Lithium-bearing donbassite and tosudite were found in veins in hydrothermally altered granite (Beauvoir granite) in the northern part of the Massif Central, France. The two minerals are characterized by their high Li contents and low Mg and Fe contents; their structural formulae are: $${\left( {S{i_{3.81}}A{l_{0.19}}} \right)_{\Sigma = 4.00}}{O_{10}}{\left( {A{l_{3.81}}L{i_{0.52}}Fe_{0.01}^{2 + }C{a_{0.02}}M{g_{0.01}}} \right)_{\Sigma - 4.38}}{\left( {OH} \right)_8}{\left( {N{a_{0.07}}{K_{0.04}}} \right)_{\Sigma = 0.11}}$$ for donbassite and $${\left( {S{i_{3.50}}A{l_{0.50}}} \right)_{\Sigma = 4.00}}{O_{10}}{\left( {A{l_{2.95}}L{i_{0.22}}Fe_{0.01}^{3 + }T{i_{0.01}}} \right)_{\Sigma = 3.19}}{\left( {OH} \right)_5}{\left( {C{a_{0.01}}N{a_{0.15}}{K_{0.18}}} \right)_{\Sigma = 0.34}}$$ for tosudite.

These chemical compositions indicate that the donbassite is an intermediate member of the donbassite-cookeite solid solution series and that the tosudite consists of interstratified Li-donbassite and beidellite. Both Li-bearing minerals show thermal behavior distinct from those previously reported for dioctahedral chlorite and tosudite.

Petrographie investigation of drill cuttings from the Echassières area indicates that the two minerals were formed in an intermediate stage of hydrothermal alteration following an early stage characterized by formation of muscovite (2M1) at >350°C and before the latest stage characterized by deposition of kaolinite and randomly interstratified illite/smectite at < 100°C. Moreover, tosudite occurs in the upper part of the granite, whereas donbassite is restricted to the lower part, suggesting the formation of tosudite at lower temperatures.

Hornblende of the Carrol Knob mafic complex (southern Blue Ridge Mountains, North Carolina) has weathered under humid, temperate conditions. Hornblende weathering appears to have been a dissolution-reprecipitation reaction, in which hornblende dissolved stoichiometrically, and the ferruginous and aluminous weathering products (goethite, gibbsite, and kaolinite) precipitated from solution (neoformation). During the earliest stage of alteration, ferruginous weathering products formed as linings of fractures within and around crystals and cleavage fragments of hornblende. Side-by-side coalescence of lenticular etch pits during more advanced weathering produced characteristic “denticulated” terminations on hornblende remnants in dissolution cavities bounded by ferruginous boxworks. Dissolution cavities are devoid of weathering products. Small “pendants” of ferruginous material project from the boxwork into void spaces. Because these products are separated from the hornblende remnants by void space, they must have been produced by dissolution-reprecipitation reactions. Complete removal of the parent hornblende left a ferruginous microboxwork or “negative pseudomorph.” Only Al and Fe were conserved over microscopic distances; alkali and alkaline-earth elements were stoichiometrically removed from the weathering microenvironment during the weathering process.

Although numerous, small, manganese oxide deposits associated with dolomite in the Eastern Transvaal escarpment, Republic of South Africa, have been known for many years, their mineralogical make-up is somewhat controversial. Chemical, mineralogical, and morphological properties of the weathering products of dolomite and the coexisting manganese oxide material in the Graskop area were therefore determined. Mn and Fe occur only in minor accessory minerals in the original rock; however, in the weathering residue, these elements are concentrated and occur as separate mineral phases, chiefly birnessite, nsutite, and goethite. Thin veins of pure muscovite and quartz traverse the residua. Rare, pure calcite and maghemite nodules were noted throughout the residual manganese material. The properties of this weathering sequence suggest that the manganese wad deposits were formed in situ as a result of the congruent dissolution of dolomite, leaving a porous, sponge-like structure, highly enriched in Mn and Fe oxides.

