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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]

La caracterización petrográfica de la secuencia de rocas metamorfizadas de Calentura Arriba en el municipio de Moa es el primer paso para establecer las implicaciones geológicas del desarrollo de esta roca en la región de Moa. Se prepararon muestras en secciones delgadas de las secuencias de rocas metamorfizadas de Calentura Arriba y fueron analizadas con un microscopio de luz polarizada modelo NP-400B, marca NOVEL. En la secuencia de metagabros se identificó la paragénesis, mineral compuesta por enstatitas+ augita + labradorita+ olivino+ clorita+ garnierita + actinolita + tremolita + ilmenita + magnetita + sericita+ saussurita. En la secuencia de serpentinitas se identificó la paragénesis, mineral compuesta por olivino+ ortopiroxenos+ bastita + lizardita + crisotilo + actinolita + tremolita + antigorita+ serpofita + cromita +magnetita. Este sector estuvo sometido a fuertes procesos de transformación reflejado en las intensas alteraciones desarrolladas que denotan la ocurrencia de metamorfismo de grado bajo a alto coincidiendo con la serie de las facies barrowiense. Las transformaciones metamórficas están en estrecha relación con la actividad de la Falla Moa y denotan un carácter regional extendiéndose en ambos extremos de esta fractura

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]

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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]

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La mega secuencia sedimentaria del Cretácico Superior de la cuenca Oriente en Ecuador se compone por las formaciones Hollín, Napo y Tena, que ha sido ampliamente estudiada debido a su interés económico en la industria petrolera. No obstante, la escasa información acerca de las características petrográficas y geoquímicas de las rocas fuente de la Formación Tena en el centro y sur de la zona Subandina ha generado incertidumbre en el modelo de evolución geológica regional, particularmente en el intervalo Maastrichtiano a Paleoceno. La sección del río Anzu, al noroeste de Puyo, proporciona la oportunidad de analizar la procedencia de la Formación Tena, exhibiendo de forma completa y continua su secuencia estratigráfica. Con el propósito de definir la fuente detrítica de la Formación Tena, esta investigación detalla la litoestratigrafía, petrografía, geoquímica y asociación de minerales pesados en la sección del río Anzu. El análisis petrográfico revela que las areniscas de la Formación Tena son litoareniscas feldespáticas, arcosas líticas y sublitarenitas, originadas a partir de fuentes sedimentarias ricas en cuarzo, con influencia ígnea y metamórfica. Las asociaciones de minerales pesados, junto con las concentraciones de elementos mayores, traza y tierras raras, indican que estas areniscas provienen principalmente de provincias sedimentarias recicladas, con influencia de provincias ígneas ácidas y metamórficas. Estas fuentes estarían vinculadas a regiones andinas que exhumaron y asimilaron bloques o cuñas tectónicas de la cuenca Oriente durante el inicio de la orogenia Andina a finales del Cretácico Superior e inicio del Paleoceno; la erosión de estos bloques controló el detrito disponible para la sedimentación de la Formación Tena en la zona de estudio.

Debido a la creciente preocupación mundial por los elevados índices de contaminación ambiental y por el calentamiento global producto de las actividades humanas, se han comenzado a generar restricciones para el uso de los combustibles fósiles, entre ellos el carbón. Colombia al ser un país rico en este recurso mineral necesita comenzar a evaluar su uso potencial en otros campos y conocer de manera detallada las posibles implicaciones ambientales asociadas a su composición química. Actualmente el Servicio Geológico Colombiano viene desarrollando diversos proyectos encaminados a este propósito. Este trabajo presenta la caracterización geológica, fisicoquímica y petrográfica de los carbones térmicos de Norte de Santander, haciendo énfasis en la composición de elementos de interés ambiental. Se tomaron 87 muestras de carbón de frentes de mina en los municipios de Arboledas, Salazar, San Cayetano, Sardinata, Toledo y Tibú en el departamento de Norte de Santander. Las muestras fueron preparadas y se realizaron los siguientes análisis: Humedad de equilibrio, análisis próximo, determinación de carbono hidrógeno y nitrógeno, azufre total, formas de azufre, poder calorífico, índice de hinchamiento (FSI), índice de molienda (HGI), mercurio total, composición de elementos mayores, menores y trazas y reflectancia media de la vitrinita. Los mantos de carbón teniendo en cuenta su clasificación según los valores de reflectancia media de la vitrinita corresponden a carbones de rango bajo y medio que corresponden a subbituminosos y bituminosos lo que indica que no son carbones con alta madurez térmica.

