Hasil untuk "Mineralogy"

Teresa Rivas, José Santiago Pozo-Antonio, Daniel Jiménez-Desmond et al.

Historical tempera paints exposed to pollutant gases suffer chemical and mineralogical deterioration which manifests through physical changes. Knowledge about these changes is fundamental to develop strategies for preventive conservation of wall paintings. In this research, binary tempera mock-ups composed of calcite, gypsum or lead white mixed with a proteinaceous binder (i.e., egg yolk or rabbit glue) were exposed to an aging test by using SO₂-rich atmosphere exposure to learn about the degradation mechanisms and forms related to the pigment–binder interaction. Reference (unaltered) and aged mock-ups were studied from a physical point of view, characterizing the morphological changes by using stereomicroscopy and profilometry, color variations by using spectrophotometry, gloss changes, and reflectance changes by using a hyperspectral camera. Also, mineralogical and chemical changes were studied by means of X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Egg-yolk-based paints showed higher chromatic changes than their counterparts made of rabbit glue binder. Also, sulfate and sulfite salts precipitated on the surface of the aged paints regardless of their binder, influencing the painting reflectance which subsequently increased. Egg-yolk-based mock-ups exhibited roughness increases while the rabbit-glue-based paints showed roughness reduction, with the exception of lead-white-based paints. Therefore, the important influence of the type of binder and the interaction between the binder and the pigment on the durability of tempera paints in atmospheres rich in SO₂ was confirmed.

M. Depret, F. Hatert, M. Blondieau et al.

<p>The mineral ardennite-(As), which belongs to the <i>ardennite</i> group, was originally described in the locality of Salmchâteau, Stavelot Massif, Belgium. In the past 10 years, several new samples of ardennites have been found at seven localities of this region, motivating us to reinvestigate the crystal chemistry of the ardennite group. Under the polarizing microscope, most ardennites form lamellae or needles included in quartz veins or constituting the matrix of red Ordovician schists. Electron-microprobe analyses, as well as single-crystal structure refinements, show a homovalent substitution of As<span class="inline-formula">⁵⁺</span> by V<span class="inline-formula">⁵⁺</span> at the <span class="inline-formula"><i>T</i></span>4 tetrahedral site, leading to a complete solid solution between ardennite-(As) and ardennite-(V). Minor substitutions on that site allow the incorporation of a maximum of 0.28 P<span class="inline-formula">⁵⁺</span> atoms per formula unit (apfu) and of less than 0.1 Si<span class="inline-formula">⁴⁺</span> pfu, except in a sample from Arbrefontaine, where Si reaches 0.74 apfu. The main substitution mechanism, affecting both the <span class="inline-formula"><i>T</i></span>4 and <span class="inline-formula"><i>M</i></span>3 sites, is <span class="inline-formula">^<i>T</i>4</span>Si<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow><msup><mi/><mrow><mn mathvariant="normal">4</mn><mo>+</mo></mrow></msup><mo>+</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="20pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="1a1a45fb1386d06f6300b4069c658080"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-36-687-2024-ie00001.svg" width="20pt" height="13pt" src="ejm-36-687-2024-ie00001.png"/></svg:svg></span></span> <span class="inline-formula">^<i>M</i>3</span>(Al,Fe)<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow><msup><mi/><mrow><mn mathvariant="normal">3</mn><mo>+</mo></mrow></msup><msup><mo>↔</mo><mrow><mi>T</mi><mn mathvariant="normal">4</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="34pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="5c69b206a94fef5312f4e7c551aaacfb"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-36-687-2024-ie00002.svg" width="34pt" height="13pt" src="ejm-36-687-2024-ie00002.png"/></svg:svg></span></span>(As,V,P)<span class="inline-formula">⁵⁺</span> <span class="inline-formula">+^<i>M</i>3</span>Mg<span class="inline-formula">²⁺</span>. Crystal-chemistry calculations indicate a positive correlation between the unit-cell parameters and the (Ca <span class="inline-formula">+</span> Mg <span class="inline-formula">+</span> Fe) contents of ardennites, as well as a negative correlation between the bond length distortion coefficients at the <span class="inline-formula"><i>T</i></span>4 and <span class="inline-formula"><i>M</i></span>3 sites. The existence of possible Si-rich and P-rich end-members, as well as the nomenclature of the ardennite group in which <i>dewalquite</i> could be revalidated, is discussed.</p>

Kathleen Fernandes, José Marques Júnior, Adriana Aparecida Ribon et al.

