Introduction

Radiogenic heat production (RHP) from the decay of uranium (U), thorium (Th), and potassium (K) constitutes one of the most important sources of heat from the Earth’s interior (Abbady and Al-Ghamdi 2018). Thus, the determination of the heat produced by the decay U, Th, and K in rocks is a key factor in geothermal exploration (Rybach 1988). The decay of U, Th, and K proceeds from the decay series of 238U, 232Th, and the isotope 40K, respectively. In the rocks, these three radioelements are associated with their mineralogical compositions. Specifically, U has an average abundance of about 3 ppm in the Earth’s crust and is a major constituent of some minerals such as uraninite, which is associated with granite-forming minerals. Uranium also appears in common accessory minerals (zircon, apatite, monazite, allanite, and sphene) in igneous and metamorphic rocks (IAEA 2003). Thorium has an average crustal abundance of about 12 ppm. This radioelement appears as a major constituent in minerals such as thorite and uranothorite. It is also found in accessory minerals, for example, monazite, xenotime, zircon, allanite, apatite, sphene, and epidote. Potassium has an average crustal abundance of 2.33 wt%. This radioelement is mainly found in many rock-forming silicate minerals, such as alkali-feldspars and micas in granitoids (IAEA 2003).

The gamma rays penetrating through geological materials are very useful for measuring the radioelement concentrations within such materials (McCay et al. 2014). The U, Th, and K concentrations can be obtained from samples or through aerial and terrestrial gamma-ray spectrometry measurements. Therefore, these concentrations can be obtained from in situ gamma radiation measurements, that is, taken directly from geological outcrops with handheld gamma-ray detectors (IAEA 2003; McCay et al. 2014; Adagunodo et al. 2019; Akingboye et al. 2021). These in situ measurements can detect gamma rays up to depths of approximately 0.15 m and over diameter of 1 m diameter in outcrops (McCay et al. 2014). According to Rybach (1988) and Aisabokhae and Tampul (2020), outcropping rocks with high concentrations of radioactive elements must have a high heat flow density. This latter, combined with RHP, provides information about the structure and temperature field of the Earth’s crust. In turn, the RHP can be inferred from the concentrations of the three radioelements and the density of the rocks considered (Rybach 1988). This is related to the heat produced in the lithosphere, the basement, and the fill of the sedimentary basins (Abbady and Al-Ghamdi 2018). These basin fills mainly consist of sedimentary (clastic and carbonate) and igneous materials, which can produce high RHP rates in sedimentary basins (McCay et al. 2014). Clastic sedimentary rocks generally contain higher U, Th, and K concentrations (IAEA 2003) and, therefore, higher RHP values than carbonate rocks (Hasterok et al. 2018; Cui et al. 2019). Acidic igneous rocks have higher radioactive element concentrations than intermediate and basic rocks (IAEA 2003), which implies an increase in the RHP with an increase in a rock’s siliceous content (Cui et al. 2019).

In Mexico, geothermal resources are distributed in marine and continental areas. The former are located mainly in the Gulf of California and the latter in five geothermal fields located in various states across the country. Heat flow studies have confirmed the great potential of geothermal resources in Mexico, with values above 100 mW/m2 (Prol-Ledesma et al. 2018). Similarly, other studies investigating the depth of magnetic sources and heat flux estimates have revealed values of 85 ± 27 mW/m2 in the continental zones and 64.7 mW/m2 in the oceanic zones (Carrillo-de la Cruz et al. 2021).

Over 150 hot spring manifestation sites have been reported in northeastern Mexico, specifically within the Sabinas Basin (Fig. 1; Torres-Rodríguez et al. 1993; Martínez-Estrella et al. 2005; Wolaver et al. 2013; Iglesias et al. 2015; Prol-Ledesma et al. 2018). Such manifestations suggest that this basin could host geothermal deposits. This basin is mainly filled with sedimentary materials (clastic, carbonate, and evaporitic) and igneous rocks (intrusive and extrusive) with basic and intermediate compositions (Eguiluz de Antuñano 2001). The RHP characteristics of each geological unit that comprises this basin should be determined to conduct future geothermal exploration work in the area. Indeed, the RHP will depend on the studied lithologies (Vila et al. 2010). Thereby, this paper presents the results of the calculation of RHP from the U, Th, and K concentrations obtained from the in situ gamma radiation measurements of sedimentary and igneous rock outcrops in the Sabinas Basin.

