groundwater chemistry and overpressure evidences in cerro

Research ArticleGroundwater Chemistry and Overpressure Evidences inCerro Prieto Geothermal Field

Ivan Morales-Arredondo Mariacutea Aurora Armienta and Nuria Segovia

Instituto de Geofısica Universidad Nacional Autonoma de Mexico Cd Universitaria 04510 Mexico City Mexico

Correspondence should be addressed to Ivan Morales-Arredondo ivanmageofisicaunammx

Received 19 May 2017 Revised 30 October 2017 Accepted 19 November 2017 Published 18 December 2017

Academic Editor Ian Clark

Copyright copy 2017 IvanMorales-Arredondo et alThis is an open access article distributed under the Creative CommonsAttributionLicense which permits unrestricted use distribution and reproduction in anymedium provided the originalwork is properly cited

In order to understand the geological and hydrogeological processes influencing the hydrogeochemical behavior of the Cerro PrietoGeothermal Field (CP) aquifer Mexico a characterization of the water samples collected from geothermal wells was carried outDifferent hydrochemical diagrams were used to evaluate brine evolution of the aquifer To determine pressure conditions at deptha calculation was performed using hydrostatic and lithostatic properties fromCP considering geological characteristics of the studyarea and theoretical information about some basin environments Groundwater shows hydrogeochemical and geological evidencesof the diagenetic evolution that indicate overpressure conditions Some physical chemical textural and mineralogical propertiesreported in the lithological column fromCP are explained understanding the evolutionary process of the sedimentarymaterial thatcomposes the aquifer

Dedicated in memory of Dr Ramiro Rodriguez C

1 Introduction

Different authors have observed that the origin of somebrinesaround the world can be caused by diagenesis evolution andporewater trapped during burial [1ndash3] Commonly porewatershows characteristics according to the depositional environ-ment [4] The different stages of diagenesis are composedof burial and compaction of material in sedimentary basinsthe sandstones and shales undergo changes in their physicalchemical textural and mineralogical properties which arereflected in the sediment density the compaction of the gran-ular package and loss of porosity [5] additionally a chemicalalteration occurs in sandstones generating cementation andlithification as a product of chemical precipitation affectingdetrital grains dissolution recrystallization ormineralogicalalteration [6] Silica is the most abundant cementing agentin sandstones compared to calcium carbonate either calciteor aragonite since the latter dissolves more easily in contactwith groundwater mainly the second [7] In the diageneticstages interstitial fluids are constantly lost in most shales[8] this phenomenon can occur at low depth and can last

for thousands or hundreds of thousands of years or havea longer duration and greater depth but when it suddenlyoccurs and the permeability of the medium is so low thatit does not allow the interstitial fluid to leak an increasingdegree of stress can be generated [9] this geological event isknown as overpressure [10] Overpressure is an abnormallyhigh pressure in the subsoil that exceeds the hydrostaticpressure at a certain depth this pressure is carried out in thepores where the pressure of the interstitial fluids increasesas the overcoat increases [11 12] Overpressure indicates thatthe high pressures developed during compaction do notdissipate efficiently [10] and can generate hydraulic fracturingin the system (stress applied to compressible rock and fluidexpansion) These processes generate overpressured fluidsrelated to porosity reduction changes on porewater flow anddiagenetic reactions due to compaction and disequilibriumin a sedimentary basin [12ndash14] Also overpressure can berelated to chemical compaction due to changes inmineralogy(eg ion exchange dissolutionprecipitation) or to diageneticprocesses and fluid expansion by thermal water in porespace

HindawiGeofluidsVolume 2017 Article ID 2395730 13 pageshttpsdoiorg10115520172395730

2 Geofluids

0 05 1 2(Km)

131138112

T-395222 D

DELTA 1

M-119AM 200

M-148A610T-350A

608

428233

601 423M111A

343

611

414442407M133A

M198403

311333 310 308

M15

670000000000

670000000000

NE

SO

BajaCalifornia

Baja California Sur

Sonora

ChihuahuaCoahuila

Nuevo Leoacuten

TamaulipasSinaloa

DurangoZacatecas

Nayarit

Jalisco

AguascalientesSan Luiacutes Potosiacute

Guanajuato

Hidalgo

MichoacaacutenColima

Estado de Meacutexico

TlaxcalaDF

Morelos

Guerrero

Puebla

Veracruz

Oaxaca

Tabasco

Chiapas

Campeche

Yucataacuten

Quintana Roo

Sal

Del

Cuc

Chi

VCP

Michoacaacuten de Ocampo

Cerro PrietoGeothermalField

GeoCerro PrietoVolcano

3245

3235

3225minus11525 minus11515

0 5(Km)

M-11M-104 M-127

E-23T-400

E-24

E-29

Quereacutetar

o

Imperial Fault

Cerro Prieto Fault

Mexicali

Figure 1 Localization of Cerro Prieto Geothermal Field and sampled wells

Cerro Prieto Geothermal Field (CP) located in north-western Mexico (32∘2410158404310158401015840N 115∘1410158404110158401015840W) is a brine withhigh-temperature geothermal system characteristics Severalstudies about the origin and behavior ofCP groundwater havebeen reported [15ndash18] According to geological evidences alarge accumulation of sedimentarymaterial from a continen-tal and marine origin overlying the depositional basin isrelated to the origin of brine [17] The sedimentary materialshows diagenetic evolution evidences and porewater trappedbetween sediment grains during burial processes The pore-water is saline with high Clminus Na+ Ca2+ and K+ concentra-tion in geothermal brines this characteristic is common [1 210] the composition depends mainly on the primary originmineralogical composition of the sediments and their modi-fication due to diagenetic processes (eg facies distribution)and hydrothermal characteristics [15 19] Among the mostevident diagenetic processes in CP are cementation mineralreplacement recrystallization authigenesis and growth ofconcretions and nodules [16] On the other hand in deepsedimentary basins as CP mechanical processes of defor-mation related to burial mechanisms are common likewisehydrostatic and lithostatic conditions increase with depthdue to an increase of the superposed fluids hydraulicallyconnected through the pore and the pressure exerted bysediments overload [10] If pore pressure in deep aquiferslike CP is higher than expected from hydrostatic condi-tions anomalous pressure (overpressure) can be generatedoverpressure is common mainly within 2ndash45 km depth[10ndash12]

According to geochemical evidences the origin of geo-thermal brine at CP could be governed by mixing processesrelated to a hydrothermal environment and the sedimentarymaterial located at depth which shows burial diagenesis evo-lution with hydrogeochemical evidences of an overpressur-ized environment The aim of the present study was to eval-uate hydrogeochemical behavior of geothermal groundwater

and its relationwith diagenetic processes including overpres-sure

2 Localization

Cerro Prieto Geothermal Field (CP) located in MexicaliValley SE of Mexicali City in Baja California State Mexico(Figure 1) is a Basin of Salton Sea [17] Climate is arid withtemperatures up to 40∘C in July and to 4∘C in winter Theaverage annual precipitation is 55mmyear and the averageannual evaporation is 2200mmyear [23] Groundwater atCP is extracted from geothermal wells that are in constantexploitation to generate electricity The Comision Federalde Electricidad of Mexico (CFE) operates and manages theGeothermal Field CP power production is up to 720MWand is composed of five individual units CP1 CP2 CP3CP4 and CP5 each unit has a total capacity of productionwith a specific number of production wells Sampled wells areindicated in Figure 1 Their localization in the five individualCP units is included in Table 1 All the wells are located inzone ldquobetardquo 1500 to 3100m depth [17]

21 CP Geology The lithology around CP is composed ofgneiss (quartz-feldspars) shale (quartz-mica) marble am-phibolite and quartzite from Permic to Jurassic [24] andmetamorphic granitic and granodiorite rocks which areintruded by batholitic rocks [16] together with dacite andandesite fromMiocene and rhyodacite fromQuaternary [25]The tectonic basin was filled by sedimentary material thatdue to burial compaction and diagenesis processes evolvedto gray shales from Late Miocene (shales and silt shalesthat vary from light gray to black) this unit overlies thegranitic basement and the mafic intrusive and is interlayeredby permeable sandstones (composed of quartz and feldsparsarkoses type) The thickness is near 3000m [21 26] Imme-diately above a layer of brown shale (shale and silt shale)

Geofluids 3

Table1Major

elem

entsconcentrationvalues

atCP

grou

ndwater

samples

measuredin

summer

2010

Well

Operatio

nareas(individu

alun

its)

Depth119879

pHCE

TSD

CaMg

Na

KHCO3

Clminus

SO4

IB

BSiO2

(Km)

(∘ C)

mScm

Calculated

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

M104

CP3

173

884

773

2045

206132

2616

509

6250

11875

415

119625

135minus28

1326

8517

M117

ACP

3289

912

7735

173155

1402

347

5575

1185

184

9375

00933

1465

9801

M119

ACP

231

879

679

35345069

3791

383

9850

26825

107

20150

009minus45

1742

14017

M127

CP2

25

768

761

248

214578

2883

311

60875

13525

284

128125

59minus67

184

8474

M133A

CP3

249

808

749

3545

365454

8194

539

10750

1840

1922200

142minus56

1986

8539

M148A

CP2

299

858

743

268

273272

3791

287

8300

16525

213

15875

71minus27

1845

10743

M155

CP3

29

805

744

3665

388638

7355

449

11325

2050

272

23800

009minus68

2792

8902

M198

CP4

28

918

752

2185

256012

1876

569

75875

15775

166

15250

009minus56

288

9159

M200

CP3

284

828

742

2585

221513

1836

251

63125

1690

284

12950

009minus52

2235

9737

112

CP1

265

8672

53305

312164

5331

479

9125

19925

148

18250

009minus36

158

12605

233

CP2

264

889

753

434

239716

1895

299

7275

1490

237

13700

36minus26

166

12626

311

CP3

294

851

756

43235488

2883

239

71375

14325

118

13550

54minus25

219

10914

323

CP3

29

946

767

2675

270189

2863

539

74375

14825

379

16750

009minus108

229737

343

CP3

2958

748

285

343097

7898

599

97125

14475

143

21587

29minus94

1756

6677

403

CP4

289

828

732

161

15503

1678

599

4540

1030

426

8950

44minus32

2885

7276

407

CP4

299

884

791

1895

2004

26

1086

359

5815

1185

19118875

85minus7

167

9694

611

CP3

252

884

787

5285

332629

7305

539

9875

1585

1920100

224minus52

2161

8774

222D

CP2

314

922

774

2975

287199

2962

275

80625

1907

9517300

009minus79

1125

11149

E-23

CP2

295

711

585

393441

5805

216

11175

27175

284

23750

009minus66

242

10807

E-29

CP2

269

833

712

794

444913

7858

144

13200

29625

213

2660

0009minus41

2655

918

E-47A

CP3

289

917

747

61350746

6476

168

10650

22475

166

20500

009minus21

2197

9951

T350A

CP2

29

82688

822

492512

10326

228

143125

27825

154

29700

009minus57

2855

13931

T395

CP2

265

801

792

488

239242

3376

275

70375

1420

47

140625

63minus46

1025

10165

T40

0CP

121

896

791973

129455

1224

335

3910

5605

207

7570

336minus52

911

6805

611lowastA

CP3

252

876

785

524

332175

7049

371

100875

1595

201

19875

225minus4

228774

4 Geofluids

the gray shale covers interlayered permeable sandstones andsands cemented by carbonates about 500m thickness [21]In these zones a rapid distribution of geothermal fluidsenhances the recharge Erratic mudstone layer and unconsol-idated clastic sediments (clays silts sand and little gravel)overlie all the previous units The thickness of these units isbetween 400 and 2500m [26] Sedimentary material showsevidence of the diagenetic evolution and recrystallizationprocesses due to an incipient low grade metamorphism

