Identifying origins of and pathways for spring waters in a semiarid basin using He, Sr, and C isotopes: Cuatrociénegas Basin, Mexico

B.D. Wolaver1,*, L.J. Crossey2,*, K.E. Karlstrom2,*, J.L. Banner3,*, M.B. Cardenas3,*, C. Gutiérrez Ojeda4,*, and J.M. Sharp, Jr.3,* 1Bureau of Economic Geology, University of Texas at Austin, 10100 Burnet Road, Austin, Texas 78758, USA 2Department of Earth and Planetary Sciences, University of New Mexico, MSCO3-2040, 1 University of New Mexico, Albuquerque, New Mexico 87131, USA 3Department of Geological Sciences, University of Texas at Austin, 1 University Station, Austin, Texas 78712-0254, USA 4Instituto Mexicano de Tecnología del Agua (IMTA), Paseo Cuauhnáhuac 8532, Colonia Progreso, 62550 Jiutepec, Morelos, México

ABSTRACT mantle-derived He (to 23% of the total He) species (Hendrickson et al., 2008; Fig. 2). ≤ –1 and CO2 (pCO2 10 atm). Mantle degas- Springs have varied spatial distribution and geo- He, C, and Sr isotopes are used to infer sing is compatible with the thinned North chemistry. Spring vents are often obscured by spring sources in a water-stressed area. American lithosphere, as shown in tomo- valley-fi ll alluvium, but high-discharge springs Spring-water origins and pathways in the graphic images. Sr isotopes in both Cuatro- generally issue directly from fractures in Creta- Cuatrociénegas Basin are revealed by linking ciénegas Basin springs and spring-deposited ceous carbonate rocks. Other springs are located structure and geochemistry via regionally travertine (87Sr/86Sr = 0.707428–0.707468) at the base of alluvial fans (Wolaver and Diehl, extensive fault networks. This study presents indicate that carbonate rocks of the regional 2011). CO2-rich spring water with pCO2 1.5–3 the fi rst dissolved noble gas and He isotopic Cupido aquifer (87Sr/86Sr = 0.7072–0.7076) orders of magnitude higher than atmosphere data from northeastern Mexico. Basement- are the main source of Sr. Rock-water inter- facilitates deposition of rare modern freshwater involved faults with complex reactivation actions with mafi c volcanic rocks (87Sr/86Sr = stromatolites (Dinger et al., 2006). histories are important in northeastern 0.70333–0.70359) are not inferred to be an The study area is in the Chihuahuan Des- Mexico tectonics and affect hydrogeologic important process. Groundwater-dissolved ert, where long-term (1942–2003) annual pre- systems. The importance of faults as con- inorganic C origins are modeled using major cipitation of 200 mm exceeds annual potential duits for northeastern Mexico volcanism is elements and C isotopes. C isotope data show evaporation (1964–1988) of 1960 mm (Aldama recognized, but connections between fault- that ~30% ± 22% of CO2 in spring water is et al., 2005). Irrigated agriculture since the mid- ing and the hydrogeologic system have not derived from dissolution of aquifer carbon- 1990s in adjacent valleys caused groundwater been extensively investigated. This research ates (Ccarb = 30%), 24% ± 16% is from soil declines of ~1 m/yr, and the main springs that tests the hypothesis that Cuatrociénegas gas and other organic sources (Corg = 24%), formed the initial basis for irrigated agriculture

Basin springs are divided into two general and 46% ± 33% is from deep sources [Cendo in the town of Cuatrociénegas no longer fl ow classes based upon discharge properties: (endogenic crust and mantle) = 46%]. This (Wolaver et al., 2008). In addition to support- (1) regional carbonate aquifer discharge study demonstrates the presence of mantle- ing groundwater-dependent ecosystems with 3 (mesogenic) mixed with contributions from derived He and deeply sourced CO2 that unique endemic species, the Cupido aquifer that deeply sourced (endogenic) fl uids contain- ascend along basement-penetrating faults fl ows to Cuatrociénegas springs supplies water 3 ing He and CO2 from the mantle that ascend and mix with Cupido aquifer groundwater to more than four million people in northeastern along basement-involved faults; and (2) car- before discharging in Cuatrociénegas Basin Mexico and is correlative to the prolifi c Texas bonate aquifer discharge mixed with locally springs. Edwards-Trinity aquifer (Johannesson et al., recharged (epigenic) mountain precipi tation. 2004). Understanding the Cuatrociénegas Basin Carbonate and/or evaporite dissolution is INTRODUCTION spring-water origins is important for both devel- indicated by Ca-SO4 hydrochemical facies. oping groundwater resources for human needs

He isotopes range from 0.89 to 1.85 RA (RA is He, Sr, and C isotopes are used to identify and preserving spring fl ow for groundwater- the 3He/4He of air, 1.4 × 10–6) and have mini- the origins of and groundwater pathways for dependent ecosystems in similar settings. mal 3H, from which it is inferred that base- Cuatrociénegas Basin springs; the basin is an This study tests the hypothesis that Cuatro- ment-involved faults permit degassing of oasis in the Chihuahuan Desert region of north- ciénegas Basin springs are divided into two eastern Mexico (Fig. 1). Dozens of springs fl ank classes based upon discharge and geochemi- *Emails: Wolaver: [email protected]; the 2300-m-high Sierra San Marcos anticline, cal properties, which are inferred to be con- Crossey: [email protected]; Karlstrom: kek1@ unm.edu; Banner: [email protected]; Cardenas: which bisects the basin and sources critical trolled by relationships between springs and [email protected]; Gutiérrez Ojeda: cgutierr fl ows to groundwater-dependent pools, streams, fault conduits. The fi rst class has characteristics @tlaloc.imta.mx; Sharp: [email protected] and marshes that are refugia for >70 endemic that imply discharge primarily from a regional

Geosphere; February 2013; v. 9; no. 1; p. 113–125; doi:10.1130/GES00849.1; 6 fi gures; 3 tables. Received 30 July 2012 ♦ Revision received 23 October 2012 ♦ Accepted 24 October 2012 ♦ Published online 13 December 2012

For permission to copy, contact [email protected] 113 © 2012 Geological Society of America Wolaver et al.

