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Update and Review of Continental Conductive Surface Heat Flow Measurements in México: An Analysis of Deep Boreholes
Abstract
Conductive heat flow is an important parameter that is used to explain, directly or indirectly, several geological, geophysical and geochemical processes in the Earth´s interior. It is also one of the main input parameters for reliable estimations of resources related with geothermal and petroleum systems. That is because heat flow is used to describe subsurface temperature profiles and heat transfer mechanisms, thereby enabling the establishment of heat storage reserves in the case of geothermal systems and conditions of thermal maturation of organic matter in petroleum genesis. Since 2014, collection of data to estimate new continental conductive heat flow values in México has been an exhaustive scientific task. As a result, data from 4159 sites have been compiled, mostly from deep geothermal and petroleum boreholes. In this context, only 3,888 new geothermal gradient data were compiled and used to estimate new heat flow values. These new values complement the 702 continental heat flow values compiled and published between 1974 and 2021. Traditionally, all efforts to measure geothermal gradient in México have focused on the five high enthalpy geothermal fields under exploitation. Therefore, this continuous updating of the continental heat flow database would be an excellent input for Geothermal Play Fairway Analysis, enabling to define areas at a regional level with thermal anomalies and discovering new prospects, resulting in better knowledge of Mexican geothermal resources. Finally, the obtained data will help interested private and public entities to improve the geothermal exploration techniques in collaboration with academic institutions. Moreover, the scientific community interested in Earth science studies will benefit from this information with application to diverse research that involves the thermal evolution of the crust.
... Regarding the temperature gradient considerations, more than 3800 new geothermal gradients were compiled by Espinoza-Ojeda et al. (2023) from deep boreholes. In the Los Humeros area, an average geothermal gradient of about 120 °C km −1 was estimated (data can be downloaded from: https:// github. ...
The influence of deep and regional geological structures is becoming increasingly important in superhot geothermal systems due to their proximity to the transition between brittleness and ductility. In the Los Humeros geothermal field in Mexico, where subsurface fluids reach temperatures of over 350 °C, the surface structures resulting from the collapse of calderas have so far only been interpreted at the local scale. The aim of this work is to place the recent tectonic and volcano-tectonic geomorphologic evolution and structures in the Los Humeros volcanic area in a regional context. NE- and NW-striking dominant structures resulting from a morpho-structural analysis on a regional scale are confirmed by negative and positive anomalies, respectively, after Butterworth filtering of gravity field data with different wavelengths over a local area of about 1000 km ² . By analyzing the slip and dilation trends of the observed directions, we show the relevance of the regional context for reservoir exploration. The magnitudes of the principal stresses we estimate indicate a trans-tensional fault regime, a combination of strike-slip and normal faulting. The structures derived from the gravity and morpho-structural analyses, which are parallel to the maximum horizontal stress, have the highest potential for tensile and shear failure. Therefore, the corresponding negative gravity anomalies could be related to fracture porosity. Consequently, we hypothesize that these structures near the transition between brittleness and ductility control fluid flow in the Los Humeros geothermal field.
Crustal fault zones provide interesting geological targets for high-temperature geothermal energy source in naturally deep-fractured basement areas. Field and laboratory studies have shown the ability of these systems to let fluid flow down to the brittle–ductile transition. However, several key questions about exploration still exist, in particular the fundamental effect of tectonic regimes on fluid flow in fractured basement domains. Based on poro-elasticity assumption, we considered an idealized 3D geometry and realistic physical properties. We examined a model with no tectonic regime (benchmark experiment) and a model with different tectonic regimes, namely a compressional, an extensional and a strike-slip tectonic regime. Compared to the benchmark experiment, the results demonstrate that different tectonic regimes cause pressure changes in the fault/basement system. The tectonic-induced pressure changes affect convective patterns, onset of convection as well as the spatial extent of thermal plumes and the intensity of temperature anomalies. Driven by poro-elastic forces, temperature anomalies around vertical faults in a strike-slip tectonic regime have a spatial extent that should be considered in preliminary exploratory phases.
Geo-thermalism has been widely recognized on the Baja California Peninsula, especially during the last decade. The current research, carried out on Bahia Concepcion, evidences the existence of geothermal springs, which get recharged mainly by groundwater and seawater. The groundwater can be characterized as Na +-Cl − and Na +-HCO3 − type, with a pH value close to neutrality. The slightly more acidic thermal sites presented temperatures between 32 °C and 59 °C at the surface. Based on the relationships of the Cl − and Br − , as well as the B/Cl − , and Br − /Cl − ratios, seawater was recognized as the main source of salinity. The spatial distribution is explained directly through marine intrusion, or via sprays and aerosols within the rainwater. Seawater ratios in thermal springs varied from 62% to 83%, corresponding mainly to shallow inflow, but seawater inputs into the deep thermal reservoir were also recognized. Temperatures in the geothermal deep reservoir were inferred from 114 to 209 °C, calculated through the SiO2 and Na +-K + geothermometers. In addition to previously reported thermal sites at Bahía Concepción, and based on their elevated temperatures, two new sites were identified. Another five springs do not fulfill the commonly used definition, based on differential temperature, but show the typical hydrogeochemical signature of thermal water. A new approach to identify this low-temperature geothermal-influenced spring water by its hydrogeochemical composition is presented, for which the term "Masked Geothermal Waters" (MGW) is introduced. Our findings increase the area of the geothermal anomaly and, therefore, the potential of geothermal resources. The approach proposed in this research will also be useful to identify more MGW in other coastal areas.
The Pontgibaud crustal fault zone (CFZ) in the French Massif Central provides an opportunity to evaluate the high-temperature geothermal potential of these naturally permeable zones. Previous 2D modeling of heat and mass transfer in a fault zone highlighted that a subvertical CFZ concentrates the highest temperature anomalies at shallow depths. By comparing the results of these large-scale 2D numerical models with field data, the depth of the 150°C isotherm was estimated to be at a depth of 2.5 km. However, these results did not consider 3D effects and interactions between fluids, deformation, and temperature. Here, field measurements are used to control the 3D geometry of the geological structures. New 2D (thin-section) and 3D (X-ray microtomography) observations point to a well-defined spatial propagation of fractures and voids, exhibiting the same fracture architecture at different scales (2.5 μm to 2 mm). Moreover, new measurements on porosity and permeability confirm that the highly fractured and altered samples are characterized by large permeability values, one of them reaching 10-12 m2. Based on a thermoporoelastic hypothesis, a preliminary 3D THM numerical model is presented. A first parametric study highlights the role of permeability, stress direction, and intensity on fluid flow. In particular, three different convective patterns have been identified (finger-like, blob-like, and double-like convective patterns). The results suggest that vertical deformation zones oriented at 30 and 70° with respect to the maximum horizontal stress direction would correspond to the potential target for high-temperature anomalies. Finally, a large-scale 3D numerical model of the Pontgibaud CFZ, based on THM coupling and the comparison with field data (temperature, heat flux, and electrical resistivity), allows us to explore the spatial geometry of the 150°C isotherm. Although simplified hypotheses have been used, 3D field data have been reproduced.