The geological evolution of CP is a complex blend ofrifting rapid deltaic sedimentation and large scale strike-slip faulting located within the Salton Basin [16 19 21 27]The Geothermal Field is placed in a shear zone where NW-SE and NE-SW fault systems intersect The more importantfaults are Cucapa Imperial Cerro Prieto and Michoacan[21] This fault system is part of a major regional lineamentthat penetrates deep into the crustal and basement rocks andserves as conduit for geothermal flow The system originatesin a tectonic basin of 5200m depth filled by alluvial anddeltaic sediments from Tertiary to Quaternary [21]

Vonder Haar and Howard [27] observed that in sand-stone and shale units a mineral dissolutionprecipitationtook place along microfractures originating secondary po-rosity and newly precipitated hydrothermalminerals causinga reduction of permeability Likewise Elders et al [20] ob-served cementation mineral replacement recrystallizationauthigenesis and growth of concretions and nodules theseprocesses are related to diagenesis

22 CP Hydrogeology Some authors consider that CP brinemay have been formed from marine evaporite dissolvedand partly by evaporated Colorado River water [16 1921 28ndash31] However according to geological evidences alarge accumulation of sedimentary material overlying thedepositional basin from a continental andmarine origin andmixing with meteoric water [30ndash33] was related to the originof brine [17] The sedimentary material shows diageneticevolution evidences and porewater trapped between grainsduring burial processes Isotopic evaluations (18O 2H) andchemical analysis (Clminus and Br) elaborated by Coplen [34] andBirkle et al [35] suggest that Salton Sea was the probablepredecessor of high chlorinated groundwater of CP

3 Methodology

A hydrogeological and hydrogeochemical study was carriedout in geothermal groundwater samples from CP followingstandard methods of APHA-AWWA [38] Water sampleswere collected from geothermal wells that are in constantexploitation Temperature pH and conductivity were mea-sured in the field during the summer of 2010 and calibratedto the water temperature at each site The chemical analysesfor the major elements B and SiO2 were performed at theAnalytical Chemistry Laboratory of the Geophysics InstituteUNAM Mexico (the laboratory participates in internationalcalibration exercises of chemical analyzes of geothermalwaters) Boron was determined by colorimetry throughreactions with carminic acid (Method 4500-B C) APHA-AWWA [38] SiO2 was determined by atomic absorption

spectrophotometry with flame and UV-visible spectroscopy(molybdosilicic acid method) Major ions were analyzedfollowing standard methods [38] HCO3

minus and CO32minus were

determined by volumetry (titrating with HCl) Ca2+ andMg2+ were determined by volumetry (titrating with EDTA)Clminus was determined by potentiometry with selective elec-trodes (4500-Clminus) [38] Na+ and K+ were determined byatomic emission spectrophotometry (3500-Na+ and K+) andSO42minus was determined by turbidimetry (4500-SO4

2minus) Ana-lytical quality was assessed through ionic balance (less than10) and the use of certified (NIST) reference solutions

In order to evaluate brine evolution of CP differenttechniques were used (a) Carpenter [39] evaluated thebehavior of major elements using a plot with concentrationsas a function of dissolved chloride concentration consideringthe composition of seawater during evaporation and diage-nesis using chemical results of CP groundwater a similarevaluation was elaborated (b) Davisson and Criss [40]devised a diagram to determine the geochemical evolutionof mineralogy in brines applying an evaluation of Na(deficit)and Ca(excess) in water samples hydrogeochemical resultsof samples from CP were evaluated with this diagram (c)Boschetti [3] considers B-Cl concentrations to explain theevolutionary process in the groundwater B-Cl diagram wasused to determine the dominant geological environmentin CP A geochemical simulation with the measured waterconcentrations was carried out using the Phreeqccopy programto determine saturation indexes

In order to determine pressure conditions a calculationwas performed using hydrostatic and lithostatic propertiesfrom CP considering geological characteristics of the studyarea and theoretical information about some basin environ-ments To estimate pressure conditions (119875119897(ℎ)) exerted bya geological column at a depth (ℎ) offshore in a geologicformation (1) was used [12]

119875119897 (ℎ) = 119892intℎ119908

0120588sea119889ℎ + 119892int

ℎ

ℎ119908

120588119887119889ℎ (1)

It is necessary to take into account pure water column weightat sea level ℎ = 0 depth of seawater column ℎ119908 seawaterdensity 120588sea = 1100 kgm3 gravity constant 119892 = 978 (ms2)and material density (rock or sediments) 120588119887 The integralabout overburden weight of sediments can be replaced by asum of the individual weights of layers [12]

119875119897 (ℎ) = 119892intℎ119908

0120588sea119889ℎ + 119892

119899sum119894=1

119889119894 [120588119908120593119894 + 120588119903119894 (1 minus 120593119894)] (2)

where it is important to consider the number of layers (119899119894)with thickness 119889119894 (119894 is the layer number measured in m)rocks density 120588119903119894 (kmm3) porosity 120593119894 and water density 120588119908(which can change with salinity variation while temperatureand pressure dependence is relatively small or negligible)

To estimate pressure in a reservoir unit from CP it wasconsidered that the study area is located onshore few metersabove seawater level therefore the integral including theweight of seawater column is zero the distinctive strataunits their thickness and depth of each sampled well were

Geofluids 5

3536373839

44142434445

35 37 39 41 43 45

CPEvap dilut curveSeawater

ＦＩＡ Cl (mgL)

ＦＩＡ

Na(m

gL)

(a)


2

22

24

26

28

3

32

34

35 37 39 41 43 45ＦＩＡ

Ca (m

gL)

ＦＩＡ Cl (mgL)

(b)


2526272829

33132333435

35 37 39 41 43 45

ＦＩＡ

K (m

gL)

ＦＩＡ Cl (mgL)

(c)


1

15

2

25

3

35

35 37 39 41 43 45

ＦＩＡ

Mg

(mg

L)

ＦＩＡ Cl (mgL)

(d)


37 39 41 43 4535ＦＩＡ Cl (mgL)

05

1

15

2

25

3

ＦＩＡ

HCO

3(m

gL)

(e)


37 39 41 43 4535ＦＩＡ Cl (mgL)

005

115

225

335

445

ＦＩＡ

SO4

(mg

L)

(f)

Figure 2 Variations in dissolved (a) Na+ (b) Ca2+ (c) K+ (d) Mg2+ (e) HCO3minus and (f) SO4

2minus concentrations as a function of dissolvedchloride concentration The solid line on each plot is the seawater evaporation-dilution curve for each cation circle is the ionic compositionof seawater

considered the porosity values reported by Olson [41] andHiriart Le Bert [42] in the geologic material from CP wereused (between 015 and 025) for lithological units withoutreported porosity theoretical values proposed by distinctauthors studied unlike geological material and depth wereused (eg mudstone and shales slate quartz feldspars unce-mented sandstones or sandstones as reservoirs) [43ndash46]

4 Results and Discussion

41 Major Elements in CP Groundwater Table 1 shows themajor solutes concentration in CP groundwater

In Table 1 chemical results from the studied wellsare shown Total dissolved solids were calculated from

conductivity measures showing values between 129455 and492512mgL These values are comprised between salinewater (gt1000mgL) and brine (gt35000) All the sampledwells are located at beta reservoir [17 47] To explaingeochemical variations in CP brine it is necessary to evaluatethe composition and removal of solutes by salt precipitationaccording to diagrams proposed by Carpenter [39] where thecircle represents the solute-chloride composition of normalseawater the line represents the limit between evaporation-dilution curves of seawater and freshwater (Figure 2)

Figure 2 shows that groundwater in CP is dominatedby high concentrations of Na+ K+ Ca2+ and Clminus WhenClminus concentration increases Na+ K+ and Ca2+ concentra-tions also increase in ratios 1 1 1 1 and 2 1 respectively

6 Geofluids

0

500

1000

1500

2000

2500

3000

3500

000050

Dep

th m

ts

Estimated porosity

Qua

rtz

Plag

iocl

ase

Feld

spar

-KM

usco

vite

-bio

tite Ill

iteIll

ite-m

ontm

orill

onite

25

Illite

-mon

tmor

illon

ite 5

0M

ontm

orill

onite

Kaol

inite

Chlo

rite

Calc

ite (s

udde

nde

crea

se 3

0ndash1

5)

Dol

omite

+ k

aolin

itede

stroy

edW

aira

kite

Talc

Pyrit

eA

mph

ibol

eEp

idot

e (de

trita

lgr

ain

size)

Anh

ydrit

eQ

uart

z and

feld

spar

-K

ov

ergr

owth

sBi

otite

Preh

nite

Montmorillonite +kaolinite zone

TransitionalChlorite + illite zone

Calc-aluminiumsilicate zone

Biotite zoneChlorite gt illite zone

Chlorite zone

Figure 3 Mineralogy and paragenesis reported in lithology from CP depth of sampled geothermal wells (modified by [20]) and estimatedporosity considering geological characteristics

(Figures 2(a) 2(b) and 2(c)) Bicarbonate ion Mg2+ andSO42minus have a low concentration (Figures 2(d) 2(e) and 2(f))

Na+ values are parallel and near coincident with their respec-tive evaporation-dilution curve (Figure 2(a)) Ca2+ valuescross the evaporation-dilution curve (Figure 2(b)) and K+also increases with Clminus but the values are enlarged relativeto the seawater evaporation-dilution curve (Figure 2(c)) InCP brine Mg2+ concentrations lie well below the seawaterevaporation trajectory indicating significant depletion ofthe element According to Hanor [48] and Kharaka andHanor [1] Mg2+ concentrations in brines decrease whentemperature increases in the subsurface and when alkalinitydecreases [49] Evaporation of continental waters has a morevariable concentration range in water samples from CP dueto evaporatingmixtures of continental andmarinewater withmeteoric water [50]

In CP brine depleted and enriched concentrations ofsome major elements are a consequence of reactions linkedwith the hydrothermal processes and water-rock interac-tions Major elements concentrations are controlled by thealteration and formation of minerals like feldspar-K plagio-clases quartz biotite amphibole chlorite pyrite wairakiteprehnite muscovite epidote and talc as reported in CP byElders et al [20] and Izquierdo et al [16] and shown bycalculated saturation index values (Figures 3 and 4)

The K+ origin is restrained by alteration of feldspar-Killite and biotite and bymuscovite formation Very low SO4

2minus

and HCO3minus concentrations in CP could be inhibited by the

water interactions with anhydrite dolomite talc pyrite orcalcite (Table 1 Figures 2 and 3) Elders et al [20] reportpyrite formation at depth Low concentration of Mg2+ andhigh concentration of Ca2+ could be related to dolomitizationof limestone as major source of Ca2+ and low Mg2+ contentsare associated with the evolution of chlorites andmicas whentemperature and depth increase according to mineralogyreported in CP (Figure 3) similar behavior has been reportedpreviously in hydrothermal brines with diagenetic evolution

evidences [51] (Figure 3) Albite reactions at depth at hightemperature can be linked with the slight Na+ decrease [1630 31]