Fig. 1
figure 1

a Structural configuration and tectonic features of northeastern Mexico (modified from Chávez-Cabello et al. 2005). Black rectangle indicates location of the study area. The hot springs were previously reported by Torres-Rodríguez et al. (1993), Martínez-Estrella et al. (2005), Wolaver et al. (2013), Iglesias et al. (2015), Prol-Ledesma et al. (2018), and Tolentino-Álvarez (2022). b Geological map of the study area, modified from Barboza-Luna et al. (2008), González-Ramos et al. (2008), Martínez-Rodríguez et al. (2008), Pérez de la Cruz et al. (2008), Romo-Ramírez et al. (2008), and Santiago-Carrasco et al. (2008). 1, 2, 3, and 4 indicate the location of the Marcelinos, Pánuco, Colorado, and Providencia intrusive bodies, respectively

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Geological setting

The Sabinas Basin constitutes a paleogeographic features at the northeastern Mexico, related to the breakup of Pangea during the Late Triassic to Middle Jurassic (Wilson 1990). This geological event allowed the formation of grabens and horsts that controlled the sedimentation patterns in the region during the Mesozoic (Padilla y Sánchez 1986). The Sabinas Basin is the principal graben in the region surrounded by horsts, such as the Coahuila block, the Burro-Peyotes Peninsula, and the Tamaulipas Archipelago. The Coahuila block is composed mainly of Permian sedimentary rocks, with intercalation of volcanic rocks (andesites and dacites). This block is intruded by Permo-Triassic granitic to granodioritic rocks. The Burro-Peyotes Peninsula is composed mainly of metasedimentary rocks. The Tamaulipas Archipelago has a sequence of Middle-Permian Pennsylvanian marine rocks and Triassic intrusive bodies on a Permo-Triassic intrusive basement. The La Mula and Monclova islands are two Permo-Triassic granitic intrusions, that constitute two high basement blocks within this basin (Fig. 1a; Wilson 1990).

The Sabinas Basin is mainly filled with evaporitic, carbonate, and clastic rocks, deposited from the Late Jurassic to the Holocene (Fig. 2). The materials deposited during the Late Jurassic were primarily terrigenous, which generated various geological formations (Eguiluz de Antuñano 2001).

Fig. 2
figure 2

Stratigraphic column of the Sabinas Basin, modified from Eguiluz de Antuñano (2001). The boxes with a thick blue line show the studied geological formations

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Carbonates and terrigenous rocks were deposited during the Early Cretaceous (Eguiluz de Antuñano 2001). Figures 1b and 2, such as La Mula (Hauterivian–Barremian), Pátula (Hauterivian–Barremian), Cupido (Hauterivian–Aptian), La Peña (Aptian), and Aurora (Albian). Up to 760 m thick shales and clayey limestones were deposited in the La Mula Formation; while sandstone, shale, and conglomerate were deposited in the Pátula Formation (González-Ramos et al. 2008). Moreover, limestone and dolomite with a total thickness of up to 500 m conform the Cupido Formation (Eguiluz de Antuñano 2001). Finally, a 200 m thick sequence of clayey limestones and shales constitutes the La Peña Formation, and micritic limestones of up to 1000 m in thickness correspond to the Aurora Formation (Eguiluz de Antuñano 2001).

The Late Cretaceous terrigenous and carbonate rocks outcrop in the study area; these include the Georgetown (Albian–Cenomanian), Del Rio (Cenomanian), Buda (Cenomanian), Austin (Coniacian–Santonian), Upson (Campanian), San Miguel (Campanian), and Olmos (Maastrichtian) formations. The Georgetown Formation consists of micritic and argillaceous limestones, with a thickness of up to 300 m (Eguiluz de Antuñano 2001). The Del Río Formation comprises shales and sandstones with a thickness of up to 80 m (Eguiluz de Antuñano 2001). Clayey limestone successions of 23 m and 700 m in thickness make up the Buda and Austin formations, respectively (Eguiluz de Antuñano 2001). The shales of the Upson Formation reach 150 m in thickness (Eguiluz de Antuñano 2001). The San Miguel and the Olmos formations are up to 260 m and 378 m thick, respectively, and both consist of sandstones and shales (Eguiluz de Antuñano 2001).

Various magmatic events originated during the development of the Sabinas Basin, represented principally by different bodies of intrusive and extrusive rocks of Tertiary age that outcrop in the region (Eguiluz de Antuñano 2001; Aranda-Gómez et al. 2005). The intrusive igneous rocks affected much of the sedimentary sequence that fills the basin. These igneous rocks are represented by monzonites, monzodiorites, quartz monzonites, granodiorites, and diorites, belonging to the Candela-Monclova magmatic belt (González-Ramos et al. 2008). The extrusive rocks mainly consist of basalts, basanites, and hawaiites, belonging to the Las Esperanzas, Ocampo, and Las Coloradas volcanic fields (Aranda-Gómez et al. 2005).

