Caliche From Archaeological Zone of Guanajuato Mexico and Nearby Deposits: Geochemical and Mechanical Characterizations

Abstract

ABSTRACTCurrently, several archaeological sites are being studied in the Mexican state of Guanajuato. Among these sites is the Cerro de Los Remedios, located in the municipality of Comonfort, in the state of Guanajuato. The archaeological site shows that among the main materials used for construction was a carbonate-based stone called caliche. Caliche is the result of carbonate sedimentation in sandstone; therefore, its physical and geochemical characteristics are specific to each archaeological zone around the world. Therefore, it was necessary to conduct a study of the chemical, physical, and mechanical properties of the material found. Samples were removed from the CZA archaeological site and characterized by infrared spectroscopy, XRD, X-ray fluorescence and SEM. The results showed that more than 93% of the caliche is composed of CaCO3 as a matrix of micrite and calcite granules. In addition, the physical and mechanical properties were determined, including density, porosity, and uniaxial compression stress. With the results obtained from the samples from the archaeological site, it was possible to identify material banks close to the caliche properties that were most like those used at the site, which can be proposed to be used in the conservation work required at the archaeological site.RÉSUMÉActuellement, plusieurs sites archéologiques sont en cours d'étude dans l'Etat mexicain de Guanajuato. Parmi ces sites se trouve Cerro de los Remedios (appelé CZA), localisé dans la municipalité de Comonfort, dans l'Etat de Guanajuato. Le site archéologique révèle que parmi les principaux matériaux utilisés pour sa construction se trouve une roche à base de carbonate appelée caliche. Le caliche résulte de la sédimentation des carbonates du grès ; ses caractéristiques physiques et géochimiques sont par conséquent spécifiques de chaque zone archéologique dans le monde entier. Il était ainsi nécessaire d'étudier les propriétés chimiques, physiques et mécaniques du matériau recueilli sur site. Des échantillons ont été prélevés sur le site archéologique CZA et caractérisés par spectroscopie infrarouge, diffraction X, spectroscopie de fluorescence de rayons X et microscope électronique à balayage. Les résultats montrent que plus de 93% du caliche sont composés de CaCO3 sous la forme d'une matrice de granules de micrite et de calcite. De plus, les propriétés physiques et mécaniques, dont la densité, la porosité et la résistance à la compression uniaxiale, ont été caractérisées. Avec les résultats obtenus à partir des échantillons du site archéologique, il a été possible d'identifier des sources locales de matériaux dont les propriétés sont proches de celles du caliche employé sur le site et qui peuvent être proposées pour réaliser les travaux de conservation-restauration qui seront à effectuer sur le site archéologique. Traduit par Johanna Salvant.RESUMOAtualmente, vários sítios arqueológicos estão sendo estudados no estado mexicano de Guanajuato. Dentre esses locais está o Cerro de los Remedios, localizado no município de Comonfort, no estado de Guanajuato. O sítio arqueológico mostra que dentre os principais materiais utilizados para a construção estava uma pedra à base de carbonato chamada caliche. Caliche é o resultado da sedimentação carbonática em arenito; portanto, suas características físicas e geoquímicas são específicas de cada zona arqueológica do mundo. Dessa forma, foi necessário realizar um estudo das propriedades químicas, físicas e mecânicas do material encontrado. As amostras foram retiradas do sítio arqueológico CZA e caracterizadas por espectroscopia no infravermelho, DRX, fluorescência de raios X e MEV. Os resultados mostraram que mais de 93% do caliche é composto por CaCO3 como matriz de grânulos de micrita e calcita. Além disso, foram determinadas as propriedades físicas e mecânicas, incluindo densidade, porosidade e tensão de compressão uniaxial. Com os resultados obtidos nas amostras do sítio arqueológico, foi possível identificar bancos de materiais próximos às construções de caliche mais parecidos com os utilizados no sítio, os quais podem ser propostos para utilização nos trabalhos de conservação exigidos no sítio arqueológico. Traduzido por Marcia Rizzo; revisado por Beatriz Haspo.RESUMENActualmente se están estudiando varios sitios arqueológicos en el estado mexicano de Guanajuato. Entre estos sitios se encuentra el Cerro de los Remedios, ubicado en el municipio de Comonfort, en el estado de Guanajuato. El sitio arqueológico muestra que entre los principales materiales utilizados para la construcción se encontraba una roca carbonática llamada caliche. El caliche es el resultado de la sedimentación de carbonatos en areniscas; por lo tanto, sus características físicas y geoquímicas son específicas de cada zona arqueológica alrededor del mundo. Por ello, fue necesario realizar un estudio de las propiedades químicas, físicas y mecánicas del material encontrado. Se extrajeron muestras del sitio arqueológico CZA y se caracterizaron mediante espectroscopia infrarroja, XRD, fluorescencia de rayos X y SEM. Los resultados mostraron que más del 93% del caliche está compuesto por CaCO3 como matriz de gránulos de micrita y calcita. Además, se determinaron las propiedades físicas y mecánicas, incluyendo