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The aim of this study is to examine how mineralogy influences the petrophysical properties, particularly porosity and permeability, of potential sandstone reservoirs in Colombia. It seeks to comprehensively understand how the presence of clay minerals impacts the overall quality of hydrocarbon reservoirs in the country. Samples of sandstones from reservoirs at various outcrops in the Eastern Cordillera and Middle Magdalena Valley basins were collected. Detailed analysis of mineralogy and petrographic characteristics of the samples was conducted through various analytical techniques such as transmitted light microscopy, X-ray diffraction, and scanning electron microscopy. Porosity and permeability were measured using automated permeametry and porosimetry equipment. The predominant composition of the analyzed reservoir rocks comprises quartz (45-50%), feldspar (35-40%), and clays (10-20%). These rocks were categorized into two distinct groups based on their permeability (K) and porosity (Φ), ranging from 0.009 to 29.220 mD and 1.88 to 20.75%, respectively. The presence of illite correlated with a reduction in both porosity and permeability, highlighting its negative impact on reservoir quality. Conversely, an elevated concentration of kaolinite was associated with favorable porosity and permeability. Samples with feldspar sericitization demonstrated inferior hydrocarbon storage quality. This study provides a deeper understanding of how mineralogy affects the petrophysical properties of sandstone reservoirs in Colombia. These findings are crucial for guiding exploration and production strategies in the Colombian oil industry, especially in challenging geological environments like those studied. [ABSTRACT FROM AUTHOR]

The Upper Cretaceous sedimentary mega-sequence of the Oriente Basin (Ecuador) is composed of the Hollín, Napo, and Tena formations, which have been extensively studied due to their economic interest in the oil industry. However, the limited information regarding the petrographic and geochemical characteristics of the source rocks of the Tena Formation in the central and southern Subandean zone has generated uncertainty in the regional geological evolution model, particularly in the Maastrichtian to Paleocene interval. The Anzu River section, northwest of Puyo, provides the opportunity to analyze the provenance of the Tena Formation, exhibiting its stratigraphic sequence fully and continuously. With the purpose of defining the detrital source of the Tena Formation, this research details the lithostratigraphy, petrography, geochemistry, and heavy mineral association in the Anzu River section. Petrographic analysis reveals that the sandstones of the Tena Formation are lithic feldspathic arenites, lithic arkoses, and sub-litharenites, originating from sedimentary sources rich in quartz, with igneous and metamorphic influence. The associations of heavy minerals and concentrations of major, trace, and rare earth elements indicate that these sandstones mainly come from recycled sedimentary provinces, with influence from acidic igneous and metamorphic provinces. These sources would be linked to Andean regions that exhumed and assimilated tectonic blocks or wedges from the Oriente Basin during the onset of the Andean orogeny in the late Upper Cretaceous and early Paleocene; the erosion of these blocks controlled the detritus available for the sedimentation of the Tena Formation in the study area. [ABSTRACT FROM AUTHOR]

The igneous rocks of Cerro Cacheuta are considered a typical expression of the Permian-Triassic magmatism within the Andes Precordillera of Mendoza, Argentina. In particular, the southwestern margin of this hilltop is characterised by intermediate volcanic and felsic intrusives from the Choiyoi Group, one of the most extensive volcano-sedimentary suites of southern South America. The Choiyoi magmatism is widely associated with dramatic tectonic and environmental changes in the Gondwana supercontinent. Therefore, a better characterisation of the igneous facies of Cerro Cacheuta is critical to understand the evolution of Gondwana and recognise the multiple events that occurred towards the end of the Permian. This paper presents new data about the mineralogy, petrography, and geochemistry of the plutonic and volcanic units of Cerro Cacheuta, which enables authors to draw additional conclusions about the genesis and evolution of the magmatism in the region. Microscope observations indicate that the volcanic rocks are largely consistent with intermediate facies dominated by a porphyry texture with plagioclase and sanidine phenocrystals within a trachytic groundmass. Coetaneous breccias of possible hydrothermal origin and geodes with cryptocrystalline silica, limonite, and quartz are also recognised in outcrops. Geochemical analysis suggests that the lavas would likely correspond to andesites from a calc-alkaline magmatic arc. Furthermore, trace elements show enrichment in LREE/HREE, a slight negative anomaly in Eu, and concentration ratios compatible with crustal extension during the initial stages of the Choiyoi Group. Based on their chemical similarities, the monzonites of the Boca del Río Pluton would correlate with the lower section of the Choiyoi Group, of Permian age. In contrast, granites of the Cacheuta Pluton show a signature typically recognised in units from the Triassic and, therefore, would be comparable to the upper member of the Choiyoi Group. [ABSTRACT FROM AUTHOR]

Due to the growing global concern about the high rates of environmental pollution and global warming as a result of human activities, restrictions have begun to be generated for the use of fossil fuels, including coal. Colombia, being a country rich in this mineral resource, needs to evaluate its potential use in other fields and to know in detail the possible environmental implications associated with its chemical composition. Currently, the Colombian Geological Service has been developing various projects aimed at this purpose. This work presents the geological, physicochemical and petrographic characterization of the thermal coals of Norte de Santander, emphasizing the composition of elements of environmental interest. 87 coal samples were taken from mine fronts in the municipalities of Arboledas, Salazar, San Cayetano, Sardinata, Toledo and Tibú in the department of Norte de Santander. The samples were prepared and the following analyzes were carried out: equilibrium humidity, proximate analysis, determination of carbon, hydrogen and nitrogen, total sulfur, forms of sulfur, calorific value, swelling index (FSI), grinding index (HGI), mercury, major, minor and trace elements and average reflectance of vitrinite. The coal seams, taking into account their classification according to the average reflectance values of the vitrinite, correspond to low and medium range coals that correspond to subbituminous and bituminous, which indicates that they are not coals with high thermal maturity. [ABSTRACT FROM AUTHOR]

