Application of mineralogical, petrological and geochemical tools for evaluating the palaeohdrogeological evolution of the PADAMOT study sites

The role of Work Package (WP) 2 of the PADAMOT project – ‘Palaeohydrogeological Data Measurements’ - has been to study late-stage fracture mineral and water samples from groundwater systems in Spain, Sweden, United Kingdom and the Czech Republic, with the aim of understanding the recent palaeohydrogeological evolution of these groundwater systems. In particular, the project sought to develop and evaluate methods for obtaining information about past groundwater evolution during the Quaternary (about the last 2 million years) by examining how the late-stage mineralization might record mineralogical, petrographical and geochemical evidence of how the groundwater system may have responded to past geological and climatological changes. Fracture-flow groundwater systems at six European sites were studied: • Melechov Hill, in the Bohemian Massif of the Czech Republic: a shallow (0-100 m) dilute groundwater flow system within the near-surface weathering zone in fractured granitic rocks; • Cloud Hill, in the English Midlands: a (~100 m) shallow dilute groundwater flow system in fractured and dolomitized Carboniferous limestone; • Los Ratones, in southwest Spain: an intermediate depth (0-500 m) dilute groundwater flow system in fractured granitic rocks; • Laxemar, in southeast Sweden: a deep (0-1000 m) groundwater flow system in fractured granitic rocks. This is a complex groundwater system with potential recharge and flushing by glacial, marine, lacustrine and freshwater during the Quaternary; • Sellafield, northwest England: a deep (0-2000 m) groundwater flow system in fractured Ordovician low-grade metamorphosed volcaniclastic rocks and discontinuous Carboniferous Limestone, overlain by a Permo-Triassic sedimentary sequence with fracture and matrix porosity. This is a complex coastal groundwater system with deep hypersaline sedimentary basinal brines, and deep saline groundwaters in crystalline basement rocks, overlain by a shallow freshwater aquifer system. The site was glaciated several times during the Quaternary and may have been affected by recharge from glacial meltwater; • Dounreay, northeast Scotland: a deep (0-1400 m) groundwater flow system in fractured Precambrian crystalline basement overlain by fractured Devonian sedimentary rocks. This is within the coastal discharge area of a complex groundwater system, comprising deep saline groundwater hosted in crystalline basement, overlain by a fracture-controlled freshwater sedimentary aquifer system. Like Sellafield, this area experienced glaciation and may potentially record the impact of glacial meltwater recharge. In addition, a study has been made of two Quaternary sedimentary sequences in Andalusia in southeastern Spain to provide a basis of estimating the palaeoclimatic history of the region that could be used in any reconstruction of the palaeoclimatic history at the Los Ratones site: • The Cúllar-Baza lacustrine sequence records information about precipitation and palaeotemperature regimes, derived largely from the analysis of the stable isotope (δ18O and δ13C) signatures from biogenic calcite (ostracod shells). • The Padul Peat Bog sequence provided information on past vegetation cover and palaeogroundwater inputs based on the study of fossil pollen and biomarkers as proxies for past climate change. Following on from the earlier EC 4th Framework EQUIP project, the focus of the PADAMOT studies has been on calcite mineralization. Calcite has been identified as a late stage mineral, closely associated with hydraulically-conductive fractures in the present-day groundwater systems at the Äspö-Laxemar, Sellafield, Dounreay and Cloud Hill sites. At Los Ratones and Melechov sites late-stage mineralization is either absent or extremely scarce, and both the quantity and fine crystal size of any late-stage fracture mineralization relevant to Quaternary palaeohydrogeological investigations is difficult to work with. The results from the material investigated during the PADAMOT studies indicate that the fracture fillings at these sites are related to hydrothermal activity, and so do not have direct relevance as Quaternary indicators. Neoformed calcite has not been found at these two sites at the present depth of the investigations. Furthermore, the HCO3 - concentration in all the Los Ratones groundwaters is mainly controlled by complex carbonate dissolution. The carbonate mineral saturation indices do not indicate precipitation conditions, and this is consistent with the fact that neoformed calcite, ankerite or dolomite have not been observed petrographically