42 Saturation Index Results of saturation index calculationsare shown in Figure 4 From these results amorphous silica(SiO2 am) albite k-feldspar and in some cases k-mica showa behavior close to equilibriumwith the fluid Besides quartzchalcedony talc and crysocole are oversaturated Dolomitecalcite and aragonite are undersaturated at some sites andoversaturated at others in agreement with Figures 2 and 3

43 Na(119889119890119891119894119888119894119905)-Ca(119890119909119888119890119904119904) Plot Figure 5 was used to explainthe initial composition of brines and the nature of fluid-rock interactions In the diagram Basinal Fluid Line (BFL)is a straight line with a unit slope that indicates a 2Na-1Ca exchange relationship [40] BFL represents the effectof plagioclase albitization on water composition Seawaterevaporation trajectory is a representation of the naturaltrends for seawater evaporation which is formed by largepositive Na(deficits) and small negative Ca(excess) reactionsinvolving seawater evaporation follow a vertical descent andafterwards produce large deficits along a horizontal trendHalite dissolution in seawater or freshwater can producenegative values along a slope of 1 4

To determine the origin and geochemical evolution of CPbrine an evaluation of Na(deficit) and Ca(excess) was appliedto explain the initial composition and nature of fluid-rockinteraction (Figure 5) All the analyzed water samples fromCP were located right and over the seawater evaporationtrajectory (SET) in the Na(deficit)-Ca(excess) diagram (Figure 5)indicating that the fluids are a product of brine that passedthe point of halite precipitation evaporated (along of Na(deficit)axis) The horizontal line of CP has a large positive Na(deficit)and a small negative Ca(excess) but the fluid is more enrichedin Ca(excess) than expected from seawater evaporation

Dolomitization produces elevatedCa contents increasingCa(excess) without changing the Na(deficit) and can explain

Geofluids 7

minus2

minus15

minus1

minus05

0

05

1

15

2

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI

ChalcedonyQuartzSiO2 (am)

minus4

minus3

minus2

minus1

0

1

2

3

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400SI

AlbiteK-feldsparK-mica

minus4minus35minus3

minus25minus2

minus15minus1

minus050

051

15

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI

AragoniteCalciteDolomite

minus202468

10121416

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI

ChloriteChrysoliteTalc

Figure 4 Saturation index diagrams

minus200

minus100

0

100

200

300

400

500

600

700

minus200 minus100 0 100 200 300 400 500 600 700

Ca ex

cess

(mEq

L)

Na deficit (mEqL)

CP

Gypsum

Seawater evaporation

Reading keyDolomitization

Albite dissolutionOverpressure

NaCl dissolution Seawaterevaporation

Mixing

Halite

1Ca for 2

Na

Exchan

ge

CaSO4 dissolution

Basinal fl

uid line

CaCO3 precipitation

Figure 5 DiagramNa(deficit) and Ca(excess) Diamonds correspond tothe CP sampled wells

the phenomenon observed in CP Other dissolved mineralscould interact in the evolutionary processes to brine asidefrom the above-mentioned ones such as calcite anhydritequartz halite and illitization to smectite transformationOften these geochemical processes are treated separately butin some situations the origin is linked to amixing of processesand is not mutually exclusive [1] Illite formation involvesreactions relevant for diagenesis (a) release of water duringtransformation of feldspar to kaolinite and smectite (b)potassium and silica budget [2 52] Some of these processescan occur in CP

Geology of CP shows equilibrium with clays (Figure 4)groundwater shows high concentrations of K+ Also reactionsbetween calcite illite and K+ to form K-feldspar could beinvolved in brine evolution According to the results (Figures2 and 5) the origin of CP groundwater is a consequence ofan evolution of dissolved evaporative products (eg halite)residual water remaining during the dissolution precipitationof seawater evaporites and different water-rock interactions(eg clays siltstones and shales) but could have a slightcontribution to exchange reactions 1Ca for 2Na in the aquiferby albitization of plagioclases which could change the ioniccomposition of fluids (Figure 5) according to the following

8 Geofluids

01

10

100

1000

10000

1 10 100 1000 10000 100000 1000000

CP

CP

Condensates

Overpressuredwaters

High-TB-release from clay

Ca-chloridebrines

Seawaterevaporation

Low-TB-uptake by clay

Ca-bicarbonateFresh waters

Evaporite-dissolvingBrackish waters

Gypdiss

Haldiss

Na-bica

rbonate

Figure 6 CP overpressure chloride versus boron concentration(mgL fields and paths from [3]) Dashed lines represent binarymixings where specific geological environments dominate Dia-monds correspond to the CP sampled wells

reaction proposed by Carpenter [39] Hanor [48] and Demirand Seyler [53]

CaAl2Si2O8(an) + 4SiO2(aq) + 2Na+= 2NaAlSi3O8(ab) + Ca2+

(3)

44 Overpressure

441 B-Cl Plot Some hydrogeochemical evidences (Figures2 and 5) shown in a B-Cl plot (Figure 6) indicate that over-pressurized fluids participate in the evolutionary process ofthe CP geothermal brine Boron behavior helps to definethese geologic environments because B is adsorbed by clayminerals and is released into the fluid in a deep environmentmainly when tectonic stresses by vertical andor lateralcompaction are high and temperature increases with depthand stronger geologic deformations are generated [10 12 54]

442 Pressure Conditions Estimated due to OverburdenSome authors [55 56] estimated pressure at depth at CP con-sidering the host rock density at a specific depthTheobtainedvalues were in the range between 05 and 42MPa Thosecalculations considered only geothermal water conditionsfrom the extraction zone and no lithologic information wasused from the stratigraphic columns of each site To confirmhydrogeochemical evidence of overpressure a calculation todetermine pressure conditions was performed using hydro-static and lithostatic properties from CP and theoreticalinformation about some basin environments (Figure 7) Itis necessary to consider that normal pressure increaseswith depth according to the hydrostatic pressure gradient(10MPaKm) higher or lower values of this gradient and

their associated depths are considered abnormal pressures(eg overpressure) Lithostatic pressure is equivalent to thetotal charge of the overlaying sediments in a geologicalformation and increases according to the lithostatic pressuregradient (23MPaKm) [10ndash12 57]

In general overpressured systems can take place whenporewater is not expelled from rock at a proper rate remain-ing under hydrostatic pressure Overpressured volume rockmust be trapped by low permeability layers where fluidsmoveslowly even when there is high pressure in the environmentThe overpressure affects the effective stress that acts betweenthe grains within the rock and generates a change in thecompaction In many areas of active sedimentation ratearound the world porewater pressure in deep groundwater(gt1 km) is higher than would be expected from hydrostaticcircumstances [10 57ndash59] It is necessary to consider ther-mal expansion in the pore space (increasing volume) andincrement of the system temperature by thermal conditionsand by fluid movement and mineral phases transition [11]According to Swarbrick et al [11] andKauerauf andHantschel[12] secondary overpressure by chemical cementation mayoccur at large depthswhen porosity is reduced by dissolution-diffusive transport-precipitation of silica cement (tempera-ture affects diffusion-precipitation rate) or by fluid expansionprocesses when gas or thermal solutions are originated inhighly permeable facies interconnected locally at certaindepth levels generating compaction rearrangement of grainsand reduction in the pore space Some of these conditionscould occur in CP aquifer [22]

The results obtained confirm that in CP overpressure ispresent (Figures 7 and 8) Positive anomalies with an increaseof depth are shown between 06 and 31 km this phenomenoncan be caused by a hydraulic seal Overpressure coincideswith lithology variation in CP [22] when sedimentary mate-rial composed of sand and clay changes to shale and sand-stone due to clay and sand diagenesis and shale compaction(Figure 7) In CP sandstone is hosted by a low permeabilitylayer of shale and siltstones creating adequate conditionsfor this process Overpressure in CP brine could occur asa consequence of a rapid sedimentation deposition andaccumulation rates of fine-grained material along time anddue to the stress increase in sediments compressibility orexpansion of fluids by hydrothermalism

Geological evidence in CP indicates that mineralogicalchanges occur at depth mainly by diagenetic processes(Figure 5) According to the geochemical behavior observedin CP it is possible that mineral dissolution precipitation pro-cesses generated this phenomenon osmosis buoyancy andtectonic or magmatic process can generate changes in miner-alogy (eg feldspar to illite or smectite to illite conversion)diagenesis and carbonate or silicate cementation In CPsandstones and shales units reveal clogging mineral dissolu-tion and mineral precipitation along microfractures as indi-cated by Vonder Haar and Howard [27] In the study area thecalcite dissolution andor cementation more likely developswhere cold water interacts with hotter rocks or precipitationof quartz and k-feldspar occurs when hot waters interact withcolder rocks [16 20] Exchange ofNa+ byK+ with a higher ionradius is carried out inmineral transformations and increases

Geofluids 9

0

1

2

3

4

5

6

7

0

500

1000

0500

1000

05001000

1500

2000

654321

2

1

213

ClaySandShaleSandstone

CP1CP2

CP3CP4

Clastic sedimentsAlluvial fanMudstoneBrown shale

SandstoneMetamorphic rockBasic intrusive

GraniteMetamorphicFault

(Km)

3

Figure 7 CP geology cross section Stratigraphic column was modified from Lira [21] and Pena et al [22]

the volume of the solid matrix [12] this process is controlledby temperature and K+ availability in minerals

The permeability of sandstones in CP facilitates reactionsbetween rocks and hydrothermal fluids (eg dissolution ofsome minerals) these reactions can reduce or increase theporosity and also generate secondary fracturing or micro-fracturing and modify physical properties [16 21] whichcould cause overpressure (Figures 7 and 8) Sandy shaleand siltstone facies in CP are most amenable to increasedmicrofracturing In sandstones (where high temperaturedominates) and shales from CP mineral dissolution precip-itation takes place along microfractures which originatessecondary porosity and newly precipitated hydrothermalminerals causing a reduction of permeability

5 Geothermometry

Alkali feldspar geothermometers are the most used toolto determine chemical equilibrium in fluids at depth in ageothermal system [60] NaK and Na-K-Ca geothermome-ters were developed to evaluate the temperature in highenthalpy geothermal systems [61] these geothermometers areless affected by chemical reequilibration in mixing zonesbut the calculated temperature may be affected by mixing

with cold water or by deposition of aluminum-rich mineralsor clays [62] NaK geothermometers are adapted for tem-peratures between 180 and 350∘C NaK geothermometershave been generally used to estimate temperatures at CP[36 37 62] We applied (4) and (5) [61 62] to evaluate thetemperature of CP reservoir

119879 = ( 1178(147 + log (NaK))) minus 27315 (4)

119879 = ( 1289(1615 + log (NaK))) minus 27315 (5)

The temperature range of CP reservoir calculated with NaKgeothermometer varies between 236 and 306∘C for (4) andbetween 251 and 318∘C for (5) (Table 2)

6 Conclusions

CP shows intermediate brine characteristics (Na-Ca-Cl) withhigh K+ Ca2+ and salinity contents the relation Na+Clminus isless than 1

The porewater composition in CP evolved from itsprimary origin and was modified by the interaction with

10 Geofluids

0

02

04

06

08

1

12

14

16

18

0 20 40

Dep

th (K

m)

Pressure (MPa)