Abstract Soil mineralogy and texture are directly related to soil carbon due to the physical properties of the clay surface. Traditional techniques for quantifying carbon in soil are time-consuming and expensive, making large-scale quantification for mapping unfeasible. The alternative is the use of soil sensors, such as diffuse reflectance spectroscopy (DRS), an economical, fast, and accurate technique for predicting carbon stocks. In this sense, this study aimed to (a) investigate the relationship of C with different soil mineralogical, chemical, and physical attributes for different geological and geomorphological compartments; (b) understand which spectral bands are most important for estimating C content; (c) estimate C content from diffuse reflectance spectroscopy using different mathematical techniques and indicate which one is the best for tropical soil conditions; and (d) map C contents in detail. The study area was the Western Plateau of São Paulo (WPSP), which covers approximately 13 million hectares (~ 48% of the State of São Paulo, Brazil). A total of 265 samples were collected in this area. The attributes clay, silt, sand, crystalline and non-crystalline iron, base saturation, soil density, total pore volume, total C, C stock, kaolinite/(kaolinite + gibbsite) and hematite/(hematite + goethite), hematite and goethite contents, and spectral curves were evaluated. The spectra were recorded at 0.5-nm intervals, with an integration time of 2.43 nm s−1 over the 350 to 2500-nm range (350–800 nm—visible—VIS and 801–2500 nm—near-infrared—NIR). The data were subjected to descriptive statistics, Spearman correlation, stepwise analysis, and cluster grouping for characterization purposes; partial least squares regression (PLSR) and random forest (RF) for estimation purposes; and geostatistics analysis for creation of spatial maps. Our results indicate that the highest C contents are associated with more clayey soils, oxidic mineralogy, higher total pore volume, and lower soil density in highly dissected basalt compartments. The random forest algorithm associated with the Vis–NIR spectral range is more efficient for estimating and mapping C contents. This suggests that integrating diffuse reflectance spectroscopy with machine learning techniques holds promise for shaping public policies related to land use, mitigating CO2 emissions, and facilitating the implementation of carbon credit policies in a rapid and economically efficient manner.

Hamed Daneshvar, Hossein Kouhestani, Mir Ali Asghar Mokhtari et al.