The Rokle bentonite deposit is part of an accumulation of argillized volcanoclastic rocks in the Tertiary stratovolcanic complex of the Doupovské Mountains east of Karlovy Vary (Carlsbad), about 100 km westnorthwest of Prague, Czechoslovakia. The arenite basalt ash was originally composed of hyaloclasts and subordinate biotite. The following types of montmorillonite aggregates were produced during the alteration of the ash in a stagnant, lacustrine environment: (1) extremely fine-grained micro-crystalline aggregates that have honeycomb textures and that replace the original hyaloclasts, and (2) coarse crystalline aggregates that have more open honeycomb textures and that fill pores and cracks in altered hyaloclasts and in pumice vesicles. Both types of aggregates have the same chemical composition according to energy dispersive X-ray analysis.

Montmorillonite, separated as the <1-¼m size fraction from olive gray bentonite, has the following crystallochemical formula: (K0.09Na0.02Ca0.29Mg0.10) (Al2.43Fe3+1.05Fe2+0.005Mn2+0.005Mg0.50) (Si7.62Al0.38) O20(OH)4. Biotite was apparently stable during the alteration of the hyaloclasts. Anatase and possible accessory heulandite-clinoptilolite were also formed in small amounts, but were not observed by scanning electron microscopy. Goethite is the youngest oxidation product in some parts of the bentonite. Minute fragments of sodium-rich plagioclase, potassium feldspar, quartz, and muscovite are ubiquitous accessories of the original hyaloclasts. Together with kaolinite, they formed from the underlying fresh or kaolinized orthogneiss.

A mineralogical investigation of the highly kaolinized Chanon granite and albite-muscovite granite of the Montebras cupola, Creuse, France, indicates that the magmatic stage was followed by two hydrothermal events related to successive cooling stages and by late weathering. The hydrothermal alteration was accompanied first by greisen formation and then a broad kaolinization process, which pervasively affected the granitic bodies. In the Chanon granite, the greisens are characterized by a trilithionite-lepidolite-quartz-tourmaline assemblage and are surrounded by concentric alteration zones. From the greisen to the fresh granite three zones were distinguished: (1) a zone characterized by secondary brown biotite (<400°C), (2) a zone characterized by secondary green biotite and phengite (300–350°C), and (3) a zone characterized by the presence of corrensite (180°–200°C) located around greisen veinlets. In the albite-muscovite granite the greisen is composed of lepidolite and quartz. This mineral assemblage was followed locally by Li-tosudite crystallization. During the second hydrothermal event (<100°C) an assemblage of kaolinite, mixed-layer illite/smectite (I/S), and illite formed pervasively and in crack fillings; the smectite layers of the US are potassic. Weathering produced Fe oxide and kaolinite. This kind of alteration developed mainly in the overlying Chanon granite. Here, Ca-Mg-montmorillonite formed in subvertical cracks, which transect the two granitic bodies, and hydrothermal I/S was obliterated by Ca-Mg-montmorillonite.

The hydrothermal parageneses were apparently controlled by magmatic albitization and the bulk chemistry of the two granitic bodies. The albitization, the formation of large micaceous greisens, and the successive recrystallizations of biotite (which was the most susceptible phase to alteration) provide information on the temperature range and chemical mobility during successive cooling stages. Si and Mg activities increased as the temperature of alteration decreased, and secondary Mg-biotite and Mg-phengite crystallized as long as the K activity was sufficient. The crystallizations of secondary biotite and phengite were followed by the crystallization of I/S during stages of low K activity. Secondary hydrothermal phases in the Chanon granite contain substantial Fe and Mg. Secondary hydrothermal phases in the albite-muscovite granite contain only small amounts of Fe and Mg, suggesting a lack of chemical exchange between the enclosing Chanon granite and the albite-muscovite granite, which is depleted in Fe-Mg-rich primary phases, such as biotite.