The La Quinta Formation is located on the western margin of the Perija Mountain Rage, Colombia, consisting of a volcanic)sedimentary sequence, which in recent years has increased the petrogenetic and economic interest due to the copper mineralizations it hosts. This research aims to mineralogically and petrographically characterize the volcanic rocks of the La Quinta Formation outcropping in the municipalities of San Diego, La Paz and Villanueva, with the purpose of evidencing the crystalline phases and petrogenetic processes that gave rise to these rocks. As a result, volcanic rocks of La Quinta were identified, ranging from basalts to rhyolites, andesite, quartzolatite and dacites, with mainly porphyritic textures. It is concluded that its mineralogy and porphyritic textures indicate a thermal contrast during the crystallization of the rock; its mineralogy constituted by olivines and oxidized pyroxenes facilitate the generation of iddingsite, magnetite, corrosion structures and fractures, due to alterations by hydrothermal fluids in conditions of low pressures and temperatures; vesicular textures and the presence of spherulites indicate degassing and devitrification processes that are generally attributed to the expansion of volatiles in a hydrated magma and partial dissolution of quartz during the ascent of the magmatic fluid to the surface. [ABSTRACT FROM AUTHOR]

On the Colombian Pacific coast there is a complex of islands and islets with an approximate height of 90 to 338 meters above sea level (masl), declared a World Heritage Site by UNESCO, forged by various geotectonic processes between the Pacific oceanic plates. (current Nazca) and South American; made up of sedimentary, volcanosedimentary and igneous rocks. This research aims to analyze the petrography and diagenesis of the heterolithic clastic sequence associated with the Cretaceous-Paleogene boundary of Gorgonilla Island: a contribution to the geological knowledge of the Colombian Pacific. Leading to the conclusion that the petrography reflects a compositional variation, bimodal behaviors, high affinity with the basement rocks of the island, processes of changes in the source and reworking within the basin. The ease of optical recognition of the constituents that make up these rocks indicate a low degree of alteration, no significant postdepositional changes and early diagenetic processes. [ABSTRACT FROM AUTHOR]

The present study aims to investigate petrography characteristics and sedimental environments of upper Olenekian-middle Anisian deposits of Nakhlak group in the sedimentary-structural zone of central Iran. To this end, a section of these deposits with a thickness of 720 meters was first selected, and 190 samples were taken from this section for preparing thin sections. Also, quantitative and qualitative laboratory tests were performed and 25 samples of sandstone were selected for point counter analysis. The results indicated that the major deposits of this formation are related to siliciclastic, carbonate, and pyroclastic types, which are in the form of two facies associations. The facies association A at the bottom of the studied section with the thickness of 90 meters has a periodicity of clastic, carbonate, and pyroclastic facies. The clastic facies of this association consists of fine-grained sandstone. In addition, the carbonate facies in association A are characterized by two microfacies consisting of intraclast oolitic grainstone and oolitic grainstone. Further, tuffite is the only pyroclastic facies related to association A, which has a laminate structure, cross-bedding lamination, herringbone bedding, and upward-thinning and thickening cycles. The facies association, B which is deposited later, is more in the middle and top part of the section. The facies association B is 660 meters thick and has a periodicity of clastic and limestone facies. Clastic facies of this association includes four lithofacies such as conglomerate, pebble coarsegrained sandstone, medium-grained sandstone to thin layer siltstone and shale. The carbonate facies consists of four microfacies such as sandy intraclastic wackestone and mudstone. Furthermore, slumping structures, cross bedding, turbulence, boudinage structure, and convolute of sediments, along with the effects of erosional channels are observed in facies B. Field and laboratory studies conducted on this succession indicate the structure of facies association A was deposited in a mixed siliciclastic carbonate ramp. Finally, submarine canyons and submarine fan environments were left by increasing the depth of the facies association B in the deep part of sea and turbidity systems. [ABSTRACT FROM AUTHOR]

The petrographic characterization of ophiolitic sequence and metamorphized rocks of Calentura Arriba sector in Moa municipality, constitutes a contribution to the updating of the geological map of the southwestern part of cartographic sheet 5277-IV "Moa". Thin sections of those rocks were analyzed using a polarized light microscope. The ore paragenesis composed of enstatites + augite + labradorite + olivine + chlorite + garnierite + actinolite + tremolite + ilmenite + magnetite + sericite + saussurite in the metagabbro sequence was identified as well as the mineral paragenesis composed of olivine + orthopyroxenes + bastite + lizardite + chrysotile + actinolite + tremolite + antigorite + serpophite + chromite + magnetite in the serpentinite sequence. This sector was subjected to strong transformation processes reflected in the intense alterations that denote the occurrence of low-grade to high-grade metamorphism, matching with the Barrowian facies series. The metamorphic transformations are closely related to the activity of the Moa Fault and denote a regional character, extending at both ends of this fracture. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Introduction--In the La Tomita sector, municipality of Manaure (Cesar), outcrop a stratigraphic sequence of biomicrite limestones, biopelmicrites, pelmicrites, wackestones and packstones intercalated with shales, corresponding to the Lagunita Formation of the Cogollo Group. Objective--To know the stratigraphic aspects, mineralogical composition and paleoenvironmental conditions of the outcropping limestones. Methodology--It proceeded with a lithostratigraphic description in the massif and taking samples in situ, twelve samples were extracted, of which seven were taken for petrographic analysis. Results--Wackestone facies with pelagic microfossils, bioclastic packstone, wackestone with worn mollusc bioclasts and wackestone with peloids were recognized. Petrographically, the limestones in this sector are made up of zircon, glauconite, sparite, micrite, pellets, planktonic foraminifera of the genus Heterohelix, of the Moremani species, and foraminifera of the genus Hedbergella and Trocoidea species. Bivalve fossils and some algae were also observed. Conclusions--These facies allowed establishing that these limestones were formed in an environment of medium platform with some external platform intervals, covering an area of facies of open sea. [ABSTRACT FROM AUTHOR]

