work has been undertaken quantifying the abundance of phyllosilicate clay minerals in soils, sediments and rocks of Earth's crust. However, no detailed global compilation of these minerals has yet been presented. Such information has implications for understanding the interactions between weathering, soil formation, plate tectonics, climate ch...

Updated mineral symbol picker for selecting new abbreviations for new minerals. It represents an updated version of the IMA-approved mineral symbols published by Warr (2021).

Diagenetic illite growth in porous sandstones leads to significant modifications of the initial pore system which result in tight reservoirs. Understanding and quantifying these changes provides insight into the porosity-permeability history of the reservoir and improves predictions on petrophysical behavior. To characterize the various stages of d...

Geopolymerization was investigated as an alternative to traditional ceramic products by developing a more sustainable approach that avoids thermal treatment. The study presents the first known alkali-activation of the raw clay and waste clay brick mixture using the solid to liquid ratios of 2.33 and 2.78. Several experimental sets were prepared to...

Quantitative X-ray diffraction of nanocrystalline calcium silicate hydrate (C-S-H) and its aluminium-substituted variants (C-AS -H) has so far been limited by a lack of appropriate structure models. In this study, atomistic structure models derived from tobermorite were combined with a supercell approach using TOPAS. By accounting for nanostructura...

Compacted bentonite is currently being considered as a suitable backfill material for sealing underground repositories for radioactive waste as part of a multi-barrier concept. Although showing favorable properties for this purpose (swelling capability, low permeability, and high adsorption capacity), the best choice of material remains unclear. Th...

Pilot sites are currently used to test the performance of bentonite barriers for sealing high-level radioactive waste repositories, but the degree of mineral stability under enhanced thermal conditions remains a topic of debate. This study focuses on the SKB ABM5 experiment, which ran for 5 years (2012 to 2017) and locally reached a maximum tempera...

Bentonite is currently proposed as a potential backfill material for sealing high-level radioactive waste in underground repositories due to its low hydraulic conductivity, self-sealing ability and high adsorption capability. However, saline pore waters, high temperatures and the influence of microbes may cause mineralogical changes and affect the...

At some stage you may have abbreviated the name of a mineral when writing a thesis, report, or publication. This could have been for a common mineral such as quartz (Qz) or muscovite (Ms). But there are some more notoriously long mineral names for which a shortened version can be rather useful. Take, for example, the 34 letter long potassicmagnesio...

Several text symbol lists for common rock-forming minerals have been published over the last 40 years, but no internationally agreed standard has yet been established. This contribution presents the first International Mineralogical Association (IMA) Commission on New Minerals, Nomenclature and Classification (CNMNC) approved collection of 5744 min...

Computer X-ray microtomography (µXCT) represents a powerful tool for investigating the physical properties of porous rocks. While calculated porosities determined by this method typically match experimental measurements, computed permeabilities are often overestimated by more than 1 order of magnitude. This effect increases towards smaller pore siz...

Short paper without abstract

There is a current need to develop buoyant and biocompatible nanoclays for removing oil pollution from the surface waters of rivers, lakes and oceans. Application of clay-based amendments should either aid dispersion, adsorption or biodegradation of hydrocarbons without introducing additional toxicity. Ultrathin (< 15 μm thick) nanoclay films of lo...

The Miocene Diatom Suite sediments of the Eastern Paratethys Sea, Azerbaijan, provide significant information to establish how Middle Miocene climate influenced erosion, sedimentation and deposition in the marine environments and continental source areas of Western Asia. Discriminant function analyses, ratios of Ti/Al, Si/Ca and Sr/Ca as well as mi...

Computer microtomography (µXCT) represents a powerful tool for investigating the physical properties of porous rocks. While calculated porosities determined by this method typically match experimental measurements, computed permeabilities are often overestimated by more than one order of magnitude. This effect increases towards smaller pore sizes,...

This note describes an autoclave chamber developed and constructed by Anton Paar and its application for in situ experiments under hydrothermal conditions. Reactions of crystalline phases can be studied by successive in situ measurements on a conventional laboratory X-ray diffractometer with Bragg–Brentano geometry at temperatures <483 K and satura...

A hydroxy-sodalite/cancrinite zeolite composite was synthesized from low-grade calcite-bearing kaolin by hydrothermal alkali-activation method at 160 • C for 6 h. The effect of calcite addition on the formation of the hydroxy-sodalite/cancrinite composite was investigated using artificial mixtures. The chemical composition and crystal morphology of...

In the multi-barrier concept for the deep geological disposal of high-level radioactive waste (HLW), bentonite is proposed as a potential barrier and buffer material for sealing the space between the steel-canister containing the HLW and the surrounding host rock. In order to broaden the spectra of appropriate bentonites, we investigated the metabo...

This cover image can be cited as: Bhabananda Biswas, Ravi Naidu et al., 2019. Inside Cover Image. Chem Soc Rev. 48: 3678-3678. Doi: 10.1039/C9CS90062D. This cover image is linked to the feature article: https://doi.org/10.1039/C8CS01019F. Original article: "Biocompatible functionalisation of nanoclays for improved environmental remediation" by B...