M104

23 MPaKm10 MPaKm

(a)

233343

611T 395T 400

23 MPaKm10 MPaKm

0 20 40 60Pressure (MPa)

25

2

15

1

05

0

Dep

th (K

m)

(b)

0

05

1

15

2

25

3

35

4

45

Dep

th (K

m)

M 117AM 119AM 127M 133AM 148AM 155M 198M 200

112311323403407222 DE-23E-29E-47AT 350A


23 MPaKm10 MPaKm

(c)

Figure 8 Plots represent pressure estimated conditions at depth pressure conditions were calculated with the following values porewaterdensity 120588119908 = 1040 kgm3 shale and mudstone density 120588sh = 2700 kgm3 sandstone density 120588sd = 2720 kgm3 slate density 120588sl = 2750 kgm3and sedimentary material density 120588sm = 1650 kgm3 [10 12]

Geofluids 11

Table 2 Results of NaK geothermometers

Well 119879 ∘C NaK[36]

119879 ∘C NaK[37] Well 119879 ∘C NaK

[36]119879 ∘C NaK

[37] Well 119879 ∘C NaK[36]

119879 ∘C NaK[37]

M 104 264 279 112 280 293 222 D 289 302M 117A 277 290 233 273 286 E-23 292 305M 119A 306 318 311 270 284 E-29 283 296M 127 282 295 323 270 284 E-47A 276 290M 133A 254 268 343 240 255 T 350A 267 281M 148A 269 283 403 284 297 T 395 271 285M 155 259 274 407 272 286 T 400 236 251M 198 274 288 611 247 262 611lowastA 246 260M 200 304 316

minerals of the sedimentary material Brine characteristicswere acquired by deep-burial diagenesis processes and lowgrade metamorphism at high temperatures Results showgeochemical evidence of overpressured fluids due to com-paction

Groundwater samples from CP show a mixing of marineand continental water this situation is partially related to acontinental and evaporative precursor The hydrogeochem-ical evidence indicates that the sedimentary material hasporewater between grains which was trapped during burialprocesses The diagenetic processes could have generatedhigh concentrations of Clminus Na+ K+ and Ca2+ Calciumenrichment Na+ depletion and K+ release could have arelationwith a contribution of exchange reactions 1Ca for 2Nain the aquifer by albitization of plagioclases or by illitizationprocesses respectively and precipitation of secondaryminer-als High K+ and low Mg2+ contents are related to alterationof feldspar-K illite biotite and muscovite formation Ca-Naexchangewith plagioclases could be a geochemical control onthe fluids of CP and may directly explain slight Ca(excess) andNa(deficit) in the brine

Overpressure in CP is related to burial mechanisms sec-ondary overpressure is related to chemical pressure by min-eralogical changes and by fluid expansion which increaseswith depth The magnitude of overpressure may be pro-duced by some characteristics of deposit formation (burial)permeability evolution of sedimentary material and thecompressibility of rock and fluid Secondary overpressure inthe system related to chemical pressure and porosity changesdue to mineral dissolution can be generated at large depthsFluid expansion takes place in the reservoir which generatescompaction rearrangement of grains and reduction of porespace Boron release at overpressure conditions can be relatedto high contents of K+ in water

Conflicts of Interest

The authors declare that they have no conflicts of interest

Acknowledgments

The authors thank Aguayo A Ceniceros N and CruzO for chemical determinations The authors acknowledge

Comision Federal de Electricidad for support on samplingwithin the Cerro Prieto Geothermal Field

References

[1] Y K Kharaka and J S Hanor ldquoDeep Fluids in the ContinentsI Sedimentary Basinsrdquo Treatise on Geochemistry vol 5-9 pp1ndash48 2003

[2] T Boschetti L Toscani O Shouakar-Stash et al ldquoSalt Watersof the Northern Apennine Foredeep Basin (Italy) Origin andEvolutionrdquo Aquatic Geochemistry vol 17 no 1 pp 71ndash108 2011

[3] T Boschetti ldquoApplication of brine differentiation and Langelier-Ludwig plots to fresh-to-brine waters from sedimentary basinsDiagnostic potentials and limitsrdquo Journal of Geochemical Explo-ration vol 108 no 2 pp 126ndash130 2011

[4] A Arche ldquoSedimentologıa del proceso fısico a la cuenca sed-imentariardquo in Consejo Superior de Investigaciones Cientıficas978-84-00-09145-3 pp 1ndash1273 Madrid Spain

[5] S J Blott andK Pye ldquoParticle shape A review andnewmethodsof characterization and classificationrdquo Sedimentology vol 55no 1 pp 31ndash63 2008

[6] A Ceriani A Di Giulio R H Goldstein and C Rossi ldquoDiage-nesis associated with cooling during burial An examplefromLower Cretaceous reservoir sandstones (Sirt basin Libya)rdquoAAPG Bulletin vol 86 no 9 pp 1573ndash1591 2002

[7] F W Witkowski D J Blundell P Gutteridge A D HorburyN H Oxtoby and H Qing ldquoVideo cathodoluminescencemicroscopy of diagenetic cements and its applicationsrdquoMarineand Petroleum Geology vol 17 no 10 pp 1085ndash1093 2000

[8] CHMoore ldquoCarbonate reservoirs Porosity evolution and dia-genesis in a sequence stratigraphic frameworkrdquo Developmentsin Sedimentology vol 55 2001

[9] M S Fantle K M Maher and D J Depaolo ldquoIsotopic ap-proaches for quantifying the rates of marine burial diagenesisrdquoReviews of Geophysics vol 48 no 3 Article ID RG3002 2010

[10] K M Hiscock and V F Bense Hydrogeology Principles AndPractice Wiley Blackwell 2nd edition 2014

[11] R E Swarbrick M J Osborne and G S Yardley ldquoComparisonof overpressure magnitude resulting from the main generatingmechanismsrdquo in Pressure Regimes in Sedimentary Basins andTheir Prediction A R Huffman and G L Bowers Eds vol76 pp 1ndash12 American Association of Petroleum GeologistsMemoir 2002

12 Geofluids

[12] A I Kauerauf and T Hantschel Fundamentals of Basin andPetroleum Systems Modeling Springer Science amp BusinessMedia 2009

[13] O Walderhaug P A Bjoslashrkum P H Nadeau and O LangnesldquoQuantitative modelling of basin subsidence caused by temper-ature-driven silica dissolution and reprecipitationrdquo PetroleumGeoscience vol 7 no 2 pp 107ndash113 2001

[14] A Zanella P R Cobbold and C Le Carlier de Veslud ldquoPhysicalmodelling of chemical compaction overpressure developmenthydraulic fracturing and thrust detachments in organic-richsource rockrdquo Marine and Petroleum Geology vol 55 pp 262ndash274 2014

[15] E Portugal and M P Verma ldquoHidroquımica de la laguna deevaporacion en Cerro Prietordquo in Ingenierıa hidraulica enMexico vol 16 pp 153ndash174 Baja California Mexico 2 edition2001

[16] G Izquierdo A Aragon E Portugal V M Arellano J de Leonand J Alvarez ldquoMineralogıa de la zona mineralizada de sılice-epidota (ZMSE) del yacimiento geotermico de Cerro Prieto BCMexicordquo Geotermia vol 19 no 2 pp 2ndash12 2006

[17] V M Arellano R M Barragan A Aragon M H Rodrıguezand A Perez ldquoThe Cerro Prieto IV (Mexico) geothermal reser-voir Pre-exploitation thermodynamic conditions and mainprocesses related to exploitation (2000-2005)rdquoGeothermics vol40 no 3 pp 190ndash198 2011

[18] M A Armienta R Rodrıguez N Ceniceros et al ldquoGround-water quality and geothermal energy The case of Cerro PrietoGeothermal Field Mexicordquo Journal of Renewable Energy vol63 pp 236ndash254 2014

[19] J M Camacho-Hernandez ldquoZonas de alteracion hidrotermaly condiciones actuales del yacimiento un enfoque para deter-minar zonas productoras al oriente del campo geotermico deCerro Prieto BCrdquo Geotermia Revista Mexicana de Geoenergiavol 22 no 2 pp 35ndash45 2009

[20] W A Elders J R Hoagland S D McDowell and J M CoboldquoHydrothermal mineral zones in the geothermal reservoir ofCerro Prietordquo Geothermics vol 8 no 3-4 pp 201ndash209 1979

[21] H H Lira ldquoActualizacion del modelo geologico conceptual delyacimiento geotermico de Cerro Prieto BCrdquoGeotermia vol 18no 1 pp 37ndash46 2005

[22] A L Pena C I Puente and C E Dıaz ldquoModelo geologico delcampo geotermico de Cerro Prieto Geothermal-Energyrdquo Com-ision Federal de Electricidad pp 29ndash52 1979 httpswwwge-othermal-energyorgpdfIGAstandardDOE-CFE1979Penapdf

[23] E Portugal J Alvarez and B I Romero ldquoHydrochemical andisotopical tracers in the lacustrine aquifer of the Cerro Prietoarea Baja California Mexicordquo Journal of Geochemical Explo-ration vol 88 no 1-3 pp 139ndash143 2006

[24] M Siem The structure and petrology of Sierra El Mayor[Master thesis] University of San Diego State NortheasternBaja Calfornia Mexico 1992

[25] A L Quintanilla-Montoya and F Suarez-Vidal ldquoCerro Prietoand its relation to the Gulf of California spreading centersrdquoCiencias Marinas vol 22 no 1 pp 91ndash110 1996

[26] R J M Cobo Configuracion de los cuerpos litologicos delodolita lutita cafe lutita gris zonas de sılice y epidota y susrelaciones con la tectonica del campo geotermico de CerroPrieto Proceedings of theThird Symposiumon theCerroPrietoGeothermal Field Mexico 1981

[27] S Vonder Haar and J H Howard ldquoIntersecting faults andsandstone stratigraphy at the cerro prieto geothermal fieldrdquoGeothermics vol 10 no 3-4 pp 145ndash167 1981

[28] A Manon E Mazor M Jimenez A Sanchez J Fausto and CZenizo ldquoExtensive geochemical studies in the geothermal fieldof Cerro Prieto Mexicordquo Tech Rep LBL-7019 1977

[29] EMazor andAManonM ldquoGeochemical tracing in producinggeothermal fields A case study at Cerro Prietordquo Geothermicsvol 8 no 3-4 pp 231ndash240 1979

[30] A H Truesdell R O Rye F J Pearson Jr et al ldquoPreliminaryisotopic studies of fluids from the Cerro Prieto geothermalfieldrdquo Geothermics vol 8 no 3-4 pp 223ndash229 1979

[31] A H Truesdell J M Thompson T B Coplen N L Nehringand C J Janik ldquoThe origin of the Cerro Prieto geothermalbrinerdquo Geothermics vol 10 no 3-4 pp 225ndash238 1981

[32] H A Truesdell M J Lippmann and H Gutierrez-Puente ldquoEv-olution of the Cerro Prieto Reservoirs under exploitationrdquo inProceedings of the Anual Meeting of the Geothermal ResourcesCouncil pp 1ndash7 Burlingame Calif USA 1997

[33] M J Lippmann A H Truesdell and K Pruess ldquoThe control offault H on the hydrology of the Cerro Prieto III Areardquo in Pro-ceedings of the Twenty-fifth Workshop on Geothermal ReservoirEngineering Standford University Standford Calif USA 2000

