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With the advent of new terminologies to categorize and characterize the simple and complex monogenetic volcanoes, also came the semantic issues, which caused a predicament for the usage of terms like simple, complex, polycyclic, polymagmatic, complex monogenetic volcanoes with polygenetic inheritance. To analyse and validate this nomenclature, we studied an overlapping volcanic structure located south of the present‐day town of Irapuato, Central Mexico, that appears to be a monogenetic complex at first sight. Field observations, tephra stratigraphy, petrography and geochemistry of the tephra deposits confirms that the structure is in fact a cluster of three simple (San Joaquin tuff ring and two scoria mounds) and one complex, polycyclic, polymagmatic (La Sanabria‐San Roque tuff ring) monogenetic volcanoes formed by independent events, governed by distinct conduits and magma bodies of different origin (subduction‐related, OIB and E‐MORB origin) and separated by different tephra sequences of dissimilar components and depositional characteristics. We estimate the magma volumes (using the juvenile content and their vesicularity percentage) to be at 0.40–1.31 × 108, 0.25 × 108 and 0.42–0.90 × 108 m3 for San Joaquin, La Sanabria and San Roque, reckoning an eruption duration of 77 and 48 and 81 days, respectively (considering an average eruption rate of 6 m3/s from the well‐documented shallow crater (<30 m), Ukinrek maars in Alaska) occurring within the age range of 40–70 k years (crater diameter and depth ratio). This study not only aided to validate the above‐mentioned terms for monogenetic volcanoes, but also reconsider a few of them and avoid confusion with the polygenetic counterparts. [ABSTRACT FROM AUTHOR]

In this paper, we evaluate chemical weathering and its climatic significance in different periods (pre- and post-industrialization) in a basin impacted by 500 years of mining activities. We consider the geochemical and mineralogical composition of stream sediments and overbank deposits from the Guanajuato River Basin (GRB) in central Mexico. This research provides information about the weathering modifications caused by anthropogenic impacts before and after mining activities. The elemental concentrations of major elements were determined using X-ray fluorescence spectrometry, and the clay mineralogy was determined using X-ray diffraction (XRD). The chemical weathering intensity was estimated using the chemical index of alteration (CIA), the plagioclase index of alteration (PIA), and the weathering index of Parker (WIP) indices. The clay minerals in overbank sediments are kaolinite > smectite > chlorite > and vermiculite influenced by climatically driven weathering. In-stream sediments, the clay minerals are chlorite > vermiculite > kaolinite > smectite, influenced by the origin of the sediments and showing that physical weathering has been dominant in recent times because of changes in the vegetation cover and accelerated erosion in the stream sediments of the GRB. The weathering indices show that chemical weathering was greater in the preindustrial epoch (overbank sediments) compared with the present day (stream sediments) in the GRB. According to the CIA, clay content, and chemical composition, we identified four paleoclimatic conditions from 2450 ± 40 yr BP to 9410 ± 40 BP. There is a wet period at the base of the column (9410 ± 40 BP), followed by an early cold period and a wet period surrounding 2450 ± 40 yr BP. The combination of weathering indices and the clay content proved to be a useful tool; it was used to determine the weathering evolution of the basin and the anthropogenic impacts in a basin where there are historical references to mining activity over the last 500 years. [ABSTRACT FROM AUTHOR]