Este trabajo presenta los primeros estudios petrográficos efectuados en la cerámica arqueológica del área lacustre del Bajo Sarmiento (lagos Colhue Huapi y Musters) en el centro-sur de la provincia del Chubut. Específicamente, se exponen los resultados de un análisis microscópico llevado a cabo en una muestra representativa de fragmentos cerámicos con el objetivo de explorar la procedencia de las materias primas empleadas en su manufactura. Los datos obtenidos de la petrografía, y su posterior contrastación con la geología regional y con muestras de material arcilloso de origen local, permiten plantear que las piezas cerámicas analizadas presentan un importante aporte piroclástico moderno (Holoceno Tardío) y habrían sido elaboradas con materiales disponibles localmente en el área de estudio.

La formación Canoa se localiza en el sector El Mangle, cantón Montecristi, provincia de Manabí, costa de Ecuador. Esta presenta afloramientos que litológicamente consiste en areniscas, areniscas arcillosas, areniscas limosas y lodolitas limosas; subyace a la formación Tablazo y sobreyace a la formación Angostura. En este trabajo se describieron cinco afloramientos con el objetivo de determinar la litología, componentes mineralógicos esenciales, deposición, procedencia tectónica, bioestratigrafía y paleoambiente; y se lo realizó de la siguiente manera, diecinueve muestras para bioestratigrafía y litología, y tres secciones delgadas para petrotectónica y petrografía. Por la ocurrencia de foraminíferos planctónicos presentes y que se extinguen en dicho periodo, la edad relativa de la formación Canoa es Plioceno (Zona N18 – N19). El paleoambiente sedimentario es de plataforma interna debido a la abundancia de los foraminíferos bentónicos calcáreos y aglutinados

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]

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Copyright of Intersecciones en Antropología is the property of Universidad Nacional del Centro de la Provincia de Buenos Aires, Facultad de Ciencias Sociales and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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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]

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A Formação Ferrífera São João Marcos (FFSJM), localizada próximo ao município de Rio Claro, no Estado do Rio de Janeiro, teve seus aspectos genéticos aqui estudados por meio de mapeamento geológico, petrografia e geoquímica. Na área mapeada, a FFSJM, de idade neoproterozoica, ocorre intimamente associada a rochas metamáficas e metaultramáficas, que ocorrem sobre embasamento arqueano a paleoproterozoico e estão sobrepostas por outras litologias, quartzitos puros a impuros, silimanita quartzito e (silimanita)-granada-biotita gnaisse, em ordem, da base para o topo, estruturadas em uma grande sinformal revirada. A petrografia da formação ferrífera indica composição modal, em sua maioria, de quartzo e magnetita titanífera, com pequenas quantidades de outros minerais (e.g. ferrosilita, muscovita, granada, zircão, turmalina, feldspatos e anfibólios); as rochas metamáficas são compostas basicamente por plagioclásio e hornblenda em proporções diversas, e as metaultramáficas, essencialmente por anfibólios e piroxênios. A litoquímica de elementos maiores, traço e terras raras da FFSJM demonstra forte correlação negativa entre SiO2 e Fe2O3t, e fortes semelhanças entre os padrões clássicos da literatura, principalmente com o tipo Algoma Neoproterozoico, além de características de precipitados químicos. Para as rochas máficas e ultramáficas, a geoquímica aponta para geração em contexto intracontinental. Essas informações de campo e petrografia, associadas com a geoquímica de rocha total e mineral, sugerem formação ferrífera gerada em ambiente extensional no Neoproterozoico, possivelmente acompanhando a quebra do supercontinente Rodínia. Trata-se do primeiro exemplo de formação ferrífera do tipo Algoma Neoproterozoico no Estado do Rio de Janeiro.

En canteras de la provincia de Buenos Aires, desarrolladas en el Sistema de Tandilia, grandes cantidades de rocas denominadas genéricamente como cuarcitas son removidas y acumuladas como pasivos ambientales, con el fin de explotar los estratos de arcillas infrayacentes. Considerando que la actividad minera de arcillas continúa en crecimiento, es necesario abordar debidamente esta problemática. La presente contribución expone los primeros estudios enfocados a caracterizar estas rocas cuarcíticas con el fin de incentivar su utilización como agregado grueso en obras viales. Los estudios petrográficos junto con los resultados obtenidos a partir del ensayo de desgaste Micro Deval (MD) permitieron definir cuatro variedades de cuarcitas. Las cuarcitas con mayor proporción de matriz (C1) tienen valores de desgaste mayores (coeficientes MD 24,6) que aquellas con mayor proporción de clastos de cuarzo (C2 y C3, coeficientes MD de 15,5 y 18,2, respectivamente). Por otro lado, el accionar de procesos de recristalización también podría haber influido en la mejor respuesta de estas rocas (C4). Si bien los coeficientes MD son aceptables a levemente por encima de los sugeridos para agregados gruesos de uso vial, se recomienda realizar mezclas que incluyan las diferentes variedades de cuarcitas con el fin de alcanzar valores admisibles en estos materiales.