La CTC STRATIGRAPHIC AND S volcanic field Coahuila Fold Belt B abia STRUCTURAL FRAMEWORK 28° LMI paleogeography F a OF NORTHEASTERN MEXICO reverse fault ^ ^ ult ^ earthquake S Cuatrociénegas Basin consists of Jurassic LMI and Cretaceous marine and nonmarine silici- San O M clastics overlying Precambrian to Paleozoic arcos Fa ult crystalline basement (Goldhammer, 1999; Fig.2 Lehmann et al., 1999). Cretaceous carbon- 27° CC ate rocks, as thick as 800 m, form the Cupido MI and Aurora Formations that are the primary regional aquifer (Wolaver and Diehl, 2011; Wolaver et al., 2008). The region has a com- C a CB lif plex tectonic history with several stages of or nia faulting (Fig. 1). During the Permian–Triassic, -T C am ^ au left-lateral motion along the Coahuila-Tamau- 26° lip as lipas transform, associated with the opening Tr ans ^ form of the Gulf of Mexico, faulted Precambrian USA and Paleozoic basement blocks of northeast- ern Mexico (Aranda-Gómez et al., 2005, 2007; Mexico ^ Dickinson and Lawton, 2001; Goldhammer, 1999). The imprinted zones of structural weak- ness infl uenced Laramide and subsequent tec- 103° 102° 101° tonic activity. First, extension along Neocomian Figure 1. Study area and regional tectonic map of Cuatrociénegas normal faults (ca. 140–136 Ma) formed fault- Basin (CC). Relief map with topography and regional tectonic fea- bounded structural highs and lows, such as the tures is after Aranda-Gómez et al. (2007, 2005), Chávez-Cabello Coahuila block and adjacent Sabinas Basin. et al. (2005), Dickinson and Lawton (2001), Eguiluz de Antuñano Then, compression folded and faulted strata in (2001), and Goldhammer (1999). Paleogeographic elements (diago- the Paleogene (ca. 45–23 Ma; Chávez-Cabello nal lines): Coahuila block (CB), La Mula Island (LMI), Monclova et al., 2005). Two less intense periods of normal Island (MI), Coahuila-Texas craton (CTC). Paleotopographic fault reactivation occurred in the Late Miocene highs (e.g., CB, CTC) are bounded by regional San Marcos and to Quaternary (Aranda-Gómez et al., 2005; La Babia faults (Eguiluz de Antuñano, 2001) with intervening Chávez-Cabello et al., 2005). downthrown Sabinas Basin (light gray shaded region; Eguiluz The tectonic activity created faults that are de Antuñano, 2001). Permian–Triassic California-Tamaulipas critical to the area hydrogeology. Mesozoic nor- transform is postulated structural feature (dashed line; Dickin- mal faults associated with the opening of the Gulf son and Lawton, 2001). Pliocene–Pleistocene volcanic fi elds: Las of Mexico created conditions that permitted the Coloradas (C), Ocampo (O), Las Esperanzas (S) (Aranda-Gómez deposition of Cretaceous carbonate rocks that et al., 2007; Chávez-Cabello, 2005); volcanic fi elds are associated now form a regional carbonate aquifer (Lehmann with Laramide-age reverse faults. Earthquakes are since 1973 et al., 1999; Wolaver and Diehl, 2011; Wolaver (U.S. Geological Survey, 2009). et al., 2008). Paleogene reactivation of reverse faults generated the ≤3000 m anticlinal uplifts that serve as recharge areas and fractured the carbonate aquifer with some deeply sourced culate mixing of three source waters that results sedimentary rocks to create secondary permea- fl uids along high-permeability fault-associated in the two spring classes. The three sources bility. Late Miocene–Quaternary normal fault- pathways. These springs have elevated discharge are: (1) epigenic waters (dominantly younger, ing fractured the carbonate aquifer, reactivated (≤550 L/s), elevated temperature (30–35 °C), locally derived mountain-front precipitation); older faulted structures, and formed foci for an absence of 3H, and distinctive water chem- (2) mesogenic waters (older, regional carbonate Pliocene–Pleistocene volcanism (Aranda-Gómez istry (high total dissolved solids, TDS > 2000 aquifer groundwater); and (3) endogenic waters et al., 2007). Wolaver and Diehl (2011) investi- mg/L, calcite saturation, high pCO2, mantle- (inputs from deep fault systems). Isotopes of Sr gated fault-associated fracture permeability infl u- derived He). The second class refl ects mixing of in groundwater have been used to identify the ences on springs. However, previous studies did regional carbonate aquifer and locally recharged source of Sr ions and to evaluate groundwater not assess the role of these faults as conduits for waters. These springs have lower discharge and fl ow paths (Musgrove et al., 2010). Sr isotopes deeply sourced fl uids. lower temperatures (<30 °C) and detectable 3H; indicate that groundwater fl uxes are dominated The study area is near the boundary between water chemistry shows lower TDS (500–1500 by mesogenic, regional carbonate aquifer fl ow. the Precambrian-cored North American craton mg/L), calcite undersaturation, and less mantle- Water chemistry shows that regional carbonate (Whitmeyer and Karlstrom, 2007) and Meso- derived He. aquifer water mixes with deeply derived fl uids zoic accreted terranes of Mexico (Dickinson This study also addresses spring origins and that fl ow along basement-penetrating faults and and Lawton, 2001). Northeastern Mexico is a pathways using major and trace element water also mountain-front recharge, resulting in the southern continuation of a region of low mantle geochemistry and Sr and He isotope data to cal- two spring classes. velocity (van der Lee and Nolet, 1997) related

114 Geosphere, February 2013 Identifying spring water origins and pathways with He, Sr, C

Sierra La Madera Sierra De Menachaca 43° 2500 30° 20° 27°00′ 36° 1000 70° Cuatrociénegas Basin Poza Anteojo

Poza Azul

1000 Poza Escobedo

Poza La Becerra 1000 Poza Churince 8° 30° Poza El Venado 10° 12° ′ 1000 A 48° A

alluvial fans La Purisíma 85° 15° 25° Sierra 23° 25° Sier Poza Santa Tecla 2° 6° 80° 2000 ra San Marcos 19 ° 26°45′ 1000 Sierra La Fragua LEGEND 8 ° Gas spring, 4° 1000 sample wetland 80° normal fault, Water inferred sample San Ma 30° reverse fault rco 4° s Travertine Fau sample lt San Marcos 5° Cenozoic Fault 16° 1000 alluvium 40° 40° strike and dip Cretaceous carbonates anticline 9° 4° Km Cretaceous 19° siliciclastics town Contour interval: 250 meters 48°024 8 12 16 102°15′ 102°00′ Figure 2. Cuatrociénegas Basin showing springs analyzed for dissolved gases. Spring locations (locations and map after Wolaver and Diehl, 2011) are strongly infl uenced by basement-involved Laramide-age reverse faults (Aranda-Gómez et al., 2007; Eguiluz de Antuñano, 2001) on the west fl ank of the Sierra San Marcos and an inferred normal fault on the east fl ank. These faults provide a mantle-derived dissolved gas conduit and account for He isotope presence. Line A–A′ shows hydrogeologic conceptual model cross section (see Fig. 6). Travertine sample locations for Sr isotopic analyses are also shown. Surface geology is from Servicio Geológico Mexicano (1998, 2008) and Chávez-Cabello et al. (2005).

to Mesozoic and ongoing mantle modifi ca- Infl uences on regional groundwater chem- Taran et al., 2002; Vidal et al., 1982; Welhan tion due to asthenospheric upwelling follow- istry caused by mantle degassing in areas of et al., 1979) and for economic geology to evalu- ing foundering of the Farallon plate (Schmandt structural weakness have been studied using He ate ore fl uids (Camprubí et al., 2006; Nencetti and Humphreys, 2010). Regions of low mantle isotopes (Crossey et al., 2006; Kennedy and van et al., 2005), but no He isotopic data are avail- velocity in the western United States are associ- Soest, 2007; Newell et al., 2005). In Mexico, He able for study area springs and groundwater ated with high 3He/4He isotopic ratios in thermal isotopes have been used to study volcanic and to confi rm the presence of deep faults in the spring waters (Newell et al., 2005). hydrothermal systems (Inguaggiato et al., 2005; regional carbonate aquifer.

Geosphere, February 2013 115 Wolaver et al.

METHODS ing CO2 sources from water chemical data fol- volcanic rocks (Table 3). An Sr-specifi c resin low Chiodini et al. (2004, 2000) and Crossey separated Sr from water and travertine samples Analytical methods used for water chem- et al. (2009), except an evaporite correction is by ion exchange (University of Texas at Aus- istry, gas chemistry (e.g., He isotopes and other used to estimate external C in high SO4 waters tin Department of Geological Sciences Isotope noble gases), C isotopes, and Sr geochemistry (i.e., deeply derived C that fl ows to springs Clean Laboratory; Banner and Kaufman, 1994). analyses are described in the following. Water via basement-involved faults) and new meth- samples were collected at springs (vents and ods are used to estimate dissolved inorganic C RESULTS pools), spring runs, and wells for water and gas (DIC) using the computer program PHREEQC chemistry analyses. Sr isotope geochemistry (Parkhurst, 1995). Water Chemistry analyses were done on water samples collected The CO2 sources include: (1) Ccarb (from car- from springs (vents and pools), spring runs, and bonate dissolution along fl ow paths); (2) Corg Water chemistry data (Table 1) are compiled travertine. Water and travertine samples were (C of organic origin); and (3) Cendo (endogenic from published data (Johannesson et al., 2004; collected to provide representative samples CO2 from crust and mantle). In a mass balance Aldama et al., 2005). Evans (2005) also pre- 2+ 2+ 2– basin-wide trends in geochemistry (Fig. 2). model, Ccarb = Ca + Mg – SO4 (Chiodini sented water chemistry data, but focused on et al., 2000; Fontes and Garnier, 1979). Many sampling spring discharge at spring run locations

Water Chemistry Cuatrociénegas Basin springs are SO4 rich, downstream of orifi ces. making this calculation problematic. In cases Cuatrociénegas springs exhibit two distinct 2– 2+ 2+ Standard methods (described in Crossey et al., where SO4 is greater than Ca + Mg , Ccarb is classes (Fig. 3): (1) one class plots as a group-

2009) were used for water chemistry analyses set to zero because there must be a sulfur source, ing of Ca-SO4–type waters (e.g., La Becerra and

(Table 1). such as H2S. Remaining C is external carbon, Escobedo springs); (2) the second class exhibits

where Cext = DICtotal – Ccarb. DICtotal is computed Ca-HCO3–type waters (e.g., Santa Tecla spring). Gas Chemistry from measured DIC (as alkalinity) and pH by a The fi rst class commonly discharges in springs speciation model (PHREEQC; Parkhurst, 1995). issuing from fractures in carbonate rocks and 3 4 The He/ He ratio is evaluated to elucidate To estimate proportions of Corg and Cendo of Cext, at elevated fl ow rates (to 550 L/s), representing terrigenic He crust and mantle source compo- the measured δ13C is corrected for each sample ~85% of total basin spring water (Wolaver et al., 3 nents by analyzing water for dissolved gases and by removing the isotopic proportion due to Ccarb. 2008). These waters have low H concentrations He isotopes. Most dissolved noble gas samples Depending on regions being studied, workers (generally below detection limits; Table 2), TDS were collected using passive diffusion samplers have used average values of 0‰ (Crossey et al., of 2000–3200 mg/L, and elevated temperatures (De Gregorio et al., 2005; Gardner and Solo- 2009; Sharp, 2007) to +2‰ (Chiodini et al., (30–35 °C). mon, 2009). Noble gas samples were processed 2000; Crossey et al., 2009). The Cext calcula- The second class has springs commonly at at the University of Utah Dissolved Gas tion is not especially sensitive to choice of this the base of alluvial fans with lower discharge Laboratory (following Manning and Solomon, value, but here we use δ13C = +0.5‰, a central rate, representing ~15% of total basin spring 2003). One copper tube sample was collected value found for the range of values (–6‰ to fl ow (Wolaver et al., 2008). These springs often from La Becerra warm vent and analyzed for +5‰) of late Paleozoic southern New Mexico have low, but measureable, 3H (i.e., Santa Tecla 3 CO2/ He (methods of Poreda and Farley, 1992). limestone (Koch and Frank, 2012). Cext is com- has 0.2 tritium units, TU) and lower TDS (i.e.,