Clay mineralogy and petrography of the Early to Middle Eocene succession of the Dammam dome, Saudi Arabia, comprising the Rus and Dammam Formations, were studied using X-ray powder diffraction, light microscopy, and scanning electron microscopy. These formations consist of alternations of dolomite, dolomitic marl, claystone, and shale. The rocks were deposited and subjected to early diagenetic dolomitization in a shallow, coastal marginal basin characterized by rapid changes in salinity. Palygorskite occurs as interwoven fibrous mats forming fine laminae in shales and as coatings and pore-filling and pore-bridging cements in dolomitic marls. This textural evidence suggests a direct chemical precipitation, mostly post-dating dolomitization. Magnesium concentrations in presence of dolomite was sufficient for palygorskite precipitation; the necessary Si and Al were derived by dissolution of silicates under alkaline conditions. The maximum development of palygorskite was near the top of the Dammam Formation, which was deposited during a marine transgression in the Lutetian. The formation of palygorskite in marginal restricted basins in eastern Saudi Arabia took place during Paleocene-Middle Eocene time and was contemporaneous with similar occurrences in the Tertiary basins of West Africa.

Stylistic shifts in ceramics are often linked with sociopolitical changes, yet adopting new ceramic designs may indicate anything from shared aesthetic appeal to emulation. Focusing on multiple ceramic technologies is critical for understanding ceramic changes as they relate to wider social fluctuations. The relationships between clay and ceramic recipes, and communities of practice, have not been studied at the urban landscape of Angamuco, Michoacán in western Mexico. Petrographic and geochemical analyses of tempers and fabrics indicate that ceramics, including imperial Purépecha (a.d. 1350–1530) vessels, were created from local and regional materials, and that these materials remained relatively stable for over 1,000 years. Ceramic archaeometry in western Mexico has been relatively limited compared to other parts of Mesoamerica, and this study may be compared to future studies in the region.

Thin section, XRD, SEM, and isotopic techniques have been used to study authigenic kaolinite occurring in reservoir sandstones of the Lower Permian Aldebaran Sandstone. Where the unit is no longer an active aquifer, kaolinite is an intermediate-stage phase, and is highly depleted in deuterium (δDSMOW = −115 to −99‰) and 18O (δ18OSMOW = +7.8 to +8.9‰), indicating that precipitation must have been from meteoric water. Deep penetration of this water is linked to Late Triassic deformation and uplift of the Denison Trough sequence, an event which led to exposure of the Aldebaran Sandstone by the Early Jurassic prior to its re-burial beneath Jurassic and Cretaceous sedimentary rocks. The same water was probably involved in the creation of secondary porosity in the interval.

Where the Aldebaran Sandstone is presently undergoing meteoric flushing, kaolinite is relatively enriched in deuterium (δDSMOW = −104 to −93‰) and 18O (δ18OSMOW = +11.7 to +14.6‰), reflecting precipitation largely from post-Mesozoic meteoric water which was isotopically heavier than the Mesozoic water involved in intermediate-stage kaolinite precipitation. This temporal shift in meteoric water isotopic composition is related to the northward drift of the Australian continent to lower latitudes since the Mesozoic Era.

Glauconites occurring within the Ukra Member of Kutch Basin have remained unexplored in terms of their economic significance. The present study aimed to present a detailed physicochemical characterization of glauconite occurring in the siliciclastic rocks of Guneri and Umarsar area of the Kutch district, Gujarat, India to explore their economic potential. The study involved an integrated petrographical, mineralogical, and geochemical investigation of glauconitic rocks to highlight the occurrence, nature, and maturity of glauconite. The characterization was carried out using X-ray diffraction (XRD), X-ray fluorescence (XRF), and electron probe microanalysis (EPMA) combined with energy dispersive X-ray (EDX), Field emission gun scanning electron microscopy (FEG-SEM), Fourier-transform infrared spectroscopy (FTIR), and inductively coupled plasma mass spectroscopy (ICP-MS). Petrographic and bulk XRD analysis revealed that the glauconite occurs as green pellets constituting ~30 and 40% of the glauconitic sandstone and shale, respectively. Whole-rock analysis showed that the value of K2O varies considerably from 3.93 wt.% (sandstone) to 5.63 wt.% (shale). Mineral chemistry indicated the distinctive chemical composition of glauconite pellets containing 7.4–8.4 wt.% of K2O. The parameters, such as the distance between the (001) and (020) peaks and the large K2O content (~8 wt.%) of the glauconite fraction reflect an evolved to highly evolved stage of maturation. The morphological and spectral signatures further support the high degree of maturation in glauconites. Trace-element analysis implied that the glauconitic sandstone and shale contain elements such as Zn, Mn, Cu, Co, Mo, and Ni, which serve as essential micronutrients for plants. These data sets collectively constitute part of a preliminary study which is prerequisite to beneficiation, but further evaluation of its potential as a potash fertilizer also is needed.