A fragmentarily preserved Byzantine icon made of steatite was discovered in 2015 during regular excavations in Chełm, eastern Poland. Identified as the left wing of a diptych illustrating the Twelve Great Feasts and created at the close of the 12th century, the find is one of the most important and beautiful Byzantine artefacts to have been found in Poland. The icon was uncovered within the confines of the palace complex which was created by Daniel (Danylo) Romanovych († 1264) in Chełm in the second quarter of 13th century. The icon, even though it was found within the borders of what is now Poland, is material evidence of contact between Byzantium and the social elite of the Galicia-Volhynia lands, rather than with the Polish Piasts.In this paper we concentrated on the presentation of the archaeological context of the find, which made it possible to establish that the icon arrived Chełm before the middle of the 13th century (terminus ante quem 1253), and especially on petrographic and traceological analyses of the icon.Assuming that greenish plaques were indeed the most characteristic steatite icon type, a decision was made to examine, apart from the Chełm artefact made from white rock, a greenish icon from the National Museum in Krakow as well.Petrographic analyses were based on optical microscopy, scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) and X-ray powder diffraction (XRPD). Both icons were carved in steatite i. e. talc rich rock but their chemical compositions indicate the presence of other components. Artifact from Chełm is white. Porous, enriched in potassium (K) and locally blistering outer rim of the icon from Chełm was formed probably during the fire event. Presence of forsterite and subordinate amount of leucite also indicate high temperature influence. Local enrichment in calcium (Ca) is related to exchange reactions with ground compounds. Accumulation of different components on the surface of the icon's surface was noted. The icon from the National Museum in Krakow is greenish probably because of the presence of chlorite.The results of the traceological analysis (icon from National Museum in Krakow was not analysed) indicate that the icon found in Chełm was created most likely by a skilled and experienced carver with access to the high-quality magnifying glass and specialist tools required for rendering minuscule objects and their details. The production of the icon also involved the use of a "mechanical" tool, probably a kind of a miller with a rotating polishing head, which also seems to point to a specialist workshop. The use-wear traces observed on artefact are limited to polish resulting from prolonged contact with human hands or storing the icon in a leather case.Most of the extant Byzantine icons are unprovenanced objects held in museum collections or church treasuries. Therefore, as the icon presented in this paper was discovered during archaeological excavations, it ranks among the few Byzantine artefacts to have been found outside of this realm. The petrographic and traceological analyses conducted are the first published natural science contributions to the study of Byzantine steatite icons and we hope they will provide the impetus for undertaking such research on other Byzantine finds, helping to develop Byzantine archaeology further. [ABSTRACT FROM AUTHOR]

The chaîne opératoire of Neolithic Korenovo ceramics is poorly known, as hitherto potsherds from only three sites, Malo Korenovo, Tomašica in central Croatia, and Becsehely–Bukkaljai dűlő in Hungary have been analysed archaeometrically. Korenovo is considered the southernmost aspect of the Linearbandkeramik (LBK). In this paper, the ceramic assemblage from Kapelica-Solarevac and Kaniška Iva (Central Croatia) will be discussed. Kapelica-Solarevac and Kaniška Iva are the only two sites in which Starčevo and Korenovo ceramics have been found together in closed contexts. Twenty potsherds from the Kapelica-Solarevac and Kaniška Iva assemblages were analysed using polarised microscopy and scanning electron microscopy with energy dispersive spectrometry (SEM-EDX). In combination with equivalent data from 49 Korenovo ceramics from Tomašica and Malo Korenovo, the results offer an insight into the practices of Korenovo potters and show the lack of exchange of technological knowledge between Korenovo and LBK potters in Austria and central Transdanubia (Hungary). On the other hand, Korenovo potters seem to closely follow ceramic recipes typical of the neighbouring Vinča potters, suggesting Korenovo to be a hybrid group between the Vinča and the LBK pottery communities. [ABSTRACT FROM AUTHOR]

The goal of this research is to understand pottery production in the Alamito sites (northwestern Argentina), inhabited during the first centuries AD. To know this craft production is to enter into the social dynamics of these human groups characterized by a particular way of building, distributing in the landscape and abandoning their dwellings. 55 sherds representative of the stylistic-morphological variability of the sample under study were selected and their fabrics were assessed using petrographic analysis. The methodology used includes the study of the clay matrix, classification of inclusions (type, size and shapes) and description of cavities. The regularities and singularities observed in this data allowed to detect six classes of fabric, which were compared with fabric recipes from nearby areas. Thus, this paper analyzed the relationships between the Alamito pottery and other ceramic productions of northwestern Argentina during the Formative Period. [ABSTRACT FROM AUTHOR]

This paper analyzes a selection of handmade pots whose petrographic characterization reveals an exogenous origin with respect to the settlements in which they were found. This situation opens up different questions regarding the mobility of this type of ceramic container in the Iberian Southeast during the Early Iron Age, as well as expanding the possibilities of these wares traditionally linked to local production and domestic spaces. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