Para el desarrollo de un campo geotérmico, el conocimiento de la distribución de fracturas, la hidrología y la evolución tectónica del sitio a través de la caracterización estructural del sistema natural es un requisito previo a la perforación de pozos exploratorios. Fallas y fracturas representan vías preferenciales por el flujo de fluidos en el subsuelo y pueden ser detectadas mediante investigaciones geológicas en la superficie y geofísicas en el subsuelo. Una anomalía magnética positiva y de forma sub-circular en planta se encuentra en el medio del lago Cuitzeo, México. A través de un levantamiento geomagnético dentro y alrededor del área que comprende la anomalía tratamos caracterizar el reservorio geotérmico que, al sur del lago, está notificado por manifestaciones hidrotermales. Utilizando filtros computacionales basados sobre el uso de operaciones con las derivadas de valores de campo a los datos magnéticos grabados, hemos puesto en luz algunas de las estructuras que influencian la circulación de los fluidos en el sistema geotermal. Nuestra atención se focalizó sobre fallas ~N-S and E-W, pertenecientes respectivamente a la tectónica Básin & Range (B&R) y a la del Cinturón Volcánico Mexicano (CVM). Según nuestra interpretación, la interacción de dos o mas estructuras de diferentes orígenes (B&R y CVM), además del entorno geodinámico específico (subducción de zona de fracturas), facilitó el surgimiento de cuerpos magmáticos básicos del profundo que, bloqueados por la capa argilosa de sedimentación lacustre del Cuitzeo, dieron lugar, enfriándose lentamente, al sistema geotermal y contribuyeron a la formación de la anomalía magnética.
doi: https://doi.org/10.22201/igeof.00167169p.2020.59.2.2084
Heat flow measurements collected throughout the Auka and JaichMaa Ja'ag' hydrothermal vent fields in the central graben of the Southern Pescadero Basin, southern Gulf of California, indicate upflow of hydrothermal fluids associated with rifting dissipate heat in excess of 10 W/m² around faults that have a few kilometers in length. Paradoxically, longer faults do not show signs of venting. Heat flow anomalies slowly decay to background values of ∼2 W/m² at distances of ∼1 km from these faults following an inverse square‐root distance law. We develop a near‐fault model of heat transport in steady state for the Auka vent field based on the fundamental Green's function solution of the heat equation. The model includes the effects of circulation in fracture networks, and the lateral seepage of geothermal brines to surrounding hemipelagic sediments. We use an optimal fitting method to estimate the reservoir depth, permeability, and circulation rate. Independently derived constraints for the model, indicate the heat source is at a depth of ∼5.7 km; from the model, permeability and flow rates in the fracture system are ∼10⁻¹⁴ m² and 10⁻⁶ m/s, respectively, and ∼10⁻¹⁶ m² and 10⁻⁸ m/s in the basin aquitards, respectively. Model results point to the importance of fault scaling laws in controlling sediment‐hosted vent fields and slow circulation throughout low permeability sediments in controlling the brine's chemistry. Although the fault model seems appropriate and straightforward for the Pescadero vents, it does seem to be the exception to the other known sediment‐hosted vent fields in the Pacific.
In the first kilometers of the subsurface, temperature anomalies due to heat conduction rarely exceed 20–30°C. However, when deep hot fluids in the shallow crust flow upwards, for example through permeable fault zones, hydrothermal convection can form high-temperature geothermal reservoirs. Numerical modeling of hydrothermal convection shows that vertical fault zones may host funnel-shaped, kilometer-sized geothermal reservoirs whose exploitation would not need drilling at depths below 2–3 km.
In the first kilometers of the subsurface, temperature anomalies due to heat conduction processes rarely exceed 20–30 ∘C. When fault zones are sufficiently permeable, fluid flow may lead to much larger thermal anomalies, as evidenced by the emergence of thermal springs or by fault-related geothermal reservoirs. Hydrothermal convection triggered by buoyancy effects creates thermal anomalies whose morphology and amplitude are not well known, especially when depth- and time-dependent permeability is considered. Exploitation of shallow thermal anomalies for heat and power production partly depends on the volume and temperature of the hydrothermal reservoir. This study presents a non-exhaustive numerical investigation of fluid flow models within and around simplified fault zones, wherein realistic fluid and rock properties are accounted for, as are appropriate boundary conditions. 2D simplified models point out relevant physical mechanisms for geological problems, such as “thermal inheritance” or pulsating plumes. When permeability is increased, the classic “finger-like” upwellings evolve towards a “bulb-like” geometry, resulting in a large volume of hot fluid at shallow depth. In simplified 3D models wherein the fault zone dip angle and fault zone thickness are varied, the anomalously hot reservoir exhibits a kilometer-sized “hot air balloon” morphology or, when permeability is depth-dependent, a “funnel-shaped” geometry. For thick faults, the number of thermal anomalies increases but not the amplitude. The largest amplitude (up to 80–90 ∘C) is obtained for vertical fault zones. At the top of a vertical, 100 m wide fault zone, temperature anomalies greater than 30 ∘C may extend laterally over more than 1 km from the fault boundary. These preliminary results should motivate further geothermal investigations of more elaborated models wherein topography and fault intersections would be accounted for.
The Gulf of California is an archetype of continental rupture through transtensional rifting, and exploitation of a thermally weakened arc to produce a rift. Volcanic rocks of central Baja California record the transition from calcalkaline arc magmatism, due to subduction of the Farallon plate (ca. 24–12 Ma), to rift magmatism, related to the opening of the Gulf of California (<12 Ma). In addition, a suite of postsubduction rocks (<12 Ma), referred to as “bajaites,” are enriched in light rare-earth and other incompatible elements (e.g., Ba and Sr). These are further subdivided into high-magnesian andesite (with 50%–58% SiO2 and MgO >4%) and adakite (>56% SiO2 and MgO <3%). The bajaites correlate spatially with a fossil slab imaged under central Baja and are inferred to record postsubduction melting of the slab and subduction-modified mantle by asthenospheric upwelling associated with rifting or slab breakoff. We report on volcanic rocks of all three suites, which surround and underlie the Santa Rosalía sedimentary rift basin. This area represents the western margin of the Guaymas basin, the most magmatically robust segment of the Gulf of California rift, where seafloor spreading occurred in isolation for 3–4 m.y. (starting at 6 Ma) before transtensional pull-apart basins to the north and south ruptured the continental crust. Outcrops of the Santa Rosalía area thus offer the opportunity to understand the magmatic evolution of the Guaymas rift, which has been the focus of numerous oceanographic expeditions.