Microbiological influences on fracture surfaces of intact mudstone and the implications for geological disposal of radioactive waste

The significance of the potential impacts of microbial activity on the transport properties of host rocks for geological repositories is an area of active research. Most recent work has focused on granitic environments. This paper describes pilot studies investigating changes in transport properties that are produced by microbial activity in sedimentary rock environments in northern Japan. For the first time, these short experiments (39 days maximum) have shown that the denitrifying bacteria, Pseudomonas denitrificans, can survive and thrive when injected into flow-through column experiments containing fractured diatomaceous mudstone and synthetic groundwater under pressurized conditions. Although there were few significant changes in the fluid chemistry, changes in the permeability of the biotic column, which can be explained by the observed biofilm formation, were quantitatively monitored. These same methodologies could also be adapted to obtain information from cores originating from a variety of geological environments including oil reservoirs, aquifers and toxic waste disposal sites to provide an understanding of the impact of microbial activity on the transport of a range of solutes, such as groundwater contaminants and gases (e.g. injected carbon dioxide)

Characterisation of sandstones : mineralogy and physical properties

Sandstones from Qwa Qwa in South Africa were characterised for their mineralogical and physical properties. Six samples (whitish, greenish, blackish, reddish, yellowish and greyish) were collected and studied. The X-ray Diffraction (XRD) revealed that the samples were quartz based. Scanning Electron Microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS) revealed the differences in the morphology and Silicon element was found present in all the samples. The X-Ray Fluorescence (XRF) exhibited that the samples contained 43.14% of Silicon (whitish). The grain sizes of the samples ranged from coarse, medium to fine grains. The Greyish sample had the highest compressive strength value of 56.74 MPa. Dielectric properties measurements were also conducted on the samples; and the results were temperature dependant. The water absorption by total immersion revealed that the blackish sand stones had the highest percentage of 6.62%

Ferromanganese nodules and micro-hardgrounds associated with the Cadiz Contourite Channel (NE Atlantic): Palaeoenvironmental records of fluid venting and bottom currents

Ferromanganese nodule fields and hardgrounds have recently been discovered in the Cadiz Contourite Channel in the Gulf of Cadiz (850–1000 m). This channel is part of a large contourite depositional system generated by the Mediterranean Outflow Water. Ferromanganese deposits linked to contourites are interesting tools for palaeoenviromental studies and show an increasing economic interest as potential mineral resources for base and strategic metals. We present a complete characterisation of these deposits based on submarine photographs and geophysical, petrographic, mineralogical and geochemical data. The genesis and growth of ferromanganese deposits, strongly enriched in Fe vs. Mn (av. 39% vs. 6%) in this contourite depositional system result from the combination of hydrogenetic and diagenetic processes. The interaction of the Mediterranean Outflow Water with the continental margin has led to the formation of Late Pleistocene–Holocene ferromanganese mineral deposits, in parallel to the evolution of the contourite depositional system triggered by climatic and tectonic events. The diagenetic growth was fuelled by the anaerobic oxidation of thermogenic hydrocarbons (δ13CPDB=−20 to −37‰) and organic matter within the channel floor sediments, promoting the formation of Fe–Mn carbonate nodules. High 87Sr/86Sr isotopic values (up to 0.70993±0.00025) observed in the inner parts of nodules are related to the influence of radiogenic fluids fuelled by deep-seated fluid venting across the fault systems in the diapirs below the Cadiz Contourite Channel. Erosive action of the Mediterranean Outflow Water undercurrent could have exhumed the Fe–Mn carbonate nodules, especially in the glacial periods, when the lower core of the undercurrent was more active in the study area. The growth rate determined by 230Thexcess/232Th was 113±11 mm/Ma, supporting the hypothesis that the growth of the nodules records palaeoenvironmental changes during the last 70 ka. Ca-rich layers in the nodules could point to the interaction between the Mediterranean Outflow Water and the North Atlantic Deep Water during the Heinrich events. Siderite–rhodochrosite nodules exposed to the oxidising seabottom waters were replaced by Fe–Mn oxyhydroxides. Slow hydrogenetic growth of goethite from the seawaters is observed in the outermost parts of the exhumed nodules and hardgrounds, which show imprints of the Mediterranean Outflow Water with low 87Sr/86Sr isotopic values (down to 0.70693±0.00081). We propose a new genetic and evolutionary model for ferromanganese oxide nodules derived from ferromanganese carbonate nodules formed on continental margins above the carbonate compensation depth and dominated by hydrocarbon seepage structures and strong erosive action of bottom currents. We also compare and discuss the generation of ferromanganese deposits in the Cadiz Contourite Channel with that in other locations and suggest that our model can be applied to ferromanganiferous deposits in other contouritic systems affected by fluid venting