Tozlou Pb-Zn mineralization, ~250-300m long, and ~50m thick, is hosted by limestone units of the Qom Formation. The main mineralization zone occurred as vein-veinlets and vug infill textures, where mineralization is observed as Pb-Zn-bearing barite veins or supergene minerals (cerussite and smithsonite). Mineralization at Tozlou can be divided into five stages. Stage 1 is the decarbonatization of the limestone host rock, which is characterized by the increased porosity and permeability of the host rock. Stage 2 is categorized with dolomitization processes along with minor pyrite. Stage 3 occurred as Pb-Zn-bearing barite and calcite (calcite II) veins. Stage 4 includes late-stage calcite (calcite III) veins. Stage 5 is related to supergene processes. Hydrothermal alterations include decarbonatization, carbonatization ± silicification, and late carbonatization. Ore minerals include galena and pyrite along with minor sphalerite. Calcite, barite, and quartz are gangue minerals. Smithsonite, cerussite, and goethite are formed by supergene processes. The ore minerals show vein-veinlets, brecciated, disseminated, vug infill, colloform, cockade, replacement, and residual textures. The Chondrite-normalized rare earth elements pattern of ore samples, fresh and altered limestones is similar, which can indicate the major role of host rocks in the concentration of ore-forming elements. This pattern is almost similar for different ore samples, which can indicate that they have been formed by the same mineralization system. Characteristics of Tozlou occurrence are comparable with intermediate-sulfidation type of epithermal deposits. Introduction Epithermal deposits are a group of base/precious-metal deposits that are formed by hydrothermal fluids in shallow environments under pressure/temperature changes and fluid-rock interactions (Hedenquist et al., 2000). Based on the host rock, epithermal deposits are divided into volcanic-hosted deposits and sedimentary-hosted deposits. According to the tectonic setting and magma type, they are divided into calc-alkaline magmas (including three subcategories of high-, intermediate-, and low-sulfidation) and alkaline magmas (White and Hedenquist, 1990; Cooke and Simmons, 2000; Hedenquist et al., 2000; Simmons et al., 2005). These types of deposits include a continuous range of deposits formed by magmatic/meteoric fluids and show different geometry, but have the same formation mechanism, especially the hydrothermal fluids circulation (Sillitoe and Hedenquist, 2003; Simmons et al., 2005). Sedimentary rock-hosted deposits are divided into two groups: Carlin-type and sediment-hosted disseminated deposits. Carlin-type deposits are often formed as strata-bound or replacements at the boundary of rock units and are controlled by faults. They are distinguished by invisible Au in As-rich pyrite and arsenopyrite and do not show compatible spatial relationships to magmatic centers (Kuehn and Rose, 1992). Sediment-hosted disseminated deposits occurred as disseminated ore in sedimentary rocks (Hofstra and Cline, 2000). These deposits are physically and chemically comparable to Carlin-type deposits, but spatially and temporally are related to sub-volcanic porphyry intrusions (Theodore et al., 2000; Hofstra and Cline, 2000). Tozlou Pb-Zn occurrence is 50km south of Qeydar in Zanjan province. This occurrence was first discovered/explored in 2017. Although general geological characteristics of Tozlou occurrence have been determined (Majidifard and Shafei, 2006), the mineralogy and origin of Tozlou occurrence have not been studied in detail. Here, detailed geology, mineralogy, alteration styles, and geochemistry of Tozlou occurrence are investigated to constrain the genetic model and type of its mineralization system. These results may have implications for future exploration of base-metal mineralization in this region and nearby areas. Materials and methods Comprehensive field and laboratory works have been carried out on Tozlou area. During the fieldwork, a detailed stratigraphic section of limestone units of Qom Formation was measured, sampled, and described. Fifty samples were collected from ore zones and limestone host rocks for laboratory analysis. Then, 34 thin and 15 polished-thin sections were prepared for mineralogical studies in the laboratory at the University of Zanjan, Iran. Fourteen typical samples from the ore zones and fresh/altered host limestone were analyzed for geochemical analysis using ICP–MS in Zarazma Analytical Laboratories, Tehran, Iran. Results and Discussion The main rock units exposed in Tozlou occurrence belong to Eocene sequence, Lower Red Formation, Qom Formation, and Quaternary units. Small outcrops of gabbro-gabbro diorite (gb) can also be seen in this region. Eocene strata include brown thin-bedded sandstone (Unit Es), alternating tuff and shale (Unit Etsh), and thin- to medium-bedded tuffs (Unit Et). Lower Red Formation includes a polygenetic conglomerate (Unit Ollrc) of Oligocene age. Qom Formation consists of massive- to medium-bedded cream-to-grey limestones (Unit OMql) and alternating marl and thin-bedded grey limestone (Unit OMqml). Quaternary units include terrigenous sediments. Pb-Zn mineralization at Tozlou has ~250-300 m leng and ~50 m thick and is hosted by limestone units of Qom Formation. The main mineralization zone occurred as vein-veinlets and vug infill textures, where mineralization is observed as Pb-Zn-bearing barite veins or supergene minerals (cerussite and smithsonite). Decarbonatization, carbonatization±silicic, dolomitization, and late carbonatization are hydrothermal alterations in Tozlou area. Mineralization processes at Tozlou can be divided into five stages. Stage 1 comprises the decarbonatization of the limestone host rock, which is characterized by the increased porosity and permeability of the host rock. Stage 2 is represented by the dolomitization of the limestone host rock, which is accompanied by minor pyrite. Stage 3 occurs as Pb-Zn-bearing barite and calcite (calcite II) veins. Stage 4 is characterized by late-stage calcite (calcite III) veins. Stage 5 is related to supergene processes. Ore minerals include galena and pyrite along with minor sphalerite. Calcite, barite, and quartz are gangue minerals. Smithsonite, cerussite, and goethite are formed by supergene processes. The ore minerals show vein-veinlets, brecciated, disseminated, vug infill, colloform, cockade, replacement, and residual textures. The Chondrite-normalized rare earth elements patterns of ore samples, fresh and altered limestones, are similar, which can indicate the major role of host rocks in the concentration of ore-forming elements. This pattern is almost similar for different ore samples, which can indicate that they have been formed by the same mineralization system. Despite carbonate host rock, we think that mineralization at Tozlou is similar to the intermediate-sulfidation style of epithermal base metal deposits.