We describe 21 distinct volcanic and hypabyssal map units in the Santa Rosalía area, using field characteristics, petrographic data, and major- and trace-element geochemical data, as well as zircon isotopic data and ten new 40Ar-39Ar ages. Lithofacies include lavas and lava domes, block-and-ash-flow tuffs, ignimbrites, and hypabyssal intrusions (plugs, dikes, and peperites). Calcalkaline volcanic rocks (13.81–10.11 Ma) pass conformably upsection, with no time gap, into volcanic rocks with rift transitional chemistry (9.69–8.84 Ma). The onset of rifting was marked by explosive eruption of silicic ignimbrite (tuff of El Morro), possibly from a caldera, similar to the onset of rifting or accelerated rifting in other parts of the Gulf of California. Epsilon Hf zircon data are consistent with a rift transitional setting for the tuff of El Morro. Arc and rift volcanic rocks were then juxtaposed by normal faults and tilted eastward toward a north-south fault that lay offshore, likely related to the north-south normal faults documented for the early history of the Guaymas basin, prior to the onset of northwest-southeast transtenional faulting. Magmatism in the Santa Rosalía area resumed with emplacement of high-magnesian andesite lavas and intrusions, at 6.06 Ma ± 0.27 Ma, coeval with the onset of seafloor spreading in the Guaymas basin at ca. 6 Ma.
The 9.69–8.84 Ma rift transitional volcanic rocks underlying the Santa Rosalía sedimentary basin provide a maximum age on its basal fill. Evaporites in the Santa Rosalía sedimentary basin formed on the margin of the Guaymas basin, where thicker evaporites formed. Overlying coarse-grained clastic sedimentary fill of the Santa Rosalía basin and its stratiform Cu-Co-Zn-Mn sulfides may have accumulated rapidly, coeval with emplacement of 6.06 Ma high-magnesian andesite intrusions and the ca. 6 Ma onset of seafloor spreading in the Guaymas basin.
We present a new 1:80,000-scale geologic map of the Acoculco caldera (Ac) located between the states of Puebla and Hidalgo in eastern México. The map, encompassing an area of 856 km2, is grounded on an ArcMap data set and is supported by nine new 40Ar/39Ar dates. The caldera lies upon Cretaceous limestones and Miocene to Pliocene volcanic rocks (13–3 Ma). The caldera consists of 31 lithostatrigraphic units formed between 2.7 and 0.06 Ma that include a wide variety of volcanic landforms (cinder cones, lava domes). The caldera has a semi-circular shape (18–16 km) bounded by the Atotonilco scarp to the north, the NW–SE Manzanito fault to the west, and scattered vents to the east and southern parts. The distribution of the Acoculco ignimbrite, the lithic breccia, and lacustrine sediments define the caldera ring fault. Late Pleistocene activity and pervasive hydrothermal alteration suggest a high geothermal potential in the area.
The number of heat flow measurements at the Earth surface has significantly increased since the last global analysis (Pollack et al., 1993, https://doi.org/10.1029/93RG01249), and the most recent of them provide insights into key locations. This paper presents a new compilation, which includes approximately 70,000 measurements. Continental heat flow (67 mWm⁻²) does not change significantly, but the differences are more important for oceanic heat flow. The divergence with conductive cooling models is reduced significantly for young ages of the seafloor, since the most recent measurements (92 mWm⁻²) are significantly higher on average than the older ones (79 mWm⁻²). This is related to a better quality and a better sampling of measurements in regions affected by hydrothermal circulation. The total Earth heat loss derived from these most recent measurements is estimated to ∼40–42 TW and represents only 3–5 TW less than with a conductive cooling model (∼45–47 TW). Hydrothermal heat loss in the oceanic domain is estimated with a new method based on the ruggedness of the seafloor and represents ∼1.5 TW more than previous estimates. The heat flow variability on continents is so large that defining a trend with stratigraphic or tectono‐thermal age is difficult and makes extrapolation from age a poor predictor. On the other hand, additional geological and geophysical information can be combined with age for better predictions. A generalized similarity method was used here to predict heat flow on a global 0.5° × 0.5° grid. The agreement with local measurements is generally good and increases with the number and quality of proxies.
This study describes a financial analysis of the low-enthalpy geothermal system "La Jolla", located in Baja California, Mexico, based on both reconnaissance and technical studies. The technical feasibility study began with the system exploration to estimate the electric power generating potential using the heat in place model with a Monte Carlo simulation. The calculated energy output was 1 MWe for a 25 year period. Based on both the calculated energy and the physical characteristics of the site, a binary cycle plant was chosen for electricity generation. Profitability was calculated using Net Present Value and Internal Rate of Return. The project risk was obtained from the sensibility analysis of all variables used in the financial parameters calculation. The highest effect on risk comes from tariff price, on the other hand, the lowest effect corresponds to drilling. Projected income was estimated to be 47,000.00 USD per year, requiring an initial inversion of 615,000.00 USD. The time of return of 15 years was calculated, using a 6.8% of interest rate with a 60% private and 40% government investment frame. The NPV was positive, IRR was 10%, greater than 6.8%; therefore, the project may be considered as profitable.
Spectral analysis of NAMAG magnetic data enabled us to estimate depths to the Curie isotherm along the Pacific-North America plate boundary. The estimated depths for the Gulf of California, and southern Baja California peninsula, correlate quite well with the depths to the Moho available from previous studies based on receiver function, and seismic refraction. In northernmost Baja California, and southwestern USA no correlation is observed between depths to the Curie isotherm and depths to the mantle obtained from receiver function analysis. Depths to the Curie isotherm are shallower. Along the coastal plains of Sonora and Sinaloa, differences between receiver function based Mantle depths and Curie depths are equally large. However, there is more consistency with depths established by seismic refraction studies. Four zones with shallow Curie isotherm are identified in southern Gulf of California (GS1, GS2, GS3, and GS4). GS1 is located at the Gulf of California mouth. The Alarcón rise is located between GS1 and GS2. Pescaderos Basin is located northwest of GS2. GS3 stretches from the Carmen Basin to the Farallón Basin. GS4 extends from Tiburón Island up to northern Guaymas Basin. Northernmost shallow Curie depth zone (GN1) comprises Upper and Lower Delfín Basins, as well as the Consag and Wagner Basins. A northern prolongation also covers Pinacate Volcanic center. The southern shallow Curie isotherm zones are associated with lithospheric-asthenospheric material upwelling zones. GN1 also includes a convective component related to the younger magmatism of the Pinacate Volcanic Field. Deeper Curie depths are found at southern Baja California peninsula, interpreted as associated with thicker continental or stretched crust. It is possible that the crust is underlain or underplated by magnetic oceanic crust as suggested by satellite magnetic anomalies centered at the Magdalena shelf. A contrasting pattern features northern Baja California: deep Curie zones to the west contrasting with relative shallower Curie isotherm areas to the east. The prolongation towards the peninsula of the extinct Shirley transform fracture zone roughly separates the two domains observed along the peninsula, and suggests that the Curie isotherm along the peninsula is controlled by differences subduction of the Guadalupe and Magdalena microplates. Major differences pointed out between northern and southern Gulf of California might indicate that subduction also played a key role at the beginning of the opening of the Gulf of California, however, currently, the Curie pattern is controlled by the rifting processes (shallow Curie zones correlating quite well with the rift basins and the lithosphere-asthenosphere upwelling material).