Adding natural and fertilized clay minerals to marine oil-contaminated water in laboratory experiments have been shown to significantly enhance the rate of hydrocarbon biodegradation1-3. Such additives may in the future represent an eco-friendly approach to biodegrade and disperse oil spills and thus remove the need to apply chemical surfactants. C...

Clays and clay minerals, in particular smectites, illites, chlorites, serpentine minerals and their mixed-layered varieties, are commonly concentrated along faults and fractures in the brittle upper parts of the continental and oceanic crust characterized by intense, low temperature (<300°C), water-rock interaction and alteration. The concentration...

Among the wide range of materials used for remediating environmental contaminants, modified and functionalised nanoclays show particular promise as advanced sorbents, improved dispersants, or biodegradation enhancers. However, many chemically modified nanoclay materials are incompatible with living organisms when they are used in natural systems wi...

Heterogeneity of geological materials poses various problems when evaluating reservoir quality and storage potential. We analysed samples of different sedimentary facies of a Rotliegend sandstone from the Flechtingen High (Northern Germany) to determine the influence of depositional environment and diagenetic history on mineralogical composition an...

A new collection of clay mineral ‘Crystallinity’ Index Standards and revised guidelines for the calibration of Kübler and Árkai indices – ERRATUM - Laurence N. Warr

The up-dip limit of seismogenesis in subduction zone forearcs depends on the lithological composition of the incoming sediment and its subsequent modification during compaction and diagenesis. Here we present results of a multimethodological approach to characterize the smectite-to-illite diagenesis in the accretionary prism of the Nankai Trough su...

Clay mineral ‘Crystallinity Index Standards’ (CIS) composed of Palaeozoic mudrocks from southwest England were investigated systematically in five sub-fractions per sample for the first time. X-ray diffraction was used to determine mineral assemblages, calibrated 001 illite full-width-at-half-maximum (FWHM) values and illite polytype compositions,...

A new set of clay mineral ‘Crystallinity’ Index Standards (CIS) is available for improved calibration of the half-peak-width values of the X-ray diffraction 001 illite reflection (the Kübler index) and the 002 chlorite reflection (the Árkai index), two widely used indices for determining the state of prograde diagenesis and low-temperature metamorp...

Laboratory experiments demonstrate that adding clay to crude oil pollution generally has a positive effect on the bacterial degradation of hydrocarbons, largely by maintaining nutrient supply. The objective of this investigation was to constrain the influence of nontronite (Fe-smectite) based clay flakes on the biodegradation of Mississippi Canyon...

As clay minerals represent the most abundant mineral phases that form under surface and near-surface environments of the Earth, they are of key importance for unravelling the processes of weathering and diagenesis. The classic approach of most studies is to characterize the type and abundance of minerals formed in paleo-soil and rock assemblages of...

The clay mineral “Crystallinity” Index Standard (CIS[1]) is a method of full-width-at-half-peak-maximum (FWHM)calibration using rock chip standards that allows the same numerical results to be obtained from the clay mineral XRD basal reflections of the same samples, regardless of interlaboratory variations. It is most commonly applied for standardi...

Transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDX) is a useful way of quantifying the chemical composition of clay minerals on a particle-by-particle basis, but the accuracy of the method is a question of debate. One difficulty in producing accurate compositional results by the TEM-EDX approach is the mi...

Cement-based materials for use as sealants in underground waste storages must be erosion-resistant and chemically stable. Placement of highly radioactive waste (HLW) in boreholes may require that the rock is cement-grouted and stabilized by constructing concrete plugs. Where smectitic clay seals are in contact with concrete there is mutual degradat...

Measuring clay mineral “crystallinity” by the illite “Kübler” or chlorite “Árkai” index has long been used to determine the metamorphic grade of pelitic metasedimentary rocks by recognition of the anchizone: a transitional state of regional metamorphism lying between diagenetic and low-grade metamorphic conditions. Originally defined by B. Kübler o...

Adding clay to marine oil pollution represents a promising approach to enhance bacterial hydrocarbon degradation in nutrient poor waters. In this study, three types of regionally available clays (Ca-bentonite, Fuller’s Earth and kaolin) were tested to stimulate the biodegradation of source and weathered oil collected from the Deepwater Horizon spil...

In this study we present first results on a set of 15 industrially available bentonites from a broad range of sources, all of are currently been investigated in terms of their suitability for the underground sealing of nuclear waste repositories. A mineralogical and geochemical database is currently been compiled to address the stability of these b...

Smectite is typically considered unsuitable for radiometric dating, as argon (40Ar) produced from decay of exchangeable potassium (40K) located in the interlayer sites can be lost during fluid–rock interaction and/or during wet sample preparation in the laboratory. However, age analysis of Late Cretaceous Argentinian bentonites and associated volca...