The He precision is ±0.5%–1% and ±1%–2% posed of both organic components (Corg) and 1,415 mg/L). Spring-water temperatures are 3 4 for all other gasses. Measured He/ He ratios are deeply sourced endogenic components (Cendo). lower, but still elevated (30 °C). 3 4 often expressed as R/RA, where R = He/ He of Data plot within a set of binary mixing curves 3 4 the sample and RA = He/ He of the atmosphere defi ned empirically by our own data, with cho- Gas Chemistry –6 (1.384 × 10 ; Clarke et al., 1976). We report air- sen end members of (1) a soil-respired CO2 end 3 4 δ13 corrected values for total He [He]c, and He/ He member with Corg = –28‰ that is compatible Most groundwater samples have high mea- δ13 4 –8 –6 (RC/RA) for the non-air portion of gases dis- with Corg = –15‰ to –30‰ from vegetated sured He concentrations between 10 and 10 solved in springs (using X the air-normalized areas (Deines et al., 1974; Robinson and Scrim- cm3/g (Table 2). The Δ4He, the percentage of He/Ne ratio correction by Hilton, 1996) by geour, 1995; Sharp, 2007) and with variable terrigenic 4He relative to 4He in the atmosphere 4 –8 3 accounting for potential amounts of He contrib- Cext = 0.0001–0.004 mol/L, and (2) an endo- in equilibrium with water (4.31 × 10 cm /g; δ13 uted by air and air saturated water to calculate genic CO2 end member of Cendo = –3‰ and Giggenbach et al., 1993), ranges from 434% to 4 ≥ Δ4 terrigenic He (i.e., He from crust and mantle Cext 0.06 mol/L that is comparable to values of 3125% with the exception of the lowest He sources; Solomon, 2000). The He isotopic ratios –5‰ (Crossey et al., 2009) to –3‰ used in other value (19%, sampled in an open canal; Table 2). are presented compared to atmospheric concen- studies (Chiodini et al., 2000), and comparable Springs with X factors >4 and air-corrected tration as R/RA. to a mid-oceanic ridge basalt (MORB) mantle RC/RA values ranging from 1.25 RA to 1.85 RA reference value of δ13C = –6‰ ± 2.5‰ (Sano (Table 2) indicate that 16%–23% of He is Carbon Isotopes and Marty, 1995). from MORB-type mantle sources. The highest 3He/4He values with lowest air corrections are

Spring water was analyzed for C isotopes Strontium Geochemistry in Poza Azul (1.84 RA; X = 19.8), Escobedo vent using methods described by Hilton (1996). (1.84 RA; X = 21.5), and La Becerra warm vent

One sample (La Becerra warm vent; Table 2) The Sr isotopes in water and travertine are (1.76 RA and 1.85 RA by two methods, X = 34 and was analyzed at the University of Rochester evaluated to estimate relative contributions of 18.3, respectively). Gas chemistry copper tube (New York), while other samples (as reported deeply sourced Sr ions from basement faults samples (Poreda and Farley, 1992) are similar to in Aldama et al., 2005) were analyzed at the and Sr ions derived from the regional carbon- those from passive diffusion samples from the University of Arizona. Methods for distinguish- ate aquifer or groundwater interactions with same spring (La Becerra warm vent; Table 2).

116 Geosphere, February 2013 Identifying spring water origins and pathways with He, Sr, C ) † 1 1 1 continued ( C* 13 (‰) Ref. δ 2 4 8 4 9 9 7 . . . 1 1 1 CO Log – – – p 7 9 3 3 2 4 . . . SI 0 0 0 – – – gypsum 0 7 7 4 7 4 . . . SI 0 0 0 – dolomite 4 3 1 2 4 1 . . . SI 0 0 0 – calcite 8 1 4 . . . 9 5 5 – 1 1 (%) – – Charge balance 0 0 0 . . . 8 4 8 4 1 3 4 3 0 6 SO 1 1 1 (ppm) 7 0 6 . . . 2 1 5 0 2 9 Cl 1 (ppm) 3 5 7 8 . . . 1 8 8 0 6 2 HCO (ppm) 2 1 2 3 5 8 . . . 7 2 7 K (ppm) 3 3 4 . . . 4 1 0 Na 5 4 8 1 1 (ppm) 0 8 0 . . . 2 7 8 6 9 0 Mg 1 (ppm) 0 1 1 . . . 8 3 6 Ca 8 5 1 TABLE 1. WATER CHEMISTRY AND CARBON ISOTOPES CHEMISTRY 1. WATER TABLE 2 2 3 (ppm) 5 2 2 9 2 3 . . . 6 7 7 9 1 3 . . . T 9 1 3 (°C) pH 2 3 3 g g g n n n i i i r r r well 31.1 7.28 207.0 66.0 46.0 4.0 240.3 128.0 534.0 –2.7 0.38 0.65 –0.73 –1.91 2 well 33.5 7.19 215.0 63.0 69.0 4.0 240.3 73.0 575.0 3.6 0.33 0.53 –0.69 –1.81 –6.5 2 well 29.4 7.21well 320.0 29.7 88.0 131.0 7.28 589.0 5.0 202.5 122.0 343.0 115.6 10.0 840.0 164.7 12.1 195.0 0.33 2000.0 0.48 6.3 –0.46 0.43 –1.94 0.54 –0.03 –2.13 2 2 well 33.4 7.16well 225.0 32.0 68.0 7.16 77.0 253.0 4.0 92.0 240.3 261.0 91.5 8.0 228.1 638.0 213.4 1.5 930.0 0.30 5.4 0.49 0.24 –0.65 –1.78 0.44 –0.53 –1.82 2 2 well 28.7 7.18 383.0 105.0 212.0 6.0 215.3 164.5 1220.0 6.7 0.34 0.48 –0.30 –1.90 2 well 29.1well 7.24 29.6 358.0 7.28 104.0 316.0 151.0 93.0 6.0 128.0 215.3 5.0 140.0 215.3 1046.0 103.5 8.2 900.0 0.40 9.5 0.63 0.42 –0.37 –1.95 0.68 –0.44 –1.99 2 2 p well 28.9 7.92 217.0 63.0 41.0 4.0 253.2 42.5 550.0 4.0 1.01 1.87 –0.70 –2.56 2 well 29.5 7.93 213.0 63.0 43.0 4.0 266.0 48.6 590.0 –0.8 1.03 1.92 –0.68 –2.54 2 p wellwell 31.8 7.01 31.2well 217.0 7.65 233.0 27.4well 74.0 7.70 45.0 69.0 31.3 199.0 55.0 4.0 7.21 226.9 66.0 4.0 243.0 214.1 44.0 42.5 68.0 4.0 42.5 48.0 610.0 226.9 690.0 4.0 4.8 30.5 215.3 0.10 2.4 570.0 48.6 0.71 0.14 3.5 –0.67 1.29 675.0 0.70 –1.66 –0.60 3.2 –2.34 1.28 0.31 –0.71 0.45 2 –2.39 –0.60 2 –4.0 –1.89 2 2 p well 31.0 7.01 224.0 67.0 51.0 5.0 214.1 42.5 640.0 3.5 0.08 0.02 –0.64 –1.69 2 from s s s Sampled a a a a a a a a – – ––– spring– spring 28.2 spring 5.91 35.0 spring 414.0 6.28 32.2 372.0 132.0 7.48 34.2 230.0 378.0 116.0 7.34 191.0 9.6 302.8 119.0 276.4 174.9 8.6 98.2 190.5 132.0 8.3 161.1 214.2 107.0 1687.0 10.6 225.5 1410.0 –2.6 87.0 –0.85 122.7 1518.4 2.2 –1.84 –0.56 971.0 –2.1 –0.19 –1.23 0.63 7.1 –0.52 –0.28 1.15 0.52 –1.00 –0.25 0.96 –2.18 1 –0.45 –2.00 1 –15.4 1 1 – de Sofi Teresa Teresa de Sofi Teresa Teresa de Sofi Teresa Teresa de Sofi Teresa Teresa Teresa de Sofi Monica 2 de Sofi de Sofi Teresa de Sofi Teresa Teresa Monica 9 Monica 7 Monica 8 Monica 5 Monica No. 6 Monica 4 Monica 10 e c o i j ow canal) n o r l e u t u (infl (vent) (cool vent) (warm vent) h n z CNA-125 Santa A CNA-143 Santa Teresa A CNA-133 Santa Sample Description CNA-124 Santa C El VenadoLa Becerra La Becerra –Santa Tecla spring 28.5 – 6.23 65.4 spring 13.1 30.0 18.4 6.68 0.7 144.0 263.6 47.7 16.9 70.4 68.5 3.0 233.7 –9.9 –0.97 33.3 –2.25 –1.79 451.7 –0.80 0.3 –0.37 –0.83 1 –0.89 –1.32 1 CNA-24CNA-27 Ej. Santa Ej. Santa CNA-003 Beta Santa CNA-25 Ej. Santa Escobedo CNA-23 Ej. Santa Escobedo PrecipitationCNA-82CNA-84CNA-83CNA-85 El Pilar – El Pilar El Pilar El Pilar precipitation 20.0 well well 6.00 well 28.0 well 14.7 28.5 8.11 28.8 7.10 30.1 1.1 629.0 7.18 642.0 7.16 650.0 197.0 5.9 653.0 186.0 504.0 188.0 454.0 3.9 185.0 12.0 472.0 11.0 38.1 457.0 126.3 12.0 139.1 11.0 126.3 249.9 3.9 114.1 213.4 225.5 2520.0 201.0 2544.0 13.5 2592.0 8.8 2568.0 6.7 7.6 1.06 6.9 0.15 7.7 –2.67 0.19 1.97 0.15 –6.18 0.12 0.21 0.03 –2.89 0.12 0.04 –3.13 0.05 –1.44 –2.03 0.05 –2.9 –2.16 –2.17 2 2 2 2 2 CNA-105 Beta Santa CNA-90CNA-107CNA-106 Nuevo Tanque Beta Santa Beta Santa well 32.1 6.99 236.0 70.0 75.0 5.0 226.9 54.6 672.0 5.4 0.11 0.09 –0.61 –1.64 2 CNA-87CNA-103 El Pilar Beta Santa well 29.1 7.20 651.0 188.0 492.0 11.0 114.1 237.5 2640.0 6.5 0.17 0.16 0.05 –2.22 2 CNA-86CNA-81CNA104CNA-102CNA-44 El PilarCNA-12 El PilarCNA-108 Beta Santa Beta Santa well Las Morenas well Buenavista Beta Santa 27.4 well 26.9 7.27 well 7.26 706.0 27.1 655.0 27.4 181.0 7.19 168.0 406.0 670.0 7.23 359.0 11.0 763.0 164.0 11.0 126.3 391.0 238.0 126.3 201.0 442.0 11.0 176.6 113.5 13.0 2540.0 126.3 2496.0 189.0 8.3 408.4 4.0 2640.0 0.31 0.26 2900.0 2.3 0.37 0.28 3.1 0.15 0.08 0.27 0.06 0.03 –2.26 –2.25 0.39 0.08 0.12 –2.22 2 –2.22 2 2 2