Materials and methods

The calculation of RHP was carried out using 970 in situ gamma-ray spectrometry measurements obtained at 23 sites in the Sabinas Basin (Fig. 1b; Table 1). Of these sites, 499 measurements were made at seven igneous rock sites, of which four represented intrusive rocks (granodiorites of the Marcelinos, Pánuco, Colorado, and Providencia intrusive bodies; 111 measurements), and three comprised extrusive rocks (basalts; 388 measurements). A total of 471 measurements were also performed at 16 sedimentary rock sites. Of these sites, four consisted of sandstone (160 measurements), six were represented by limestone (251 measurements), and six were composed of shale (60 measurements). The granodiorite (Tertiary) sites were located at the Candela-Monclova magmatic belt, and the basalt (Tertiary) sites in the Las Esperanzas, Ocampo, and Las Coloradas volcanic fields (Fig. 1b). The sites hosting the sedimentary rocks were characterized by clastic rocks (shale and sandstone) and carbonates (limestone). These rocks belong to different Early Cretaceous (Figs. 1b, 2; La Mula, Pátula, Cupido, La Peña, and Aurora) and Late Cretaceous (Georgetown, Del Río, Buda, Austin, Upson, San Miguel, and Olmos) geological formations.

Table 1 Studied sites and rocks
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Gamma spectrometric measurements were performed using a portable NaI(Tl) γ-ray spectrometer (spectrometer RS-125) manufactured by Radiation Solution Inc. The measurements were obtained directly from the surface of each rock's outcrop as far as possible from fractures and voids in the rocks, with a counting time of 120 s (IAEA 2003). This sampling period is used normally in most conditions because gives good quality data (Radiation Solution Inc. 2015). The device had a self-stabilizer to correct for surrounding background radiation. This allowed data to be obtained without the influence of changes in temperature or significant changes in gamma-ray emission. This equipment had been factory-calibrated using test pads, did not need radioactive sources for proper operation, and had a high sensitivity using a large 2.0 × 2.0 NaI crystal of 103 cm3 in size to detect concentrations of U (ppm), Th (ppm), and K (%) (Radiation Solution Inc. 2015). The equilibrium conditions of the 238U and 232Th decay series were considered, and therefore, the term “equivalent” and its abbreviation “e” are used (i.e., eU and eTh) to refer to the U and Th concentrations estimated from these series.

Rock samples were obtained from each studied site and their density was measured using the hydrostatic immersion method classic; these average density values were used to calculate the RHP (Table 2). For the granodiorite samples, a density of 2.74 g cm−3 was used. A density of 2.65 g cm−3 was used for the basalts; 2.61 g cm−3 for the sandstones; 2.64 g cm−3 and at some sites 2.6 g cm−3 (Colorado and Candela) for the shales; and 2.60 g cm−3 and at some sites 2.64 g cm−3 (Autopista) for the limestones. The RHP (µWm−3) produced by radioactivity in the Sabinas Basin rocks was computed using the following equation (Rybach 1988):

$${\text{RHP}} = \rho \left( {9.52{ }C_{{\text{U}}} { } + { }2.56{ }C_{{{\text{Th}}}} { } + { }3.48{ }C_{{\text{K}}} } \right)10^{ - 5} ,$$
(1)

where ρ is the bulk density of the rock; CU and CTh are the U and Th concentrations in weight ppm; CK is the K concentration in weight %. These concentrations were multiplied by the heat generation constants (the amount of heat released per gram of U, Th, and K per unit time). Statistical parameters such as the minimum, maximum, and average values, and standard deviation of the radioelements and RHP in each studied rock type of the Sabinas Basin were computed. Rocks with RHP values greater than 4 µWm−3 were considered as having a high RHP potential (McCay et al. 2014). Similarly, rocks with RHP values of less than 2 µWm−3 were considered as having a low RHP rate while rocks with RHP values between 2 and 4 µWm−3 exhibited moderate RHP.

Table 2 Rock densities of the study sites (g cm−3)
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Results

In all the studied rocks, the obtained concentrations of eU ranged from 0 to 13.4 ppm with an average of 2.02 ppm, the concentrations of eTh varied from 0 to 47.3 ppm with an average of 6.86 ppm, and the range of K concentrations ranged from 0 to 9.1% with an average of 1.55%. According to the concentrations of these radioelements, RHP values from 0.11 to 6.42 µWm−3 (average of 1.11 µWm−3) were obtained (Table 3). Most RHP values (85.15%) were less than 2 µWm−3 (Fig. 3), while 13.5% of the values ranged from 2 to 4 µWm−3, and only 1.35% exceeded 4 µWm−3. These results indicate that most of the studied rocks were considered to have a low heat production potential. Only 1.35% of the measurements (13 measurements out of a total of 970) yielded high RHP values (McCay et al. 2014). Later, the radioactive characteristics and the RHP of each geological formation and lithologies studied will be described.

Table 3 Statistical parameters (SP) of the gamma-ray spectrometric data and radioactive heat production (RHP) of the Sabinas Basin rocks
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Fig. 3
figure 3

Histogram showing the distribution of the radiogenic heat production (RHP, µWm−3) of all studied rock samples from the Sabinas Basin. The percentage of total measurements is indicated above the vertical bars. Group 1: RHP < 2 µWm−3), low RHP; group 2: RHP between 2 and 4 µWm−3, moderate RHP; group 3: RHP > 4 µWm−3, high RHP

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Figure 4 shows that all three radioelements correlated very well with the RHP; the higher the concentrations of the three radioelements, the higher the RHP. Of these three radioelements, the eU was the one that contributed the most to the RHP (48.1%), followed by the eTh (40.6%; Table 4).