During the prehispanic late occupations (ca. 1000-1500 AD), the Peña del Medio (Paicuqui, microregion of Antofagasta de la Sierra, Province of Catamarca), had a strong ritual connotation linked to astronomical observations and cult of the ancestors and, related to micro and macrorregional interaction practices. This paper presents the results obtained from stylistic and petrographic studies of the ceramics recovered on the place. An important stylistic variability in the vessels, their elaboration with allochthonous raw materials and the predominance of suitable forms for food consumption is detected. Ceramic similarities of the Antofalla region and of different sectors of the Calchaquíes valleys are recognized. It is concluded that the ceramic set is consistent with the interpretation of Paicuqui as a meeting place and interaction mediated by ritual practices. [ABSTRACT FROM AUTHOR]

There are several organic matter-rich shale geologic formations in Mexico that could be considered non-conventional potential oil reservoirs; one of those formations is the Eagle Ford Formation (Late Cenomanian - Turonian), aim of this study. The Eagle Ford Formation is located within the Sabinas paleobasin and along the Burros-Peyote paleoplatform, in the Coahuila State. This formation has been previously described as a transgression system deposited in a shallow marine environment with a total organic carbon between 0.5 to 8% with type II organic matter. For these reasons, it could be considered a potential source for non-conventional hydrocarbons. Therefore, it is considered that a reservoir of shale gas must have certain requirements, such as: 1) high total organic carbon (> 2% of COT), 2) presence of types II and III kerogen, 3) vitrinite reflectance values greater than 1.2% Ro (0.7% for shale oil), 4) thickness greater than 30 m and large extension, 5) fracturability (<40% clays or absence of expandable clays) or the presence of a microcracking system, 6) overpressure, 7) adequate depth, 8) heterogeneity, and others. A systematic sampling was carried on outcrops of Coahuila State with the goal to determine the thermal maturity degree of the Eagle Ford Formation using a detailed stratigraphic analysis of three columns (CSI, CSII and CSV) and micro-thermometric of fluid inclusions. Our results indicate that the Eagle Ford Formation is a sedimentary sequence rich in organic matter, locally composed of carbonaceous carbonate shale in laminar stratification alternating with shaly limestone (mudstone- wackestone) and clastic o bioclastic limestone (packstone-grainstone). Regarding the diagenetic alteration, primary porosity is affected by compaction and cementation processes. However, it was also observed a secondary micro-porosity development due to neomorphism, dolomitization, fracturing and stylolitization processes. Measured homogenization temperatures (Th) in fluid inclusions are between 65 °C and 125 °C, reaching the temperature window to generate oil and humid gas. The thermal evolution through its facies changes in the basin is not homogeneous. Our results indicate that the Eagle Ford Formation is a sedimentary sequence rich in organic matter, locally composed of carbonaceous carbonate shale in laminar stratification alternating with shaly limestone (mudstone- wackestone) and clastic o bioclastic limestone (packstone-grainstone). [ABSTRACT FROM AUTHOR]

The article presents the analysis of the correlation between the self-ignition parameters and the ultimate and proximate analysis, as well as the petrographic properties of Polish lignite, sub-bituminous coal, bituminous coal and anthracite. The following coal properties were determined: the moisture, ash content, volatile matter and sulfur content, gross calorific value, net calorific value, C, O, N and H contents, total porosity, ash oxide composition, rates of spontaneous combustion in 237°C and 190°C, and activation energy. During the petrographic analysis, maceral composition and random reflectance were determined. To determine the linear correlation between the self-ignition parameters and the analyzed coal properties, the Pearson correlation coefficient was calculated. The results show that there is no strong linear correlation between the lignite tendency to self-ignition and its petrographic properties. However, a strong negative correlation between the rate of spontaneous combustion and moisture and volatile matter content was observed. In the case of bituminous coal, strong correlations between self-combustion parameters and various coal properties were confirmed. The most noteworthy are the correlations between self-ignition parameters and the maceral composition, that is, between the content of macerals of the inertinite group in coal and content of macerals of the huminite/vitrinite group. The obtained results suggest that the spontaneous combustion tendency of coal increases with the increasing content of semifusinite and liptinite. [ABSTRACT FROM AUTHOR]

The rocks of interest in the present study (mudstones) show inherently a heterogeneous pore-size distribution in the matrix. They can present organic and inorganic pores and the transport mechanism through pores is different, and, therefore, it is necessary to describe their organic and inorganic porosity. This work uses different microscopy techniques to characterize mudstones from the Galembo Member of the Cretaceous La Luna Formation, Middle Magdalena Valley Basin, Colombia. These rocks present several pore types, including interparticle pores due to flocculation of clay minerals, organoporosity due to burial and thermal maturity, intraparticle pores from organisms, intraparticle pores within mineral grains, and microchannels and microfractures. The existence of interconnected pores in such complex fracture-pore system provides effective pathways for primary gas migration and it also provides a storage space for the residual hydrocarbon in mudstones, which is important for the primary migration and storage in gas reservoir rocks. The pore connectivity is high and increases towards the top of the sedimentary sequence. [ABSTRACT FROM AUTHOR]