Geosphere, February 2013 117 Wolaver et al. ) † continued ( C* 13 (‰) Ref. δ 2 CO Log p SI gypsum SI dolomite SI calcite (%) Charge balance 4 ) SO (ppm) continued Cl (ppm) 3 HCO (ppm) K (ppm) Na (ppm) Mg (ppm) Ca (ppm) TABLE 1. WATER CHEMISTRY AND CARBON ISOTOPES ( AND CARBON ISOTOPES CHEMISTRY 1. WATER TABLE T (°C) pH well 30.1 7.09 234.0 62.0 47.0 4.0 240.3 42.7 710.0 –3.4 0.20 0.20 –0.59 –1.73 2 well 30.4 7.11 258.0 72.0 57.0 4.0 228.1 54.6 750.0 1.5 0.23 0.29 –0.55 –1.77 –4.5 2 well 31.1 7.02 229.0 111.0 243.0 12.0 253.2 158.5 940.0 6.9 0.10 0.27 –0.57 –1.64 2 well 31.5 7.01 239.0 87.0 231.0 8.0 228.1 176.6 1004.0 –0.6 0.06 0.06 –0.52 –1.67 2 well 32.5 7.06 376.0 101.0 159.0 7.0 266.0 91.5 1280.0 1.2 0.34 0.51 –0.29 –1.66 –5.5 2 well 32.6 6.86 188.0 61.0 51.0 4.0 288.7 39.2 528.0 –0.4 0.02 –0.04 –0.76 –1.40 2 well 32.6 6.96 217.0 57.0 74.0well 4.0 278.8 30.3 48.8 7.20 377.0 560.0 124.0 4.2 156.0 0.16 11.0 278.8 0.14 79.1 –0.70 –1.51 1234.0 7.2 0.48 2 0.86 –0.31 –1.80 2 well 29.7 7.76 363.0 117.0 154.0 9.0 253.2 79.1well 1240.0 28.7 5.1 6.48 0.96 229.0 1.81 65.0 –0.32 34.0 –2.41 2.0 316.6 2 67.0 543.0 –0.3 –0.29 –0.75 –0.69 –1.00 –8.3 2 from spring 30.4 7.22 323.0 62.0 9.0 2.0 215.3 12.3 800.0 3.7 0.41 0.48 –0.44 –1.91 2 spring 24.9 8.07 377.0 12.0 173.0 7.0 184.2 103.0 1256.7 –10.0 1.08 0.99 –0.24 –2.89 2 springspring 32.1 7.24 34.5 377.0 7.42 393.0 115.0 160.0 108.0 160.0 8.0 240.3 8.0 253.2 91.5 91.5 1296.0 1340.0 3.9 0.47 2.0 0.71 0.82 –0.29 1.27 –1.89 –0.27 –2.03 2 2 spring 31.7spring 7.24 153.0 26.8 7.75 44.0 370.0 47.0 125.0 3.0 265.0 253.2 13.0 253.2 30.5 140.0 350.0 1400.0 5.1 5.7 0.30 0.90 0.45 1.68 –0.95 –0.28 –1.83 –2.42 2 2 Sampled spring run 30.1 7.35 798.0 353.0 529.0 27.0 319.6 318.0 3264.0 8.8 0.82 1.65 0.13 –1.94 2 spring run 30.3 8.17 612.0 280.0 409.0 21.0 289.5 244.8 2562.0 7.4 1.48 3.00 –0.01 –2.83 2 spring run 28.9 7.70 426.0 122.0 182.0 8.0 167.8 113.0 1460.0 5.7 0.76 1.34 –0.21 –2.54 2 a a Monica 1 Monica 14 Hundidos Los Gueros Churince Manriquez Nueva Anteojo de Sofi Monica 3 de Sofi Becerra Escobedo Mineros del Norte Lorenzo Atalaya Atalaya Tortugas Los Alamos Tecla Sample Description CNA-100 Beta Santa P-14P-15P-16 Poza Azul 11 Los Riachuelos Blanca Tierra spring run spring 32.8 spring 32.1 8.09 31.6 7.48 679.0 240.0 7.18 539.0 350.0 844.0 71.0 53.0 108.0 103.0 180.6 158.0 6.0 10.0 545.0 206.2 231.2 4520.0 70.0 101.0 2.5 1266.7 855.0 1.16 –2.0 1.0 2.61 0.52 0.36 0.11 0.91 0.60 –2.96 –0.54 –0.32 –2.18 –1.84 2 2 2 CNA-121 Canoas well 22.9 7.37 74.0 28.0 10.0 5.0 342.2 12.1 33.0 –0.6 0.25 0.41 –2.09 –1.87 2 CNA-43CNA-39P-01 El Campizal El Campizal Poza Churince well well spring 29.0 28.5 31.3 7.48 7.38 7.57 675.0 648.0 362.0 182.0 168.0 100.0 613.0 439.0 160.0 12.0 11.0 240.3 8.0 126.3 215.3 304.9 207.0 103.5 3100.0 2690.0 1230.0 –1.3 1.8 0.74 2.9 0.38 0.73 1.28 0.53 1.29 0.10 0.07 –0.31 –2.18 –2.36 –2.28 –7.2 2 2 2 P-13 Posa Los CNA-243P-09CNA-191 El Venado 8 ETA Rio Mezquites spring spring run 31.3 29.7 well 7.82 7.23 330.0 88.0 24.2 128.0 6.73 15.0 213.0 271.0 15.0 11.0 108.0 266.0 1.0 57.0 189.7 115.6 2.0 1225.0 24.4 342.2 6.6 87.5 61.0 1.02 6.2 768.0 2.01 0.02 –0.37 4.4 –0.33 –0.04 –2.44 –1.59 –0.16 –1.94 –0.54 2 –1.26 2 2 CNA-112 Beta Santa P-20 Laguna CNA-41 El Campizal well 28.2 7.57 646.0 180.0 467.0 12.0 114.1 249.9 2621.0 4.5 0.52 0.84 0.05 –2.60 2 P-18CNA-161P-19 Ampuero 6 Poza XYZ Poza well spring 23.7 29.5 6.83 7.99 414.0 484.0 288.0 138.0 293.0 195.0 13.0 6.0 173.2 316.0 130.0 532.0 1800.0 1613.3 0.5 4.1 1.07 0.06 1.96 0.28 –0.12 –0.27 –2.84 –1.43 2 2 P-12 Poza Ramon CNA-241 Papalote CNA-227CNA-252P-10 Las Carpas La Vega well spring San Josedel 27.0 25.7 7.07 7.22 102.0 92.0 13.0 11.0 7.0 2.0 1.0 278.8 1.0 202.5 9.9 8.0 40.0 82.5 7.0 3.5 0.06 0.01 –0.39 –0.55 –1.87 –1.58 –1.63 –1.93 –11.0 2 2 CNA-101 Beta Santa CNA-142 Santa Teresa CNA-144 Santa Teresa P-17 El Mojarral spring run 33.2 7.30 340.0 100.0 145.0 9.0 209.2 94.7 1196.7 1.6 0.46 0.78 –0.34 –2.00 2 P-02 Poza La CNA-199CNA-250 Jonuco EL Papalote San P-11 well 26.6 6.75 367.0 Las Playitas 103.0 spring run 46.0 26.8 2.0 8.32 240.3 550.0 36.5 216.0 430.0 1008.0 20.0 7.3 114.1 –0.05 219.5 –0.30 2560.0 –0.35 –1.42 3.5 1.13 2.20 2 –0.01 –3.41 2 P-03P-04CNA-216 Poza Antiguos Poza Azul I spring 27.8 7.90 400.0 131.0 193.0 9.0 228.1 109.8 1455.0 4.0 1.04 1.95 –0.24 –2.62 2 CNA-233 Nueva A.P. P-06P-07P-08CNA-186 Poza Orozco Poza Azul Poza Las Rancho spring spring 31.2 7.63 31.2 378.0 7.15 103.0 394.0 159.0 113.0 167.0 8.0 215.3 8.0 266.0 91.5 91.5 1240.0 1276.0 5.2 0.80 5.7 0.44 1.43 –0.30 0.71 –2.34 –0.28 –1.76 2 2 CNA-178P-05 El Nogalito Poza Santa well 24.3 6.79 254.0 81.0 41.0 3.0 303.8 97.5 576.0 4.5 –0.02 –0.21 –0.64 –1.37 2