Fig. 4
figure 4

Relationship between the radiogenic heat production (RHP) and the activity concentration of radioelements in all studied rock samples from the Sabinas Basin. a RHP and eTh; b RHP and eU; c RHP and K

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Table 4 Average concentrations of radioelements and radiogenic heat production (RHP) in rocks from the Sabinas Basin
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Radioelement contents and heat production in sedimentary rocks

The highest concentrations of eU, eTh, and K, as well as the highest values of RHP, were obtained from sedimentary rocks, (Tables 3, 4); therefore, sedimentary rocks were found to produce the highest amounts of radiogenic heat in the Sabinas Basin. These rocks were characterized by eU concentrations ranging from 0.01 to 13.4 ppm with an average of 2.39 ppm; their eTh concentrations varied from 0 to 47.3 ppm with an average of 7.79 ppm, and K concentrations from 0 to 9.1% with an average of 1.73%. In addition, these rocks yielded RHP values ranging from 0.11 to 6.42 µWm−3 with an average of 1.27 µWm−3. These values were higher than those obtained from sedimentary rocks from the Gulf of Mexico (0.4–1.5 µWm−3; Nagihara et al. 1996; Netto 2017) and other regions of the world, for example, values from 1 µWm−3 in a compilation study worldwide (Vila et al. 2010) and 0.97 µWm−3 in Sichuan Basin, China (Zhu et al. 2018).

Most of the RHP values obtained from the sedimentary rocks of the Sabinas Basin (75.58%, 356 measurements out of a total of 471) were less than 2 µWm−3 (Fig. 5a). These values indicate that most sedimentary rocks had a low RHP potential. Out of the measurements, 22.51% (106 measurements) had RHP values between 2 and 4 µWm−3, characterizing rocks with a moderate RHP potential. Less than 2% of the values (nine measurements) exceeded 4 µWm−3. These latter values (2–4 µWm−3 and greater than 4 µWm−3) were recorded in clastic rocks (Fig. 5b), mainly shales of the Olmos Formation and sandstones of the Pátula Formation (Table 3; Fig. 6); these were considered as producing high amounts of heat (McCay et al. 2014; Adagunodo et al. 2019).

Fig. 5
figure 5

Histogram showing the distribution of the radiogenic heat production (RHP, µWm−3) of sedimentary rocks from the Sabinas Basin. a All types of sedimentary rocks; b clastic rocks; c) carbonate rocks. The percentage of total measurements is indicated above the vertical bars. The horizontal axis indicates the RHP ranges (0–2, 2–4, 4–6, and 6–8 µWm.−3

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Fig. 6
figure 6

The relation between the radiogenic heat production (RHP) and the activity concentration of radioelements in the sedimentary rocks from the Sabinas Basin. a RHP and eTh; b RHP and eU; c RHP and K. SO shale of the Olmos formation, SP sandstone of the Pátula formation. The dotted red, green, and black line indicate the limits of the carbonated rocks, shales, and sandstones, respectively

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In the sedimentary rocks, the RHP values correlate very well with the three radioelements (Fig. 6), mainly with eTh and eU, Fig. 6 shows that the carbonate rocks fit better than clastic rocks with the general correlation of the three radioelements with RHP. This fit must be related to the lower radioactive heterogeneity of the carbonate rocks according to the SD values (Table 3). Therefore, this correlation indicates a greater linear dependence of the heat production with the concentrations of the radioelements in the carbonate rocks. For the clastic rocks, the Olmos Formation shales fit better with the general correlation and showed the highest eTh, eU, and RHP values (Fig. 6a, b). The Pátula Formation (sandstones) exhibited a similar behavior but with a lower fit and lower eTh, eU, and RHP values (Fig. 6a, b). The analysis of the correlation between the RHP and K indicates that the Olmos Formation shales did not fit the general correlation of the sedimentary rocks, although these were associated with the highest RHP values (Fig. 6c). In the sedimentary rocks, eU was the radioelement that most contributed to the RHP (56.8%), followed by eTh (34.6%), and K (8.6%; Table 4). These contributions are like those reported by Cui et al. (2019) in Meso-Cenozoic sedimentary rocks of the Bohai Bay basin, China.

Among the sedimentary rocks, the clastic rocks had the highest radioactive element concentrations and highest RHP (Table 3; eU, from 0.01 to 13.4 ppm, and an average of 3.23 ppm; eTh, from 0.4 to 47.3 ppm, and an average of 14.6 ppm; K, from 0.1 to 91%, and an average of 9.45%; RHP, from 0.21 to 6.42 µWm−3, and an average of 2.1 µWm−3). Most of these rocks exhibited low-moderate RHP values, because 49.10% (108 measurements out of a total of 220) of the RHP values were less than 2 µWm−3, and 46.82% (103 measurements) ranged between 2 and 4 µWm−3. Some clastic rocks exhibited a high RHP potential; indeed, a little more than 4% (nine measurements) of the RHP values exceeded 4 µWm−3 (Fig. 5).