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]

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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]

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Copyright of Intersecciones en Antropología is the property of Universidad Nacional del Centro de la Provincia de Buenos Aires, Facultad de Ciencias Sociales and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

Copyright of Acta Geologica Lilloana is the property of Fundacion Miguel Lillo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A lo largo de los últimos años las excavaciones arqueológicas llevadas a cabo en el yacimiento de Revenga (Comunero de Revenga, Burgos) han permitido recuperar algunos materiales cerámicos de cronologías tardoantiguas y altomedievales. Dado su estado de conservación muy precario, el carácter utilitario de este tipo de producciones y las dificultades que aún hoy existen en el estudio de la cerámica común altomedieval, dichos materiales plantean algunos problemas interpretativos que hemos intentado resolver a partir de una caracterización petrográfica de los mismos. Los resultados obtenidos aportan nuevos datos muy significativos para el conocimiento de las comunidades del Alto Arlanza, permiten precisar las distintas fases de ocupación del asentamiento de Revenga y abren nuevas perspectivas para la investigación futura.

A área de estudo localiza-se na porção extremo norte do Cinturão Salvador-Esplanada-Boquim, nas porções sul do estado de Sergipe e nordeste do estado da Bahia, Brasil. Este Cinturão apresenta três faixas litológicas de rochas metamórficas denominadas Complexo Migmatítico Rio Real-Riachão do Dantas (CMRR), Complexo Granulítico Esplanada-Boquim (CGEB) e Complexo Gnáissico/Migmatítico-Granulítico Costa Atlântica (CGGCA). Esse artigo se restringe aos estudos petrológicos da primeira faixa de migmatitos que foi subdividida em Ortognaisse Migmatítico Granítico Leste (OMGL) e Ortognaisse Migmatítico Granítico Oeste (OMGO). Ambas, macroscopicamente e petrograficamente são similares, cujas paragêneses minerais indicam a ocorrência de processos metamórficos de médio grau, da fácies anfibolito com faixas retrometamórficas. Litoquimicamente, notou-se características particulares das porções claras e escuras de cada um desses tipos de migmatitos e que, embora tenham sofrido migmatização, mantiveram as características dos protólitos, permitindo identificar as porções félsicas como provenientes de magma variando entre cálcio-alcalino normal a cálcio-alcalino de alto K.

Copyright of Geologia USP: Série Científica is the property of Geologia USP and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Boletin de Geologia is the property of Universidad Industrial de Santander and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

O Cinturão Salvador-Esplanada-Boquim se localiza na porção nordeste do Cráton do São Francisco, nos estados da Bahia e do Sergipe, apresentando duas faixas litológicas de rochas metamórficas, denominadas Complexo Gnáissico-Migmatítico e Complexo Granulítico Esplanada-Boquim. O presente trabalho abrange os estudos de campo, petrográficos e litoquímicos do Complexo Gnáissico-Migmatítico, porção norte do Cinturão Salvador-Esplanada-Boquim. Ocorrem rochas metamórficas de médio grau, de composição granítica a granodiorítica e, subordinadamente, tonalítica, sendo comuns as evidências de processos de migmatização, principalmente na sua porção ocidental. Com base nos estudos de litoquímica, as rochas foram subdivididas em rochas sódicas, potássicas e intermediárias e caráter peraluminoso a metaluminoso. Análises dos elementos-traço, terras raras e as razões Eu/Eu* sugerem a atuação de processos metamórficos e de contaminação crustal a partir de fonte de natureza calcioalcalina. Ainda a partir da análise litoquímica, as rochas desse complexo foram classificadas como sendo de arco vulcânico a sincolisional.