[34] T B Coplen ldquoOrigin of geothermal waters in the ImperialValley of southern California Cooperative Investigation ofGeothermal Resources in the Imperial Valley and their PotentialValue for Desaltine of Water and other purposesrdquo R W RexEd Rwerslde Report IGPP-UCR-72-33 pp E1ndashE31 Universityof California 1972

[35] P Birkle E P Marın D L Pinti and M C Castro ldquoOriginand evolution of geothermal fluids from Las Tres Vırgenes andCerro Prieto fields Mexico - Co-genetic volcanic activity andpaleoclimatic constraintsrdquo Applied Geochemistry vol 65 pp36ndash53 2016

[36] D Nieva and R Nieva ldquoDevelopments in geothermal energy inMexico-part twelve A cationic geothermometer for prospect-ing of geothermal resourcesrdquo Heat Recovery Systems and CHPvol 7 no 3 pp 243ndash258 1987

[37] S P Verma and E Santoyo ldquoNew improved equations forNaK NaLi and SiO2 geothermometers by outlier detectionand rejectionrdquo Journal of Volcanology and Geothermal Researchvol 79 no 1-2 pp 9ndash23 1997

[38] AWWA APHA and WWF Standard methods for the Exami-nation of Water and Wastewater American Public health Asso-ciation The American Water Works Association AssociationWater Environment Federation Washington DC USA 2005

[39] A B Carpenter ldquoOrigin and chemical evolution of brines insedimentary basins Oklahomardquo Geological Survey Circular vol79 pp 78ndash88 1978

[40] M L Davisson and R E Criss ldquoNa-Ca-Cl relations in basinalfluidsrdquo Geochimica et Cosmochimica Acta vol 60 no 15 pp2743ndash2752 1996

[41] E R Olson ldquoOxygen and Carbon isotopes studies of calcitefrom the Cerro Prieto Geothermal Fieldrdquo in Proceedings of theFirst Symposium on the Cerro Prieto Geothermal Field BajaCalifornia Mexico 1978

[42] Hiriart Le Bert Evaluacion de la Energıa Geotermica enMexico Informe para el Banco Interamericano de Desarrolloy la Comision Reguladora de Energıa httpwwwcregobmxdocumento2026pdf 2011

Geofluids 13

[43] W J Harrison and L L Summa ldquoPaleohydrology of the Gulf ofMexico basinrdquo American Journal of Science vol 291 no 2 pp109ndash176 1991

[44] E D Pittman and R E Larese ldquoCompaction of lithic sandsexperimental results and applicationsrdquo The American Associa-tion of PetroleumGeologists Bulletin vol 75 pp 1279ndash1299 1991

[45] J Gluyas and C A Cade ldquoPrediction of porosity compactedsandsrdquo in Reservoir Quality Prediction in Sandstones and Car-bonates A Kupecz Gluyas J and S Bloch Eds vol 69 pp19ndash28 AAPG Memoir 1997

[46] S N Ehrenberg and P H Nadeau ldquoSandstone vs carbonatepetroleum reservoirs A global perspective on porosity-depthand porosity-permeability relationshipsrdquo AAPG Bulletin vol89 no 4 pp 435ndash445 2005

[47] RM Prol-Ledesma C Arango-Galvan andM-A Torres-VeraldquoRigorous analysis of available data from cerro prieto and lastres virgenes geothermal fields with calculations for expandedelectricity generationrdquo Natural Resources Research vol 25 no4 pp 445ndash458 2016

[48] J S Hanor ldquoOrigins of saline fluids in sedimentary basinsrdquo inGeofluids Origin Migration and Evolution of Fluids in Sedimen-tary Basins J Parnell Ed pp 151ndash174 Geological Society ofLondon 1994

[49] A W Hounslow Water Quality Data Analysis and Interpreta-tion Taylor amp Francis Group 1995

[50] J NValette-Silver JMThompson and JW Ball ldquoRelationshipbetweenwater chemistry and sedimentmineralogy in theCerroPrieto Geothermal Field A preliminary reportrdquo GeothermalEnergy pp 263ndash273 1981

[51] K H Wolf and G V Chilingarian ldquoChapter 1 IntroductionrdquoDevelopments in Sedimentology vol 51 no C pp 1ndash17 1994

[52] P Kaur N Chaudhri A W Hofmann et al ldquoTwo-stageextreme albitization of A-type granites from Rajasthan NWIndiardquo Journal of Petrology vol 53 article egs003 no 5 pp 919ndash948 2012

[53] I Demir and B Seyler ldquoChemical composition and geologichistory of saline waters in Aux Vases and Cypress FormationsIllinois Basinrdquo Aquatic Geochemistry vol 5 no 3 pp 281ndash3111999

[54] G V Chilingarian T F Donaldson and T F Yen ldquoSubsidencedue to fluid withdrawalrdquo in Developments in Petroleum Sciencevol 519 41 Elsevier Sciences 1995

[55] A Garcia F Ascencio G Espinosa E Santoyo H Gutierrezand V Arellano ldquoNumerical modeling of high temperatura deelWells in the Cerro Prieto geotermal fiels Mexicordquo GeofisicaInternacional vol 38 pp 251ndash260 1999

[56] M J Lippmann A H Truesdell and H Gutierrez-PuenteldquoWhat will a 6 km deep well at Cerro Prieto findrdquo in Pro-ceedings of the twenty-first Workshop on Geothermal ReservoirEngineering Stanford University 1997 httpspangeastanfordeduEREpdfIGAstandardSGW1997Lippmannpdf

[57] M J Osborne and R E Swarbrick ldquoMechanisms for generatingoverpressure in sedimentary basins A reevaluationrdquo AAPGBulletin vol 81 no 6 pp 1023ndash1041 1997

[58] AM Stueber and LMWalter ldquoOrigin and chemical evolutionof formation waters from Silurian-Devonian strata in theIllinois basin USArdquo Geochimica et Cosmochimica Acta vol 55no 1 pp 309ndash325 1991

[59] N H Mondol K Bjoslashrlykke J Jahren and K Hoslasheg ldquoExper-imental mechanical compaction of clay mineral aggregates-Changes in physical properties of mudstones during burialrdquoMarine and Petroleum Geology vol 24 no 5 pp 289ndash311 2007

[60] R O Fournier and J J Rowe ldquoEstimation of undergroundtemperatures from the silica content of water from hot springsand wet-steam wellsrdquo American Journal of Science vol 264 no9 pp 685ndash697 1966

[61] R Sonney Groundwater flow heat and mass transport ingeothermal systems of a Central Alpine Massif The cases ofLavey-les Bains Saint-Gervais-les-Bains and Val drsquoIlliez Geo-chemistry Universite de Neuchatel 2010

[62] F DrsquoAmore and S Arnorsson ldquoIsotopic and chemical tech-niques in geothermal exploration development and use Sam-plingmethods data handling interpretationrdquo inGeothermome-try S Arnorsson Ed pp 152ndash199 International Atomic EnergyAgency Vienna Austria 2000

Submit your manuscripts athttpswwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Geological ResearchJournal of


Geology Advances in

2 Geofluids

0 05 1 2(Km)

131138112

T-395222 D

DELTA 1

M-119AM 200

M-148A610T-350A

608

428233

601 423M111A

343

611

414442407M133A

M198403

311333 310 308

M15

670000000000

670000000000

NE

SO

BajaCalifornia

Baja California Sur

Sonora

ChihuahuaCoahuila

Nuevo Leoacuten

TamaulipasSinaloa

DurangoZacatecas

Nayarit

Jalisco

AguascalientesSan Luiacutes Potosiacute

Guanajuato

Hidalgo

MichoacaacutenColima

Estado de Meacutexico

TlaxcalaDF

Morelos

Guerrero

Puebla

Veracruz

Oaxaca

Tabasco

Chiapas

Campeche

Yucataacuten

Quintana Roo

Sal

Del

Cuc

Chi

VCP

Michoacaacuten de Ocampo

Cerro PrietoGeothermalField

GeoCerro PrietoVolcano

3245

3235

3225minus11525 minus11515

0 5(Km)

M-11M-104 M-127

E-23T-400

E-24

E-29

Quereacutetar

o

Imperial Fault

Cerro Prieto Fault

Mexicali

Figure 1 Localization of Cerro Prieto Geothermal Field and sampled wells

Cerro Prieto Geothermal Field (CP) located in north-western Mexico (32∘2410158404310158401015840N 115∘1410158404110158401015840W) is a brine withhigh-temperature geothermal system characteristics Severalstudies about the origin and behavior ofCP groundwater havebeen reported [15ndash18] According to geological evidences alarge accumulation of sedimentarymaterial from a continen-tal and marine origin overlying the depositional basin isrelated to the origin of brine [17] The sedimentary materialshows diagenetic evolution evidences and porewater trappedbetween sediment grains during burial processes The pore-water is saline with high Clminus Na+ Ca2+ and K+ concentra-tion in geothermal brines this characteristic is common [1 210] the composition depends mainly on the primary originmineralogical composition of the sediments and their modi-fication due to diagenetic processes (eg facies distribution)and hydrothermal characteristics [15 19] Among the mostevident diagenetic processes in CP are cementation mineralreplacement recrystallization authigenesis and growth ofconcretions and nodules [16] On the other hand in deepsedimentary basins as CP mechanical processes of defor-mation related to burial mechanisms are common likewisehydrostatic and lithostatic conditions increase with depthdue to an increase of the superposed fluids hydraulicallyconnected through the pore and the pressure exerted bysediments overload [10] If pore pressure in deep aquiferslike CP is higher than expected from hydrostatic condi-tions anomalous pressure (overpressure) can be generatedoverpressure is common mainly within 2ndash45 km depth[10ndash12]

According to geochemical evidences the origin of geo-thermal brine at CP could be governed by mixing processesrelated to a hydrothermal environment and the sedimentarymaterial located at depth which shows burial diagenesis evo-lution with hydrogeochemical evidences of an overpressur-ized environment The aim of the present study was to eval-uate hydrogeochemical behavior of geothermal groundwater

and its relationwith diagenetic processes including overpres-sure

2 Localization

Cerro Prieto Geothermal Field (CP) located in MexicaliValley SE of Mexicali City in Baja California State Mexico(Figure 1) is a Basin of Salton Sea [17] Climate is arid withtemperatures up to 40∘C in July and to 4∘C in winter Theaverage annual precipitation is 55mmyear and the averageannual evaporation is 2200mmyear [23] Groundwater atCP is extracted from geothermal wells that are in constantexploitation to generate electricity The Comision Federalde Electricidad of Mexico (CFE) operates and manages theGeothermal Field CP power production is up to 720MWand is composed of five individual units CP1 CP2 CP3CP4 and CP5 each unit has a total capacity of productionwith a specific number of production wells Sampled wells areindicated in Figure 1 Their localization in the five individualCP units is included in Table 1 All the wells are located inzone ldquobetardquo 1500 to 3100m depth [17]

21 CP Geology The lithology around CP is composed ofgneiss (quartz-feldspars) shale (quartz-mica) marble am-phibolite and quartzite from Permic to Jurassic [24] andmetamorphic granitic and granodiorite rocks which areintruded by batholitic rocks [16] together with dacite andandesite fromMiocene and rhyodacite fromQuaternary [25]The tectonic basin was filled by sedimentary material thatdue to burial compaction and diagenesis processes evolvedto gray shales from Late Miocene (shales and silt shalesthat vary from light gray to black) this unit overlies thegranitic basement and the mafic intrusive and is interlayeredby permeable sandstones (composed of quartz and feldsparsarkoses type) The thickness is near 3000m [21 26] Imme-diately above a layer of brown shale (shale and silt shale)