Three-dimensional petrographical investigations on borehole rock samples: a comparison between X-ray computed- and neutron tomography

Technical difficulties associated with excavation works in tectonized geological settings are frequent. They comprise instantaneous and/or delayed convergence, sudden collapse of gallery roof and/or walls, outpouring of fault-filling materials and water inflows. These phenomena have a negative impact on construction sites and their safety. In order to optimize project success, preliminary studies on the reliability of rock material found on site are needed. This implies in situ investigations (surface mapping, prospective drilling, waterflow survey, etc.) as well as laboratory investigations on rock samples (permeability determination, moisture and water content, mineralogy, petrography, geochemistry, mechanical deformation tests, etc.). A set of multiple parameters are then recorded which permit better insight on site conditions and probable behavior during excavation. Because rock formations are by nature heterogeneous, many uncertainties remain when extrapolating large-scale behavior of the rock mass from analyses of samples order of magnitudes smaller. Indirect large-scale field investigations (e.g. geophysical prospecting) could help to better constrain the relationships between lithologies at depth. At a much smaller scale, indirect analytical methods are becoming more widely used for material investigations. We discuss in this paper X-ray computed tomography (XRCT) and neutron tomography (NT), showing promising results for 3D petrographical investigations of the internal structure of opaque materials. Both techniques record contrasts inside a sample, which can be interpreted and quantified in terms of heterogeneity. This approach has the advantage of combining genetic parameters (physico-chemical rock composition) with geometric parameters resulting from alteration or deformation processes (texture and structure). A critical analysis of such 3D analyses together with the results of mechanical tests could improve predictions of short- and long-term behavior of a rock unit. Indirect methods have the advantage of being non-destructive. However, as it is the case with large-scale geophysical surveying, XRCT and NT are affected by several error factors inherent to the interaction of a radiation modality (X-ray or neutron beam) with the atomic structure of the investigated materials. Recorded signals are therefore in particular cases not artifact-free and need to be corrected in a subsequent stage of data processin

Savanyú vulkáni üvegek ásványtan-geokémiai vizsgálata, petrológiai és vulkanológiai kiértékelése = Mineralogical and geochemical study of acid volcanic glasses, and its interpretation from petrological and volcanological point of view

Változatos lemeztektonikai környezetben képződött obszidián minták fő- és nyomelemtartalmának összehasonlító vizsgálata során megállapítottuk, hogy az eredetileg gránitokra kidolgozott diszkriminációs diagramok alkalmazhatók a savanyú kiömlési kőzetek esetében is. Megállapítottuk, hogy az óceáni sziget bazaltok (OIB) és a szigetív mészalkáli bazaltok (IAB) chondritra normált spiderdiagramjainak néhány alapvető jellegzetessége (pl. a relatív Nb-Ta minimum, ill. relatív Nb-Ta maximum) az obszidiánminták spiderdiagramjának patternjénél is felismerhető. Vizsgáltuk a mikro-PIXE elemzések megbízhatóságát és felhasználhatóságát, s bemutattuk, hogy az ezzel a módszerrel készített piroxénelemzési eredmények alkalmasak geotermometriai számítások elvégzésére. Savanyú vulkáni üvegek mállási folyamatát riolittuffa mintákon vizsgáltuk. A minták ásványos és főelem-összetételének valamint termoanalitikai paramétereinek (TG) összehasonlítása alapján megállapítottuk, hogy a mállási fok jellemzésére egyes TG paraméterek a nemzetközi gyakorlatban elterjedt indexhez (CIA) hasonló megbízhatósággal rendelkezik. Részt vettünk egy olyan berendezés kifejlesztésében, ami magas hőmérsékleten direkt mintavételt tesz lehetővé tömegspektrometriai vizsgálatokhoz. E berendezést vulkáni üvegek termális bomlási folyamatainak tanulmányozásánál is hasznosítani lehet. | Major and trace element spectra of obsidian samples from various tectonic settings were performed by LA-ICP-MSand PIGE techniques. The results suggest that discrimination diagrams for granites may be used for acidic volcanic rocks, too. We found that some characterisctic patterns of chondrite normalised spider diagram of OIB and IAB (such as relative Nb-Ta minimum and relative Nb-Ta maximum, respectively) can be observed in the case of obsidians, too. We demonstrate that analytical data yielded by micro-PIXE measurements can be applied even for geothermometric estimations. Weathering process of acidic volcanic glasses was studied on rhyolite tuff samples. Comparing mineralogical and major element composition as well as some thermoanalytical parameters of the samples it can be stated on the basis of some TG parameters weathering degree of rhyolite tuffs can be determined with a reliability that similar to that of the internationally accepted CIA index. We participated in construction of high temperature direct probe coupled to a quadrupole MS. This device can be also used for monitoring thermal decomposition of volcanic glasses