Definition of geothermal provinces is a key factor for regional exploration. Mexico’s geothermal potential is underdeveloped, and government policies have aimed to simplifying regulations and providing insurance to reduce the risk and support developers. Additionally, geothermal resources inventories were made available to
encourage further development. Here, the correlation of heat flow measurements, recent thermal events and tectonic-geological setting is used to define 11 geothermal provinces that may serve as guide to identify areas with geothermal potential for exploitation/utilization of high, medium and low-enthalpy resources, based on geothermal play definition: 1 – Province CV1-MVB (Mexican Volcanic Belt); 2 – Province CV3-CP (Cerro Prieto); 3 – Province CV3-GE (Gulf Extensional); 4 – Province CV2-SMO (Sierra Madre Occidental); 5 – Province CV3- RGR (Río Grande Rift); 6 – Province CV2-CIV (Central Intraplate Volcanism); 7 – Province CD2-SMOr (Sierra Madre Oriental); 8 – Province CV2-EIV (Eastern Intraplate Volcanism); 9 – Province CD2-SMS (Sierra Madre del Sur); 10 – Province CV1-SEV (Southeast Volcanism); 11 –Province GP (Geo-pressurized).
Heat flow maps are a powerful tool for regional exploration of geothermal resources. Mexico is one of the main producers ofgeothermal energy and the search for undiscovered resources at a regional level should be based on heat flow values. Here, we present a heat flow map at 1:4,000,000 scale, produced with heat flow data compiled from open data bases and previously unpub-lished data. The compiled heat flow data includes bottom hole temperature, temperature logs, transient temperature measurements and measured temperature logs. The new data were calculated from temperature gradient information and estimating a mean con-ductivity value characteristic for the type of rock present in the stratigraphic column or assigning the mean conductivity value for the crust. Geothermal gradient and the thermal resistivity (inverse thermal conductivity) were plotted and heat flow was calculatedusing the Bullard method. The map covers the whole continental territory of Mexico and shows that most of the country has valueshigher than the world average. The highest heat flow values are concentrated in two provinces: the Gulf of California extensionalprovince and the Trans-Mexican Volcanic Belt.
A promissory low-to-medium temperature geothermal system located in Sonora (Mexico) has been studied. In the present work, a detailed geochemical survey was carried out to understand the hydrogeochemical signatures of hot spring waters. A field work campaign was conducted for collecting water samples from twelve hot springs placed in four major zones (NW, NE, C, and S). The collected samples were analysed by chemical and isotopic methods for determining their chemical (major and trace elements) and isotopic (18O/16O and D/H) compositions. Using geochemometric analyses of the fluid composition and fractionation, depletion and enrichment processes exhibited by major and trace elements were analysed. Hydrogeochemical classification was used to indicate the presence of sodium-sulphate (Na-SO4) waters in the North (NW and NE) and South hydrothermal zones; whereas calcium-magnesium-bicarbonate (Ca-Mg-HCO3) waters were identified for the Central zone. Some hot spring waters located in the NE zone were also typified as sodium-bicarbonate (Na-HCO3). In relation to the isotopic signatures of 18O/16O and D/H, four water samples from NE and C zones lie near to the global meteoric water line; whereas the remaining eight samples showed a shift for both oxygen and deuterium isotopes. A mixing line with a small shift of δ18O was identified and used as a proxy to discriminate waters with different isotopic signatures. After applying a geochemometric outliers detection/rejection and an iterative ANOVA statistical test, the mean temperature inferred from the most reliable solute geothermometers was 149±40 °C, which suggests to be considered as the minimum value of the reservoir temperature. As most of the hot spring waters fall outside of the full equilibrium curve, the original reservoir conditions were corrected by using a mixing conductive model, which predicted a deep equilibrium temperature of 210±11 °C. As this temperature is considerably higher than the mean temperature inferred from the geothermometers, it was suggested as an optimistic maximum reservoir temperature of the Sonora geothermal system. Using 150 °C and 200 °C as rounded-off reservoir temperatures (or min-max estimates), geochemical equilibria modelling based on fluid-mineral stability diagrams was carried out. An equilibrium process among local hydrothermal waters and albite-potassium feldespar and muscovite-prehnite-laumontite mineral assemblages was found. These minerals were proposed as representative mineral assemblages of low-grade metamorphism, which seems to indicate that the geothermal fluid equilibria were probably reached within the intermediate to acidic volcanic rocks from the Tarahumara Formation.
Play Fairway Analysis (PFA) is a methodology adapted from the petroleum industry that
integrates data at the regional or basin scale to define favorable plays for exploration in a
systematic fashion. Phase 2 of our Play Fairway Analysis of the Western Snake River Plain
(WSRP) province in southern Idaho had three primary goals: first, to fill data gaps in critical
areas in order to better define potential prospects, second, to integrate these data into new
thermal and structural models, and finally, to infer the location of potential resources and drilling
targets that could be validated during Phase 3. Prospects in the WSRP identified as potential
target resources for Phase 3 validation include the Mountain Home region close to the Air Force
Base, and the Camas Prairie. The Mountain Home region represents a blind geothermal resource
in an area of high heat flow and young volcanism. The Camas Prairie is a, structurally controlled
resource in an area with indicators of magmatic heat. New geophysical data acquired at these
sites includes reflection seismic, gravity and magnetic surveys, and a magnetotelluric field
survey. New geochemical data collection focused on the Camas Prairie, and included the
aqueous and isotope geochemistry of hot springs, cold springs, and wells (geothermal,
groundwater, and irrigation). New field mapping, sampling, and basalt flow chronology was also
conducted at Camas Prairie. Integrated results from Phase 1 and 2 studies suggest that the system
near the Mountain Home Air Force Base is located at ~1.5–2.3 km depth, and the structurallycontrolled
system at Camas Prairie is shallower, with upper reservoir depths perhaps only ~0.5–
0.7 km.
The present thermal state of the Chicxulub impact crater was determined. First, a 3D sub-surface structural model was constructed based on the gravity data set of northern Yucatan. An inversion gravity model was computed to obtain de central basin that includes a structural high. A 2D Euler deconvolution helped in locating the sources of the magnetic anomalies (i.e. melt/breccia sequence). The deeper magnetic sources correlate with the central uplift as obtained from the gravity inversion. The lithology information obtained from the boreholes drilled by UNAM was used to complement the gravity and magnetic models. Subsequently the obtained 3D sub-surface geometric model was used to establish the thermal state of the impact basin and its relation to the ground water flow. The mean temperature gradient in the studied area was 0.03ºC/m, the thermal conductivity varies from 2.11 to 2.67 W/mºC for the different rocks. We obtain a mean heat flow of 64 mW/m2.
As an important factor affecting the mangrove wetland ecosystem, water quality has become the focus of attention in recent years. Therefore, many studies have focused on the prediction of water quality to help establish a regulatory framework for the assessment and management of water pollution and ecosystem health. To make a more accurate and comprehensive forecast analysis of water quality, we propose a method for water quality prediction based on the multi-time scale bidirectional LSTM network. In the method, we improve data integrity and data volume through data preprocessing. And the network processes input data forward and backward and considers the dependencies at multiple time scales. Besides, we use the Box–Behnken experimental design method to adjust hyper-parameters in the process of modeling. In this study, we apply this method to the water quality prediction research of Beilun Estuary, and the performance of our proposed model is evaluated and compared with other models. The experiment results show that this model has better performance in water quality prediction than that of using LSTM or bidirectional LSTM alone.