Geofluids 3

Table1Major

elem


atCP

grou

ndwater

samples

measuredin

summer

2010

Well

Operatio

nareas(individu

alun

its)

Depth119879

pHCE

TSD

CaMg

Na

KHCO3

Clminus

SO4

IB

BSiO2

(Km)

(∘ C)

mScm

Calculated

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

M104

CP3

173

884

773

2045

206132

2616

509

6250

11875

415

119625

135minus28

1326

8517

M117

ACP

3289

912

7735

173155

1402

347

5575

1185

184

9375

00933

1465

9801

M119

ACP

231

879

679

35345069

3791

383

9850

26825

107

20150

009minus45

1742

14017

M127

CP2

25

768

761

248

214578

2883

311

60875

13525

284

128125

59minus67

184

8474

M133A

CP3

249

808

749

3545

365454

8194

539

10750

1840

1922200

142minus56

1986

8539

M148A

CP2

299

858

743

268

273272

3791

287

8300

16525

213

15875

71minus27

1845

10743

M155

CP3

29

805

744

3665

388638

7355

449

11325

2050

272

23800

009minus68

2792

8902

M198

CP4

28

918

752

2185

256012

1876

569

75875

15775

166

15250

009minus56

288

9159

M200

CP3

284

828

742

2585

221513

1836

251

63125

1690

284

12950

009minus52

2235

9737

112

CP1

265

8672

53305

312164

5331

479

9125

19925

148

18250

009minus36

158

12605

233

CP2

264

889

753

434

239716

1895

299

7275

1490

237

13700

36minus26

166

12626

311

CP3

294

851

756

43235488

2883

239

71375

14325

118

13550

54minus25

219

10914

323

CP3

29

946

767

2675

270189

2863

539

74375

14825

379

16750

009minus108

229737

343

CP3

2958

748

285

343097

7898

599

97125

14475

143

21587

29minus94

1756

6677

403

CP4

289

828

732

161

15503

1678

599

4540

1030

426

8950

44minus32

2885

7276

407

CP4

299

884

791

1895

2004

26

1086

359

5815

1185

19118875

85minus7

167

9694

611

CP3

252

884

787

5285

332629

7305

539

9875

1585

1920100

224minus52

2161

8774

222D

CP2

314

922

774

2975

287199

2962

275

80625

1907

9517300

009minus79

1125

11149

E-23

CP2

295

711

585

393441

5805

216

11175

27175

284

23750

009minus66

242

10807

E-29

CP2

269

833

712

794

444913

7858

144

13200

29625

213

2660

0009minus41

2655

918

E-47A

CP3

289

917

747

61350746

6476

168

10650

22475

166

20500

009minus21

2197

9951

T350A

CP2

29

82688

822

492512

10326

228

143125

27825

154

29700

009minus57

2855

13931

T395

CP2

265

801

792

488

239242

3376

275

70375

1420

47

140625

63minus46

1025

10165

T40

0CP

121

896

791973

129455

1224

335

3910

5605

207

7570

336minus52

911

6805

611lowastA

CP3

252

876

785

524

332175

7049

371

100875

1595

201

19875

225minus4

228774

4 Geofluids





3 Methodology








119875119897 (ℎ) = 119892intℎ119908

0120588sea119889ℎ + 119892int

ℎ

ℎ119908

120588119887119889ℎ (1)


119875119897 (ℎ) = 119892intℎ119908

0120588sea119889ℎ + 119892

119899sum119894=1

119889119894 [120588119908120593119894 + 120588119903119894 (1 minus 120593119894)] (2)



Geofluids 5

3536373839

44142434445

35 37 39 41 43 45


ＦＩＡ Cl (mgL)

ＦＩＡ

Na(m

gL)

(a)


2

22

24

26

28

3

32

34

35 37 39 41 43 45ＦＩＡ

Ca (m

gL)

ＦＩＡ Cl (mgL)

(b)


2526272829

33132333435

35 37 39 41 43 45

ＦＩＡ

K (m

gL)

ＦＩＡ Cl (mgL)

(c)


1

15

2

25

3

35

35 37 39 41 43 45

ＦＩＡ

Mg

(mg

L)

ＦＩＡ Cl (mgL)

(d)


37 39 41 43 4535ＦＩＡ Cl (mgL)

05

1

15

2

25

3

ＦＩＡ

HCO

3(m

gL)

(e)


37 39 41 43 4535ＦＩＡ Cl (mgL)

005

115

225

335

445

ＦＩＡ

SO4

(mg

L)

(f)









6 Geofluids

0

500

1000

1500

2000

2500

3000

3500

000050

Dep

th m

ts

Estimated porosity

Qua

rtz

Plag

iocl

ase

Feld

spar

-KM

usco

vite

-bio

tite Ill

iteIll

ite-m

ontm

orill

onite

25

Illite

-mon

tmor

illon

ite 5

0M

ontm

orill

onite

Kaol

inite

Chlo

rite

Calc

ite (s

udde

nde

crea

se 3

0ndash1

5)

Dol

omite

+ k

aolin

itede

stroy

edW

aira

kite

Talc

Pyrit

eA

mph

ibol

eEp

idot

e (de

trita

lgr

ain

size)

Anh

ydrit

eQ

uart

z and

feld

spar

-K

ov

ergr

owth

sBi

otite

Preh

nite





Chlorite zone






2minus








Geofluids 7

minus2

minus15

minus1

minus05

0

05

1

15

2

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI


minus4

minus3

minus2

minus1

0

1

2

3

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400SI


minus4minus35minus3

minus25minus2

minus15minus1

minus050

051

15

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI


minus202468

10121416

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI



minus200

minus100

0

100

200

300

400

500

600

700

minus200 minus100 0 100 200 300 400 500 600 700

Ca ex

cess

(mEq

L)

Na deficit (mEqL)

CP

Gypsum





Mixing

Halite

1Ca for 2

Na

Exchan

ge

CaSO4 dissolution

Basinal fl

uid line

CaCO3 precipitation




8 Geofluids

01

10

100

1000

10000

1 10 100 1000 10000 100000 1000000

CP

CP

Condensates

Overpressuredwaters


Ca-chloridebrines

Seawaterevaporation




Gypdiss

Haldiss

Na-bica

rbonate




(3)

44 Overpressure







Geofluids 9

0

1

2

3

4

5

6

7

0

500

1000

0500

1000

05001000

1500

2000

654321

2

1

213


CP1CP2

CP3CP4




(Km)

3




5 Geothermometry



119879 = ( 1178(147 + log (NaK))) minus 27315 (4)

119879 = ( 1289(1615 + log (NaK))) minus 27315 (5)


6 Conclusions



10 Geofluids

0

02

04

06

08

1

12

14

16

18

0 20 40

Dep

th (K

m)

Pressure (MPa)

M104

23 MPaKm10 MPaKm

(a)

233343

611T 395T 400

23 MPaKm10 MPaKm


25

2

15

1

05

0

Dep

th (K

m)

(b)

0

05

1

15

2

25

3

35

4

45

Dep

th (K

m)

M 117AM 119AM 127M 133AM 148AM 155M 198M 200

112311323403407222 DE-23E-29E-47AT 350A


23 MPaKm10 MPaKm

(c)


Geofluids 11


Well 119879 ∘C NaK[36]

119879 ∘C NaK[37] Well 119879 ∘C NaK

[36]119879 ∘C NaK

[37] Well 119879 ∘C NaK[36]

119879 ∘C NaK[37]







Acknowledgments



References












12 Geofluids
































Geofluids 13




























Mining


Journal of









Journal of




Advances in











Geology Advances in

Geofluids 3

Table1Major

elem


atCP

grou

ndwater

samples

measuredin

summer

2010

Well

Operatio

nareas(individu

alun

its)

Depth119879

pHCE

TSD

CaMg

Na

KHCO3

Clminus

SO4

IB

BSiO2

(Km)

(∘ C)

mScm

Calculated

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

(mgL)

M104

CP3

173

884

773

2045

206132

2616

509

6250

11875

415

119625

135minus28

1326

8517

M117

ACP

3289

912

7735

173155

1402

347

5575

1185

184

9375

00933

1465

9801

M119

ACP

231

879

679

35345069

3791

383

9850

26825

107

20150

009minus45

1742

14017

M127

CP2

25

768

761

248

214578

2883

311

60875

13525

284

128125

59minus67

184

8474

M133A

CP3

249

808

749

3545

365454

8194

539

10750

1840

1922200

142minus56

1986

8539

M148A

CP2

299

858

743

268

273272

3791

287

8300

16525

213

15875

71minus27

1845

10743

M155

CP3

29

805

744

3665

388638

7355

449

11325

2050

272

23800

009minus68

2792

8902

M198

CP4

28

918

752

2185

256012

1876

569

75875

15775

166

15250

009minus56

288

9159

M200

CP3

284

828

742

2585

221513

1836

251

63125

1690

284

12950

009minus52

2235

9737

112

CP1

265

8672

53305

312164

5331

479

9125

19925

148

18250

009minus36

158

12605

233

CP2

264

889

753

434

239716

1895

299

7275

1490

237

13700

36minus26

166

12626

311

CP3

294

851

756

43235488

2883

239

71375

14325

118

13550

54minus25

219

10914

323

CP3

29

946

767

2675

270189

2863

539

74375

14825

379

16750

009minus108

229737

343

CP3

2958

748

285

343097

7898

599

97125

14475

143

21587

29minus94

1756

6677

403

CP4

289

828

732

161

15503

1678

599

4540

1030

426

8950

44minus32

2885

7276

407

CP4

299

884

791

1895

2004

26

1086

359

5815

1185

19118875

85minus7

167

9694

611

CP3

252

884

787

5285

332629

7305

539

9875

1585

1920100

224minus52

2161

8774

222D

CP2

314

922

774

2975

287199

2962

275

80625

1907

9517300

009minus79

1125

11149

E-23

CP2

295

711

585

393441

5805

216

11175

27175

284

23750

009minus66

242

10807

E-29

CP2

269

833

712

794

444913

7858

144

13200

29625

213

2660

0009minus41

2655

918

E-47A

CP3

289

917

747

61350746

6476

168

10650

22475

166

20500

009minus21

2197

9951

T350A

CP2

29

82688

822

492512

10326

228

143125

27825

154

29700

009minus57

2855

13931

T395

CP2

265

801

792

488

239242

3376

275

70375

1420

47

140625

63minus46

1025

10165

T40

0CP

121

896

791973

129455

1224

335

3910

5605

207

7570

336minus52

911

6805

611lowastA

CP3

252

876

785

524

332175

7049

371

100875

1595

201

19875

225minus4

228774

4 Geofluids





3 Methodology








119875119897 (ℎ) = 119892intℎ119908

0120588sea119889ℎ + 119892int

ℎ

ℎ119908

120588119887119889ℎ (1)


119875119897 (ℎ) = 119892intℎ119908

0120588sea119889ℎ + 119892

119899sum119894=1

119889119894 [120588119908120593119894 + 120588119903119894 (1 minus 120593119894)] (2)



