Willy Viaene

Nineteenth century hydraulic restoration mortars in the Saint Michael's Church (Leuven, Belgium) natural hydraulic lime or cement?

Abstract This research focuses on the characterization of nineteenth century hydraulic restoration mortars used in the Saint Michaels Church in Leuven (Belgium). The mortars were used as restoration mortars for weathered mortar joints. A historical study of old work descriptions and mineralogical, petrographical and chemical analyses have been used to characterize these hydraulic mortars. The different hydraulic phases are identified using petrographical analysis, X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDX) and chemical analyses. Based on the presence of gehlenite (C2AS), the dominance of C2S, the large amounts of portlandite, the chemical analyses and on the historical sources, these hydraulic mortars are characterized as natural hydraulic lime mortars.

Primary minerals of Zn-Pb mining and metallurgical dumps and their environmental behavior at Plombières, Belgium

The primary phases and minerals of the Plombières dumps include typical smelting furnace products such as metallic Fe, Pb, Cu, Zn, Fe-Zn alloys, carbides, phosphides, sulfides of Fe, Zn, Pb, Cu, Mn (alabandite), and FeAs. Spinels, mainly of Fe and Al, are common constituents of the primary assemblage; substitution by Zn, V, Cr, Ti, Mg, and Ca occurs. Primary phases also include the most common Zn-rich fayalite, Zn-rich Ca-Fe silicates, melilite, corundum, and apatite. Most of the Zn is incorporated in iron silicates, ZnO and ZnS. Lead occurs mainly as PbS, metallic lead, and is also present in coal residues. Cadmium is found mainly in metallic zinc and its alloys and in ZnO. The dumps also contain mining wastes composed of pyrite, melnikovite, and iron oxides produced by natural weathering of Zn-Pb ores. Melnikovite and iron oxides are rich in As, Pb, and Zn and possess an increased content of Tl. Leaching tests carried out on the surfaces of polished sections indicate that acid rain (solutions I and II) will mobilize mainly Zn and Cd and, to a much smaller extent, Pb and Sb. Leaching of metals by sulfate-chloride fluids present in the pore network of dumps (solutions III, IV, and V) depends on the pH, which in the dumps is controlled by the proportion of carbonates to sulfides. The more acid fluids leach both sulfides and silicates.

Geochemical constraints on the origin and migration of palaeofluids at the northern margin of the Variscan foreland, southern Belgium

Three major fracture types in the Dinantian of the Namur syncline at the northern margin of the Variscan foreland in southern Belgium, have been investigated by fluid inclusion and stable isotope analysis. The oldest and volumetrically most important fracture type is characterized by conjugated and sigmoidal en-echelon calcite veins which formed during the Variscan folding. These veins, and the surrounding limestones, have both a similar dull brown-orange luminescence and stable isotopic composition (δ18O = −11ℵ. to −8‰ PDB and δ13C = 0ℵ. to + 3‰ PDB). This indicates precipitation of the calcite cement from a fluid buffered by the rock. In the area studied, only a limited amount of fluids was expelled through the Dinantian during the main phase of Variscan compressional tectonism. Fractures filled with ferroan calcites cross-cut the Variscan .folds. Fluid inclusion and stable isotopic evidence indicates that the calcites precipitated at 40°–60°C from a saline fluid (9.2 to 23.2 eq. wt% NaCl) with an estimated δ18O composition between −2.0‰ and −0.6ℵ. SMOW. The most likely origin of these high-salinity fluids with a relatively low-oxygen isotopic composition is a gravity-driven meteoric water which underwent an intense water-rock interaction. The topographic relief created by the Variscan tectonism could have allowed groundwater to penetrate into the deeper subsurface and to migrate towards the margin of the foreland basin. Non-ferroan, fracture-filling calcites formed later during the Mesozoic or Tertiary. Low-salinity meteoric waters and high-salinity CaCl2NaCl brines with a temperature around 50°C migrated through this fracture system. Along these fractures, meteoric water migrated down into the subsurface and the brines could have flowed upward from the basement.

Man and environment in the territory of Sagalassos, a classical city in SW Turkey

Abstract Since 1990 archaeological research by the Catholic University of Leuven (Belgium) has been carried out at the ancient site of Sagalassos (Aǧlasun, Burdur province, Southwestern Turkey). At first, research focused on the excavation of the city and the study of the immediate vicinity which provided it with raw materials. The main objective was to obtain a clear picture of the history and development of the city. Since 1993 research has also incorporated a study of the territory of the Roman city, from prehistoric to modern times, in order to understand why the site was selected for settlement, why it developed into a middle-sized town, its economy and subsistence, how it affected and exploited the environment, its decline, and what changes have taken place in the district subsequently. The focus has now shifted towards obtaining a better understanding of the linkages between human and environment systems so that inter-relations between the two can be more readily understood. As a result, a number of environmental topics concerning the territory of the Roman city are presently being studied. This territory extended from Lake Burdur in the West to the Aksu canyon in the East, from the Aǧlasun Daǧlari in the North to Mt. Kestel in the South. Interdisciplinary research revealed that for the early Neolithic and the Roman period there was a slightly warmer climate, a richer vegetation and more fertile soils for agricultural practice.