The Choiyoi Group from the Permo-Triassic, is one of the most conspicuous volcano-sedimentary suites of southern South America, considered critical to understand the geological evolution of the western margins of Gondwana. In this regard, petrography, geochemistry, and structural data were examined to better elucidate the physical character and emplacement conditions of the unit in the Cordón del Plata range, within the Frontal Cordillera of Mendoza, Argentina. The site is representative of the magmatism and deformation through different Andean cycles. Results of the study indicate three facies of increasing felsic composition upwards. Mafic units consist of basalts, andesite and andesitic breccias at the base of the sequence. Felsic rocks such as rhyodacites, granites and welded tuffs are predominant above. The fault zone of La Polcura -- La Manga is the most prominent structural feature in the region, which presumably controlled the emplacement of breccias and ignimbrites within the middle and upper members. These compositional variations suggest a magma evolution from subduction to a rifting environment after the San Rafael orogeny in the Late Palaeozoic. In this line, the Lower Choiyoi was observed to overlie the San Rafael structures indicating thus, that compression ceased before the volcanic extrusion. Geochemistry data indicate that mafic rocks are mostly high-potassium, calc-alkaline volcanics derived from the mantle wedge above the subduction zone. In contrast, the Upper Choiyoi corresponds to high-potassium rhyolites to shoshonites, typically depleted in Eu. This indicates partial melting of a lithospheric mantle in an average to thin crust. [ABSTRACT FROM AUTHOR]

In this article we present the results obtained from the macro and microscopic analysis of the pottery assemblies of four sites located in the Copacabana river basin (Ischilín, Córdoba, Argentina). The purpose of this study is to investigate the different ways of manufacturing ceramics. Firstly, a typology was elaborated, and then the variability of the identified groups was tested trough the implementation of petrographic techniques. Based on these first analyzes, four petrographic groups were identified which indicate a difference in the addition of antiplastic in ceramic pastes and, therefore, different ways of making pottery are inferred. [ABSTRACT FROM AUTHOR]

We present the results about the last researches carried out on ceramic fabrics of Las Garzas, an Early site (600 a.C.-650 d.C.) located in the Lerma Valley (Province of Salta, Argentina). This approach implied a revision of previous studies initiated by Cremonte (Cremonte et al., 1987), which allowed us to adjust the petrography of the ceramic pastes, expanding the analyzed sample and completing the previous analyzes incorporating different recording procedures. Data obtained in relation to the local geology allowed us to hypothesize about foreign or in situ production of the vessels represented in the studied sample. Likewise, comparisons with other pottery groups from the Lerma Valley and more distant pottery traditions such as Tafí and San Francisco valleys, allowed us to evaluate links in the manufacturing techniques that contribute to our knowledge about early pottery technological traditions in Northwestern Argentina. [ABSTRACT FROM AUTHOR]

During the first millennium B.C. finely decorated Cupisnique Rojo Grafitado bottles appeared in small numbers on different sites of north-central Peru. Petrographic and portable digital microscopy of the paste, chemical analysis of the pigments, and stylistic studies point to a production in the hands of specialized potters sharing similar paste recipes and technology of manufacture, but not resources, and working independently in different workshops. Mineral composition and granulometry are similar for vessels found on different sites, pointing to the use of crush rock temper or sediments rich in intrusive rock fragments probably derived from outcrops in the northern coastal batholith. Shiny black designs over a highly polished red slipped surface gave the name to the style but recent analysis showed that not all designs were done with graphite. Scanning Electron Microscopy (SEM-EDS) analysis revealed that, at least in one case, the black pigment used for surface decoration was manganese, while in seven other cases high C peaks, low Fe peaks, and no Mn were detected. For these wares, this suggests surface carbonization in reduced conditions. In Kuntur Wasi, the Cupisnique Grafitado style was imitated on other forms and style variants. [ABSTRACT FROM AUTHOR]

From an archaeological perspective, the practice of pottery making can be studied from different theoretical and analytical perspectives on the stages of pottery production. In this paper, we present the results obtained through technological analysis of prehispanic pottery from the Costa de Reyes N° 5 archaeological site (Tinogasta, Catamarca). The main goal of this analysis is to explore the pottery-making practices developed by ancient potters during the Late Period and through the arrival of Incas at the southern sector of Abaucán Valley. Our methodology consisted of the reconstruction of typical ceramic forms, the use of a stereoscopic microscope to study fresh transversal cuts, and thin-section analyses by ceramic petrography, carried out on pottery samples recovered from both surface collection and excavations in two structures at Costa de Reyes N° 5. Through this approach, we are able to explore and visualize continuities and ruptures in both the pottery-making practices and paste recipes during the Late Period (ca. 900-1450 aC), and how pottery-making was reconfigured when the Inca (ca. 1480-1532 aC) arrived in the region. While pottery production during the Late Period is characterized by technological variability and heterogeneous ceramic pastes, during Inca times there was a homogenization of the recipes used by ancient potters. This is interpreted as a strict control of both the raw materials available and over the pottery production as a whole. [ABSTRACT FROM AUTHOR]

This paper presents the petrographic analysis of ceramic pastes from Formative archaeological sites (700 BC-1000 AD) in Quebrada del Toro (Salta, Argentina). The results allow us to define the presence of fifteen modes of ceramic paste, some of which persist throughout the entire period. The vast majority of the analyzed sherds were of local origin, while others refer to modalities that are characteristic of the pottery from different sectors of the southern Andean area, such as the San Francisco Valley (Jujuy) and San Pedro de Atacama (Chile). [ABSTRACT FROM AUTHOR]