Graphical AbstractSchematic of research work
The presence of hydrothermal manifestations on the coast of Bahía Concepción is associated with an extensional tectonic regime related to the formation of the Gulf of California. In this work, the geochemical composition of the intertidal springs is analysed to characterize the geothermal reservoirs associated with different groups of superficial manifestations. The La Posada hot springs present the highest temperature of the intertidal springs in the study area (66 °C). The hot springs in Bahía Concepción correspond to the sodium-chloride type and its chemical and isotopic composition shows the incidence of mixing phenomena with seawater and probably with high salinity. Compared to seawater, the thermal water has lower concentrations of Na⁺, Cl⁻, Mg²⁺, SO4²⁺ and HCO3⁻ ions, and higher concentrations of Si and cations such as Ca²⁺, Sr²⁺ and K⁺. The isotopic composition indicates that the thermal water from the intertidal manifestations in the northern part of the bay lies along a mixing line of sea water with groundwater with a shift towards oxygen enrichment due to water-rock interaction. Therefore, it is likely that one single reservoir feeds all sampled hot springs.
Within the scope of the Project CeMIE-Geo P07 “Estimation of the power generation potential of the Enhanced Geothermal Systems (EGS) in Mexico”, we have estimated the Theoretical Potential of the crystalline basement outcrops in Mexico. We used the methodology described in “A Protocol for Estimating and Mapping Global EGS Potential” (Beardsmore et al., 2010). In it, the Theoretical Potential is defined as “an estimate of the physically usable energy supply over a certain time span in a given region”. It is defined solely by the physical limits of use and thus marks the upper limit of the theoretically realizable energy supply contribution”. Only a portion of the Theoretical Potential will be accessible and extractable and represent a Geothermal Resource as defined by public Reporting Codes. Here we present the geographical distribution of the outcropping basement in continental Mexico and its rock type, on a grid of 5’×5’ cells (latitude, longitude), as required by the Protocol. The estimation includes 2,785 cells and a depth interval of 3 to 10 km. The estimation is derived using the following assumptions: (i) all the heat above the base temperature (surface T + 80°C) is theoretically recoverable in all locations; (ii) 30 years life span of power generation; (iii) the cycle thermal efficiency is a function of resource temperature as per the tabulation recommended by the Protocol. The Theoretical Potential estimated for the outcropping basement in continental Mexico is 17,894,409.28 MWe. The six states with greater potential, in decreasing order are Oaxaca (4,821,469.56 MWe), Guerrero (2,851,275.90 MWe), Baja California (2,735,239.59 MWe), Sonora (1,572,280.26 MWe), Jalisco (1,117,772.67 MWe) and Chiapas (1,007,850.21 MWe). We present a table with the estimated Theoretical Potential of all the Mexican states; for nine of them potential is zero because of lack of outcropping basement. Furthermore, we present maps of the geographical distribution of Theoretical Potential for seven depth levels (3 to 10 km), each 1 km thick, as required by the Protocol. Considering that the area of the outcropping basement amounts to only 10.67% of the Mexican continental area one concludes that the Theoretical Potential of continental Mexico is significantly greater than 17,894,409.28 MWe. © 2016, Gerencia de Proyectos Geotermoelectricos. All rights reserved.
The objective of this study was to determine the influence of marine shallow-water hydrothermal systems in Mapachitos, bahia Concepcion, on the composition of surficial sediments in the surrounding area of this bay. The following elements Al, As, Ba, Ca, Cd, Co, Cs, Cu, Fe, Hg, Li, Mn, Mo, Ni, Rb, S, Ti, U, Zn, C-org, and C-inorg were determined in sediment samples. The calculated CaCO3 values in the sediments within some spots of the study area were as high as 90% (with an average of 61 %). The concentration of organic carbon in the sediments was approximately 1%. The total element contents in the sediments were compared with Earth's crustal average, and enrichment factors (EF) were calculated using Al as normalizing element. The results showed that the most of the elements (Ba, Co, Cs, Cu, Fe, Li, Mn, Ni, Rb, Ti, U, V, and Zn) are conservative, with average EF close to unity. Lithium, mollybdenum and uranium were enriched in the sediments with average values of EF between 2 and 10. The highest average EF determined in the study were for the following elements: As, Ca, Cd, and Hg. The average concentrations of potentially toxic elements in the sediments from the Mapachitos vents were 60 mg kg(-1) for As, and 21849 mu g kg(-1) for Hg. The surface sediments of the adjacent area, however, have low average concentrations for As and Hg: 3.7 mg kg(-1) and 52 mu g kg(-1), respectively. Other elements such as Cd (0.9 mg kg(-1)) and Ca (28.3%) are highly enriched in the sediments of the study area, comparing to their average crustal abundances. The results of Principal Component Analysis allowed to determine three factors which explain 91% of data variance, as well as to differentiate four associations including terrigenous elements, calcareous components, elements of the hydrothermal origin and redox-sensitive elements in the surface sediments off the Mapachitos in the north-western portion of bahia Concepcion. Furthermore, the results confirmed the influence of the hydrothermal inputs of some trace elements on the sediments of the area surrounding the vents, in particular As and Hg, and to a lesser extent Al, Fe, and Mn at the venting site.
Los nuevos conceptos sobre la movilidad de la litosfera han conducido en los últimos años a un replanteamiento de los principales problemas tectónicos y paleogeográficos de México. La estructura geológica de México y Centroamérica revela una de las más complejas historias de integración y evolución cortical, caracterizada por episodios de concurrencia de diversos fenómenos geodinámicos y de interacción de segmentos continentales mayores y menores.
doi: https://doi.org/10.22201/igeof.00167169p.1986.25.1.799
We have examined the problem of bottom-hole temperatures (BHTs) in the Colorado and Nebraska portions of the Denver Basin with the use of three existing correction schemes; the Förster Correction, the Harrison Correction, and the Kehle Correction. We integrated the results of these three equations with the results of equilibrium temperatures to quantify which existing correction works best with Denver Basin stratigraphy. Of the three existing corrections, we determined that the Förster Correction has the least amount of area between curves for the integration, thus it is the best correction. Since we had the equilibrium data, we created a tailored correction scheme for the Denver Basin: Temperature Correction Factor (Tcf) = 0.0124x + 7.8825.