Geochemistry, Geochronology and mineralisation potential of the granites in the Central Iberian Zone: The Jalama batholith

The Jalama batholith (Spain and Portugal) is one of the numerous granites ofthe Central Iberian Zone with Sn- and W-associated mineralisation. On the basis of petrographical and geochemical characterisation three types of granite have been distinguished: inhomogeneous granitoids, porphyrytic granites and leucogranites, all of these being peraluminous and subalkaline. All the granites correspond to S-type granites. The field data, the petrography and lack of geochemical affinity relationships of the leucogranites with the remaining granites indicate that their geneses correspond to an independent magma batch and superimposed fractional crystallisation process. The granitic units show subparallel REE patterns. There is a decrease in total REE and an increase in the negative Eu anomaly from the inhomogeneous granitoids to leucogranites. Some leucogranites show relatively low contents of Sn and W almost certainly due to segregation in the magma of a melt rich in water carrying Sn-W. These elements are concentrated in the water phase, which eventually gives rise to Sn-W-associated mineralisation. The ages obtained by means of a whole-rock Rb-Sr isochron for the granites mainly indicate an early intrusion of the inhomogeneous granitoids (319 ± 10 Ma), followed in time by porphyrytic granites (279 ±9 Ma), which can be associated to the late-post-kinematic granites within the third Variscan deformation phase (D3). Apart from the average Sn content, the variations of trace elements, principally Sr, Ba, Rb, Th and P, establish that the porphyritic granites and the inhomogeneous granitoids will be barren granites while the leucogranites and the subfacies at the margin of the porphyritic granites correspond to granites with mineralisation potential. It is precisely in these granites ofthe Jálama batholith that the Sn-W mineralisation is located, for which the criteria utilised has been demonstrated to be effective