A. Altieri, F. Pezzotta, G. B. Andreozzi et al.

<p>Tourmaline crystals from the island of Elba commonly display a sharp transition to dark colors at the analogous termination due to the incorporation of Fe and/or Mn during the latest stages of crystallization in pegmatites. The formation of such color anomalies is related to a dramatic physicochemical change in the crystallization environment as a consequence of an opening of the geochemical system. However, mechanisms that may lead to the availability of Fe and/or Mn in the residual cavity fluids have been unclear. On the basis of chemical and spectroscopic investigations, combined with structural and paragenetic observations of the cavities, we propose a general genetic model in which, as a consequence of a pocket rupture event, chemical alteration of Fe- and Mn-rich minerals that formed early in the pegmatitic rock surrounding the cavities occurred through leaching processes, produced by the action of the highly reactive late-stage cavity fluids. Such processes were responsible for the release of Fe and Mn in the geochemical system, allowing the formation of the late-stage dark-colored terminations in the tourmaline crystals. In some cavities, a high availability of Mn and/or Fe determined the evolution of the crystals from an initial elbaite/fluor-elbaite composition to celleriite, foitite or schorl. This compositional evolution trend can be described by the following general chemical substitution: <span class="inline-formula">^X</span>Na<span class="inline-formula">⁺</span> <span class="inline-formula">+</span> <span class="inline-formula">^Y</span>(Li<span class="inline-formula">_1.5</span> <span class="inline-formula">+</span> Al<span class="inline-formula">_0.5</span>)<span class="inline-formula">³⁺</span> <span class="inline-formula">+</span> <span class="inline-formula">^W</span>F<span class="inline-formula">⁻</span> <span class="inline-formula">↔</span> <span class="inline-formula">^X□</span> <span class="inline-formula">+</span> 2<span class="inline-formula">^Y</span>(Fe,Mn)<span class="inline-formula">²⁺</span> <span class="inline-formula">+</span> <span class="inline-formula">^W</span>OH<span class="inline-formula">⁻</span>.</p>

Thaís Nascimento Pessoa, Talita Rosas Ferreira, Luiz Fernando Pires et al.

Soil structure controls soil hydraulic properties and is linked to soil aggregation processes. The aggregation processes of Oxisols are controlled mainly by clay mineralogy and biological activity. Computed microtomography (µCT) may be a tool for improving the knowledge of the hydraulic properties of these soils. Thus, this study brings an advance in the use of 3D image analysis to better comprehend the water behavior in tropical soils. In this work, three Oxisols were studied with the objective to (i) characterize the soil water retention curve (SWRC), the corresponding pore size frequency, and the saturated hydraulic conductivity (K_sat); (ii) use µCT to obtain, based on 3D images of soil structure and pore size distribution; and (iii) correlating parameters from SWRCs, K_sat, and µCT with other physical-hydric, chemical, and mineralogical attributes. Rhodic Haplustox—P1, Anionic Acrustox—P2, and Typic Hapludox—P3 were the three studied Oxisols. The differences among the SWRCs were related to the microgranular and block type’s structure morphology, which modified the soil pore space. The pore size frequency was calculated from SWRCs for pores with diameters of 87 ± 2 μm in P1, 134 ± 11μm in P2, and 175 ± 18 μm in P3. Pore size distribution from µCT was determined for the range of 20–100 µm, mainly with the highest percentages: 12 ± 1.09% for P1 and 12 ± 1.4% for P2. Pore connectivity was assessed from images by calculating Euler Numbers (EN), with the differences related to the biggest pore (EN_bigpore): P1 (−44,223 ± 10,096) and P2 (−44,621 ± 12,573) showed more connected pores (EN_bigpore) in comparison to P3 (−11,597 ± 6935). The parameter EN_bigpore was decisive in understanding the water retention and conduction processes of the studied soils. The better-connected pore space increased K_sat in P1 (220 ± 0.05 mm h⁻¹) and P2 (189 ± 0.1 mm h⁻¹) in comparison to P3 (20 ± 0.3 mm h⁻¹) and modified the shape of SWRCs.

Jian Chen, Huawei Tong, Jie Yuan et al.