Mississippi Valley-type Pb-Zn mineralization in eastern Belgium: Indications for gravity-driven flow

Mississippi Valley-type deposits are widespread in Carboniferous strata in eastern Belgium. Five successive Fe-rich, fracture-filling calcite generations have been recognized in the veins containing the Pb-Zn mineralization of Bleiberg. Fluid-inclusion evidence indicates that all the calcites formed from fluids with salinities between 16.0 and 23.1 equivalent wt% NaCl. The trapping temperature of the fluid inclusions decreases from ∼125 °C in the first two calcite generations to ≤50 °C in the last two vein cements. The δ 13 C values of the calcites vary between -0.1‰ and -8.3‰ relative to PDB (Peedee belemnite). The oxygen isotopic composition of the ambient fluids, calculated from the trapping temperature and the isotopic composition of the calcites, varies between -5.2‰ and +7.6‰ relative to SMOW (standard mean ocean water). The low δ 13 C values of the calcites are explained by the contribution of 12 C from CO 2 released during the oxidation of organic matter in the upper Carboniferous shales and the coupled reduction of sulfate in the mineralizing brine. The highly variable oxygen isotopic composition of the ambient fluids, the low δ 18 C value of the water from which one calcite cement precipitated, and the intense water-rock interaction necessary to leach metals indicate that the original fluids had a low δ 18 C, and that those fluids became enriched in 18 O by water-rock interaction. Waters with such low δ 18 C, values must have had a meteoric origin. Flow of these waters into the deeper subsurface was likely gravity driven and took place from the uplifted parts of the Variscan orogen toward the foreland basin.

Evolution of porosity in extruded stoneware as a function of firing temperature

Abstract The porosity of extruded test objects has been studied by different methods in order to follow its evolution during firing. This evolution is not linear. Pores, (partly) closed at intermediate temperatures, open again at temperatures above 1000°C. Two populations of pores are recognized. Their average sizes differ by a factor of 10.

Origin of shallow burial cements in the late viséan of the Campine Basin, Belgium

Abstract The diagenesis of Late Visean buildup and shelf carbonates from three boreholes in the Campine Basin (northern Belgium) has been studied to determine the early diagenetic pore fluid evolution in the basin. The earliest cementation occurred by isopachous fibrous and radiaxial fibrous calcites, which precipitated in a marine environment under oxidizing conditions. Neomorphism during subsequent diagenesis altered these cements extensively. Precipitation of these first stage cements was followed by an episode of dissolution of carbonate components (gastropods, pelecypods and echinoderms). After this episode, non-, bright and dull luminescent stages successively developed in the shelf carbonates in response to the pore waters becoming progressively more anaerobic. Fluid inclusions and oxygen stable isotopes in the dull luminescent stage indicate that this cement formed in a meteoric fluid at relatively low temperatures (∼ 30 °C) and thus under burial conditions of a few hundred metres. Buildup carbonates from the shelf margin show a similar diagenetic evolution, but dull luminescent cements appear to have precipitated at higher temperatures (∼ 45 °C) than in the shelf carbonates. The meteoric waters responsible for the cementation are interpreted to have been sourced from near the Brabant Massif, where dissolution of Visean limestones could have taken place when the limestones to the north were already buried underneath Namurian strata. Lateral gravity-driven groundwater flow may be a very important type of fluid flow causing the cementation of shelf carbonates. Fracturing of the Late Visean strata started before the precipitation of the meteoric cements, but was most intense just before and during the precipitation of the dull luminescent calcites. This fracturing probably took place during the Sudetic phase at the end of the Visean and Early Namurian times.