118 Geosphere, February 2013 Identifying spring water origins and pathways with He, Sr, C † C* 13 (‰) Ref. δ 2 CO Log p SI gypsum SI dolomite SI calcite (%) Charge balance 4 ) SO (ppm) continued Cl (ppm) 3 HCO (ppm) K (ppm) Na (ppm) Mg (ppm) C is blank, not reported. 13 Ca δ (ppm) TABLE 1. WATER CHEMISTRY AND CARBON ISOTOPES ( AND CARBON ISOTOPES CHEMISTRY 1. WATER TABLE T (°C) pH wellwell 26.5 7.07 24.3 277.0 7.36 81.0 58.0 166.0 21.0 3.0 81.0 211.9 1.0 10.7 305.5 692.0 10.5 22.0 31.3 0.15 22.8 –0.04 0.24 –0.54 –1.79 0.25 –2.08 –1.90 2 2 well 27.3 7.05 285.0 58.0 157.0 3.0 218.2 10.8 698.0 21.4 0.16 –0.01 –0.53 –1.75 2 wellwell 28.8 8.51 27.2 600.0 7.90 1536.0 642.0 10.3 1908.0 380.0 10.8 101.7 500.0 9360.0 138.3 14400.0 9360.0 –73.7 16590.0 0.91 –70.6 0.50 2.58 1.82 0.22 –3.74 0.26 –2.94 2 2 well 24.3 7.52 80.0 21.0 84.0 1.0 314.0 9.9 30.2 22.5 0.41 0.58 –2.11 –2.05 2 well 26.6 7.64 794.0 2650.0 11.7 498.0 231.9 6500.0 20437.5 –61.8 0.52 1.90 0.38 –2.46 2 well 26.3 7.61 587.0 2160.0 9.6 425.0 222.8 6300.0 19980.0 –69.9 0.34 1.58 0.26 –2.43 2 wellwell 27.7well 8.01 27.7well 1058.0 7.97 26.6 3105.0 707.0 8.31 26.1 15.8 2010.0 707.0 870.0 8.41 2123.0 11.2 213.9 780.0 542.0 14100.0 2055.0 11.4 218.0 533.0 26175.0 11.4 9750.0 225.3 –70.6 571.0 17550.0 9975.0 0.93 207.4 –70.5 17850.0 9900.0 2.68 0.80 –69.7 17400.0 0.53 1.10 –68.8 2.40 –2.89 1.18 3.01 0.31well 3.13 –2.81 0.31 –3.19 0.35 27.2 2 –3.35 7.63 2 552.0 2 2178.0 2 9.8 429.0 207.3 6360.0 20040.0 –70.3 0.31 1.56 0.24 –2.47 2 well 26.5 8.21 536.0 1278.0 9.7 287.0 106.5 9240.0 12600.0 –75.5 0.64 2.00 0.16 –3.37 2 well 27.9 7.71 540.0 945.0 8.1 325.0 195.5 5550.0 13575.0 –78.1 0.43 1.45 0.20 –2.55 2 well 27.4 7.82 528.0 468.0 4.7 173.0 136.4 3060.0 7560.0 –73.2 0.49 1.28 0.13 –2.80 2 well 28.0 7.82 528.8 115.0 1.1 52.0 107.9 649.6 2728.0 –48.1 0.64 0.96 0.02 –2.87 2 from spring 27.4 7.23 74.0 24.0 23.0 2.0 273.3 15.5 59.5 4.7 0.07 0.03 –1.84 –1.80 2 spring 32.4 6.92 360.0 105.0 142.0 14.8 200.0 104.0 1262.0 1.4 0.07 –0.01 –0.31 –1.64 3 spring 29.3 7.17 96.9 18.0 18.0 1.2 245.6 22.0 83.1 6.0 0.10 –0.14 –1.60 –1.77 2 Sampled spring run 18.6 7.50 393.0 124.0 186.0 11.0 180.0 121.0 1547.0 –0.7 0.42 0.59 –0.20 –2.36 3 —temperature; dash in Description column indicates no additional description is needed. T La Ximena del Anteojo Anteojo La Ximena La Ximena Rivero Garabatal La Becerra Rivero Rivero Rivero Rivero Rivero Rivero Rivero Rivero Rivero Rivero Venado Rivero Rivero C, with exception of La Becerra from Aldama et al. (2005). Where C, with exception of La Becerra from 13 δ SI—saturation index; References: 1—this study; 2—Aldama et al. (2005); 3—Johannesson (2004). † Note: *Water *Water Sample Description CNA-170B-1 (50 m)CNA-170B-2 (80 m) Rancho Rancho Poza El Anteojo (17 m)Poza El San Jose CNA-119-B Rancho CNA-162 (25 m)CNA-115 (39 m)CNA-115 (64 m)CNA-115 El Pilar El Pilar Ampuero 5 El Pilar well well well well 30.2 24.7 28.7 8.85 28.8 7.02 8.23 411.0 189.0 7.48 495.0 535.0 154.0 66.0 182.0 35.0 198.0 68.0 38.0 10.0 37.0 11.0 1.0 37.2 10.0 278.8 68.9 97.6 188.1 123.6 186.6 187.0 1929.0 2088.0 332.0 –20.5 2280.0 –13.7 10.2 1.02 –14.7 0.86 0.10 0.33 1.99 1.65 0.09 –0.15 0.59 –0.07 –0.93 –4.52 –0.03 –3.51 –1.62 –2.56 2 2 2 2 Laguna del Garabatal Laguna del Poza de La Becerra Poza de CNA-139 (69 m) Florentino Pozos BonitosLaguna Anteojo Pozos Bonitos Laguna Anteojo spring run spring 26.2 26.2 6.94 7.03 232.0 440.0 63.0 54.0 29.0 140.0 5.3 9.3 190.0 171.0 17.0 108.0 1250.0 706.0 –0.5 1.8 –0.10 0.12 –0.42 –0.33 –0.58 –0.21 –1.70 –1.86 3 3 CNA-129 (70 m)CNA-129 (85 m) Florentino CNA-129 (100 m) Florentino P-21 Florentino La Teclita spring 31.3 7.23 133.0 40.0CNA-139 (66 m) 41.0 3.0 Florentino Anteojo (10 m)Poza El 241.6 San Josedel 29.6 311.4 2.6 0.22 0.31 –1.03 –1.84 2 CNA-139 (50 m) Florentino CNA-129 (30 m) Florentino CNA-115 (95 m)CNA-115 CNA-129 (24 m) El Pilar Florentino well 28.9 7.54 525.0 181.0 360.0 13.0 97.6 187.0 2270.0 3.8 0.37 0.65 –0.05 –2.62 2 CNA-129 (40 m) Florentino CNA-139 (36 m) Florentino CNA-37CNA-37 El Hundido El Hundido well well 26.5 28.0 7.37 7.55 688.0 540.0 1098.0 2177.0 5.4 6.8 394.0 510.0 1144.5 293.4 4069.3 4671.4 10454.3 16457.1 –63.1 –59.5 1.01 0.43 2.57 1.81 0.24 0.19 –1.45 –2.24 2 2 CNA-129 (60 m) Florentino CNA-139 (26 m) Florentino CNA-227CNA-225CNA-228CNA-229CNA-252Manantial Las Carpas Las Carpas Las Carpas San Vicente Las Vegas well Cueva del well well well 27.6 spring 24.9 7.23 26.4 26.2 7.46 26.1 107.0 7.26 105.0 7.23 7.21 108.0 18.0 126.0 105.0 17.0 10.0 18.0 18.0 6.0 16.0 1.2 8.0 16.0 1.2 254.6 3.0 1.1 1.5 259.5 0.9 260.3 250.5 6.9 264.3 5.4 11.9 7.0 103.0 3.0 91.3 172.0 103.0 6.2 0.18 80.0 5.1 3.3 5.1 0.38 –0.03 0.20 0.21 5.3 –1.47 –0.09 0.32 0.16 0.01 –1.83 –1.22 –1.52 –0.13 –1.47 –1.85 –2.07 –1.57 –1.86 –1.80 2 2 2 2 2 CNA-243CNA-37 El Venado El Hundido spring well 30.0 6.87 26.9 7.33 98.6 602.0 18.0 670.0 22.0 3.7 1.3 298.0 260.3 2080.4 2880.0 26.2 6720.0 –62.7 83.2 1.26 5.0 –0.16 2.91 –0.66 0.12 –1.59 –1.13 –1.44 2 2 CNA-37CNA-139 (21 m) Florentino El Hundido well 27.4 7.06 594.0 18000.0 22.6 132.0 846.2 9300.0 100200.0 –56.8 0.17 2.16 0.48 –1.40 2 CNA-37 El Hundido well 27.2 7.24 590.0 10800.0 14.8 940.0 613.5 7280.0 61100.0 –50.9 0.25 2.10 0.38 –1.70 2