Bituminous coal samples were collected from mine excavations of six mines in the Upper Silesian Coal Basin. In the mentioned mining excavations, the stratighaphic sections, in the form of spot samples, were measured. Based on the macroscopic and microscopic observation, an attempt was made to determine the different lithotypes of coal. Vitrain coal is made of tellinite and collotelinite; the thickness of the layers varies from very thin, thin, medium, to coarse. Durain, which is dominated by macerals from the vitrinite group, is characterized by a darker, almost black color, genetically linked to heavily flooded peat areas, where the deposited phytogenic material is subjected to humification and gelification processes. A brighter durain, with a dark gray color, is dominated by macerals from the inertinite group that originated in the shallower areas of peat bogs where the water level was periodically lowered, which has led to the oxidation of the material deposited in the peat bog. Fusain is another coal component or constituent; it is produced as a result of peat bog fires. It is a charred (not burned) material deposited in the form of layers, lenses, usually with a thickness of up to several millimeters (or, less commonly, several centimeters), or dispersed in the form of shreds in the durain. The petrographic composition is dominated by fusinite and inertodetrinite. Fusain occurs in two varieties: soft (empty cellular spaces) and hard, usually mineralized with carbonates (siderite) or sulphides (pyrite, marcasite). The structure of bituminous coal is, due to its origin, most often laminated and consists of alternating dull and bright layers. Occasionally, such layering can be observed in bright coal, which is the result of layering of large parts of gelified plant materials. When it comes to larger sections of dull coal (without bright coal) in the profile, a solid structure can be observed. Some of the sections in the coal seam profiles show a distorted structure; warped, sometimes shredded layers of vitrain in durain, often containing lenses or shreds of fusain, can be observed. [ABSTRACT FROM AUTHOR]

This work addresses the issue of ceramic production during the Late Period in the ravine of Las Pitas River (Antofagasta de la Sierra micro region). From this perspective, stylistic, petrographic and chemical information are integrated. Items of local and nonlocal pottery are identified and their production patterns are characterized. Therefore, this information is supplemented with the raw materials sampled in the region and compared with compositional data of vessels and gredas of El Bolsón Valley (Belén Department), a section of the Sierra Valley of Northwest of Argentina (NOA) that shows evidence of relationships with the area of Antofagasta for this Period. Results are problematized in relation to different ways of interaction that coexisted in this zone, and it is concluded that local pottery was produced combining knowledge resulting from various regions. [ABSTRACT FROM AUTHOR]

Due to dynamic climatic changes resulting, among others, from the use of coal, the content of harmful substances in coal is of particular importance. Dangerous air pollution resulting from the burning of coal (e.g. As, S e, Hg, Pb, S b) is often associated with sulfide minerals in coal. The study focused on the sulphides occurring in Polish hard coal deposits. S ulfides are one of the forms of occurrence of sulfur in coal. I n this paper, an emphasis has been placed on on the characteristics of forms of occurrence of sulphides on both macroscopic and microscopic scale and on the chemical analysis in the micro area. The study has been conducted for the No. 301-308 seams from the eastern part of the Upper S ilesian C oal Basin, stratigraphically belonging to the highest part of the Orzesze Beds s.s. (Westphalian B). The coal samples have been collected from the coal seams in the underground excavations of the following coal mines: Jan Kanty, S obieski Jaworzno III, Wesoła and Z iemowit hard coal mine. Iron sulfides (pyrite, marcasite) in coal seams of the Orzesze Beds s.s. form various forms of macroscopically visible aggregates. These include massive, vein, pocket-like (impregnation) or dispersed forms. On the basis of microscopic observations, the following forms of occurence of iron sulphides in the tested coal have been determined: skeletal and massive vein forms, massive pocket-like (impregnation) forms, framboidal pyrite and euhedral crystals. The most common form of sulfides in the studied coal seams are vein forms cutting across bedding, usually creating complex dendritic and skeletal forms. I ron sulfides often occur in pocket-like (impregnation) forms, not directly linked with vein forms and fusinite. The WDS analysis in the micro area has revealed the chemical composition of sulfides in eight coal samples. As follows from the analysis, the tested coal seams are dominated by FeS2 iron sulfides. I t has been shown that the iron sulfides contained small admixtures of Pb, Hg, Z n, Cu, Ag, C o S b and Ni. The admixtures of As and C d have been observed only in individual minerals. Lead, reaching up to 1.06%, has the highest concentration out of all admixtures in pyrite and marcasite. S mall amounts of galena, titanium oxides (rutile), monazite and barite have also been found in the tested coal samples. L ocally, vein forms, pyrite and dolomite were interlaying each other; the same applies to pyrite and apatite. I n addition, dolomite fills part of the cells in fusinite. [ABSTRACT FROM AUTHOR]

W-Mo skarns deposits in the Borborema Province have been known since the 40's, however, until this study there were no records of Fe-Cu skarns. In Ceará State, Brazil, the first occurrences of Fe-Cu skarns were identified recently in the Magmatic Arc of Santa Quiteria, product of superposition of several magmatic arcs, ranging from juvenile arc (870 - 800 Ma), up to continental collision (625 - 600 Ma). The skarns are associated with calc-silicate rocks and dolomitic and/or calcitic marbles, cut by Neoproterozoic, early to tardi-collisional quartz monzonite. In the area several skarn system types are found such as endoskarns, hornfels, skarnoids and exoskarns. The exoskarns show two mineral assemblages, reflecting different carbonate protolith: the first consists of clinopyroxene-garnet (prograde stage) and magnetite-pyrrhotite-chalcopyrite-pyrite-biotite (retrograde stage), characteristic of calcitic protolith, and the second, consists of olivine-spinel-diopside in prograde phase and serpentine in retrograde phase, representative of dolomitic protolith. Garnets partly zoned exhibit composition dominated by andradite (82 - 52 mol%) with subordinate grossularite (16 - 45 mol%) and minor pyrope (2 - 3 mol%). The pyroxene of the marble calcitic protolith is typical of the diopside-hedenbergite series, with average composition Diopside- 46Hedenbergite52Johannsenite2. Three types of iron-dominated skarn related ores are distinguished: i) banded magnetite; ii) disseminated magnetite; iii) vein massive magnetite. Takes place also a sulphide copper ore with and without associated magnetite and gossans blocks. The geological and metallogenic data obtained indicate that the genesis of these skarns are associated with the influence of monzonitic Brasilian granites and although there are two types of skarn, there is a predominance of Fe-Cu Skarn. [ABSTRACT FROM AUTHOR]