La expansión del Tawantinsuyu en el valle del Aconcagua (Chile central) fue culturalmente mediada y evitando la coerción militar, lo que derivó en distintas formas de aceptación, resistencia y aculturación. En este contexto, son casi inexistentes los estudios que discutan cómo este proceso se manifestó en la tecnología metalúrgica del Período Tardío (ca. 1400-1530 DC). Presentamos los resultados del estudio tecnológico sobre un conjunto de crisoles y moldes encontrados en el valle del Aconcagua y asociados a piezas metálicas hechas en base a cobre, utilizando microscopía óptica, petrografía, SEM-EDS, XRD y FTIR. Nuestros resultados indican que las materias primas utilizadas fueron rocas ígneas obtenidas de depósitos probablemente locales, mezcladas con pequeñas cantidades de arcillas tipo esmectitas-montmorillonitas. En el caso de los moldes, estos además contenían hueso molido como antiplástico. Todas las cerámicas fueron cubiertas con una pasta de hueso puro para mejorar su refractariedad. Las temperaturas de cocción se estimaron entre 800 y 850 °C para los moldes y superior a los 900 °C para los crisoles. La morfología y tecnología utilizada sugieren que una tradición tecnológica originada en el Noroeste Argentino fue introducida al valle del Aconcagua y aceptada por ciertas comunidades locales durante la expansión del Tawantinsuyu.

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]

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En este trabajo se presentan los resultados de los trabajos de campo y de laboratorio llevados a cabo sobre una amplia diversidad de rocas plausibles de ser aprovechadas como recursos líticos que se encuentran naturalmente disponibles en el sur del nordeste argentino. El objetivo general de estos estudios es el desarrollo de un marco de referencia útil para la interpretación de los conjuntos líticos del sector bajo estudio. Para esto, se desarrolla una síntesis que recopila información tanto arqueológica como geológica junto a datos novedosos generados mediante prospecciones a escala regional y estudios petrográficos a nivel micro y macroscópico. De este modo fue posible precisar, desde un enfoque arqueológico, la localización y la accesibilidad espacial de diversos afloramientos rocosos y caracterizar la morfología, estructura y composición mineralógica de una amplia diversidad de fuentes de materia prima lítica. Finalmente, se hizo foco sobre las características de una de las materias primas más frecuentemente mencionadas en la literatura arqueológica, las areniscas, y se llevaron a cabo estudios tendientes a discriminar la procedencia de las mismas y las transformaciones que estas rocas pudieron sufrir por termoalteración en el pasado prehispánico.

El estudio de la tecnología y la procedencia de la cerámica ha contribuido a establecer la existencia de conexiones entre diversas áreas y comunidades. Conocer estos aspectos es importante para entender las relaciones que se dan entre los grupos humanos y aproximarnos a sus formas de organización social. En este trabajo abordamos la procedencia de la cerámica vinculada a los primeros momentos del período Formativo en la quebrada de Miriguaca, en la zona de Antofagasta de la Sierra (Catamarca, Argentina). Para ello, analizamos la tipología, los rasgos estilísticos, la composición petrográfica y química mediante activación neutrónica instrumental de la cerámica recuperada del sitio Las Escondidas (ca. 2000-1600 AP). Los resultados obtenidos permiten complementar los modelos explicativos aplicados a las sociedades del período Formativo y evidencian que la cerámica de la quebrada no responde a producciones locales, aunque la amplia mayoría parece tener un mismo origen. Esta situación mostraría la existencia de vínculos sociales entre los distintos grupos humanos que habitaron la Puna catamarqueña durante este momento. Esta conectividad habría potenciado la existencia de estrategias de cohesión social a nivel macro-regional, que pudieron ser especialmente importantes en un contexto de creciente complejidad social y de profundos cambios en las formas de organización de estas poblaciones.