This article presents an example of ceramic circulation and exchange networks in the southern Andean region during the first centuries AD, derived from the study of the production, circulation, and consumption of the pottery assemblages found in the villages of Cardonal and Bordo Marcial, located in the Cajón Valley in Catamarca, Argentina. Our analysis of the technical, morphological, and design aspects of the ceramics suggested six morphological groups using three representation techniques and 16 paste recipes; we also found that locally manufactured vessels were used together with ceramics of nonlocal origin in similar domestic contexts. In addition, the foreign ceramic materials suggest that there were networks of interaction between Cardonal and Bordo Marcial and other regions, such as the southern Puna, the Hualfín Valley, the Rosario-Lerma Basin, and the San Francisco Valley in northwestern Argentina.

Production and consumption of pottery tempered with fresh volcanic ash peaked in the Late to Terminal Classic periods in the Maya lowlands. Differences in the type of volcanic inclusion and vessel form indicate that the pottery was produced in multiple locations by different groups of potters. In this article, we characterize pottery from household contexts at Baking Pot, Belize, using thin-section petrography and neutron activation analysis (NAA) to document mineralogical and chemical variability and determine provenance. The pottery was produced by adding fresh volcanic ash to a micritic clay. The petrographic and chemical data indicate that this paste recipe was produced locally in the Belize Valley. Variation in the paste recipes used is likely due to both production differences and postdepositional alteration. We argue that it is critical to use both petrography and NAA to understand pottery production and provenance in the Maya region.

Here, we consider the last decades of ceramic manufacture among the Pawnee in the Central Great Plains, using petrographic analysis to explore raw material availability and use at the Kitkahahki Town site (14RP1). Historical documents reveal tremendous regional pressures and conflicts in the Kitkahahki Town area during its occupation in the late eighteenth and early nineteenth centuries—processes that could have altered or restricted the movement of women outside village boundaries. Contact-era Pawnee pottery from Kitkahahki Town exhibits atypical paste textures, atypical inclusions, or both. At least one potter used atypical materials available immediately adjacent to the village, which suggests that ceramic raw material collection was at least occasionally adjusted to reduce risk. Petrographic analysis contributes to our understanding of Indigenous communities in colonial settings, particularly to questions of technological change and landscape use when both were intensely negotiated and rapidly changing.

This article investigates the mechanisms by which different communities were articulated during the Late Intermediate period (ca. AD 1000–1450) in the Río Grande de San Juan Basin, also called the Chicha Region, located in the border region of Bolivia and Argentina. Through analyses of systems of pottery production, circulation, and consumption, we examine interaction networks, social integration, and alliance building at a regional level. Yavi-Chicha pottery from two sites in the Chicha Region—Chipihuayco, in the Talina Valley (Bolivia), and Finispatria, in San Juan Mayo (Argentina)—provide key insights into regional integration and constellations of practice through their localized technological style and shared consumption strategies. This study reveals that people of Finispatria incorporated the entire Yavi-Chicha-style household assemblage—partly produced in Chipihuayco, partly in Finispatria, or partly at some unknown location—into their everyday lives. We argue that the entire household ceramic repertoire of the study region played a fundamental and socially integrative role as it circulated across the region.