Niespalona substancja organiczna w popiołach lotnych występuje najczęściej w formie ziaren masywnych lub porowatych, niekiedy przyjmujących postać cenosfer. W badanych popiołach lotnych ze spalania węgli brunatnych i kamiennych pochodzących z elektrowni cieplnych stwierdzono występowanie mikrocząstek należących do następujących grup: glinokrzemiany (kwarc, mulit), tlenki żelaza, węglany oraz niespalona substancja organiczna. Substancja organiczna w badanych próbkach występuje w ilości 3,6-9,5%. Cząstki węglowe wykazują duże zróżnicowanie zarówno pod względem wielkości jak i morfologii. Ich wielkość waha się w przedziale od kilku μm do około 1 mm. Można wyróżnić kilka form ich występowania. Są to formy sferyczne porowate cienkościenne i grubościenne. Ponadto niespalona substancja organiczna tworzy nieregularne ziarna porowate, których ścianki są o zmiennej grubości. W badanych próbkach występuje również substancja organiczna inertynitowa w formie fuzynitu wykazującego strukturę komórkową lub niekiedy są to formy masywne lub zwarte. Częstą formą występowania substancji organicznej w badanych popiołach lotnych są cząstki detrytyczne o wymiarach poniżej 10 μm. Występują również cząstki węglowe zawierające domieszki mineralne. W przypadku, gdy ilość substancji mineralnej przekracza 50%, cząstki te klasyfikowane są jako mineralne. W celach dokumentacyjnych oraz do określenia porowatości wykonano zdjęcia mikroskopowe obserwowanych cząstek węglowych. Porowatość określono stosując komputerową analizę obrazu poprzez binaryzację i progowanie odcieni szarości. Dla struktur porowatych obliczono współczynnik porowatości jako iloraz wartości powierzchni zajmowanej przez pory do powierzchni substancji węglowej, w obrębie której występują pory. Wielkość ta jest największa dla ziaren cienkościennych o kształcie nieregularnym oraz cenosfer i osiąga wartości powyżej 80%, maksymalnie 87%. Współczynnik porowatości dla cząstek o podobnym kształcie ale grubościennych osiąga wartości od powyżej 50 do 79%, co jest pomierzoną wartością maksymalną. Dla struktur typu fusinoid/solid porowatość wynosi od kilku do 80%. Unburned organic matter in the fly ash occurs most commonly in the form of solid or porous grains. It has been shown that tested fly ash resulting from the combustion of lignite and hard coal from pulverized boilers contained microparticles belonging to the following groups: aluminosilicates (quartz, mullite), iron oxides, carbonates, and unburned organic matter. The organic matter content in the tested samples is in the range of 3.6-9.5%. Coal particles show a large variation in terms of size and morphology. Their size ranges from a few micrometers to about 1 mm. Several forms of their occurrence can be distinguished. These include: porous, thin and thick-walled spherical forms. In addition, unburned carbonaceous substance creates irregular porous grains with walls of variable thickness. What is more, the tested samples contain macerals from the inertinite group in the form of fusinite showing cellular structure; sometimes these include massive or dense forms. The organic matter in the tested fly ash usually occurs in the form of detrital particles with dimensions below 10 micrometers. There are also coal particles containing mineral admixtures. If the mineral matter content exceeds 50%, the particles are classified as minerals. The microscopic pictures of the tested coal particles were made for documentation purposes and to determine the porosity. The porosity was determined with the use of computerized image analysis using binarization and thresholding a grayscale. The void ratio for porous structures was calculated as the ratio of the area occupied by pores to the surface of the carbonaceous material containing pores. This ratio is the largest for the thin-walled grains of irregular shape and cenospheres, reaching values above 80%, maximally up to 87%. The porosity ratio for particles of similar shape but thick-walled ranges from above 50% to 79% which is the maximum value measured. In the case of fusinoid/solid structures, the porosity ranges from several to 80%. [ABSTRACT FROM AUTHOR]

The petrologic analyses of 40 thin sections from two wells located in Atalaia High, offshore of Sergipe Sub-Basin, allowed the identification of primary composition and diagenetic patterns of Barra de Itiúba Formation. The original detrital compositions included arkoses, sublithic, and lithic sandstones. The main diagenetic processes observed were: compaction of metamorphic rock fragments and mud intraclasts, generating pseudomatrix; precipitation of quartz and feldspar overgrowths and outgrowths, cementation and grain replacement by kaolinite; dolomite and ferrous dolomite/ankerite; pyrite; iron oxides and hydroxides; and diagenetic titanium minerals, in addition to dissolution phases during eo-, meso- and telogenesis. The macroporosity in the two studied wells is primary intergranular, but there is secondary porosity due to dissolution of primary and diagenetic constituents, as well as fracture porosity. Thirteen reservoir petrofacies were defined and grouped into four reservoir petrofacies associations. They reflect the reservoir quality in microscale: good, medium and low-quality and non-reservoir. The good-quality is characterized by average total porosity greater than 15%, whereas the medium shows average total porosity greater than 7%. Lowquality presents average total porosity between 1 and 4%, and the non-reservoir has an average total porosity consistently less than 1%. Overall, the studied reservoirs consist on low-quality and non-reservoir rocks, which are intercalated with levels of medium and good-quality. The loss of original porosity was mainly due to mechanical compaction (generating pseudomatrix), and cementation by kaolinite and dolomite. Preservation of primary porosity was favored by the presence of quartz overgrowths. [ABSTRACT FROM AUTHOR]