Geosphere, February 2013 119 Wolaver et al.

A All spring waters are signifi cantly above crustal /R C radiogenic production values of 3He/4He = = A 0.02 RA (Craig et al., 1978). XR Carbon Isotopes A 1.21.81.3 5.0 19.80.9 1.25 1.1 7.2 1.84 8.8 1.35 1.8 1.3 0.89 21.5 1.41 1.6 1.84 13.71.8 1.65 18.3 1.85 1.5 6.3 1.59 3 He of sample, R Water chemistry, CO / He ratios, and C iso- 4 2 –7 –7 –7 –7 –7 –7 –7 –7 –7

He/ tope data elucidate different C sources contrib- 3 /g) R/R

3 uting to CO2-rich springs in the Cuatrociénegas Ne 13 20 : R = δ

A Basin. C isotopes reported as C range from (cm

1.97 × 10 2.41 × 10 1.78 × 10 1.63 × 10 1.64 × 10 2.76 × 10 2.37 × 10 2.20 × 10 1.70 × 10 –15.4‰ (La Becerra warm vent) to –2.9‰ (CNA-82; Table 1). –9 –9 –9 –9 –9 –9 –9 –9 –9 The CO /3He value for the copper tube

/g) 2 3 Xe sample (1.2 × 1010; Table 2) is within the range 129 (cm 3 8 14 2.46 × 10 2.79 × 10 2.13 × 10 2.01 × 10 2.07 × 10 3.20 × 10 2.83 × 10 2.61 × 10 2.10 × 10 of crustal CO2/ He (10 to 10 ; O’Nions and Oxburgh, 1988). For 117 total groundwater –8 –8 –8 –8 –8 –8 –8 –8 –8 samples (Table 1), Ccarb from carbonate dis- /g) 3 Kr solution varies spring to spring, but has a 84

(cm mean value of 23% ± 25%. C (computed as 4.11 × 10 4.11

4.65 × 10 3.45 × 10 3.51 × 10 3.38 × 10 5.57 × 10 4.54 × 10 4.16 × 10 3.32 × 10 ext

DICtotal – Ccarb) has a mean of 77% ± 25% for 13

–4 –4 –4 –4 –4 –4 –4 –4 –4 δ 117 springs. The Cext values calculated for

/g) 13

3 δ

Ar each groundwater sample with C relative 40 —temperature; TDG—total dissolved gas; R/R (cm to Cext are described by binary mixing models T (Fig. 4). For 9 water samples with C isotope

values, Ccarb = 30% ± 22%, Corg = 24% ± 16%; 19 2.86 × 10 He n.r. n.r. n.r. n.r. n.r. 1.8 34.3 1.76 4 434 3.43 × 10 598684 3.01 × 10 2.92 × 10 487 2.85 × 10 (%) and C = 46% ± 33%. Δ 2499 × 10 3.90 3125 × 10 4.64 1666 × 10 3.92 2095 × 10 3.61 endo –7

–7 –6 –7 –7 –9 –6 –7 –7 –7 Strontium Geochemistry /g) 3 He Terri- genic

(cm There are 17 spring-water samples that 1.9 × 10 1.1 × 10 2.6 × 10 2.9 × 10 8.0 × 10 1.3 × 10 7.2 × 10 9.0 × 10 2.1 × 10 7.79 × 10 exhibit high homogeneity, with 87Sr/86Sr = –7 –6 –7 –7 –6 –7 –7 –7 –7 –8 0.707429–0.707468 (Table 3; Fig. 5); two sam- /g)

3 ples from a travertine quarry at the southwest He 4

TABLE 2. GAS CHEMISTRY TABLE fl ank of the Sierra San Marcos (Fig. 2) with an (cm measured age estimated by Aldama et al. (2005) as Pleisto- cene (~17,000 yr) have 87Sr/86Sr = 0.707448 /g) 3 and 0.707449. One modern travertine sample air 87 86 (cm Excess (Fig. 2) has Sr/ Sr = 0.707428. Results of Sr isotope analyses of rock samples from Creta- ceous carbonate (and gypsum bearing) rocks of .

TDG 87 86 (atm) 10 the regional aquifer have similar Sr/ Sr val- ues of 0.7072–0.7076 (Fig. 5; Lehmann et al., 2000). In contrast, volcanic rocks of nearby Las (yr) res. Est. time Coloradas, Las Esperanzas, and Ocampo vol- canic fi elds (Fig. 2) have much lower 87Sr/86Sr H 3

(TU) values, 0.70333–0.70359 (Aranda-Gómez et al., 2007; Chávez-Cabello, 2005). T (°C) DISCUSSION TDS

(mg/L) Water Chemistry = total air-corrected He. C The fi rst water class is sourced from a regional carbonate aquifer (mesogenic fl uids) mixed with endogenic fl uids that ascend along basement- (m) pH 703 5.91703 3564 6.28765 28.2 3197 7.48768 <0.1 35.0 2853 7.34 >60768 32.2 0.4 2999 0.9720 7.34 >60 34.2 0.3 2999 0.1554 1.6450 <0.1 >60 34.2 × 10 5.11 >60 0.1020 1.3150 n.r. 1.39 × 10 1.2580 0.0367 n.r. 0.0311 7.61 × 10 n.r. 9.46 × 10 n.r. × 10 8.02 Elev. involved faults (e.g., La Becerra and Escobedo springs). The 3H analyses, as indicated by levels He for La Becerra warm vent copper tube sample is 1.2 × 10 3 Elev.—elevation; n.r.—not reported; TDS—total dissolved solids; TU—tritium units; Est. res. time—estimated residence time; TDS—total dissolved solids; reported; n.r.—not Elev.—elevation; /

† below the detection limit, indicate regional car- 2 He of atmosphere; R ow canal 4

CO bonate aquifer residence times in excess of 60 yr. vent cooler vent hot vent hot vent *Rainwater sample collected in 2004 (Aldama et al., 2005). Note: copper tube infl † He/ AzulChurinceEl VenadoEscobedo 745 722 730Escobedo 7.22 6.23 7.32La Becerra 2382 551 3032 31.1La Becerra 28.5 33.0 <0.1La Becerra <0.1 1.1 >60 >60 >60 1.0580 1.4010 0.9590 0.0506 0.0346 0.1035 3.01 × 10 1.12 × 10 3.38 × 10 Santa TeclaSanta 714 6.68 1415 30.0 0.2 >60 0.9560 0.0221 2.53 × 10 Anteojo 735 6.95 1972 29.9 <0.1 >60 1.0920 0.0958 × 10 2.30 3 Sample Rain** 750 n.r. n.r. n.r. 5.4 n.r. n.r. n.r. n.r. n.r.Ca-SO n.r.4–type n.r. waters n.r.suggest rock-water n.r. n.r.inter- n.r. n.r. n.r.