Clay soil is a common building foundation material, and its permeability is very important for the safety of foundation pits and the later settlement of buildings. However, the traditional Kozeny-Carman (K-C) equation shows serious discrepancies when predicting the permeability of clay in building foundation treatment. Therefore, solving the application of K-C equation in clay is a problem faced by the engineers and scholars. In this paper, the influence of clay mineralogy on pore structure and permeability is analyzed, and then the effective <i>e</i> (<i>e</i>_eff) and effective SSA (<i>S</i>_eff) are proposed. Based on the <i>e</i>_eff and <i>S</i>_eff, the permeability prediction model modified on Kozeny-Carman is built. Then, seepage experiments are conducted on two types of clay samples to test this prediction model; at the same time, the MIP combining freeze-drying methods are used to obtain the <i>S</i>_eff and <i>e</i>_eff. Through the discussion of the test results, three main conclusions are obtained: (1) there are invalid pores in clay due to the influence of clay mineral, this is the reason for which K-C equation is unsuitable for clay; (2) the <i>e</i>_eff and <i>S</i>_eff can reflect the structural state of clay during seepage; (3) the results of the permeability prediction model in this paper agree well with the test results, which indicates that this prediction model is applicable to clay. The research results of this paper are significant to solve the academic problem that K-C equation is not applicable to clay and significant to ensure the safety of building foundation pits in clay areas.

Hüseyin Baştürkçü, Kaan Özçelik, Mete Tayhan Serdengeçti et al.

Slag, which is now considered as a secondary source, attracts attention due to the metallic values they contain. Copper slags having economical operating grades in terms of Zn, Cu, Ce, Ni, Co, Mo, and V show complex mineralogy due to its thermal processing history. Various methods for the recovery of copper and other precious metals from this byproduct have been studied, and there are many operating flotation plants in industrial scale. However, in cases where physical or physo-chemical mineral processing methods are not sufficient, hydrometallurgical methods are applied. In this study, flotation was applied to copper slag with 0.9% Cu grade. Copper recovery and concentrate grade were found as around 40 and 22.7% Cu, respectively. Further, metal extractions were examined by conducting direct leaching tests. Gel formation was observed, when H2SO4was used in the leach process, therefore, the leach parameters were investigated using HCl. Cu and Ce extractions of around 70-80% were reached as a result of a test performed for 2 hours with the addition of 25 g/L H2O2 at a rate of 20-25% solids and 300 g/L HCl concentration. When the relationship of dissolved metals with each other wasexamined, dissolution behavior of Cu and Ce was quite similar to Al dissolution (R2=0.9).

Jorge Otero

Abstract Global cultural heritage is a lucrative asset. It is an important industry generating millions of jobs and billions of euros in revenue yearly. However, despite the tremendous economic and socio‐cultural benefits, little attention is usually paid to its conservation and to developing innovative big‐picture strategies to modernize its professional field. This perspective aims to compile some of the relevant current global needs to explore alternative ways for shaping future steps associated with the 2030 Agenda for Sustainable Development. From this perspective, it is conceptualized how emerging artificial intelligence (AI) and digital socio‐technological models of production based on democratic Peer‐2‐Peer (P2P) interactions can represent an alternative transformative solution by going beyond the current global communication and technical limitations in the heritage conservation community, while also providing novel digital tools to conservation practitioners, which can truly revolutionize the conservation decision‐making process and improve global conservation standards.

Aubineau, Jérémie, Bankole, Olabode M., Baron, Fabien et al.

The mineral paragenetic sequence of the 2.1-billion-year-old (Ga) Francevillian basin is important for understanding the diagenetic fluid history that allowed the preservation of the oldest ecosystem, including bacterial and more advanced forms of life in the $\mathrm{FB}_{2}$ Member. However, a full characterization of the clay mineralogy of the $\mathrm{FB}_{2}$ microbial mat-related structures (MRS) and associated host sediments (sandstones and black shales) is yet to be determined. Petrographic, microscopic, and mineralogical analyses reveal the concurrent presence of authigenic vermiform kaolinite and sudoite in the MRS and host sediments. Kaolinite formed along cleavages of altered muscovite and as pore-filling during early diagenesis, while sudoite likely precipitated at the expense of kaolinite that undergone secondary dissolution later in the diagenetic sequence. The formation of sudoite was promoted by fault-controlled acidic and oxidized brines that might have migrated during the Francevillian basin inversion. These results imply that the porosity and permeability of sedimentary rocks dominantly control the mineralogical assemblage of the $\mathrm{FB}_{2}$ Member.