En la Cuenca Neuquina (Argentina) y asociada a la Formación Lajas (Jurásico) se mencionó por primera vez una mineralización de esfalerita y galena asociada a carbonatos. En el área del yacimiento Puesto Gregor, esta Formación está constituida por una secuencia clástico carbonática. Para caracterizar el ambiente de depositación de la dolomía hospedante de la mineralización de Zn y Pb se realizaron estudios petrográficos y geoquímicos. Entre los últimos los más utilizados son los análisis e interpretación de isótopos estables (O, C), elementos mayoritarios y trazas e inclusiones fluidas. En el horizonte dolomítico de 0,90 m de espesor y 300 m de corrida se distinguen petrográficamente dos tipos de dolomita: el primer tipo es penetrativo, sin preservación de la fábrica sedimentaria original y es anterior a la mineralización, el segundo tipo está vinculado a la precipitación de sulfuros y consiste en una dolomita de tipo silla de montar (saddle). El estudio de las inclusiones fluidas en la dolomita penetrativa indica la presencia de fluidos orgánicos y fluidos acuosos. Determinaciones microtermométricas sobre inclusiones fluidas acuosas revelaron temperaturas de 140º C. Geoquímicamente la capa presenta proporciones casi estequiométricas y promedios de CaCO3 y MgCO3 iguales al 52 y 48% molar, respectivamente. En cuanto a los elementos trazas, el Sr varió entre 79 y 159 ppm y el Na entre 74 y 225 ppm. Los contenidos de Mn y Fe son mucho más altos que los valores determinados para estos elementos en rocas carbonáticas. El contenido en ETR es bajo y los diagramas de ETR muestran una anomalía negativa de Ce y de Eu. Se determinaron valores de isótopos de C y O. Los valores de ?13 C (VPDB) entre -2,9 y -9 0/00 no son coherentes con los datos informados para calizas marinas de edad jurásica mientras que los valores de ?18O(VPDB) entre -2,6 y -4 ‰ coinciden con los valores informados para carbonatos de igual edad. Los datos de ä18O indican que la interacción entre el fluido y la roca de caja fue baja. Los valores del ?18O del fluido en equilibrio con la dolomía a temperaturas de 140ºC indican que este fluido corresponde a una salmuera de cuenca. Por otro lado, los isótopos de carbono indican un aporte de carbono procedente de la diagénesis de la materia orgánica causada por un aumento de temperatura vinculada al soterramiento de la cuenca. Los resultados petrográficos y geoquímicos son consistentes con la dolomitización de un carbonato de origen marino que sufrió soterramiento.

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]

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Copyright of Trace: Travaux et Recherches dans les Amériques du Centre is the property of Centro de Estudios Mexicanos & Centroamericanos and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Se presentan los resultados obtenidos del análisis del material cerámico proveniente del sitio Las Escondidas (Quebrada de Miriguaca, Puna Meridional Argentina) con el objetivo de abordar las características de la producción cerámica de los primeros momentos del Formativo (entre ca. 2000 AP y 1700 AP), para así tratar de indagar en el contexto social en el que esta cerámica fue producida y usada. Para ello se proponen dos etapas de análisis, la primera a través del uso de lupa binocular y la segunda, mediante análisis petrográficos. Los resultados obtenidos permitieron establecer las características y la posible funcionalidad del repertorio cerámico, además de lograr determinar la composición de las pastas. Se identificaron ciertas elecciones tecnológicas constantes y una importante homogeneidad en el uso de materias primas específicas, que no han podido ser correlacionadas directamente con el entorno geológico local. Posteriormente, a partir de la detallada descripción petrográfica, se pudo comparar este conjunto con otros analizados previamente, tanto de la Puna meridional argentina como de otros sectores circundantes, contribuyendo a establecer redes de relaciones en las cuales los objetos se vieron inmersos en los primeros momentos de la era.

En el presente artículo, se describen los resultados de un proyecto de investigación llevado acabo para caracterizar las propiedades fisicoquímicas de cinco tipos de roca volcánica (riodacita), comúnmente conocida como "cantera", tradicionalmente utilizada para la construcción y restauración de edificios históricos en la ciudad de Oaxaca, México. En el programa experimental, se analizaron cinco tipos de piedra para conocer sus características mineralógicas y petrográficas mediante fluorescencia de rayos X y análisis petrográfico. De la misma manera, se llevaron a cabo pruebas de resistencia a la compresión, densidad y absorción. Finalmente, los resultados obtenidos en el programa experimental fueron analizados y correlacionados con las propiedades de resistencia y durabilidad de los cinco tipos de piedra evaluados.

El objetivo de este trabajo es caracterizar tecnológicamente el conjunto cerámico de El Sequero (Arrúbal), yacimiento de fondos de cabañas del siglo IX cal BC. El conjunto reproduce formas características del Bronce Final en el valle medio de Ebro, con decoraciones plásticas, motivos acanalados, incisos y excisos. La caracterización mediante análisis petrográfico de una selección de muestras del conjunto cerámico ha permitido identificar dos grupos que se corresponderían con distintas ‘formas de hacer’ en cuanto al aprovisio- namiento de la materia prima y el procesado de las arcillas. Su comparación con yacimientos del País Vasco y de Aragón permite integrar y comparar el conjunto con otros grupos tecnológicos del alto y medio valle del Ebro. Los resultados indican una conexión con las elecciones tecnológicas detectadas en otros yacimientos del alto valle, mientras hay notables diferencias con los del valle medio, como el Cabezo de la Cruz de La Muela (Zaragoza).