120 Geosphere, February 2013 Identifying spring water origins and pathways with He, Sr, C

TABLE 3. Sr GEOCHEMISTRY genic production values (Craig et al., 1978). 87Sr/86Sr 1/Sr Tritiogenic 3He contribution to R/R values in Sample values [1/ppb] A Cuatrociénegas Basin springs is miniscule, as Water 3 Anteojo 0.707432 0.0001437 groundwater H concentration is ≤0.4 TU and Azul 0.707436 0.0000794 generally less than the method detection limit Churince 0.707468 0.0000723 ≤ Escobedo vent 0.707450 0.0000711 ( 0.1 TU; Table 2). Spring distribution rela- Escobedo inflow canal 0.707438 0.000071 7 tive to faults (Fig. 2; e.g., Poza Churince, Poza Escobedo outflow canal 0.707446 0.000072 7 Azul, and Poza Anteojo springs) indicates that Laguna Salada 0.707429 0.0000484 Las Playitas 0.707446 0.0000440 fl uids containing appreciable mantle gases fl ow Los Gatos marsh 1 0.707439 0.0000290 to a near-surface groundwater system along Los Gatos marsh 2 0.707435 0.0000361 basement-penetrating faults. Los Hundidos 0.707437 0.0000593 Mojarral Este 0.707434 0.0000718 Cuatrociénegas Basin He isotopes (RC/RA = Mojarral Oeste 0.707454 0.0000719 0.89–1.85; Table 2) show that western United Río Puente Chiquito 0.707432 0.0000686 Saca Salada Canal 0.707437 0.0000735 States regional mantle degassing (Newell et al., Santa Tecla 0.707465 0.0003860 2005) continues into northern Mexico south Tío Cándido 0.707451 0.0000834 of the Proterozoic Laurentia basement edge Travertine (Whitmeyer and Karlstrom, 2007). Published Los Hundidos, modern age 0.707428 0.0135 Quarry, inferred 0.707449 0.0689 Mexican He isotope data (R/RA) for volcanic, Pleistocene age hydrothermal, and economic geology stud- Quarry, inferred 0.707448 0.0863 Pleistocene age ies are consistent with mantle He degassing: Volcanic rocks 0.3–0.6 RA (Vidal et al., 1982), 2.36–6.33 RA Las Coloradas, minimum* 0.703327 n.r. (Welhan et al., 1979), 0.66–7.5 R (Taran et al., Las Coloradas, maximum* 0.703379 n.r. A Las Esperanzas, minimum† 0.70334 n.r. 2002), 1.25–2.84 RA (Inguaggiato et al., 2005), † Las Esperanzas, maximum 0.70359 n.r. 0.5–2.0 RA (Camprubí et al., 2006), and 0.57– † Ocampo, minimum 0.70337 n.r. 1.03 R (Nencetti et al., 2005). Mantle degas- Ocampo, maximum† 0.70346 n.r. A Carbonate rocks§ sing along the plate margin of western Mexico is Barremian to Albian, minimum 0.7072 n.r. not surprising, but is also taking place in north- Barremian to Albian, maximum 0.7076 n.r. eastern Mexico because of the importance of Note: Sr isotope results of water and travertine are normalized to an accepted NIST basement-involved faults. SRM 987 value of 0.710250. Based on the reproducibility for the standard, with a 95% confidence (= 2× the standard error of the mean), the uncertainty on a given analysis is ±0.000016. n.r. = not reported. Carbon Isotopes *Sr isotope results reported in Chávez-Cabello (2005). †Sr isotope results reported in Aranda-Gómez et al. (2007). §Sr isotope results reported in Bralower et al. (1997) and Lehmann et al. (2000). Waters in the Cuatrociénegas Basin have high

endogenic CO2 and mantle He isotopes that show crust and mantle fl uid input along base- actions of a limestone aquifer with concomitant carbonate aquifer that discharges along an ment faults into the regional aquifer. He gas gypsum dissolution in a regional fl ow system inferred normal fault. transport through the mantle and crust is partly

(Fig. 3). Gypsum dissolution in Cuatrociénegas PHREEQC modeling of the two groundwater coupled to movement of CO2/H2O supercritical groundwater is consistent with the presence of classes (Parkhurst, 1995) shows equilibrium fl uids (Giggenbach et al., 1993). Gas transport –0.5 hundreds of meters of cyclic carbonates and pCO2 values as high as 10 atm, indicating from the mantle is also supported by the CO2-

evaporites (Lehmann et al., 2000; Lehmann high CO2 relative to meteoric waters. Alkalinity rich character of Cuatrociénegas springs, which – ≤ et al., 1999). as HCO3 is also high ( 229 mg/L), suggest- have two to three orders of magnitude higher δ13 The second water class is consistent with ing that CO2 degassing from endogenic fl uids pCO2 than air and C = –15.4‰ to –2.9‰. a regional aquifer (mesogenic fl uids) source ascending along basement-involved faults infl u- mixed with locally recharged mountain precip- ences basin water chemistry. Strontium Geochemistry

itation (epigenic fl uids). These Ca-HCO3–type waters have slightly higher 3H (i.e., 0.2 TU Gas Chemistry Cuatrociénegas Basin water, travertine, and at Poza Santa Tecla; Fig. 2) and lower TDS, carbonate rock have similar Sr isotopic ratios. refl ecting shorter residence time consistent The Δ4He (434%–3125%; Table 2) indicates Volcanic and basement rocks do not appear to with localized fl ow systems. Water chemistry that 4He from terrigenic sources is greater than be signifi cant Sr ion sources to groundwater also refl ects mixing between meteoric recharge atmosphere-sourced 4He. Spring waters contain (Table 3; Fig. 5). Spring-water and travertine 87 86 (epigenic waters) and an SO4-rich end member nonatmospheric gases from a deep endogenic Sr/ Sr data show that the regional carbonate (mesogenic), consistent with dissolution and fl uid system (i.e., crust or mantle). However, the aquifer is the Sr source. Rock-water interaction near equilibration with gypsum (Fig. 3). Can- lowest Δ4He value (19%) is an air-contaminated of volcanic rocks and deeply sourced waters yons in the Sierra San Marcos, associated with sample approaching atmospheric equilibrium recirculated through granitic basement (Kesler alluvial fans (located in Cenozoic alluvium from an open canal that fl ows into Escobedo and Jones, 1980–1981) do not appear to contrib- 2–4 km south of the A–A′ cross-section line in spring. ute measurable Sr (we use 87Sr/86Sr > 0.72 for Fig. 2), permit mixing of epigenic ground water The presence of mantle-derived fluids the Precambrian to Paleozoic crystalline rock recently derived as mountain precipitation in spring water is supported by 3He/4He = Sr end member; Crossey et al., 2009). Assum- with mesogenic groundwater from the regional 0.02 RA, significantly above crustal radio- ing that the Pleistocene climate was cooler and

Geosphere, February 2013 121 Wolaver et al.