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This study investigates the natural hydrogeochemical mechanisms that govern groundwater chemistry at the margins of the Silao-Romita, Valle de León, and La Muralla aquifers in Mexico's "Bajío Guanajuatense". The wells of the La Muralla aquifer have temperatures ranging from 25 to 45 °C, while in the valleys, the temperatures range from 25 to 29 °C. In the Sierra de Guanajuato recharge zone, the thermal spring registers 95 °C. High Na concentrations (125 to 178 mg/L) are measured due to thermalism. One sample includes 316 mg/L of SO4, which is related to a potential gypsum zone. Three hydrogeochemical facies are identified (Ca-Mg HCO3, Na-Ca-HCO3, and Na-HCO3). The hydrogeochemical characterization and processes imply hydraulic linkage via regional thermal flows enhanced by faults and the mixing of local flow waters with intermediate flows. The isotopic results indicate that part of the groundwater volume has been exposed to local evaporation processes due to the presence of surface water bodies and irrigation returns. The highest isotopic enrichment is observed near or in the recharge regions. In contrast, the most depleted zones are in the valleys, where there is a more significant interaction with the rock and a longer residence time, implying a mixture of local water flows with deeper or intermediate flows, which, when combined with water geochemistry, indicates a connection between the aquifers studied. The Kruskal–Wallis variance tests, used to compare the differences between aquifers, show that the Valle de León aquifer has more significant differences with respect to the Silao-Romita and La Muralla aquifers. This study's findings are essential for one of central Mexico's most populous and economically active areas. [ABSTRACT FROM AUTHOR]

Trace quantities of erionite series minerals were identified along with chabazite, clinoptilolite, and morderite within Chichindaro rhyolites (~ 30 Ma) at latitude 21°8′30″–21°17′00″ and longitude 101°5′00″–101°10′00″, ~ 15 km south of the present-day town of San Felipe in the state of Guanajuato, Mexico. Special attention was given to the erionite -K, Na, and Ca varieties. Despite their occurrence in trace amounts, image analyses of these minerals with the aid of Scanning Electron Microscope indicates the existence of both hair-like and needle-like fibers that are 5.85–29.26 μm long and 2.510–0.252 μm thick, which allows them to be categorized as "inhalable" (with length > 5 μm and thickness < 3 μm) that readily enters the respiratory tract of human and their livestock residing in this region. Chemical data along with the atomic% and apfu values obtained based on 72 oxygen atoms reveals that six crystals spots from SF-14-a and sample SF-12 show Si/(Si + Al) = 0.69–0.78, similar to the cancerogenic erionite identified at Tierra Blanca, Mexico; Lessini Mountains, NE Italy; Cappadocia, Turkey, and North Dakota, USA. However, these spots fail the E% and Mg content test. On the contrary, spots SF-14-2A, 2B, and 2C show Mg content in the range of 0.35–0.54 and balance error E% of − 2.90% (only in SF-14-2B) and pass the positive identification tests for erionites. Therefore, it is advisable to comment that the erionite series minerals identified within Chichindaro rhyolites area are of "undifferentiated" type and may not be carcinogenic. [ABSTRACT FROM AUTHOR]

This study describes monument-mapping method for detected damages, and verify in qualitative and quantitative way the decay of stone on historical building. Proposes a methodology that would allow quick and easy way to identify during the processing of digital images five weathering forms; fractures, salts, oxides, scaling, and lichen. The aim of the present work were (i) to identify the various stones used in decorating the music school of the University of Guanajuato; (ii) to undertake a basic mineralogical and petrophysic characterizations of the less known stones; (iii) quantify the extension of the weathering and the damage degree of the music school using the monument mapping method. The monument mapping method was used to identify damages over green sandstone used in the construction and restoration of buildings of the eighteenth and nineteenth centuries in Guanajuato city. The output data were classified images showing the different kind of damages that affect the green sandstone. The analyses of these data allow obtaining maps with the size and position of damages. [ABSTRACT FROM AUTHOR]