Geofluids 5

3536373839

44142434445

35 37 39 41 43 45


ＦＩＡ Cl (mgL)

ＦＩＡ

Na(m

gL)

(a)


2

22

24

26

28

3

32

34

35 37 39 41 43 45ＦＩＡ

Ca (m

gL)

ＦＩＡ Cl (mgL)

(b)


2526272829

33132333435

35 37 39 41 43 45

ＦＩＡ

K (m

gL)

ＦＩＡ Cl (mgL)

(c)


1

15

2

25

3

35

35 37 39 41 43 45

ＦＩＡ

Mg

(mg

L)

ＦＩＡ Cl (mgL)

(d)


37 39 41 43 4535ＦＩＡ Cl (mgL)

05

1

15

2

25

3

ＦＩＡ

HCO

3(m

gL)

(e)


37 39 41 43 4535ＦＩＡ Cl (mgL)

005

115

225

335

445

ＦＩＡ

SO4

(mg

L)

(f)









6 Geofluids

0

500

1000

1500

2000

2500

3000

3500

000050

Dep

th m

ts

Estimated porosity

Qua

rtz

Plag

iocl

ase

Feld

spar

-KM

usco

vite

-bio

tite Ill

iteIll

ite-m

ontm

orill

onite

25

Illite

-mon

tmor

illon

ite 5

0M

ontm

orill

onite

Kaol

inite

Chlo

rite

Calc

ite (s

udde

nde

crea

se 3

0ndash1

5)

Dol

omite

+ k

aolin

itede

stroy

edW

aira

kite

Talc

Pyrit

eA

mph

ibol

eEp

idot

e (de

trita

lgr

ain

size)

Anh

ydrit

eQ

uart

z and

feld

spar

-K

ov

ergr

owth

sBi

otite

Preh

nite





Chlorite zone






2minus








Geofluids 7

minus2

minus15

minus1

minus05

0

05

1

15

2

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI


minus4

minus3

minus2

minus1

0

1

2

3

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400SI


minus4minus35minus3

minus25minus2

minus15minus1

minus050

051

15

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI


minus202468

10121416

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI



minus200

minus100

0

100

200

300

400

500

600

700

minus200 minus100 0 100 200 300 400 500 600 700

Ca ex

cess

(mEq

L)

Na deficit (mEqL)

CP

Gypsum





Mixing

Halite

1Ca for 2

Na

Exchan

ge

CaSO4 dissolution

Basinal fl

uid line

CaCO3 precipitation




8 Geofluids

01

10

100

1000

10000

1 10 100 1000 10000 100000 1000000

CP

CP

Condensates

Overpressuredwaters


Ca-chloridebrines

Seawaterevaporation




Gypdiss

Haldiss

Na-bica

rbonate




(3)

44 Overpressure







Geofluids 9

0

1

2

3

4

5

6

7

0

500

1000

0500

1000

05001000

1500

2000

654321

2

1

213


CP1CP2

CP3CP4




(Km)

3




5 Geothermometry



119879 = ( 1178(147 + log (NaK))) minus 27315 (4)

119879 = ( 1289(1615 + log (NaK))) minus 27315 (5)


6 Conclusions



10 Geofluids

0

02

04

06

08

1

12

14

16

18

0 20 40

Dep

th (K

m)

Pressure (MPa)

M104

23 MPaKm10 MPaKm

(a)

233343

611T 395T 400

23 MPaKm10 MPaKm


25

2

15

1

05

0

Dep

th (K

m)

(b)

0

05

1

15

2

25

3

35

4

45

Dep

th (K

m)

M 117AM 119AM 127M 133AM 148AM 155M 198M 200

112311323403407222 DE-23E-29E-47AT 350A


23 MPaKm10 MPaKm

(c)


Geofluids 11


Well 119879 ∘C NaK[36]

119879 ∘C NaK[37] Well 119879 ∘C NaK

[36]119879 ∘C NaK

[37] Well 119879 ∘C NaK[36]

119879 ∘C NaK[37]







Acknowledgments



References












12 Geofluids
































Geofluids 13




























Mining


Journal of









Journal of




Advances in











Geology Advances in

4 Geofluids





3 Methodology








119875119897 (ℎ) = 119892intℎ119908

0120588sea119889ℎ + 119892int

ℎ

ℎ119908

120588119887119889ℎ (1)


119875119897 (ℎ) = 119892intℎ119908

0120588sea119889ℎ + 119892

119899sum119894=1

119889119894 [120588119908120593119894 + 120588119903119894 (1 minus 120593119894)] (2)



Geofluids 5

3536373839

44142434445

35 37 39 41 43 45


ＦＩＡ Cl (mgL)

ＦＩＡ

Na(m

gL)

(a)


2

22

24

26

28

3

32

34

35 37 39 41 43 45ＦＩＡ

Ca (m

gL)

ＦＩＡ Cl (mgL)

(b)


2526272829

33132333435

35 37 39 41 43 45

ＦＩＡ

K (m

gL)

ＦＩＡ Cl (mgL)

(c)


1

15

2

25

3

35

35 37 39 41 43 45

ＦＩＡ

Mg

(mg

L)

ＦＩＡ Cl (mgL)

(d)


37 39 41 43 4535ＦＩＡ Cl (mgL)

05

1

15

2

25

3

ＦＩＡ

HCO

3(m

gL)

(e)


37 39 41 43 4535ＦＩＡ Cl (mgL)

005

115

225

335

445

ＦＩＡ

SO4

(mg

L)

(f)









6 Geofluids

0

500

1000

1500

2000

2500

3000

3500

000050

Dep

th m

ts

Estimated porosity

Qua

rtz

Plag

iocl

ase

Feld

spar

-KM

usco

vite

-bio

tite Ill

iteIll

ite-m

ontm

orill

onite

25

Illite

-mon

tmor

illon

ite 5

0M

ontm

orill

onite

Kaol

inite

Chlo

rite

Calc

ite (s

udde

nde

crea

se 3

0ndash1

5)

Dol

omite

+ k

aolin

itede

stroy

edW

aira

kite

Talc

Pyrit

eA

mph

ibol

eEp

idot

e (de

trita

lgr

ain

size)

Anh

ydrit

eQ

uart

z and

feld

spar

-K

ov

ergr

owth

sBi

otite

Preh

nite





Chlorite zone






2minus








Geofluids 7

minus2

minus15

minus1

minus05

0

05

1

15

2

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI


minus4

minus3

minus2

minus1

0

1

2

3

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400SI


minus4minus35minus3

minus25minus2

minus15minus1

minus050

051

15

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI


minus202468

10121416

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI



minus200

minus100

0

100

200

300

400

500

600

700

minus200 minus100 0 100 200 300 400 500 600 700

Ca ex

cess

(mEq

L)

Na deficit (mEqL)

CP

Gypsum





Mixing

Halite

1Ca for 2

Na

Exchan

ge

CaSO4 dissolution

Basinal fl

uid line

CaCO3 precipitation




8 Geofluids

01

10

100

1000

10000

1 10 100 1000 10000 100000 1000000

CP

CP

Condensates

Overpressuredwaters


Ca-chloridebrines

Seawaterevaporation




Gypdiss

Haldiss

Na-bica

rbonate




(3)

44 Overpressure







Geofluids 9

0

1

2

3

4

5

6

7

0

500

1000

0500

1000

05001000

1500

2000

654321

2

1

213


CP1CP2

CP3CP4




(Km)

3




5 Geothermometry



119879 = ( 1178(147 + log (NaK))) minus 27315 (4)

119879 = ( 1289(1615 + log (NaK))) minus 27315 (5)


6 Conclusions



10 Geofluids

0

02

04

06

08

1

12

14

16

18

0 20 40

Dep

th (K

m)

Pressure (MPa)

M104

23 MPaKm10 MPaKm

(a)

233343

611T 395T 400

23 MPaKm10 MPaKm


25

2

15

1

05

0

Dep

th (K

m)

(b)

0

05

1

15

2

25

3

35

4

45

Dep

th (K

m)

M 117AM 119AM 127M 133AM 148AM 155M 198M 200

112311323403407222 DE-23E-29E-47AT 350A


23 MPaKm10 MPaKm

(c)


Geofluids 11


Well 119879 ∘C NaK[36]

119879 ∘C NaK[37] Well 119879 ∘C NaK

[36]119879 ∘C NaK

[37] Well 119879 ∘C NaK[36]

119879 ∘C NaK[37]







Acknowledgments



References












12 Geofluids
































Geofluids 13




























Mining


Journal of









Journal of




Advances in











Geology Advances in

Geofluids 5

3536373839

44142434445

35 37 39 41 43 45


ＦＩＡ Cl (mgL)

ＦＩＡ

Na(m

gL)

(a)


2

22

24

26

28

3

32

34

35 37 39 41 43 45ＦＩＡ

Ca (m

gL)

ＦＩＡ Cl (mgL)

(b)


2526272829

33132333435

35 37 39 41 43 45

ＦＩＡ

K (m

gL)

ＦＩＡ Cl (mgL)

(c)


1

15

2

25

3

35

35 37 39 41 43 45

ＦＩＡ

Mg

(mg

L)

ＦＩＡ Cl (mgL)

(d)


37 39 41 43 4535ＦＩＡ Cl (mgL)

05

1

15

2

25

3

ＦＩＡ

HCO

3(m

gL)

(e)


37 39 41 43 4535ＦＩＡ Cl (mgL)

005

115

225

335

445

ＦＩＡ

SO4

(mg

L)

(f)









6 Geofluids

0

500

1000

1500

2000

2500

3000

3500

000050

Dep

th m

ts

Estimated porosity

Qua

rtz

Plag

iocl

ase

Feld

spar

-KM

usco

vite

-bio

tite Ill

iteIll

ite-m

ontm

orill

onite

25

Illite

-mon

tmor

illon

ite 5

0M

ontm

orill

onite

Kaol

inite

Chlo

rite

Calc

ite (s

udde

nde

crea

se 3

0ndash1

5)

Dol

omite

+ k

aolin

itede

stroy

edW

aira

kite

Talc

Pyrit

eA

mph

ibol

eEp

idot

e (de

trita

lgr

ain

size)

Anh

ydrit

eQ

uart

z and

feld

spar

-K

ov

ergr

owth

sBi

otite

Preh

nite





Chlorite zone






2minus








Geofluids 7

minus2

minus15

minus1

minus05

0

05

1

15

2

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI


minus4

minus3

minus2

minus1

0

1

2

3

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400SI


minus4minus35minus3

minus25minus2

minus15minus1

minus050

051

15

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI


minus202468

10121416

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI



minus200

minus100

0

100

200

300

400

500

600

700

minus200 minus100 0 100 200 300 400 500 600 700

Ca ex

cess

(mEq

L)

Na deficit (mEqL)

CP

Gypsum





Mixing

Halite

1Ca for 2

Na

Exchan

ge

CaSO4 dissolution

Basinal fl

uid line

CaCO3 precipitation




8 Geofluids

01

10

100

1000

10000

1 10 100 1000 10000 100000 1000000

CP

CP

Condensates

Overpressuredwaters


Ca-chloridebrines

Seawaterevaporation




Gypdiss

Haldiss

Na-bica

rbonate




(3)

44 Overpressure







Geofluids 9

0

1

2

3

4

5

6

7

0

500

1000

0500

1000

05001000

1500

2000

654321

2

1

213


CP1CP2

CP3CP4




(Km)