Aurelie R. Marcotte, Ariel D. Anbar, Brian J. Majestic et al.

There is significant iron deposition in the oceans, approximately 14–16 Tg annually from mineral dust aerosols, but only a small percentage (approx. 3%) of it is soluble and, thus, bioavailable. In this work, we examine the effect of mineralogy, particle size, and surface area on iron solubility in pure mineral phases to simulate atmospheric processing of mineral dust aerosols during transport. Pure iron-bearing minerals common to Saharan dust were partitioned into four size fractions (10–2.5, 2.5–1, 1–0.5, and 0.5–0.25 µm) and extracted into moderately acidic (pH 4.3) and acidic (pH 1.7) leaching media to simulate mineral processing during atmospheric transport. Results show that, in general, pure iron-bearing clay materials present an iron solubility (% dissolved Fe/total Fe in the mineral) an order of magnitude higher than pure iron oxide minerals. The relative solubility of iron in clay particles does not depend on particle size for the ranges examined (0.25–10 μm), while iron in hematite and magnetite shows a trend of increasing solubility with decreasing particle size in the acidic leaching medium. Our results indicate that while mineralogy and aerosol pH have an effect on the solubilization of iron from simulated mineral dust particles, surface processes of the aerosol might also have a role in iron solubilization during transport. The surface area of clay minerals does not change significantly as a function of particle size (10–0.25 µm), while the surface area of iron oxides is strongly size dependent. Overall, these results show how mineralogy and particle size can influence iron solubility in atmospheric dust.

Krisztián Fintor, Andrea Varga

In the basement areas of the southern Pannonian Basin, Central Europe (Tisia Composite Terrane, Hungary), Variscan blocks are essential components. The existing paleogeographic reconstructions, however, are often unclear and contradictory. This paper attempts to give a contribution for paleogeographic correlation of the Tisia using paleohydrological features (e.g., vein mineralization types, inclusion fluid composition and origin) of the Pennsylvanian continental succession and neighboring crystalline complexes. Vein-type mineralization in the studied samples dominantly forms blocky morphological types with inclusion-rich quartz and carbonate crystals. The evolution of hydrothermal mineralization and host rock alteration in the study area comprises three major stages. The first one is characterized by chloritization, epidotization, and sericitization of metamorphic rocks together with subsequent formation of Ca-Al-silicate and quartz-sulfide veins (clinopyroxene-dominant and epidote-dominant mineralization). The related fluid inclusion record consists of high-temperature and low-salinity aqueous inclusions, corresponding to a reduced retrograde-metamorphic fluid phase during the Late Westphalian (~310 Ma). The next mineralization stage can be related to a generally oxidized alkaline fluid phase with a cross-formational character (hematite-rich alkali feldspar-dominant and quartz-dolomite veins). High-salinity primary aqueous inclusions probably were originated from the Upper Permian playa fluids of the region. The parent fluid of the third event (ankerite-hosted inclusions) was derived from a more reductive and low-salinity environment and can represent a post-Variscan fluid system. Fluid evolution data presented in this paper support that the W Tisia (Mecsek–Villány area) belonged to the Central European Variscan belt close to the Bohemian Massif up to the Early Alpine orogenic phases. Its original position is presumably to the northeast from the Bohemian Massif at the Late Paleozoic, north to the Moravo-Silesian Zone. The presented paleofluid evolution refines previous models of the paleogeographic position of the Tisia and puts constraints on the evolution of the Variscan Europe.

Rajaa Bouamoud, Ely Cheikh Moine, Raphaèl Mulongo-Masamba et al.