The study of rocks has become more important, because through the rocks analysis I can be obtained information that can be useful in a lot of fields from mining to construction, passing through many different action fields from materials to processes. In order to analyze the rocks is required a preliminary macroscopic examination of several samples from the field in which one is going to work. The objective of this study is to describe properties such as color, hardness, texture, etc. Then we proceed to do a microscopic analysis, for that we use thin sections that have been prepared in advance from the samples that were used in the initial macroscopic examination, in order to know more properties that can only be seen with a microscope. From this analysis of the optical properties of minerals and mineral associations we can define the type of rock, the formation environments and the behavior of these, among other properties that are outstanding when carrying out a work in a field. [ABSTRACT FROM AUTHOR]

On the hill in the municipality of La Paz, César, outcrop stratigraphic sequences of sedimentary carbonate rocks interbedded with thin shales and calcite veinlets belonging to the Cogollo group. In order to know the mineralogical composition of the outcropping limestone, paleoenvironmental conditions and industrial use, we proceeded to a study of surface geology, consisting of lithostratigraphic description of the exposed rocks, apiques and sampling site in a total of 6 samples (LP-1 LP-2 LP- 3 LP-4 LP-5, LP-6) along the hill, which were taken 4 to go forward for studies, two of this 4 sample were selected for petrographic analysis practiced in laboratories petrographic analysis and the remaining two for X-ray diffraction. The results of the studies allowed to establish that the hill were formed from two marine environments, one neritic and the other bathyal, thus giving rise to biomicriticas limestone, micritic and dismicritas quantitatively and qualitatively are composed of 95% calcium carbonate, silica 0.6% amorphous and others 4.40%. The NTC 5163 (ICONTEC) translation rules to the standard ASTM C 51-02 and NTC 4915 (ICONTEC) equivalent to reference ASTM C 911-99, these limestones are suitable for the manufacture of cement and stone aggregate. [ABSTRACT FROM AUTHOR]

Ophiolitic rocks are found abundantly in the area of Yaguaneque, which is part of the Moa Baracoa massif. Dike rocks occur inside basic bodies (gabbro). Dike rocks contain tremolite-actinolite, chlorite, epidote, clinochlore and zoisite corresponding to green schist facies, indicating that metasomatic processes occurred in the basic rocks as well as retrograde metamorphism. Rodingites in association with gabbros occur in the form of lens or dikes in light color, with thicknesses varying from 30 to 70 cm and up to 1,1 m in length. The mineralogical composition is: clinochlore, calcic amphiboles (tremolite-actinolite), zoisite, epidote and chlorite. It is inferred that these rocks are the product of calcic metasomatism, contemporaneous to the serpentinization of ultrabasic rocks in two events: the first one associated with hydrothermal metamorphism as evidenced by the preservation of magmatic textures, the second one, during the tectonic emplacement, under the P-T conditions associated with greenschist facies, which resulted in retrograde metamorphism where supposedly garnets were transformed into chlorites. Gabbros are box rocks having the following mineralogical composition: plagioclase (anorthite), clinopyroxenes (diopside) and subordinately, olivine which occurs in the shape of relictic grains with an alteration edge to chlorite. [ABSTRACT FROM AUTHOR]

The focus of this study is identification of mineral veins from central part of Khibina massive, which are late Devonian alkaline intrusion. Khibina Massive are product of continental magmatism connecting with a hot spot, which are present in this area, making a lot of the same intrusion. It was identificated a microsyenite, tinguaite and melteigite mostly. From these rocks was collected a few of samples, which made a petrology observation (optical microscopy, XRD analysis). These rocks are strongly important in to description a final crystallization and injection of a small addition of magmas, which was present in the Khibina Massive. Most interested are melteigite rocks which are a product of mixing a primary magma with alkaline fluids, which is visible in mineral composition in these rocks and secondary processes. [ABSTRACT FROM AUTHOR]

A series of archaeological interest mortars has been characterized, located in the historical set of the city of Oviedo, proceeding from constructions considered of medieval origin. The samples are lime mortars with siliceous aggregates, very coarse sand grain size and in some the pebble size dominates (rock and ceramic fragments). The binder is a carbonated lime that mainly appears as micrite or microsparite, and is distributed in a homogeneous form among the aggregates or tends to form lumps. Granular texture dominates, and to a lesser extent the floating and massive textures are present, as well. Based on their petrographic characteristics the mortars were classified and the obtained types were related to constructive period and phase. [ABSTRACT FROM AUTHOR]

This work presents new results of a detailed geological and structural investigation focusing the easternmost Uruguayan Mesozoic magmatic occurrences related to the south Atlantic opening. Lithological descriptions, their stratigraphic relationships and complimentary lithochemical characterizations carried out in the San Miguel region (East Uruguay) are presented. Three volcanic/sub-volcanic units have been recognized. The felsic volcanic association is composed by rhyolitic - dacitic flows, mainly with porphyritic textures and sub-alkaline nature and related pyroclastic rocks. The felsic sub-volcanic association is characterized by granophyres of about 25 km2 of exposed area, cross- cut by mafic and felsic dykes. Finally, a mafic association has been identified characterized by dykes and a small intrusion of gabbroic composition. All these units are Mesozoic in age (130 - 127 Ma) and according to their chemical nature they correspond to sub-alkaline to weak peralkaline magmas. [ABSTRACT FROM AUTHOR]