The Wagner basin, located in the northernmost Gulf of California, hosts a large reservoir with geothermal potential documented in recent heat flow surveys. Although there is evidence of heat generation above the average value for an oceanic crust in the Wagner basin, it is unclear what the heat source is. To better understand the thermal structure in the northern Gulf of California, we acquired four 2D multichannel seismic reflection profiles and two systematic heat flow profiles across the Wagner basin. The survey targeted a geothermal anomaly, which we denominated “Devil's Hole” in a clear reference to pockmarks on the seafloor, and very high heat flow values. The heat flow profiles are ∼12 and ∼9 km long, are sub perpendicular to each other, have a nominal measurement spacing of ∼1 km, and were located along the transects of two of the four seismic reflection profiles. The two remaining seismic profiles are ∼34 and ∼40 km long, respectively, and are oriented SWW-NEE. To obtain seismic images, we used a conventional seismic processing workflow. After heat flow data correction, the minimum, maximum, and standard deviation of heat flow values for the Wagner basin are 295±42 and 10,894±114 mW/m². We interpret the relatively high heat flow and large variability in the central part of the acquired profiles is caused by upward fluid flow at the Wagner fault zone. In contrast, the lower heat flow in the western flank of the basin suggest conductive heat transfer given the absence of faults. Based on these observations, we develop a geological model in which venting is not the product of a nascent spreading center as other authors have suggested. Instead, hydrothermal activity appears to result from isolated thermal plumes, rising from the base of the sedimentary column, captured by permeable fracture systems.
New high heat flow data confirm the presence of a heat source in the passive margin of the southern Baja California Peninsula that is not linked with volcanic activity. The high heat discharge is spatially associated with low seismic velocity, crustal thinning, intense seismic activity, documented local extension, shallow Curie Point Depth and silica geothermometer temperatures above 100ºC. The highly oblique rifting regime in the centre of the Gulf of California generates a transtensional setting conducive to local extension in its SW margin. Similar high heat flow in a rifted margin has been reported only in the Gulf of Aden that is also an obliquely spreading ridge. The intense heat discharge, with heat flow values as high as 613 mW·m‐2, indicates the presence of a heat source consistent with mantle upwelling. Heat transfer calculations indicate that the heat source emplacement would be at most 2 My old.
Thermal manifestations are commonly found in central Mexico as result of the volcanic activity originating from the formation of the Trans-Mexican Volcanic Belt during the Quaternary. The Rancho Nuevo hot spring is one of them that has not been described before with a discharge temperature near 92 °C. The goal of the present study is to provide geothermal characteristics of thermal manifestations at Rancho Nuevo location based on geochemical and mineralogical results to explain deep-subsurface processes that occurred in the geothermal system. The presence of kaolinite, montmorillonite, opal, zeolite, barite, pyrite, and stibnite in altered soil sediments or around the hot springs identified by the techniques used in the present study, confirms the presence of hydrothermal activity. In addition, based on the X-ray diffraction, calcite precipitates at the surface of the thermal springs. This mineral association reflects deep geothermal processes and is eventually deposited in shallow zones. Fluid mixing processes and variations in redox conditions are suggested by mineral association and isotopic sulfur data. Finally, based on the physicochemical data provided by the water samples and the discharge conditions of the springs, stability diagrams were constructed for pyrite, barite, and zeolites using the Geochemist’s Work Bench program to corroborate these data with the mineralogical results. The mineralogical results and distribution, as well as the N-S trend of mineral associations suggest interaction processes between geothermal fluid and rocks of the stratigraphic sequence, and active major faults, enabling the upward flow of deep geothermal fluids. The approach to the conceptual model of the Rancho Nuevo geothermal prospect reveals an attractive potential for the exploration of a viable geothermal resource in central Mexico.
A hydrogeological conceptual model has been developed that describes the geothermal system located at the Maneadero region in Ensenada, Baja California, Mexico. In addition, a two-dimensional steady state simulation of water flow and heat transfer of a model profile using COMSOL Multiphysics software is also presented. The proposed hydrogeological conceptual model considers that the old local anoxic subsurface seawater feeds the system, and a remnant magmatic intrusion in the surface from past volcanism at 2 km of depth works as heat source. The intersection between the south Agua Blanca Fault and the L3 alignment promote the fluids ascent to the submarine hydrothermal vent. The results of the simulation show a reservoir temperature of 164 °C and an affluent temperature of 105 °C, varying between 1 °C and 3 °C, respectively, with previous studies. Moreover, a geothermal potential of 0.48 MW was estimated for the simulated profile. The current policy of exploitation of geothermal resources in Mexico makes the development of these models particularly relevant, serving as a tool for their evaluation and management.
La Primavera caldera is a Quaternary rhyolitic volcanic field located in the western part of the Trans-Mexican-Volcanic-Belt (TMVB). The caldera forming eruption of La Primavera occurred ∼95 ka with the emplacement of the Tala ignimbrite. Here, we present a new stratigraphy and evolution of the post-caldera activity based on intense fieldwork, correlation of deposits, and ten ²³⁰Th/U geochronology dates in zircons. The collapse produced an 11-km wide caldera followed by the formation of an intra-caldera lake. After the caldera collapse, several rhyolitic domes were extruded, inside and outside the caldera ring-fault until 26.8 ka. The first post-caldera event took place 86.4 ka with the eruption that emplaced the Giant Pumice (GP) followed by the occurrence of at least fourteen pyroclastic units (UA to UN). The intra-caldera explosive activity came from the central resurgent Nejahuete composite dome with the deposition of the GP and A to D units between 86.4 and 71.5 ka. The extra-caldera explosive activity came from the San Miguel, Planillas and Tajo volcanic centers with the deposition of the E to N units inside the caldera and south of the caldera ring fault between 71.5 and 26.8 ka. Three eruptions were originated at San Miguel volcanic center between 71.5 and 60.3 ka (units E, G and H) and six eruptions dated between 68.9 and 44.7 ka were originated at Planillas volcanic center (units F, I, J, K, L and M). The last eruption of the caldera occurred between 44.7 and 26.8 ka at the Tajo volcanic center (UN). The eruptions appear as pyroclastic successions interbedded with lake deposits (units A-B) and as subaerial deposits separated by paleosols or lahar deposits (units C-M). The revised stratigraphy indicates that the caldera resurgence occurred right after the caldera collapse 93.8 ka and continued until 75.8 ka. This new pyroclastic stratigraphy provides key information on the post-caldera evolution of La Primavera.
The Sureste Basin of Mexico is a story of split exploration maturity, with more than 139 discoveries in the onshore and shallow-water area of the Sureste in a series of stacked prolific plays, but less than 12 exploration wildcat wells on the Campeche slope, in water depths greater than 500 m. Over 50% of the basin area lies in this under-explored deep-water Campeche slope, with future oil potential shown by the presence of wide seabed oil seepage indicating a regionally mature world-class source rock to be present. With the 2014 opening of Mexico's oil industry, basin-wide 3D seismic imaging of this under-explored deep-water extension to the Sureste Basin is now in the hands of international oil companies that hold substantial exploration well commitments over the next few years. This paper discusses the hydrocarbon play potential of both the classic Tertiary slope clastic reservoir systems as well as the significant Mesozoic carbonate reservoir potential for which there are fewer analogues outside of Mexico.
Subsurface challenges originating from dry hole analysis relate to charge timing and deep charge focus, subsalt deep structural imaging, deep reservoir quality issues and uncertainty in column height prediction, given the high-relief nature of many undrilled salt related structures.