Roman metallurgical ceramics: an archaeometrical approach

Die vorliegende Doktorarbeit beschäftigt sich mit technischen Keramiken aus fünf verschiedenen archäologischen Ausgrabungen in West- und Zentraleuropa. Diese technischen Keramiken umfassen Schmelztiegel für Kupferlegierungen, Zementationstiegel für die Herstellung von Messing und Abgussformen. Wesentliche Fragen beziehen sich auf: (1) den Herstellungsprozess bezogen auf verwendetes Material, Brenntemperaturen, Anzahl der Nutzung einzelner Tiegel, usw.; (2) den Wissensaustausch zwischen unterschiedlichen römischen Siedlungen und Städten; (3) den möglichen Handel von Schmelztiegeln zwischen unterschiedlichen Städten beziehungsweise Fabrikationsorten und den Städten. Die 18 Schmelztiegel, acht Zementationstiegel und 16 Fragmente von Abgussformen aus Autun/Frankreich wurden bezüglich ihrer petrographischen (Mikroskopie), geochemischen (REM-EDS, EMS, RFA-WDS) und mineralogischen (RPD) Eigenschaften hin untersucht. Zusätzlich wurden 15 Schmelztiegelfragmente aus Augst/Schweiz und zehn Schmelztiegelbruchstücke aus Avenches/Schweiz hinsichtlich optischer Eigenschaften (z.B. Form, Größe, etc.), geochemischer und mineralogischer Eigenschaften, sowie dem Handel von Schmelztiegeln verglichen. Außerdem wurden acht Schmelztiegelbruchstücke aus Xanten/Deutschland in der gleichen Weise analysiert und den anderen Schmelztiegeln gegenübergestellt. Zudem wurden fünf Schmelztiegelfragmente, drei Bruchstücke von Ofenwandungen, ein „Bouchon“, welcher für die Herstellung von Plastiken verwendet wurde, und neun nicht eindeutig zugeordnete keramische Probenstücke aus Marsens En Barras/Schweiz untersucht. Diese wurden jedoch nicht mit den anderen analysierten technischen Keramiken verglichen. Diese Arbeit besteht aus sieben einzelnen Artikeln, welche entweder bereits publiziert oder für die Publikation akzeptiert wurden, beziehungsweise sich gerade unter Begutachtung bei achzeitschriften befinden oder für die Eingabe bei einer Zeitschrift bereit sind. Der erste Artikel (Kapitel 3) beschäftigt sich mit Schmelztiegeln aus Autun/Frankreich. Die 18 Tiegelbruchstücke zeigen einen zwei-lagigen Aufbau mit einer nicht verglasten inneren Lage und einer mehr oder minder gut verglasten äußeren Lage. Zusätzlich ist eine verglaste Engobe in den meisten Fragmenten zu finden. Die Schmelztiegel sind mit einer Metallkapazität von 19 kg relativ groß. Ermittelte Brenntemperaturen erreichen ein Maximum von 1400 °C. Die zweite Publikation (Kapitel 4) beschreibt Zementationstiegel und Abgussformen aus Autun/Frankreich hinsichtlich ihrer Struktur (z.B. Anzahl der keramischen Lagen) und geochemischen/ mineralogischen Zusammensetzung. Die Zementationstiegel bestehen aus einer nicht verglasten keramischen Lage mit einer Engobe und einer im oberen Drittel auftretenden äußeren nicht verglasten Lage, die zur Abdichtung von Tiegel und Deckel verwendet wurde. Hingegen bestehen die Abgussformen aus einem nicht verglasten keramischen Körper der im direkten Kontakt mit dem Metall einen feinen Tonüberzug aufweist. Der Ausgangston und die zugegebene Magerung in diesen beiden Keramiken ist der gleiche wie der, der für die Schmelztiegel von Autun/Frankreich Verwendung fand. Die drei Typen von technischen Keramiken aus Autun/Frankreich werden hinsichtlich ihrer nachgewiesenen Eigenschaften miteinander verglichen. Artikel drei (Kapitel 5) befasst sich mit Schmelztiegeln aus Xanten/Deutschland bezogen auf deren Struktur und geochemischmineralogische Zusammensetzung. Alle Tiegel sind zweilagig aufgebaut, wobei die innere Lage nicht verglast und die äußere Lage vollständig verglast ist. Allen Proben gemein ist eine innere Engobe. Die Schmelztiegel sind mit einer Metallkapazität von 1,5 kg deutlich kleiner als die aus Autun/ Frankreich stammenden. Die mineralogischen Befunde deuten auf geringere maximale Brenn-temperaturen (rund 1100 °C) hin. Mit römischen Schmelztiegeln aus zwei Ausgrabungen in der Schweiz (Augusta Raurica und Aventicum) beschäftigt sich der vierte Bericht (Kapitel 6). Bruchstücke beider Ausgrabungen wurden hinsichtlich ihrer Vergleichbarkeit der Analyseergebnisse sowohl untereinander, als auch mit den zuvor beschriebenen Schmelztiegeln untersucht. Chemische Daten die mittels portabler RFA Analyse erhoben wurden, ergänzen die geochemischen Labor-untersuchungen. Dieser Bericht befasst sich nicht ausschließlich mit der Struktur der Tiegel, welche mit denen aus Autun/Frankreich und Xanten/Deutschland vergleichbar ist, sondern auch mit der Tonherkunft und möglichem Handel von Schmelztiegeln zwischen beiden römischen Städten respektive möglichem Handel zwischen einem unbekannten Produktionsort und den beiden römischen Städten. Im Appendix I findet sich ein weiterer in deutscher Sprache verfasster Aufsatz über die Proben aus Augst und Avenches (beide: Schweiz). Der Bericht befasst sich ausschließlich mit den gefundenen Schmelztiegeln in Bezug auf deren Tonzusammensetzung, Aufbau, Form und Brenntemperaturen als auch mit dem Handel der Tiegel. Der Vergleich zwischen den in Artikel eins bis vier untersuchten Schmelztiegeln wird in der fünften Publikation (Kapitel 7) bezüglich ihrer Form, Aufbau, petrographischen und geochemischen usammensetzung hin betrachtet. Diese Arbeit versucht ein allgemeingültiges Rezept für römische Schmelztiegel zumindest für die untersuchten Standorte in Zentraleuropa aufzuzeigen und zu erörtern. Bei dem letzten Kapitel (Kapitel 8) handelt es sich um einen Teilbericht für eine archäologische Publikation im Rahmen der Ausgrabung Marsens En Barras/Schweiz. Die Proben stammen aus einer kleinmaßstäblichen Kupfer erarbeitenden Werkstatt, in deren Umfeld in großem Maßstab Eisen verarbeitet wurde. Die untersuchten Schmelztiegel sind verglichen mit den anderen nicht eindeutig zweilagig. Sie zeigen zwar unterschiedliche Eigenschaften bezüglicher der Verglasung (innen - nicht verglast, außen - verglast), jedoch sind diese beiden Bereiche in keinem der untersuchten Fragmente voneinander trennbar. Der verwendete Ton entstammt den lokalen Molassevorkommen und weist eine geringe thermische Stabilität auf. Zusätzlich treten organische Magerungsbestandteile auf, welche in keiner sonstigen, der im Rahmen dieser Dissertation untersuchten, technischen Keramiken auftreten