densidad, porosidad y esfuerzo de compresión uniaxial. Con los resultados obtenidos de las muestras del sitio arqueológico se pudieron identificar bancos cercanos de materiales cuyas propiedades del caliche eran más parecidas a los utilizados en el sitio, los cuales pueden ser propuestos para ser utilizados en los trabajos de conservación que requiere el sitio arqueológico. Traducción y revisión: Soledad Tancoff y David Cohen; revisión final: Amparo Rueda e Irene Delaveris.KEYWORDS: Calichegeochemical characterizationmechanical characterizationarchaeologic site Cerro de Los Remediosmaterial bank AcknowledgementsWe thank the technical support provided by staff at the LICAMM-MEB-UG (Laboratorio de Investigación y Caracterización de Minerales y Materiales (microscopio electrónico de barrido) de la Universidad de Guanajuato) for conducting the XRD, XRF and SEM-EDS analysis.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThe authors are grateful to CONACyT Mexico for the financial support provided within the framework of the project CB / 284510-2016.Notes on contributorsAlexis Ahedo-DíazAlexis Ahedo-Díaz graduated from the University of Guanajuato with a degree in Geological Engineering. He currently works at the National Institute of Statistics and Geography (National Institute of Anthropology and History, INAH) in Aguascalientes, Mexico, within the areas of hydrology and natural resources, developing collaborative projects on groundwater, coastal erosion, satellite image processing (radar and optical).Miguel A. Luna-MuñozMiguel A. Luna-Muñoz obtained a bachelor's degree in Archeology from the National School of Anthropology and History (Escuela Nacional de Antropología e Historia, ENAH), Mexico, in 2002. Miguel works in the area of technical archaeological protection at the National Institute of Archeology and History (INAH-Mexico State). He was nominated for the Alfonso Caso Award in the category of best bachelor's degree thesis (INAH Award 2023). Miguel has experience in archaeological salvage and rescue projects in Mexico City, Guanajuato, and Irapuato.Raúl Miranda-AvilésRaúl Miranda-Avilés hold a PhD in Geology from the Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (IPN), Mexico. He is a research professor at the Department of Engineering in Mines, Metallurgy, and Geology of the University of Guanajuato. Raúl's principal field of interest in geology is the characterization of different stones applied for conservation and restauration of the cultural heritage. He is also a member of the National Research System (SNI, México).Mercedes Salazar-HernándezMercedes Salazar-Hernández received a BS degree (2003) and a PhD degree (2009) in Chemistry from the University of Guanajuato, Mexico. Since 2009, Mercedes has been a research professor at the Department of Engineering in Mines, Metallurgy, and Geology of the University of Guanajuato. Her principal field of interest is synthesis and characterization of different materials applied to conservation and restauration for cultural heritage. She has been a member of the National Research System (SNI, México) since 2016.Jorge CervantesJorge Cervantes holds a BS degree in Chemistry (1975) and a MSc in Inorganic Chemistry (1979), both from the University of Guanajuato, Mexico. He also has a PhD in Chemistry (1990) from the Metropolitan University, México, in collaboration with the University of Texas El Paso. He has been a professor at the Chemistry Department of the University of Guanajuato since 1980. Jorge's principal field of interest is the different aspects on silicon chemistry and technology when applied to building conservation and restoration. He has been a member of the National Research System (SNI, México) since 1988.Omar Cruces-CervantesOmar Cruces-Cervantes received a BS (2007) and PhD (2010) in Archeology from the National School of Archeology and History (Escuela Nacional de Antropología e Historia, ENAH), Mexico. Since 1998, Omar has been working in several archeological projects around Mexico with the National Institute of Archeology and History (INAH-Mexico), and in 2013 he became archaeologist coordinator of the archeological project “Cerro de Los Remedios” in Comonfort, Guanajuato, Mexico. He has also served as the archaeologist coordinator to the archeological area open to the public at “Cañada de la Virgen” since 2014.Carmen Salazar-HernándezCarmen Salazar-Hernández holds a BS in Chemical Engineering (2003) and a PhD in Chemistry (2009), both from the University of Guanajuato, Mexico. Since 2009, Carmen has been a research professor at UPIIG-Instituto Politécnico Nacional. Her principal field of interest is the synthesis and characterization of different materials applied to the conservation and restauration for cultural heritage. She has been a member of the National Research System (SNI, México) since 2011. Email: msalazarh@ipn.mx.María Jesús Puy-AlquizaMaría Jesús Puy-Alquiza received a PhD degree in Geology from the Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (IPN), Mexico. María is a research professor at the Department of Engineering in Mines, Metallurgy, and Geology of the University of Guanajuato. Her principal field of interest in geology is the characterization of different stones applied for conservation and restauration of the cultural heritage. She is a member of the National Research System (SNI, México). Email: yosune@ugto.mx.