Hydrochemical and mineralogical analyses were performed to identify the main processes that contribute to the concentration of total inorganic arsenic (iAs) in groundwater within the northern portion of the Laguna Seca aquifer in Guanajuato State, Mexico. The spatial extent of the study area spans across a large graben with pore-waters that contain the highest dissolved arsenic concentrations in the basin. This scale of study was chosen to test the hypothesis that normal faults act as conduits for rising geothermal waters carrying arsenic into the shallow aquifer that has been historically depressurized by irrigation pumping. The arsenic content in outcrops ranged from 3.5 to 19.5 ppm. The major minerals are quartz, plagioclase, micas, and zeolites. Multivariate cluster and Principal Components Analyses on the chemical composition and temperature of 15 wells in the study area suggest that silicate weathering is the dominant water-rock interaction that explains the observed concentrations of major ions and arsenic in groundwater. The sampled irrigation and municipal wells ranged from 190 to 550 m in depth and had temperatures ranging from 28.3 to 45.2 °C. Cluster II had the highest temperature, and greatest mineralization (total dissolved solids), and it was more influenced by regional flow than Cluster I. The concentration of iAs ranged from 16 to 229 μgL−1, all of the samples exceeded the maximum concentration suggested by the World Health Organization (10 μgL−1). Four samples belonging to Cluster II exceeded the maximum concentration set by Mexican regulations (25 μgL−1) by at least five times. The highest concentration of arsenic in surface rock coincides spatially with Cluster II wells. Geothermal heat and long pore-water-residence times enables the dissolution of silicate minerals which increases the pH (from 7.3 to 9.1) and consequently drives desorption of arsenic from mineral surfaces. During the dry season the iAs content increased in all wells from 6 to 138 μgL−1 compared to the wet season. This could be attributed to the increase in pumping that occurs then. The close proximity of Cluster II wells to newly mapped faults within the graben supports the hypothesis that Cluster II wells intercept regional groundwater flow that ascends through those previously unmapped faults. [Display omitted] • Silicate mineral dissolution increases pH and arsenic concentrations in groundwater. • Buried normal faults were mapped using geochemical and remote sensing techniques. • Geothermal waters ascend through vertical faults. • Arsenic concentrations increase during the dry season due to increased irrigation pumping. [ABSTRACT FROM AUTHOR]

• Areas with accelerating drawdown can be utilized to identify unregistered wells. • Forecasting future water-table change is possible with annual measurements. • Groundwater availability is indirectly influenced by La Niña and El Niño phenomena. • Water-table velocity and acceleration maps are useful for water resource management. The evolution of the water-table in the Cuenca Alta del Río Laja aquifer (CARL aquifer) was investigated using Empirical Bayesian Kriging (EBK) utilizing ArcGIS ® and the Curve-Fit tool developed by the United States Geological Survey (USGS). We created a new methodology to identify areas of the aquifer that can host unregistered wells, or users that overdraft the permitted extraction volume, and forecast water-table change based on historical annual water levels. Short-term climate variability, specifically the El Niño and La Niña phenomena, had an indirect influence on groundwater availability driven by less or more groundwater demand for irrigation, respectively. La Niña phenomena (2011–2012) caused severe drought driving a mean water-table velocity (WTV) of −1.57 m/year (drawdown). This contrasted to a wet El Niño period (2014–2015) driving a mean WTV of +1.12 m/year (recovery). Across the period 2008–2015, the WTV and water-table acceleration maps revealed mean values of −0.43 m/year and 0.93 m/year2, respectively. These numbers suggest that the problem of dewatering of the CARL aquifer continued, but that the rate of drawdown has slowed. If the observed drawdown rate continues, by the year 2035, 45% of the surface area of the CARL aquifer will have a water-table greater than 120 m below surface, 24% of the area will exceed 150 m and 5% of the area will exceed 180 m. Whereas deeper water tables increase the cost of lifting water to the surface, there is also a risk of worsening groundwater quality as deeper parts of the aquifer are sourced. Furthermore, the demand for irrigation is likely to increase under the most likely near-term climate change scenarios published by the Intergovernmental Panel on Climate Change. A 5–10% reduction in rainfall is predicted by 2040. Given these potential negative future consequences of over-exploiting aquifers, this original approach will help water managers make more informed decisions for the development of groundwater resources. [ABSTRACT FROM AUTHOR]