Shales were the clastic rocks of the study region with the highest eU concentrations (from 0.4 to 13.4 ppm, and an average of 4.54 ppm; Table 3) and the highest RHP values (from 0.43 to 6.42 µWm−3, and an average of 2.17 µWm−3). These values indicate that the shales produced the most heat in the Sabinas Basin. The sandstones showed the highest eTh concentrations (from 0.4 to 47.3 ppm, with an average of 15.0 ppm) and K (from 0.1 to 9.1%, and an average of 4.19%), with RHP values ranging from 0.21 to 4.73 µWm−3 (average of 2.06 µWm−3).

Among the sedimentary rocks, the clastic rocks showed a higher RHP potential from eTh and K than carbonate rocks, which are in agreement with the results obtained from previous research in other countries, for example, China (Cui et al. 2019). Particularly in shales, the eU contributed 51.1% of RHP, followed by the eTh (41.0%), while in sandstones, the eTh contributed 48.1% and the eU, 34.5%. The highest eU concentrations in the shales were recorded in the Olmos Formation (Tables 2 and 3), with values ranging from 0.9 to 13.4 ppm, and an average of 5.06 ppm. The sandstone rocks with the highest eTh and K concentrations and high RHP values belong to the Pátula Formation (Tables 2, 3). The sandstone rocks from the Olmos Formation also yielded high eTh concentrations.

Higher RHP values were reported in the sedimentary rocks of the Sabinas Basin than in other regions worldwide, particularly in the shales and sandstones. For example, in a compilation study worldwide (Vila et al. 2010) and in Sichuan Basin, China (Zhu et al. 2018), average RHP values from shales of 1.7 and 1.07 µWm−3, respectively, are reported. Hasterok et al. (2018), in another compilation study worldwide, also reported values of 2.9 µWm−3 for aluminous shales and 1.7 µWm−3 for iron shales. In our study area, the average RHP value (2.17 µWm−3) in the shale was greater than most of the average values obtained by the abovementioned authors. This difference likely suggests the presence of aluminous and iron shales in this basin (Hasterok et al. 2018). In the sandstones, Vila et al. (2010) and Zhu et al. (2018) reported average RHP values of 0.90 and 0.83 µWm−3, respectively. Hasterok et al. (2018) also reported average RHP values ranging from 0.31 to 2.2 µWm−3 in different types of sandstone. In the sandstones of the Sabinas Basin, the average RHP value (2.06 µWm−3) was twice as high as most of the values reported in the aforementioned literature.

Within the sedimentary rocks of the Sabinas Basin, the carbonate rocks (limestone) were characterized by having the lowest eU, eTh, and K concentrations, as well as the lowest RHP values. Therefore, the limestones of the studied basin were the rocks with the lowest RHP potential. Most of these rocks were characterized by a low heat production because 98.80% of the RHP values (248 measurements out of a total of 251) were less than 2 µWm−3 (Figs. 5c, 6). Only three measurements (1.20% of the total) ranged between 2 and 4 µWm−3, representing rocks with a high RHP potential. In limestones, the RHP was mainly correlated with the eU (0.87), followed by K (0.77) and eTh (0.74), indicating that increases in these three radioelements could generate increases in RHP. Of these three radioelements, the eU was the one that contributed the most to the RHP with 72.3.8%, followed by the eTh with 24.2% (Table 4).

The comparison of the RHP values of the limestones from the Sabinas Basin with limestones from other regions of the world (Vila et al. 2010; Hasterok et al. 2018; Zhu et al. 2018) shows that the former had higher or relatively similar RHP values (Table 4). Indeed, Vila et al. (2010), Hasterok et al. (2018), and Zhu et al. (2018) reported average RHP values of 0.47, 0.56, and 0.40 µWm−3, respectively, for limestones from other regions worldwide.

Radioelement contents and heat production in igneous rocks

The igneous rocks comprise the second most significant rock group contributing to the RHP at the Sabinas Basin (Table 3). These rocks had eU concentrations ranging between 0 and 9.1 ppm, with an average of 1.67 ppm. In addition, they yielded eTh concentrations between 0.9 and 30.2 ppm, with an average of 5.98 ppm, and K concentrations between 0.3 and 6.0 ppm, with an average of 1.38. The RHP values of these rocks ranged between 0.19 and 4.57 µWm−3 with an average of 0.97 µWm−3. The highest values of the three radioelements and the RHP were obtained from the intrusive igneous rocks (granodiorites). In these rocks, the average values of U, Th, K, and RHP were 3.11 ppm, 9.83 ppm, 2.69%, and 1.76 µWm−3, respectively. This average RHP value was greater than 0.99 µWm−3, which was reported by Carrillo-de la Cruz et al. (2020) as the highest average value recorded in the Sabinas Basin and associated with the youngest intrusive igneous rocks. In extrusive igneous rocks (basalts), up to 4.4 ppm, 10.7 ppm, and 2.9% concentrations of eU, eTh, and K, respectively, and a maximum of 1.60 µWm−3 of RHP, were reported (Table 3).