3




5 Geothermometry



119879 = ( 1178(147 + log (NaK))) minus 27315 (4)

119879 = ( 1289(1615 + log (NaK))) minus 27315 (5)


6 Conclusions



10 Geofluids

0

02

04

06

08

1

12

14

16

18

0 20 40

Dep

th (K

m)

Pressure (MPa)

M104

23 MPaKm10 MPaKm

(a)

233343

611T 395T 400

23 MPaKm10 MPaKm


25

2

15

1

05

0

Dep

th (K

m)

(b)

0

05

1

15

2

25

3

35

4

45

Dep

th (K

m)

M 117AM 119AM 127M 133AM 148AM 155M 198M 200

112311323403407222 DE-23E-29E-47AT 350A


23 MPaKm10 MPaKm

(c)


Geofluids 11


Well 119879 ∘C NaK[36]

119879 ∘C NaK[37] Well 119879 ∘C NaK

[36]119879 ∘C NaK

[37] Well 119879 ∘C NaK[36]

119879 ∘C NaK[37]







Acknowledgments



References












12 Geofluids
































Geofluids 13




























Mining


Journal of









Journal of




Advances in











Geology Advances in

6 Geofluids

0

500

1000

1500

2000

2500

3000

3500

000050

Dep

th m

ts

Estimated porosity

Qua

rtz

Plag

iocl

ase

Feld

spar

-KM

usco

vite

-bio

tite Ill

iteIll

ite-m

ontm

orill

onite

25

Illite

-mon

tmor

illon

ite 5

0M

ontm

orill

onite

Kaol

inite

Chlo

rite

Calc

ite (s

udde

nde

crea

se 3

0ndash1

5)

Dol

omite

+ k

aolin

itede

stroy

edW

aira

kite

Talc

Pyrit

eA

mph

ibol

eEp

idot

e (de

trita

lgr

ain

size)

Anh

ydrit

eQ

uart

z and

feld

spar

-K

ov

ergr

owth

sBi

otite

Preh

nite





Chlorite zone






2minus








Geofluids 7

minus2

minus15

minus1

minus05

0

05

1

15

2

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI


minus4

minus3

minus2

minus1

0

1

2

3

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400SI


minus4minus35minus3

minus25minus2

minus15minus1

minus050

051

15

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI


minus202468

10121416

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI



minus200

minus100

0

100

200

300

400

500

600

700

minus200 minus100 0 100 200 300 400 500 600 700

Ca ex

cess

(mEq

L)

Na deficit (mEqL)

CP

Gypsum





Mixing

Halite

1Ca for 2

Na

Exchan

ge

CaSO4 dissolution

Basinal fl

uid line

CaCO3 precipitation




8 Geofluids

01

10

100

1000

10000

1 10 100 1000 10000 100000 1000000

CP

CP

Condensates

Overpressuredwaters


Ca-chloridebrines

Seawaterevaporation




Gypdiss

Haldiss

Na-bica

rbonate




(3)

44 Overpressure







Geofluids 9

0

1

2

3

4

5

6

7

0

500

1000

0500

1000

05001000

1500

2000

654321

2

1

213


CP1CP2

CP3CP4




(Km)

3




5 Geothermometry



119879 = ( 1178(147 + log (NaK))) minus 27315 (4)

119879 = ( 1289(1615 + log (NaK))) minus 27315 (5)


6 Conclusions



10 Geofluids

0

02

04

06

08

1

12

14

16

18

0 20 40

Dep

th (K

m)

Pressure (MPa)

M104

23 MPaKm10 MPaKm

(a)

233343

611T 395T 400

23 MPaKm10 MPaKm


25

2

15

1

05

0

Dep

th (K

m)

(b)

0

05

1

15

2

25

3

35

4

45

Dep

th (K

m)

M 117AM 119AM 127M 133AM 148AM 155M 198M 200

112311323403407222 DE-23E-29E-47AT 350A


23 MPaKm10 MPaKm

(c)


Geofluids 11


Well 119879 ∘C NaK[36]

119879 ∘C NaK[37] Well 119879 ∘C NaK

[36]119879 ∘C NaK

[37] Well 119879 ∘C NaK[36]

119879 ∘C NaK[37]







Acknowledgments



References












12 Geofluids
































Geofluids 13




























Mining


Journal of









Journal of




Advances in











Geology Advances in

Geofluids 7

minus2

minus15

minus1

minus05

0

05

1

15

2

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI


minus4

minus3

minus2

minus1

0

1

2

3

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400SI


minus4minus35minus3

minus25minus2

minus15minus1

minus050

051

15

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI


minus202468

10121416

112

M11

9AM

148A

T350

AE2

9M

200

403

233

E47A E2

3M

133A

T395

M15

5M

198

311

M11

7A61

1A 611

407

343

222D

M12

732

3M

104

T400

SI



minus200

minus100

0

100

200

300

400

500

600

700

minus200 minus100 0 100 200 300 400 500 600 700

Ca ex

cess

(mEq

L)

Na deficit (mEqL)

CP

Gypsum





Mixing

Halite

1Ca for 2

Na

Exchan

ge

CaSO4 dissolution

Basinal fl

uid line

CaCO3 precipitation




8 Geofluids

01

10

100

1000

10000

1 10 100 1000 10000 100000 1000000

CP

CP

Condensates

Overpressuredwaters


Ca-chloridebrines

Seawaterevaporation




Gypdiss

Haldiss

Na-bica

rbonate




(3)

44 Overpressure







Geofluids 9

0

1

2

3

4

5

6

7

0

500

1000

0500

1000

05001000

1500

2000

654321

2

1

213


CP1CP2

CP3CP4




(Km)

3




5 Geothermometry



119879 = ( 1178(147 + log (NaK))) minus 27315 (4)

119879 = ( 1289(1615 + log (NaK))) minus 27315 (5)


6 Conclusions



10 Geofluids

0

02

04

06

08

1

12

14

16

18

0 20 40

Dep

th (K

m)

Pressure (MPa)

M104

23 MPaKm10 MPaKm

(a)

233343

611T 395T 400

23 MPaKm10 MPaKm


25

2

15

1

05

0

Dep

th (K

m)

(b)

0

05

1

15

2

25

3

35

4

45

Dep

th (K

m)

M 117AM 119AM 127M 133AM 148AM 155M 198M 200

112311323403407222 DE-23E-29E-47AT 350A


23 MPaKm10 MPaKm

(c)


Geofluids 11


Well 119879 ∘C NaK[36]

119879 ∘C NaK[37] Well 119879 ∘C NaK

[36]119879 ∘C NaK

[37] Well 119879 ∘C NaK[36]

119879 ∘C NaK[37]







Acknowledgments



References












12 Geofluids
































Geofluids 13




























Mining


Journal of









Journal of




Advances in











Geology Advances in

8 Geofluids

01

10

100

1000

10000

1 10 100 1000 10000 100000 1000000

CP

CP

Condensates

Overpressuredwaters


Ca-chloridebrines

Seawaterevaporation




Gypdiss

Haldiss

Na-bica

rbonate




(3)

44 Overpressure







Geofluids 9

0

1

2

3

4

5

6

7

0

500

1000

0500

1000

05001000

1500

2000

654321

2

1

213


CP1CP2

CP3CP4




(Km)

3




5 Geothermometry



119879 = ( 1178(147 + log (NaK))) minus 27315 (4)

119879 = ( 1289(1615 + log (NaK))) minus 27315 (5)


6 Conclusions



10 Geofluids

0

02

04

06

08

1

12

14

16

18

0 20 40

Dep

th (K

m)

Pressure (MPa)

M104

23 MPaKm10 MPaKm

(a)

233343

611T 395T 400

23 MPaKm10 MPaKm


25

2

15

1

05

0

Dep

th (K

m)

(b)

0

05

1

15

2

25

3

35

4

45

Dep

th (K

m)

M 117AM 119AM 127M 133AM 148AM 155M 198M 200

112311323403407222 DE-23E-29E-47AT 350A


23 MPaKm10 MPaKm

(c)


Geofluids 11


Well 119879 ∘C NaK[36]

119879 ∘C NaK[37] Well 119879 ∘C NaK

[36]119879 ∘C NaK

[37] Well 119879 ∘C NaK[36]

119879 ∘C NaK[37]







Acknowledgments



References












12 Geofluids
































Geofluids 13




























Mining


Journal of









Journal of




Advances in











Geology Advances in

Geofluids 9

0

1

2

3

4

5

6

7

0

500

1000

0500

1000

05001000

1500

2000

654321

2

1

213


CP1CP2

CP3CP4




(Km)

3




5 Geothermometry



119879 = ( 1178(147 + log (NaK))) minus 27315 (4)

119879 = ( 1289(1615 + log (NaK))) minus 27315 (5)


6 Conclusions



10 Geofluids

0

02

04

06

08

1

12

14

16

18

0 20 40

Dep

th (K

m)

Pressure (MPa)

M104

23 MPaKm10 MPaKm

(a)

233343

611T 395T 400

23 MPaKm10 MPaKm


25

2

15

1

05

0

Dep

th (K

m)

(b)

0

05

1

15

2

25

3

35

4

45

Dep

th (K

m)

M 117AM 119AM 127M 133AM 148AM 155M 198M 200

112311323403407222 DE-23E-29E-47AT 350A


23 MPaKm10 MPaKm

(c)


Geofluids 11


Well 119879 ∘C NaK[36]

119879 ∘C NaK[37] Well 119879 ∘C NaK

[36]119879 ∘C NaK

[37] Well 119879 ∘C NaK[36]

119879 ∘C NaK[37]







Acknowledgments



References












12 Geofluids
































Geofluids 13




























Mining


Journal of









Journal of




Advances in











Geology Advances in

10 Geofluids

0

02

04

06

08

1

12

14

16

18

0 20 40

Dep

th (K

m)

Pressure (MPa)

M104

23 MPaKm10 MPaKm

(a)

233343

611T 395T 400

23 MPaKm10 MPaKm


25

2

15

1

05

0

Dep

th (K

m)

(b)

0

05

1

15

2

25

3

35

4

45

Dep

th (K

m)

M 117AM 119AM 127M 133AM 148AM 155M 198M 200

112311323403407222 DE-23E-29E-47AT 350A


23 MPaKm10 MPaKm

(c)


Geofluids 11


Well 119879 ∘C NaK[36]

119879 ∘C NaK[37] Well 119879 ∘C NaK

[36]119879 ∘C NaK

[37] Well 119879 ∘C NaK[36]

119879 ∘C NaK[37]







Acknowledgments



References












12 Geofluids
































Geofluids 13




























Mining


Journal of









Journal of




Advances in











Geology Advances in

Geofluids 11


Well 119879 ∘C NaK[36]

119879 ∘C NaK[37] Well 119879 ∘C NaK

[36]119879 ∘C NaK

[37] Well 119879 ∘C NaK[36]

119879 ∘C NaK[37]







Acknowledgments



References












12 Geofluids
































Geofluids 13




























Mining


Journal of









Journal of




Advances in











Geology Advances in

12 Geofluids
































Geofluids 13




























Mining


Journal of









Journal of




Advances in











Geology Advances in

Geofluids 13




























Mining


Journal of









Journal of




Advances in











Geology Advances in








Mining


Journal of









Journal of




Advances in











Geology Advances in

groundwater chemistry and overpressure evidences in cerro

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