While the basic sequence of innovations that characterise ceramic production in southern Britain during the first centuries b.c. and a.d. is well-established, our understanding of resistance to these innovations remains in its infancy. Led by the theoretical principles of social constructionism, this paper presents a detailed technological characterisation of Silchester ware, a hand-built ceramic type common in late Iron Age and early Roman Berkshire and northern Hampshire, and a conspicuous example of technological and stylistic anachronism when compared to contemporary wheel-made pottery. Multi-period analyses using radiography, petrography and typology indicate that Silchester ware was not merely a technological ‘hangover’, but a traditional form of material culture with its own role in changing socio-economic structures. Contextualisation of the findings within the local archaeological background further suggests that Silchester ware may have been instrumental in the maintenance of local community and identity at a time when these aspects of social life were under threat. Supplementary material available online (https://doi.org/10.1017/S0068113X20000355) comprises a characterisation of the chaînes opératoires of Silchester ware and its middle Iron Age antecedents, and a summarised version of the data, interpretations and the original radiographs.

En Mendoza (Centro-Oeste argentino), ciudad colonial meridional, los alfareros indígenas locales manufacturaron cerámica desde el siglo dieciséis, aunque su origen étnico fue documentalmente invisibilizado. La presencia de platos tipo Viluco Colonial en los contextos urbanos evidencia que los artesanos integraron técnicas locales, ligadas a la anterior dominación inca, con técnicas y formas de origen europeo. Con el objetivo de conocer las tecnologías de producción de los platos, realizamos análisis macroscópicos, petrográficos y con microscopía electrónica de barrido. A partir de esto, caracterizamos sus pastas, microfábricas y huellas de superficie. Proponemos que dichas vasijas fueron producidas tempranamente en la colonia por alfareros huarpes —sin excluir la posibilidad de participación de artesanos de otros grupos— quienes incorporaron el torno, pero continuaron con la tradición alfarera prehispánica y los lenguajes visuales andinos ligados al imperio inca. Analizar la producción cerámica como parte de la agencia social permitió visibilizar a los alfareros como agentes de cambio en la conformación de las nuevas identidades y culturas coloniales mendocinas, ya que sus productos híbridos pudieron ser usados por los colonos europeos, generando transformaciones identitarias como parte del proceso de etnogénesis.

The 161-ka Kos Plateau Tuff (KPT) eruption deposited widespread unwelded ignimbrites, but the Dikeos and Sympetro mountains on the SE of Kos Island blocked all but the most energetic pyroclastic flows. KPT remnants north of Sympetro mountain comprise reworked tuffite containing pumice and lithic clasts that petrologically and geochemically resemble those found in KPT unit E tephra, and reworked accretionary lapilli similar to those in KPT unit F. Tuffite is found only downslope from a 375-m-high pass between the Dikeos and Sympetro mountains, which was breached at the eruption climax by pyroclastic flows that then accelerated down the 10° north slope of Sympetro. The tuffite crops out in the palaeocliffs of a prominent terrace at an elevation of 75 m, interpreted as the transgressive ravinement surface of the first interglacial marine highstand after the KPT eruption during marine isotope stage (MIS) 5e. A similar ravinement surface cuts KPT deposits in central Kos at elevations of up to 135 m and implies post-MIS 5e uplift rates of 0.7–1.0 m ka−1, confirmed by the elevation of a previously reported raised beach beneath the KPT. A Holocene raised beach on the east coast of Kos contains pumice clasts from the Yali-4 eruption at 4–3 ka. Its elevation of 2 m above sea level is consistent with the elevation of the local MIS 5e terrace. Its present erosion results from the blocking of discharge from ephemeral streams by human infrastructure. Our study provides the first integrated chronologic and neotectonic interpretation of the prominent plateau and terrace surfaces on Kos Island.

The Danish onshore subsurface contains very large geothermal resources that have the potential to make a significant contribution to transforming Danish energy consumption toward a more sustainable energy mix. Presently, only a minor fraction of this green energy is exploited in three small plants. The main factors that have hampered and delayed larger-scale deployment are related to uncertainties in the geological models, which inevitably lead to high economic risks that are difficult for smaller district heating companies to mitigate without support from a compensation scheme. To facilitate and stimulate much wider use of the Danish geothermal resources, the Geological Survey of Denmark and Greenland (GEUS) and other research institutes have conducted several regional research projects focusing on the geological and geochemical obstacles with the principal objective of reducing the exploration risks by selecting the best geological reservoirs.