Most igneous rocks were characterized by a low RHP, and 94.18% of the RHP values (470 measurements) were less than 2 µWm−3 (Fig. 7). Only 5.01% of the RHP values (25 measurements) were between 2 and 4 µWm−3, and 0.81% (four measurements) exceeded 4 µWm−3; this indicates that some these rocks were associated with moderate and high RHP potentials. These rocks mainly consisted of the granodiorites from the Marcelinos intrusion (Fig. 8). In the granodiorites, 73.87% of the RHP values were less than 2 µWm−3, 22.53% varied between 2 and 4 µWm−3, and 3.60% (only four measurements) exceeded 4 µWm−3. Such values indicate that only some rocks (i.e., the granodiorites from the Marcelinos intrusion) were characterized by a high RHP potential (McCay et al. 2014). Generally, most of the studied granodiorites from all intrusions exhibited low–moderate heat production. In turn, all of the studied basalts revealed a low RHP potential, because 100% of the RHP values were less than 2 µWm−3.

Fig. 7
figure 7

Histogram showing the distribution of the radiogenic heat production (RHP, µWm−3) of the igneous rocks from the Sabinas Basin. a All types of igneous rocks; b intrusive rocks (granodiorite); c extrusive rocks (basalt). The percentage of total measurements is indicated above the vertical bars. The horizontal axis indicates the RHP ranges (0–2, 2–4, 4–6, and 6–8 µWm.−3

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Fig. 8
figure 8

The relation between the radiogenic heat production (RHP) and the activity concentration of radioelements in the igneous rocks from the Sabinas Basin. a RHP and eTh; b RHP and eU; c RHP and K. L, O, and C denote the Las Esperanzas, Ocampo, and Las Coloradas volcanic fields, respectively. The dotted red line indicates the boundary of the extrusive igneous rocks and the zone where are mixture of extrusive and intrusive rocks

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In general, the RHP values of the igneous rocks correlated very well with the three radioelements (Fig. 8). Figure 8 shows that the extrusive rocks (basalts) had lower concentrations of the three radioelements and lower values of RHP (less than 2 µWm−3) than their intrusive counterparts (granodiorites). Indeed, the granodiorites showed higher RHP values from eU and eTh than the basalts (eU, 45.3%, and eTh, 39.4% in granodiorite; eTh, 48%, and eU, 38% in basalts; Table 4). The basalts experienced the highest heat production from Th (48%).

In the extrusive rocks, the basalts of the Las Coloradas volcanic field yielded the highest radioactive element concentrations and RHP values, followed by the Ocampo and Las Esperanzas fields (Fig. 8).. The zone characterized by intrusive rocks in Fig. 8 mainly consists of rocks belonging to the Marcelinos intrusion, which are characterized by the highest values of the three radioelements and the RHP (greater than 2 µWm−3). The mixed zone of extrusive and intrusive rocks (Fig. 8) is occupied by the Pánuco, Providencia, and Colorado intrusions, of which Pánuco revealed the highest radioactive element concentrations and RHP values, while Colorado had the lowest values.

The average RHP value (1.76 µWm−3) of the granodiorites in the Sabinas Basin was lower than that reported in some regions of the world (e.g., 2.07 µWm−3 in Vila et al. 2010) and higher than that of others (e.g., 1.5 µWm−3 in Hasterok et al. 2018 and 1.404 µWm−3 in Aisabokhae and Tampul 2020). In turn, the average RHP value of the basalts in this basin (0.74 µWm−3) was higher than that reported by Hasterok et al. (2018) (0.54 µWm−3) in other regions of the world. Similarly, the average RHP value of the basalts from this basin was higher than the averages of alkalic, calc-alkaline, and tholeiitic basalts (0.7, 0.3, and 0.05, respectively) reported by Vila et al. (2010). This result must be related to the alkaline character of the basalts of the Sabinas Basin (Valdez-Moreno 2001; Aranda-Gómez et al. 2005; Valdez-Moreno et al. 2011).