Abstract The Democratic Republic of the Congo holds important reserves of oil shale which is still under geological status. Herein, the characterization and pyrolysis kinetics of type I kerogen-rich oil shale of the western Central Kongo (CK) were investigated. X-ray diffraction, Fourier-transform infrared spectroscopy and thermal analysis (TG/DTA) showed that CK oil shale exhibits a siliceous mineral matrix with a consistent organic matter rich in aliphatic chains. The pyrolysis behavior of kerogen revealed the presence of a single mass loss between 300 and 550 °C, estimated at 12.5% and attributed to the oil production stage. Non-isothermal kinetics was performed by determining the activation energy using the iterative isoconversional model-free methods and exhibits a constant value with E = 211.5 ± 4.7 kJ mol−1. The most probable kinetic model describing the kerogen pyrolysis mechanism was obtained using the Coats–Redfern and Arrhenius plot methods. The results showed a unique kinetic triplet confirming the nature of kerogen, predominantly type I and reinforcing the previously reported geochemical characteristics of the CK oil shale. Besides, the calculation of thermodynamic parameters (ΔH*, ΔS* and ΔG*) corresponding to the pyrolysis of type I kerogen revealed that the process is non-spontaneous, in agreement with DTA experiments.

Marina Lebedeva, Alexander Makeev, Alexey Rusakov et al.

Surface Kastanozem of the Lower Volga area was first studied as a part of the pedocomplex, with the lower part (148&#8315;160 cm) formed in Early Khvalynian Chocolate clays (13&#8315;15 ka), the middle part (100&#8315;148 cm) in a mixed clay-loess sediment sand, and the upper part (0&#8315;100 cm) in loess. This resulted from local aeolian transport, with the source material derived from the rewinding of marine sediments. They are enriched in aggregates of Chocolate clays and glauconitic grains of a fine sand-course silt size and have similar contents of clay minerals. The high salinity of similar types evidences marine genesis for both Chocolate clays and source material for loess sediments. Clay fragments of a sand and silt size are responsible for the heavy texture and high gypsum content of loess. The study of soils with the focus on micromorphology and clay mineralogy allows the identification of the complex character of a shift from marine to sub-areal sedimentation. This shift was accompanied by short breaks in sedimentation, allowing the development of synlithogenic soil horizons of Late Khvalynian, after-Khvanynian, and Boreal time. The features of shallowly buried soil horizons confirm increased aridity after the last deglaciation. Surface Calcic Kastanozem is a full Holocene soil reflecting the present environment. However, it is deeply influenced by shallow buried soil horizons and Chocolate clays.

Mustafa Can Canoğlu, Bedri KURTULUŞ

Bu çalışma, Savcıbey Göleti (Söğüt/Bilecik) eksen yerinin geçirimsizliğini sağlamak amacıyla yapılması planlanan enjeksiyon perdesinin boyutlandırılmasını kapsamaktadır. Arazi çalışmaları kapsamında mühendislik jeolojisi haritası yapılmış, araştırma sondajları açılmış ve bu araştırma sondajlarında geçirimlilik deneyleri gerçekleştirilmiştir. Arazi çalışmaları ile eksen yerindeki Triyas yaşlı Bozüyük Metamorfitleri’ne ait şistlerin içerdiği süreksizliklerin özellikleri ve geçirimliliğe olan etkisi, süreksizliklerin eksen yerine göre konumları göz önüne alınarak gözlemsel olarak belirlenmiştir. Süreksizlik konumları genel olarak K-G ile KKD-GGB arasında değişen doğrultulara sahiptir. Baraj ekseninde 5 adet, memba batardosu üzerinde 2 adet, çevirme tüneli güzergâhında 3 adet, dolusavak yerinde ise 2 adet olmak üzere toplam 245 m derinliğinde araştırma sondajları açılmıştır. Eksen yerindeki kayaçların geçirimliliğinin belirlenebilmesi ve enjeksiyon perdesinin boyutlandırılabilmesi amacıyla, Bozüyük Metamorfitleri’ne ait birimlerde Lugeon deneyleri, talvegdeki alüvyonlarda ve sağ yamaçta yüzeylenen yamaç molozunda ise düşen seviyeli geçirimlilik deneyleri gerçekleştirilmiştir. Lugeon deneyleri sonucunda Bozüyük Metamorfitleri’nin genel olarak geçirimli ve yer yer az geçirimli özellikte olduğu belirlenmiştir. Alüvyon ve yamaç molozu ise çok geçirimlidir. Ayrıca, eksen yerinde gerçekleştirilen sondaj çalışmaları, Triyas yaşlı Bozüyük Metamorfitlerinde ayrışma derecesinin artmasıyla geçirimliliğin de arttığını göstermiştir. Tüm çalışmaların sonucunda Savcıbey Göleti’nin geçirimliliği ile ilgili bilgiler toplanmış ve enjeksiyon perdesi boyutlandırılmıştır. Buna göre, 1.50 m’lik sıyırma kazısından itibaren ortalama 40 m derinliğinde oluşturulacak bir enjeksiyon perdesinin muhtemel kaçakları engelleyeceği öngörülmüştür.