Basin and Range–type normal faults along P precipitation mountain fronts are inferred based on spring C B spring C 80% CCCC alignment on the east side of Sierra San Marcos A spring run C and the presence of mantle-derived fl uids in C B B 80% well ACC these springs. Normal faults have offsets below 60% BABC Ca + Mg CCC BCABBCABACC CCCCCCBCBBBCBACCACA gravity survey resolution (Wolaver and Diehl, C CC BB 60% + Cl C AB C 2011). Normal faulting has reactivated older 4 C 40% C BCB CCC deeply penetrating reverse faults and provides SO B C 40% endogenic fl uid pathways. Deeper fl uid conduit 20% B B CC system components likely involve hydrothermal BCB B 20% fl uid transfer through the lithospheric mantle C BB and lower crust. C P Sr isotopes indicate that carbonate rock-water interactions dominate Cupido aquifer spring- water chemistry. Paleogene–Quaternary reacti- C va tion of basement-involved faults associated C C C 20% with the opening of the Gulf of Mexico gener- CCCC BBABCACAC ated fractures in the regional Cretaceous car- CC 20% 3 BCBBBAACC 80% C Na + K CACCBBA 80% CC BAB bonate aquifer (Ca-SO4 facies) that focus spring C 40% CCCCBCC C CCCCC C 87 86 CC + CO CCCC C SO discharge ( Sr/ Sr = 0.707429–0.707468). 3 CBC C C 60% C 40% BCCC CC 60% Basement-involved faults also provide conduits B C 4 Mg C HCO C C 60% CC for Pliocene–Pleistocene mafi c volcanism, but C C 40% C 60% 40% spring waters show no detectable contribution CCCC A CC A 80% CB B of Sr ions sourced from volcanic rock-water CACCCCBCC A C C CBCCBCCBCBABABBBCBCBAC B BP interactions (with 87Sr/86Sr = 0.70333–0.70359). B CCCCCC 80% B 20% BCCCBBBB CCCCCC B 20% BCC C A comparison of Sr isotopes from recent and B C P C inferred Pleistocene aged travertine shows that B 80% 60% 40% 20% the Sr ion source to the groundwater fl ow sys-

20% 40% 60% 80% tem has remained the same, despite long-term Ca Cl climatic fluctuations. The likely dominant source of Sr ions to springs is the regionally Figure 3. Piper plot of Cuatrociénegas Basin water chemistry. Cuatrociénegas Basin waters extensive Cupido aquifer. are generally of two classes: (1) primarily Ca-SO4 water discharging from a carbonate aqui- He isotopes show that basement-involved fer regional fl ow system mixed with some fl uids that ascend along basement-involved faults, faults create pathways for mantle-derived gases 3 4 and (2) Ca-HCO3 water that is a mixture of mountain recharge and carbonate aquifer ground- to escape and discharge into springs ( He/ He = water. Water chemistry data are in Table 1. 0.89–1.85 RA). Mantle degassing is consistent with regional tomographic images that show low-velocity mantle at shallow sublithospheric wetter, homogeneous 87Sr/86Sr from travertine fer groundwater with endogenic sources (e.g., depths. Similar to the western U.S. (Bethke and of modern and inferred Pleistocene age sug- Poza La Becerra) and younger meteoric moun- Johnson, 2008; Crossey et al., 2009), north- gest that the regional carbonate aquifer has tain front recharge (e.g., Poza El Venado). He, ern Mexico is undergoing regionally pervasive remained the spring-water source despite dry- Sr, and C isotope data indicate that basement- mantle degassing through CO2-rich cool and ing Holocene climate (Musgrove et al., 2001). involved faulting (1) is a critical factor con- warm springs located along faults. A comparison of 87Sr/86Sr in Cuatrociénegas trolling spring vent locations, and (2) provides Spring-water C isotopes have high dissolved –1 –0.3 Basin spring water with the Cretaceous section conduits for circulation of deeply derived gases CO2 (pCO2 = 10 to 10 compared to atmo- 3 –3.5 (Lehmann et al., 2000) reveals matches with the charged with mantle-derived He and CO2. Sr spheric concentrations of 10 atm) and alka- ≤ – Albian Aurora and Barremian–Aptian Cupido isotopes show that the Cupido aquifer is the pri- linity 230 mg/L (as HCO3 ) and are similar to Formations. Because the Aurora Formation is mary Cuatrociénegas Basin spring source and Colorado Plateau travertine-depositing springs relatively thin compared to the Cupido Forma- the most important regional aquifer. (Crossey et al., 2006). Water chemistry analy- tion (Lehmann et al., 1999), this suggests that From the hydrogeologic conceptual model ses indicate that CO2 is (1) 33% ± 15% Corg, the Cupido Formation is the most important explaining groundwater, He, Sr, and CO2 fl uxes derived from soil gas and other organic sources, regional aquifer. (Fig. 6), it is inferred that neotectonic exten- (2) 30% ± 22% Ccarb, derived from dissolu- sional faults facilitate fl uid ascent along reac- tion of carbonate in the aquifer, and (3) 37% ±

CONCLUSIONS AND IMPLICATIONS tivated, older, deeply penetrating Laramide 29% Cendo, derived from endogenic (i.e., deep, OF SPRING GEOCHEMISTRY ON reverse faults. The hydrogeologic conceptual geologic) sources. Faults act as conduits for

WATER ORIGINS AND PATHWAYS model is based upon regional structural styles, elevated CO2 fl ux with concomitant elevated hydrogeologic data, and geophysical surveys groundwater alkalinity, as observed in other Cuatrociénegas Basin springs exhibit He, Sr, in Wolaver and Diehl (2011; refer to table 1 North American travertine-forming springs and C isotopes that indicate mixing of ground- therein for a generalized hydrostratigraphic (Bethke and Johnson, 2008; Crossey et al., water from the regional carbonate Cupido aqui- column). 2006, 2009).

122 Geosphere, February 2013 Identifying spring water origins and pathways with He, Sr, C

) = carb carb org = 30% ± 22%, C carb sources include: (1) C sources 2 org C, C C 13 δ 0

carb 20 (total dissolved inorganic carbon – C ext endmembers: 0.004, –5 endmembers: 0.004, 40 in C Cuatrocienegas +0.5 Cuatrocienegas mean C endo 60 80 100 endo 0 C mean CC mean CP and deeply sourced C and deeply sourced 20 C = +0.5‰). For nine water samples with nine water C = +0.5‰). For org is 2–3 orders of magnitude higher than air). CO is 2–3 orders of magnitude higher 13 2 δ 40 CO p 60 (mol/L) rich ( 2 (modeled as 80 ext carb C 0 20 40 60 80 100 endmembers: 0.004, –3 endmembers: 0.004, 100 carb CP—Colorado Plateau. uid input along basement-involved faults). CC—Cuatrociénegas; C endmembers: 0.0001, –3 endmembers: 0.0001, (endogenic crust and mantle). Proportions of C (endogenic crust and mantle). Proportions endo C by removing isotopic proportion due to C isotopic proportion C by removing sources to Cuatrociénegas springs, which are CO springs, which are to Cuatrociénegas sources 13 2 δ Rancho Los Alamos Rancho Los Nueva Atalya La Vega El Campizal La Becerra Hot (organic); and (3) C org Beta Santa Monica 1 El Pilar Santa Teresa de Sofia Teresa Santa Beta Santa Monica 10 = 46% ± 33% (consistent with crust and mantle fl 0.00 0.02 0.04 0.06 0.08 endo 5 0 –5

–10 –15 –20 –25 –30

ext

(permil) C δ 13 are estimated by correcting measured measured estimated by correcting are (carbonate dissolution); (2) C 24% ± 16%, and C Figure 4. Chiodini plot elucidating CO Figure

Geosphere, February 2013 123 Wolaver et al.

Plio-Pleistocene Carbonate rocks ACKNOWLEDGMENTS mafic volcanic rocks and gypsum 5×10–4 This study was partially funded by the the Uni- Precambrian to versity of Texas, the Geological Society of America, –4 3×10 Traverne Paleozoic crystalline BHP Billiton, the Gulf Coast Association of Geologi- 1×10–4 Spring water basement >0.72 cal Societies, the Houston Geological Society, and the 1/Sr (ppb) 0 Tinker Foundation. Larry Mack and John Lansdown 0.703 0.704 0.705 0.706 0.707 0.708 provided Sr isotope and cation analyses expertise. Alan 87 86 Sr/ Sr Rigby provided analytical expertise with dissolved noble gas analyses. Robert Poreda provided He isotope Figure 5. Ratio of 87Sr/86Sr for spring water, travertine, volcanic analyses of one of the samples. Dean Hendrickson and rocks, and carbonate rocks. Cuatrociénegas spring water 87Sr/86Sr Suzanne Pierce collected water samples for Sr analy- (black squares) and Sr isotope ranges for Cuatrociénegas Basin ses. Gareth Cross, Peyton Gardner, Dean Hendrick- son, Randall Marrett, Juan Manuel Rodriguez, and travertine samples (blue line) and Pliocene–Pleistocene mafi c vol- Vsevolod Yutsis provided helpful conversations. Laura canic rocks, carbonate rocks, and gypsum are shown. Dashed Merner and Dawn Saepia of the Environmental Sci- arrows (indicating 87Sr/86Sr > 0.72 for Precambrian–Paleozoic crys- ence Institute’s National Science Foundation Research talline rock) are after Crossey et al. (2009). Experience for Undergraduates program (NSF, EAR- 0552940) assisted with fi eld work. NSF grant EAR- 0838575 supported Crossey and Karlstrom’s work. A (West) A′ (East) Publication is authorized by the Director, Bureau of Economic Geology, Jackson School of Geosciences, Sierra San Marcos Sierra La Purísima the University of Texas at Austin.

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