In the very deep borehole (VDH) concept for high level radioactive waste disposal, the combined usage of clay and concrete provides an attractive way of achieving both high strength and low permeability required for sealing the various sections of the hole. The concrete is required for mechanical stability where water-bearing fracture zones are int...

A concept for the disposal of highly radioactive waste at depth in the Earth's crust using very deep bore-holes requires that the upper 2 km's of the 800 mm diameter, steeply drilled holes, be effectively sealed. This can be achieved by using dense smectitic clay where the rock is weakly fractured and strengthening with concrete when fracture zones...

The integrity of the caprock plays a major role for the long-term safety of CCS projects. Salt-induced anticline structures in NE Germany that are capped by Toarcian claystones could store up to 1,5 Gt CO2. This study focused on the interaction between Lower Jurassic claystones and CO2-charged brine in an attempt to identify pathways within the cap...

In much of the global ocean, iron is a limiting nutrient for marine productivity. The formation of pyrite has been considered the most important sink of reactive iron in modern, organic-rich sediments. However, clay mineral transformations can also lead to long-term sequestration of iron during late diagenesis and in hydrothermal settings. Here we...

Rectorite, the regular interstratification of dioctahedral swelling and non-swelling 2:1 layers from North Little Rock, Arkansas, although described previously, has not had its crystal chemistry and structural parameters (e.g., layer charge of the different layers, presence of cis/trans-vacancies) adequately defined. Here, X-ray diffraction, simult...

Following a round-table discussion at the Mid-European Clay Conference in Dresden 2014, new recommendations for illite' crystallinity' Kübler index standardization have been agreed upon. The use of Crystallinity Index standards in the form of rock-fragment samples will be continued, along with the same numerical scale of measurement presented by Wa...

The diagenesis of clay minerals and organic matter in Posidonia Shale has been typically studied independently of each other. Here, the results of an experimental investigation focused on the mineralogical changes of organic-rich shales are presented to understand the dissolution and precipitation processes of minerals as a function of thermal matu...

We present a new approach to identifying the source and age of paleofluids associated with low-temperature deformation in the brittle crust, using hydrogen isotopic compositions (δD) and 40Ar/39Ar geochronology of authigenic illite in clay gouge-bearing fault zones. The procedure involves grain size separation, polytype modeling, and isotopic analy...

The paper describes the performance of a concrete intended for sealing deep boreholes in the host rock of radioactive repositories. The concrete will form plugs where fracture zones are intersected and be located between very tight seals of smectite clay installed where the surrounding rock is tight. The concrete must be able to carry the clay segm...

The San Andreas Fault is one of the most studied earthquake-generating structures on Earth, but the reason that some sections are anomalously weak, and creep without apparent seismicity, remains poorly understood. Here, we present results from nanoscale (FIB-SEM) 3D microstructural observations of weak (friction coefficient of 0.095) clay fault gou...

A perlite sample representative of an operating mine in Milos was investigated with respect to the type and spatial distribution of water. A set of different methods was used which finally provided a consistent view on the water at least in this perlite. Infrared spectroscopy showed the presence of different water species (molecular water and hydro...

The Crystallinity Index Standard (CIS) developed by Warr & Rice (1994: Journal of Metamorphic Geology) is a calibration approach used to standardized the Full-width-at-half-peak-maximum (FWHM) parameter of the X-ray diffraction basal reflections of clay minerals so that different laboratories can more easily produce the same results from the same r...

Geophys Res Abs, 16, #9757

Field sampling of multiple surface locations along the trace of the North Anatolian Fault Zone (Turkey) has yielded clay-rich fault gouge. Clay gouge has been proposed as an explanation for weak fault behavior on the San Andreas Fault and has the potential to date the timing of fault-related neomineralization as well as identify the source of miner...

The environmental conditions and reaction paths of shallow-water glauconitization ( Green clay authigenesis at Hole 959C occurred mainly in the tests of calcareous foraminifera which provided post-depositional conditions ideal for glauconitization. Within this organic-rich micro-environment, Fe-smectite developed The rate of glauconite formation at...

Fault creep on the SAFOD section of the San Andreas Fault occurs along mechanically weak fault gouge characterized by high proportions of hydrous clay minerals, namely smectite, illite-smectite and chlorite-smectite phases. These minerals are concentrated along closely spaced, interconnected polished slip surfaces that give the gouge its characteri...

Deep investigation boreholes in crystalline rock for site selection of repositories for high-level radioactive waste are proposed to be sealed by installing a series of dense concrete and clay plugs. These should prevent radionuclides from leaking canisters at depth to migrate to the biosphere through the holes. The concrete seals will be installed...

Much oil spill research has focused on fertilizing hydrocarbon oxidising bacteria, but a primary limitation is the rapid dilution of additives in open waters. A new technique is presented for bioremediation by adding nutrient amendments to the oil spill using thin filmed minerals comprised largely of Fullers Earth clay. Together with adsorbed N and...