Discussion

Clastic sedimentary rocks specifically shales, and sandstones, are the ones that produce the most radiogenic heat in the Sabinas Basin (Table 3). Its RHP values are higher than those reported in the Gulf of Mexico and other sites, which indicates its high contribution to the relatively high heat flow reported in northeastern Mexico (60–80 mWm−2; Prol-Ledesma et al. 2018; Prol-Ledesma and Morán-Zenteno 2019). Specifically, the higher RHP values (mainly due to uranium; Table 4) are related to shales of the Olmos Formation, located northeast of the study area (north of the Las Esperanza volcanic field) in areas with a high geothermal gradient and relatively high heat flow (62–67 mWm−2) proposed by Carrillo-de la Cruz et al. (2020). The shales (also sandstones) of this formation belong to the coal seam carrier sequence, in which these rocks are characterized by high contents of transformed organic matter (Eguiluz de Antuñano 2001) and clay, quartz, and feldspar (Piedad-Sánchez et al. 2015), minerals that can contribute to the concentrations of radioelements (IAEA 2003). This mineral and organic matter content could be the principal cause of the high eU, eTh, and K concentrations and, therefore, the high RHP of these rocks (Vila et al. 2010). Moreover, other causes for the higher RHP may be related to the low thermal conductivities of the shales, which allow heat to remain inside these rocks over long geological timescales (McCay et al. 2014). The site of this Olmos Formation shales is located close to a deep geological structure (La Babia Fault) in a zone where Carrillo-de la Cruz et al. (2020) previously reported a relatively high heat flow (62–67 mWm−2), obtained through Curie temperature depths estimated from aeromagnetic data. Therefore, their relationship with that geological structure can also contribute to radioactive concentrations and RHP, which, in turn, contributes to heat flow.

The sandstones of the Pátula Formation are the second group of rocks that contribute the most to the RHP, mainly due to their eTh and K concentrations (Table 4). Such concentrations must be related to the type of sandstone (arkose) and their quartz and K-feldspars contents and other minerals (clays, muscovite, biotite, apatite, and zircon) reported by Ocampo-Díaz (2013), Ocampo-Díaz et al. (2014) and Batista-Rodríguez et al. (2017b). In other regions worldwide, such as Nigeria, rocks with high contents of these minerals present high concentrations of both mentioned radioelements (Akingboye et al. 2021). Therefore, the high RHP in these rocks would have mainly been related to their high SiO2 and F-feldspars concentrations (Hasterok and Webb 2017; Hasterok et al. 2018). The site of the Pátula Formation is located in the proximity of the San Marco fault (Fig. 1) within a zone of high heat flow (67–73 mWm−2; Carrillo-de la Cruz et al. 2020). Its relationship with this deep structure also contributes to its RHP values, and these, in turn, contribute to the heat flow recorded in this region.

The RHP comparison of these sandstones and shales with others located in different regions of the world, such as the United States, Finland, Australia, Norway, and China (Vila et al. 2010; Hasterok et al. 2018; Zhu et al. 2018) suggests that these rocks, mainly the Olmos Formations shales and Pátula Formation sandstones are more enriched in the minerals as quartz, and feldspars. Similarly, some limestones have higher RHP than in other regions, which must have mainly been related to the clay and quartz contents, reported by Lucas et al. (2010), Torres de la Cruz et al. (2020), and Loucks et al. (2021) in Cupido, Buda, and Austin Formation of the Sabinas Basin. Also, it is likely that the relationship of some deeply faulted shale and sandstone sites (La Falla and San Marco) has contributed to the higher RHP values relative to other regions.

The differences in radioactive element concentrations and RHP values between the three volcanic fields must be related to the U-, Th-, and K-bearing minerals content of these rocks (IAEA 2003), as well as their enrichment in incompatible elements (Slagstad 2008), and their degree of alteration (Dostal et al. 1984). Therefore, the basalts of Las Coloradas could be more enriched in bearing minerals U, Th, and K (IAEA 2003) and/or in incompatible elements and/or have less degree of alteration. In this research, only are available petrographic or geochemical data available for basalts de Ocampo y Las Esperanzas. Both volcanic fields are reported apatite, and in Ocampo, K-feldspars are reported (Valdez-Moreno 2001; Valdez-Moreno et al. 2011). The first mineral is a carrier of U and Th, while the latter is carrier K (IAEA 2003). Therefore, the basalts of the Las Coloradas volcanic field can have higher contents of apatite and K-feldspars. The presence of K-feldspars in the Ocampo basalts explains their higher radioactivity and RHP, concerning the Las Esperanzas field. The geochemical data referring to the K2O contents (up to 2% in Ocampo and up to 1.6% in Las Esperanzas; Valdez-Moreno 2001; Valdez-Moreno et al. 2011) also justify this approach. It is possible that the relationship of these volcanic fields with high and low blocks of the basement could be another factor in their differences in the RHP. For example, Las Coloradas (with higher RHP) and Ocampo (with intermediate RHP) are located at the high basement block zones (Las Coloradas in the Coahuila block and Ocampo in La Mula Island; Fig. 1). On the other hand, Las Esperanza, with a lower RHP, is located at the zone of blocks below the basement within the Sabinas Basin. Also, the RHP values are related to the heat flow calculated by Carrillo-de la Cruz et al. (2020). The two volcanic fields with the highest RHP (Las Coloradas and Ocampo) are located above zones of relatively high heat flow (67–73 mWm−2), while Las Esperanzas is related to zones of lower heat flow (62–67 mWm−2). This evidence the contribution of the rocks of these two volcanic fields to the reported heat flows.