Fluid flow, alteration and polysulphide mineralisation associated with a low-angle reverse shear zone in the Lower Palaeozoic of the Anglo-Brabant fold belt, Belgium

Abstract In the Lower Palaeozoic rocks of the Brabant Massif (Belgium), a recently discovered polysulphide mineralisation is related to a low-angle reverse shear zone. This shear zone has been attributed to the main early Devonian deformation event. Data from boreholes and outcrops allow a detailed investigation of the alteration pattern and palaeofluid flow along this shear zone. Macroscopic observations of the mineralogy and quantitative changes in the phyllosilicate mineralogy indicate that this shear zone is characterised by an envelope of intense sericitisation and silicification. In addition, chloritisation is associated with this alteration. The alteration zone may reach a thickness of 250 m. Ore mineralisation occurred synkinematically and is spatially related to the shear zone. The mineralisation consists of pyrite, marcasite, arsenopyrite, pyrrhotite, chalcopyrite, sphalerite, galena, stibnite and smaller amounts of tetrahedrite and other sulphosalts. It is concentrated in quartz–sulphide veins or occurs diffusely in the host rock. The mineralising fluids have a low-salinity H 2 O–CO 2 –CH 4 –NaCl–(KCl) composition and a minimum temperature of 250–320 °C. The δ 18 O values of quartz vary between +12.3‰ and +14.5‰ SMOW, and δ D compositions of the fluid inclusions in the quartz crystals range from −65‰ to −35‰ V-SMOW. The δ D and the calculated δ 18 O values of the mineralising fluids fall in the range typical for metamorphic fluids and partly overlap with that for primary magmatic fluids. The δ 34 S values, between +4.7‰ and +10.6‰ CDT, fall outside the interval typical for I-type magmas. Important migration of likely metamorphic fluids, causing a widespread alteration and a polysulphide mineralisation along a low-angle shear zone, has, thus, been identified for the first time in the Caledonian Anglo-Brabant fold belt.

Peloids in stratabound Zn-Pb deposits and their genetic importance

Peloids from sediment-hosted Zn-Pb deposits in Belgium, Ireland and Poland are composed of Zn-calcite, siderite, smithsonite, silica, pyrite, melnikovite, sphalerite, galena, thiosulphates and Zn-As-bearing limonite. The size of peloids is between 7 and 60 μm. The core and the shell of peloids are composed of different minerals and the shell is usually coarsely crystalline. Peloids are present in collapse breccias of karst cavities, stromatactis cavities, debris-flow breccias, and fractures cross-cutting carbonates hosting the mineralization. In places peloids form a major microtexture of the sulfide mineralization. Peloids are cemented and replaced by sulfides. Organic acids extracted from sulfide peloids are composed of amido-acids considered to be characteristic of bacterial origin. The size and specific texture of peloids are independent of mineralogy, location and age of the mineralization. Therefore the peloids disussed are considered as forms induced by bacterial activity rather than forms precipitated inorganically.

The sigillata manufactories of Pergamon and Sagalassos

The Late Hellenistic period saw the intensification of pottery mass-production processes, of which Eastern Sigillata may be considered the pearl in the crown. Reddish tableware had a long tradition in the Levant and its evolution culminated around 150 B.C., in the region between Tarsos and Laodikeia, with the production of Eastern Sigillata A (ESA). More or less simultaneously, but independently, the manufacturing of Eastern Sigillata C (ESC) was initiated at Pergamon. Within a couple of decades the new range of tableware would establish itself in both regions of production, and other pottery production centres picked up the trend with, for instance, the production of Eastern Sigillata D (ESD) in SW Cyprus and the Late Hellenistic predecessor of Sagalassos red slip ware (SRSW) at Pisidian Sagalassos. No doubt, many more regional centres followed suit. The new tableware only gradually made its way, starting to replace other common Late Hellenistic types of fine ware. Only by the end of the Hellenistic period did sigillata become common on most Eastern tables. ESA was clearly in a league of its own, predominating through out the E Mediterranean and beyond. ESD was mainly restricted to Cyprus and the Levant, whereas ESC and Late Hellenistic SRSW remained of regional importance. More research is needed to evaluate the supra-regional demand for ESA in a social context, how this demand may have formed part of wider-ranging commercial activities of Levantine merchants in the E Mediterranean, how the geo-political shifts orchestrated by Rome may have influenced the exchange patterns, and how the other types of Eastern Sigillata and Late Hellenistic tablewares fit into this pattern and relate to prototypes in precious metal, For instance, the island emporion of Delos, handed over to Athens in 167 B.C. and especially favoured by the Romans after the destruction of Corinth in 146 B.C., may have been of crucial importance in establishing the distribution pattern of early ESA. Delos catered to the needs of Italy, which had grown powerful and rich in the 2nd c. B.C., by funnelling large numbers of slaves and a wide variety of luxury products, mainly from the Near East, to Rome. Levantine merchants contributed greatly to the success of Delos by controlling the supply mechanisms. As a result, ESA may have grown into a desirable surrogate for Eastern precious metal plate and thus acquired an esteemed position in the tableware market (cf. Cic, ad Att. 115 [VI.1] 13, dated 50 B.C., on vasa Rhosica ).