Three-dimensional petrographical investigations on borehole rock samples: a comparison between X-ray computed- and neutron tomography

Technical difficulties associated with excavation works in tectonized geological settings are frequent. They comprise instantaneous and/or delayed convergence, sudden collapse of gallery roof and/or walls, outpouring of fault-filling materials and water inflows. These phenomena have a negative impact on construction sites and their safety. In order to optimize project success, preliminary studies on the reliability of rock material found on site are needed. This implies in situ investigations (surface mapping, prospective drilling, waterflow survey, etc.) as well as laboratory investigations on rock samples (permeability determination, moisture and water content, mineralogy, petrography, geochemistry, mechanical deformation tests, etc.). A set of multiple parameters are then recorded which permit better insight on site conditions and probable behavior during excavation. Because rock formations are by nature heterogeneous, many uncertainties remain when extrapolating large-scale behavior of the rock mass from analyses of samples order of magnitudes smaller. Indirect large-scale field investigations (e.g. geophysical prospecting) could help to better constrain the relationships between lithologies at depth. At a much smaller scale, indirect analytical methods are becoming more widely used for material investigations. We discuss in this paper X-ray computed tomography (XRCT) and neutron tomography (NT), showing promising results for 3D petrographical investigations of the internal structure of opaque materials. Both techniques record contrasts inside a sample, which can be interpreted and quantified in terms of heterogeneity. This approach has the advantage of combining genetic parameters (physico-chemical rock composition) with geometric parameters resulting from alteration or deformation processes (texture and structure). A critical analysis of such 3D analyses together with the results of mechanical tests could improve predictions of short- and long-term behavior of a rock unit. Indirect methods have the advantage of being non-destructive. However, as it is the case with large-scale geophysical surveying, XRCT and NT are affected by several error factors inherent to the interaction of a radiation modality (X-ray or neutron beam) with the atomic structure of the investigated materials. Recorded signals are therefore in particular cases not artifact-free and need to be corrected in a subsequent stage of data processin