X. Wu, X. Wu, X. Zhang et al.

Eberswalde Crater, a hotspot of Mars exploration, possesses an unambiguous hydrological system. However, little research has been performed on the large-scale mineral abundances retrieval in this region. Hence, we employed hyperspectral unmixing technology to quantitatively retrieve mineral abundances of the delta region in Eberswalde. In this paper, the single-scattering albedos were calculated by the Hapke bidirectional reflectance function from Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) data (FRT000060DD) and CRISM spectral library respectively, and a sparse unmixing algorithm was adopted to quantitatively retrieve mineral abundances. The abundance maps show that there are six kinds of minerals (pyroxene, olivine, plagioclase, siderite, diaspore, and tremolite). By comparing minerals spectra obtained from images with corresponding spectra in spectral library, we found the similar trend in both curves. Besides, the mineral abundance maps derived in this study agree well spatially with CRISM parameter maps. From the perspective of mineralogy, the instability of pyroxene and olivine indicates the area in which they distribute is close to provenance, and the original provenance is ultrabasic rock (e.g. peridotite) and basic rock (e.g. gabbro), respectively. And minerals, existing in the area of alluvial fan, also distribute in the outside of alluvial fan, which might be caused by fluid transportation.

Meng Li, Long-Yi Shao, Lei Liu et al.

Based on an extensive borehole survey of the Middle Jurassic coal-bearing sequences in the Saishiteng coalfield, northern Qaidam Basin (NQB), a total of 20 rock types and 5 sedimentary facies were identified, including braided river, meandering river, braided delta, meandering river delta, and lacustrine facies. The distribution of rock types and sedimentary facies contributed to the reconstruction of three periods' sedimentary facies maps of the Middle Jurassic in the Saishiteng coalfield, namely, the Dameigou age, the early Shimengou age and the late Shimengou age. That also provided the basis for the development of a three-stage depositional model of the Middle Jurassic in the NQB, indicating the lacustrine basin of the NQB in the Dameigou age and early Shimengou age were corresponding to an overfill basin, and that in the late Shimengou age was related to a balanced-fill basin. The analysis of the stability and structure of coal seams based on sedimentary facies maps showed that the preferred coal-forming facies in the Saishiteng coalfield were inter-delta bay and interdistributary bay of lower delta plain in the Dameigou age. In particular, the swamps that developed on the subaqueous palaeohigh favored the development of thick coal seams. Thus, minable coal seams may also be found along the Pingtai palaeohigh in the western part of the Saishiteng coalfield.

Daiane Aviz, Clara Ferreira de Mello, Patrícia Fernandes da Silva

Este estudo teve como objetivo caracterizar a macrofauna associada às galerias perfuradas por Neoteredo reynei em toras de Rhizophora mangle em uma área de manguezal do estuário do rio Mojuim (São Caetano de Odivelas, Pará). As coletas foram realizadas em três ocasiões do período menos chuvoso (junho, julho e agosto de 2004), na zona de médio-litoral em três sítios de amostragem. Em cada ocasião, foi retirada, de cada sítio, uma tora de R. mangle em estado inicial de decomposição. Paralelamente à coleta biológica, foram registrados a temperatura do ar, o pH, a salinidade e a temperatura da água. Neoteredo reynei foi a única espécie de Teredinidae presente nas amostras. A macrofauna associada às suas galerias foi composta por um total de 452 indivíduos, distribuídos em 31 táxons pertencentes aos filos: Nemertea (um táxon), Mollusca (três táxons), Annelida (seis táxons) e Arthropoda (21 táxons). A composição da fauna registrada foi tipicamente estuarina, com exceção de alguns grupos terrestres. Os descritores biológicos (abundância, riqueza, diversidade e equitatividade) aumentaram seus valores ao longo dos meses, como provável reflexo do aumento da salinidade no estuário. A diversidade da macrofauna registrada no interior das toras reflete a importância deste nicho para os organismos e, consequentemente, para o funcionamento do ecossistema manguezal.

Holger Stünitz

G. Giester