Investigating, from surface, deep-seated geothermal systems below hundreds to thousands of meters of thick clastic and unconsolidated sediments is always a timely theme for geothermal exploration. In this paper we describe a fieldwork and remote approach to the San Agustín del Maíz area, located in the central sector of the Trans-Mexican Volcanic Belt. Here, several geothermal manifestations are distributed in a broad basinal area, characterized by fluvio-lacustrine sediments unconformably resting on volcanic rocks. The tectonic control on the geothermal fluid circulation is highlighted by the alignment of thermal springs, by their temperature distribution and by the morphology of silica-sinter deposits, these latter aligned along the main trend of the regional faults, controlling dykes-feeding volcanoes, too. By integrating these data with structural and kinematic analyses collected in the fault-surfaces exposed in the volcanic bedrocks, it derives that permeable rock volumes, guarantying the arising of geothermal fluids from depth to the surface, are located at the intersection between WSW- striking normal faults and NNW- striking transfer faults, both framed in the current ∼NW-SE extension, active since Pliocene, at least. The proposed model offers new inputs for the geothermal exploration in México, and, overall, for those areas worldwide with a similar tectonic setting.
Hot springs and related deposits are common features in active geothermal areas around the world. In this study, centered on the Ixtlán de los Hervores geothermal zone (Michoacán, Mexico), we analyzed the distribution of active hydrothermal manifestations and hot-spring deposits as well as the local stratigraphy to determine the influence of the faults in the hydrothermal fluid circulation. The hydrothermal manifestations are mainly represented by hot springs with water temperatures up to 92 °C (depositing silica sinter at the surface). All the hydrothermal features are located within a tectonic depression controlled by the potentially active Ixtlán-Encinal fault. Inside this depression, lacustrine sediments were deposited from Pliocene up to the Hispanic colony period (~XVI–XIX centuries). A pre-Hispanic silica-sinter layer was identified beneath the lacustrine sediments, as well as a debris flow deposit, rich in pottery, suggesting that the debris flow may have affected local inhabitants during pre-Hispanic times.
This chapter presents an overview of the volcanic eruptions that have occurred in Mexico during the Holocene. Although volcanic regions are distributed all over the country, Holocene eruptions are mainly concentrated in the southern half of the country and, in particular, in the Trans-Mexican Volcanic Belt. Here, we summarize the details of the eruptions from the stratovolcanoes and monogenetic volcanoes, which have been extensively documented in the volcanological literature, and their radiometric or historical dates. Out of the 153 Holocene eruptions described so far, ~63.4% have occurred at active stratovolcanoes and calderas, while the remaining ~36.6% have occurred from vents within monogenetic volcanic fields. Surprisingly, it seems that volcanism increased through time from Early (~17.7%), Middle (~26.8%) to Late Holocene (~55.5%). These figures may be biased because younger deposits are better preserved than older ones, and the latter usually are eroded through time especially around active stratovolcanoes. Around 24 eruptions (~15.6%) have taken place in pre-Hispanic and historical time out of which 11 occurred during the Little Ice Age. These eruptions have posed a serious threat to the surrounding regions and their populations. Some stratovolcanoes have collapsed at least once, covering and destroying previous deposits and making it difficult to reconstruct past eruption records. Large, Plinian to sub-Plinian eruptions at stratovolcanoes are well recorded in the stratigraphy, but the small eruptions that did not produce widespread deposits are difficult to define. Eruptions from monogenetic volcanic fields were fed from central vents and fissures and mostly dominated by Strombolian activity and lava flows. The Holocene-collected data suggests that an eruption has taken place every ~65 years in Mexican territory during the past 10 ka. Monogenetic volcanoes should not be underestimated because at least 56 volcanoes have been created in Mexico during the Holocene, yielding an average recurrence of ~176 years. This chapter stresses the need to improve our knowledge of Holocene volcanism (e.g. still limited studies in some volcanoes) aimed to define average recurrence intervals and provide the data for probabilistic studies and hazard assessment to reduce future volcanic hazards.
Geophysical prospecting has become essential to identify low enthalpy areas with geothermal potential, mainly, for direct uses. The present study uses two seismic techniques and lithological information from shallow boreholes located northeast of the Tres Virgenes Geothermal Field, B.C.S., Mexico, to identify geological structures of geothermal interesting. Using the Multichannel Analysis of Surface Waves method (MASW), it was possible to correlate the S-wave velocity model with the lithology from two wells drilled over the seismic profile. Additionally, we generated a seismic reflection model to describe the geological distribution of deeper structures. The reflection profile, which reached depths of about 500 m, was complemented with superficial information from a MASW velocity model. We found a relationship between the velocity distribution of P and S waves from both models. The integration of seismic and lithological information allows us to identify a very fractured subsurface and a deep zone with possible geothermal interest.
We present a 3D numerical crustal temperature model with inverse optimisation methodology and analyse the present-day conductive thermal field of the Danish onshore subsurface. The model is based on a comprehensive analysis and interpretation of borehole and well-log data for thermal and petrophysical rock properties and their regional variability and spatial distribution across the country. New values of terrestrial surface heat flow derived from 21 deep well locations are 65–76 mW m−2 (mean: 72 ± 3) for the Danish Basin, 77–86 (81 ± 5) for the Danish part of the North German Basin, and 61–63 (62 ± 1) for the Sorgenfrei-Tornquist-Zone/Skagerrak-Kattegat Platform, respectively. The observed heat flow variations are consistent with the position of the Danish area in the transition zone between the old Precambrian Baltic Shield (low heat flow) and central European accreted terrains and deep basin systems (significantly higher heat flow).
For the temperature modelling, conductivities and heat flow are constrained and validated (rms: 1.2 °C, ame: 0.7 °C) by borehole temperature data covering a depth range of up to 5 km (137 values from 46 wells). Significant modelled temperature variations are caused by (i) complex geological structures (thickness variations, salt structures) and (ii) the variation of rock thermal conductivity between and within geological formations as well as lateral variation in background heat flow. Modelled temperature for major geothermal reservoirs indicate substantial potential for low enthalpy heating purposes. Reservoir temperatures above 130 °C, of interest for the production of electricity, are observed for some local areas, however, likely, too deep for non-stimulated sufficient reservoir quality.
The La Escalera and Agua-Caliente Tzitzio geothermal areas are newly discovered geothermal prospects in Mexico that may have the potential to be utilized using binary cycle plants. Hot springs (40-50 °C) are constrained to the river banks in both areas, but gas discharges occur on the banks as well as in the riverbeds. The thermal water is predominantly bicarbonate type. Reconnaissance work yielded encouraging results, as the Na/K geothermometer indicates temperatures between 139 and 245 °C for La Escalera water samples in a partial equilibrium. La Escalera and Tzitzio have strong surface gas discharges, and dry gas samples were collected for δ 13 C isotopic analysis of CH 4 and CO 2 ; the results indicate a magmatic origin for the gas discharged.