One of the most important geological factors causing uncertainty is the quality of the reservoirs and their ability to produce the expected volume of warm geothermal brine. Thus, great emphasis has been placed on investigating and understanding the relationships between reservoir sandstone, porosity, permeability, petrography, diagenetic processes and alterations related to variable sediment sources, basin entry points, depositional systems and climate, burial and thermal history. Mesozoic sandstones comprise the most important geothermal reservoirs in Denmark. Details concerning the reservoir quality are compiled and compared for the Lower Triassic Bunter Sandstone, Triassic Skagerrak, Upper Triassic – Lower Jurassic Gassum and Middle Jurassic Haldager Sand formations. The Bunter Sandstone Formation contains extensive aeolian and more confined fluvial sandstones with high porosity and permeability. However, highly saline formation water could be unfavourable. The Skagerrak Formation comprises well-sorted braided stream sandstones in the centre of the basin, and is otherwise characterised by muddy sandstones and alluvial fan conglomerates. An immature mineralogical composition has caused intensive diagenetic changes in the deepest buried parts of the basin. The Gassum Formation consists of shoreface, fluvial and estuarine sandstones interbedded with marine and lacustrine mudstones. In the upper part of the formation, the sandstone beds pinch out into mudstones towards the basin centre. Pervasive siderite- and calcite cement occurs locally in shallowly buried sandstones, and with burial depth the maximum abundances of quartz and ankerite cement increase. Sandstones of shallow burial represent excellent reservoirs. The relatively coarse grain size of the Haldager Sand Formation results in high porosity and permeability even at deep burial, so the formation comprises a high-quality geothermal reservoir.

Substantial progress has been made, and a well-established regional geological model combined with reservoir quality is now available for areas with cored wells. This has enabled an improved estimation of reservoir quality between wells for exploration of geothermal reservoirs.

Dating to the Early Formative period, Vaquerías pottery is the earliest polychrome ceramic in the Argentine Northwest. Questions about its provenance, use and circulation persist, however. To address these, the authors employ, for the first time, an integrated methodology comprising petrographic, morphological, iconographic and contextual analyses of ceramic samples from three regions of north-western Argentina. The results suggest five distinct modes of manufacture of Vaquerías ceramics, the non-centralisation of their production, their wide geographic distribution and their use in a variety of functional contexts. The methodology is applicable elsewhere and illustrates the potential of this approach over traditional stylistic-morphological studies.

Shifts in ceramic technology are often assumed to reflect wider social changes. Closer attention, however, needs to be directed to the fundamental issue of production. Shifts in the ceramic record of the Tao River Valley in north-western China (c. 2100 BC) are no exception and the relationships between ceramic form, clay recipes and communities of practice have not been previously investigated for this region. Here, petrographic analysis demonstrates that, despite major shifts in ceramic form and surface treatment, production techniques, raw materials and exchange relationships show surprising continuity through time.

Las prácticas alfareras en perspectiva arqueológica pueden ser estudiadas abordando diferentes aristas concernientes al proceso de producción y los restos materiales asociados a cada etapa. En este trabajo se presentan los resultados obtenidos del análisis tecnológico integral de una muestra extensiva de alfarería procedente del tambo Incaico de Costa de Reyes N°5 (Tinogasta, Catamarca, Argentina). La metodología implementada para lograr los objetivos consiste en la reconstrucción de formas típicas, la observación de cortes frescos en lupa binocular y la petrografía en secciones delgadas, aplicadas a un conjunto alfarero recolectado tanto de contextos superficiales como de excavaciones estratigráficas realizadas en dos recintos del sitio de Costa de Reyes N°5. A través de esta aproximación se han logrado visualizar continuidades y rupturas en el proceso de producción de alfarería y en las recetas aplicadas por los alfareros durante momentos de los períodos Agroalfarero tardío (ca. 900–1450 dC) e Inca (ca. 1480–1532 dC). Mientras que la producción de alfarería durante el período Tardío presenta características heterogéneas y una mayor variabilidad, en momentos Incaicos se observa que las recetas aplicadas por los alfareros para elaborar las pastas cerámicas se homogenizan, lo que se interpreta como un control más estricto sobre las fuentes de materia prima y sobre el proceso de hacer alfarería como un todo.