The highest values of the three radioelements and the RHP in Marcelinos intrusion, followed by Pánuco, Providencia and Colorado, suggest higher U-, Th-, and K-bearing minerals contents, and possibly also silica, in the rocks of the Marcelinos intrusion than those of the Pánuco, Providencia, and Colorado bodies. This research does not have petrographic or geochemical data either about Marcelinos intrusion, but the petrography studies in the other three intrusions reported radioelement-bearing minerals (Valdez-Reyes 2001; Fuentes-Guzmán 2016; Herrera-León 2019). The main K-bearing minerals are K-feldspars (microcline, orthoclase), hornblende, and biotite, while U- and Th-bearing minerals are sphene, zircon, and apatite. Therefore, in the Marcelinos intrusion, the granodiorite must have higher contents of some of those mentioned minerals. According to the geochemical data available in the Pánuco, Providencia, and Colorado intrusions (Valdez-Reyes 2002; Fuentes-Guzmán 2016; Herrera-León 2019), the highest Si2O, K2O, and Th contents are obtained in the Pánuco rocks (Si2O up to 70%, K2O up to 12.69% and Th up to 25.7 ppm), and the lowest in Colorado (Si2O up to 65%, K2O up to 4% and Th up to 8 ppm) or Providencia (Si2O up to 62%, K2O up to 4.59% and Th up to 21 ppm). Therefore, these data also justify the higher contents of radioelements and RHP in Pánuco, compared to Providencia and Colorado. Pánuco's location in a high basement block (Monclova Island; Fig. 1) also contributes to its RHP values. The likely higher silica content in the Marcelinos intrusion may in fact indicate a higher degree of magmatic differentiation in the Marcelinos igneous body relative to the other three intrusions (Batista-Rodríguez et al. 2020). The contents of radioelements, RHP values, and the geochemical data indicate that the Pánuco intrusion must present a lower degree of magmatic differentiation than Marcelinos, but at the same time greater than Colorado and Providencia. Therefore, of the intrusive igneous rocks analyzed, the Marcelinos body had the least basic composition, and the Providencia body the most basic one. The radioactive element concentrations and RHP values of the Pánuco, Colorado, and Providencia igneous bodies were like those of the rocks comprising the Las Esperanzas and Ocampo volcanic fields. This similarity indicates that it is probable that both groups of rocks in those sites have similar contents of radioelements-bearing minerals.

All the igneous and sedimentary rock sites studied were located at the characterized areas by a high geothermal gradient and relatively elevated heat flow, as proposed by Carrillo-de la Cruz et al. (2020). According to Carrillo-de la Cruz et al. (2020), the magnetic sources in these areas and, therefore, the basement of the basin, is located at a shallow depth. Eguiluz de Antuñano (2001) reports depths from 1.7 to 6 km, and Batista-Rodríguez et al. (2017a) from 1.5 to 7 km. Both investigations indicate basin areas with a basement less than 2 km deep. The relatively high RHP values in the studied rocks indicate their contribution to the geothermal gradient and relatively high heat flow, reported in previous research.

Conclusions

Using in situ gamma radiation measurements, radiogenic heat production in rocks from the Sabinas Basin was determined. The analysis of the RHP in the Sabinas Basin showed that the sampled rocks could be classified as having low (< 2 µWm−3), moderate (2–4 µWm−3), and high (> 4 µWm−3) RHP potentials. Most sampled rocks showed low RHP values below 2 µWm−3. Only a little over 14% of the measurements indicated moderate and high RHP potentials. This proportion was mainly associated with clastic rocks (shales and sandstones) and intrusive igneous rocks (granodiorites). The highest RHP values are obtained in a shale site of the Olmos Formation, followed by another sandstone site of the Pátula Formation. Apparently the quartz, K-feldspars, and clay contents in these rocks, and their proximity to two deep faults (La Babia and San Marcos) are the causes of the highest RHP values reported. The variations in the radioelement-bearing minerals content (K-feldspars, sphene, zircon, and apatite) cause differences between in the RHP of the granodiorites of the four intrusions (Marcelinos, Colorado, Providencia, and Pánuco). According to the RHP values, these minerals should be more enriched in the Marcelinos intrusion and less enriched in the Colorado and Providencia intrusion. Also, the difference in the RHP of the three volcanic fields (Las Esperanzas, Ocampo, and Las Coloradas) is associated with radioelement-bearing minerals, such as K-feldspars and apatite, and also to their relationship with some paleo-structures of the region (high and low basement block). The two volcanic fields with the highest RHP, Las Coloradas, and Ocampo, are located at the two high basement blocks, the Coahuila Block and La Mula Island, respectively. The Las Esperanza volcanic field is located above a zone of low basement block. The relationship of the RHP values with previously reported heat flow zones indicates the radiogenic contribution of the measured rocks to these heat flows, therefore, these RHP values may be used in future updates of the heat flow schemes heat of the Sabinas Basin.