La Primavera (LP) is a rhyolitic caldera located in the western sector of the Trans-Mexican Volcanic Belt (TMVB). LP is located close to the triple point junction of the Chapala, Colima and Tepic-Zacoalco rifts. To understand the internal structure of the LP and its relationship with the Tepic-Zacoalco rift we carried out a geophysical study with different techniques. Satellite gravity, airborne data followed by ground-based gravity and magnetic surveys were used to performed semi-quantitative analysis to understand the structure of the LP. Residual gravity anomalies (22–15 mGal) occuring on the entire volcanic structure are attributed to its rhyolitic nature. Aeromagnetic anomalies ~125 nT occur on the south and western portions of LP. Analyzed lineaments in the area (Tilt Derivative Algorithm) follow predominantly regional NW-SE and W-E trends. Modeled Werner anomalies, identify the presence of numerous contacts and dikes, especially along main faults, such as Rio Caliente, La Gotera, Mesa Nejahuete, and the caldera ring fracture. Strikinlgy, the higher parts of intrusive bodies and dikes appear at variable depths ≤7.3 km beneath San Miguel and Las Planillas domes. These results were replicated by using an Euler's solution map. The deepest parts of these bodies occur at around 7.8 km south of Las Planillas and El Tajo domes. We developed a 3D smooth model of the magnetic susceptibility isosurfaces with five magnetized bodies beneath the LP structure. Depth and geometry of surface volcanic structures were determinate, thus providing a preliminary visualization of the main isosurface of 0.0343 SI located in the southern area of the caldera. Additionally, the upper part of the magnetic source is 5.5 km in depth. The present study, therefore, reveals the presence of various intrusive bodies existing at different depths inside the caldera. Further, structures and lineaments within the caldera provide evidence for understanding the presence of intrusive bodies, geological structures associated with the caldera structure and geothermal activity.
Southern California and the northern part of the peninsula of Baja California form a common region affected by a number of regional-scale active faults, all constituting part of the San Andreas-Gulf of California fault system. All the faults are seismically active to different degrees as a result of the interaction between the Pacific-North American plates in the Gulf of California region. A structural relationship should exist between the Guaymas lineament and the Puertecitos extensional region, which is the conduit where movement is induced to the onshore peninsular faults. -from Authors
A primary control on the geodynamics of rifting is the thermal regime. To better understand the geodynamics of rifting in the northern Gulf of California we systematically measured heat-flow across the Wagner Basin, a tectonically active basin that lies near the southern terminus of the Cerro Prieto fault. The heat flow profile is 40 km long, has a nominal measurement spacing of ~ 1 km, and is collocated with a seismic reflection profile. Heat flow measurements were made with a 6.5-m violin-bow probe. Although heat flow data were collected in shallow water, where there are significant temporal variations in bottom water temperature, we use CTD data collected over many years to correct our measurements to yield accurate values of heat flow. After correction for bottom water temperature, the mean and standard deviation of heat flow across the western, central, and eastern parts of the basin are 220±60, 99±14, 889 ± 419 mW m-2, respectively. Corrections for sedimentation would increase measured heat flow across the central part of basin by 40 to 60%. We interpret the relatively high heat flow and large variability on the western and eastern flanks in terms of upward fluid flow at depth below the seafloor, whereas the lower and more consistent values across the central part of the basin are suggestive of conductive heat transfer. Based on an apparent fault depth of 1.75 km we estimated the maximum Darcy velocities through the western and eastern flanks as 2 and 8 cm yr-1, respectively. Heat flow across the central basin is consistent with gabbroic underplating at a depth of 15 km and suggests that continental rupture here has not gone to completion.
The continuous sediment cover has allowed detailed and extensive mapping of the distribution of surface heat flow throughout the Guaymas basin; more than 400 heat-flow measurements have been collected since 1959 in crust ranging in age from 0 to about 3 Ma. Away from the sites of crustal accretion, the background heat flow throughout the Guaymas Basin is about 180±10 mW/m². Within the two spreading centers of the basin, known as the northern and southern troughs, heat-flow values range from 0 to nearly 9 W/m², and variations of two orders of magnitude occur over distances as short as a few hundred meters. Heat-flow patterns generally follow the northeast-southwest structural trend of the central troughs but are locally controlled by recent intrusive activity and associated hydrothermal circulation. -from Authors
Results indicate a shallow magnetic horizon with depths to source tops between 2.3 and 4.1km below sea level; an intermediate-depth horizon between 3.6 and 6.4km; and a deep magnetic horizon between 6.7 and 9.5km. Computed depths to the bottom of the magnetized crust yield an average depth of 11.5km below sea level. An average thermal gradient of 51.8°C/km is determined and average computed heat flow for the central part of the northern Gulf of California is found to be 114 mW/m². Plots of fault traces are also presented, which were determined using a deconvolution method based on Werner's (1953) simplified thin-dike assumption. This technique identifies fault traces for the northern Gulf which are very similar to those proposed by Ness and Lyle (1991). -from Authors
The main objective of this study is to report an update of the surface heat flow database of México. To our knowledge, this work is the first data compilation that integrates existing published and unpublished measurements to create a new heat flow map using a variety of data sources from 108 sites (transient borehole temperatures and temperature-depth profiles). Heat flow measurements in México are still relatively sparse. Updates of heat flow and geological data is required for a better understanding of the thermal regime of México, an accurate characterization of heat flow provinces, and to create a consistent geothermal map.
A better understanding of suballochthonous salt petroleum systems can be achieved by thermal modeling a series of vertical pseudowell profiles that are positioned along ramps and flats identified at the base salt level. This allows the changing 2D shape of the highly conductive salt to be taken into account and assesses the physical parameters that control the thermal evolution. A case study of a typical cross section through the Burgos Basin and Perdido Fold Belt is analyzed in an area of very active oil exploration in northern Mexico. Numerical experiments indicated how the extrusion of salt cools the underlying basin and significantly prolongs the period of Tithonian source rock maturity. The rapid extrusion of thick allochthonous salt sheets, and the associated transient heat flow effects, can also cause peaks in oil generation, in places postdating the trap formation during the Oligo-Miocene folding event. The principal Tithonian source rock is predicted to have remained in the oil window since Paleogene times, despite being buried to present-day depths of approximately 8 km subsea. This upgrades the oil potential of some of the subsalt areas that are currently on offer in the CNH-R01-L04/2015 Mexico deepwater Licensing Round. © 2017 Society of Exploration Geophysicists and American Association of Petroleum Geologists. All rights reserved.
High values of heat flow (2.3 – 2.9 hfu) (1 hfu=1μcal/cm²= 41.8mW/m²) and reduced heat flow (1.2 – 2.1 hfu) in portions of eastern Chihuahua, eastern Durango, and central Zacatecas suggest the possibility of a southeast trending, but discontinuous, incipient rift across the Central Plateau of northern Mexico. Calculated isotherms for this zone appear to be elevated in the Central Plateau and exhibit patterns that loosely follow the western edge of the Sierra Madre Oriental. The 1000°C isotherm extends to between 20 and 30 km depth in eastern Chihuahua and central Durango-Zacatecas. East-west cross-sections display a sharp transition from projected high temperatures beneath the Central Plateau to more moderate values under the Sierra Madre Oriental. These thermal aspects combined with the geographic continuity of this zone with the Rio Grande rift proper suggest a relation between the two features.