Proceedings World Geothermal Congress 2005 Antalya, Turkey, 24-29 April 2005

Hydrostratigraphical Study, Geochemistry of Thermal Springs, Shallow and Deep Geothermal Exploration in : Hydrogeothermal Potentialities

Yassine Zarhloule1, Salem Bouri2, Abderahim Lahrach3 , Mimoun Boughriba1 ,Abdenbi El Mandour1 and Hamed Ben Dhia2. 1: Faculty of Sciences, Department of Geology, Laboratory of hydrogeology & environement, , Morocco.

2: ENISfax, Department of Geology, Laboratory of water, energy & environment, , .

3: Faculty of Sciences, Department of Geology, Fès, Morocco.

[email protected], [email protected]

Keywords: aquifers, thermal springs, geochemistry, Alkaline geothermometers used for the thermal springs are temperatures, oil wells, shallow wells, hydrodynamism, not reliable for prospecting, inasmuch as the chemical geothermal gradient, thermal anomalies, conceptual model, composition is greatly affected by the enormous dilution with Morocco. the shallow cold water and probably affected by interaction with the evaporitic rocks that are ubiquitous in the basin.The ABSTRACT application of Giggenbach method to springs revealed that the waters result from mixing of deep water with shallow The aim of this paper is to obtain a first reliable evaluation of cold water. In this case the reservoir deep temperature is the geothermal potential of the country. It’s caracterised by given by the mixing model. more than 70 hot springs, several deep hot aquifers, more than 1000 petroleum exploration wells and various existing The deep geothermal study is based on the petroleum well geological, geophysical and hydrogeological data. So, its was data which present 1126 BHT and 78 DST. A statistical possible to distinguish the mains geothermal features if the method is used to process these temperature indications and country, by evaluating both the underground temperature and gives a geothermal gradient ranging from 16 to 41°C/Km. In the potential reservoirs. order to establish the first geothermal gradient map for the whole of Morocco , the country is subdivided to five The hydrostratigraphical study of each basin revealed several hydrogeothermal basins. Each basin is characterized by its potentiel reservoir layers in which the carbonate aquifer of geodynamical evolution and its specific reservoirs and Turonian (Tadla basin and basin) and Liasic (North- hydrodynamism. Also, The data were treated separately and western basin of Morocco and North-Eastern basin) are the five maps of geothermal gradient were realized. The resulting most important hot water reservoirs in Morocco. this study map of Morocco shows that the geothermal anomalies are made it possible to identify the main aquifers, their related to deeper hydrodynamic, recent tectonic, volcanism or temperatures, depth and extension. to elevation of the Moho. A shallow geothermal prospecting has been performed in four zones in Morocco for wich few deep thermal data are 1. INTRODUCTION available (North-western basin of Morocco, North-Eastern For Morocco, the oil crises and the decrease in local energy basin of Morocco, Tadla basin and Agadir basin). These areas ressources, gave impetus to geothermal energy, for potential are different geologically and hydrogeologically. The shallow assessment, exploration and utilisation. The evaluation of temperature measurements program has been launched to hydrogeothermal resources of Morocco is mainly done by the estimate the natural geothermal gradient in these areas, to knowledge of the temperature, the chemical characteristics of determine the principal thermal anomalies, to identify the water, the hydrodynamics of the reservoirs containing hot main thermal indices, and to characterize the recharge, water. The research undertaken showed a country with real discharge and potential mixing limits of the aquifers.The potentialities either by its important deep aquifers or by the main thermals clues and the principal thermal anomalies that relatively high values of geothermal gradient. It is expected coincide with zone of artesianism of Turonian and Liasic that these efforts of geothermal investigation will continue in aquifers have been identified, as well as the potential mixing the future. limit of the aquifers systems. Also,for each basin a conceptual model is presented to interpret the relation between 2. GEOLOGICAL SETTING temperature, hydrodynamism and topography within the sedimentary basins . Morocco is located in a strategic area at the interaction of several plates (Africa, European, Mediterranean and The chimical of several thermal springs, in the north part of Atlantic). The structural framework is characterized by Morocco, has been investigated. Measured temperature transition from the African domain in the southern part of ranges from 21 to 54°C, discharges rates range from 2.5 to Morocco to Alpin foldeed structures (Atlasic domain and Rif 40l/s and TDS range 132 mg/l to 3g/l. The waters are mainly troughs). Four main structural units are defined from South to HCO3-Ca-Mg type, resulting from the great influence of North (Fig. 1): Anti-Atlas and Saharian domain corresponds carbonate rocks, and the Na-Cl type, resulting from the to the Precambrian basement, Atlas corresponds to an Alpine interaction of water with marine sediments.The geochimical intracontinental range, Mesetas corresponds to stable prospecting using geothermometers(silica, Na/K, Na-K-Ca, Paleozoic-Mesozoic basement, Rif represents the Alpine belt around the Western Mediterranean .

Morocco was subdivided into five hydrogeothermal basins Na-K-Ca-Mg, Mg/Li and Na/Li) has been applied and only (Fig. 1), distinguished by specific geological and the silica geothermometrs seem to give plausible values. hydrogeological feautres (North-Western basin, North- 1 Zarhloule et al.

Eastern basin, South-Western basin, Tadla basin, Errachidia- High-Atlas Ourzazate-Boudnib basin and . -Moroccan 0 Atlantic -200 -400 basin). Ocean 0 +400 -400 +200 0 -200 Tagatrant na 0 ou -200 Sebta G Aquiclude Mediterraean Sea El Sidi Bourja N Agadir -1000 Bou Rbia Rif Reservoir domain 4 -800 -400 El Haffaia N Hydrogeothermal 3 Oujda -600 Od Teima Fes eta -400El Kléa Reservoir Meseta Mes Q Anti-Atlas in -200 Tadla 2 oma 6 Q Biougra sic d S 10 km Atla Errachidia Q S 1 in ma Tr Tr do M Turonian visible fault Fault from electric Oil well Hydrogeological well Agadir tlas Pl-Q C South limit of Turonian deposit ti-A C 200 Structural curve of Turonian aquifers An Q Og Q Mp S H-B IC Tarfaya S Tr 5 Saharian Tr C Pr-K Laayoune domain Ms-Eo Npr BB Figure 2a: Structural map of Turonian aquifer. C P-K Ox A Mp n Sahara H-Be Cal-Ox To a D S Pl Do C Ba-To High-Atlas Morocc Pr-K L Ts Ts Atlantic 170 230 C-Tr D Pz Ox L 140 Pz Ocean 200 6 El Gouna Tagatrant D L Ts 5 IC Pz Ts L Agadir Sidi Bourja Ts Pz 4 200 km 110 Bou Rbia Ts Pz 3 El Haffaia N 1 Pz 2 El Klea Od Teima Anti-Atlas areas studies: 1:South-Western basin, 2:Tadla basin, 3:North-Western basin (Saïss), 4:North-Eastern basin, 5:Tarfaya-Laayoune-Moroccan Sahara basin, 6:Errachidia-Ourazazate-Boudnib basin. 1.2.3.4.5.6:Deep geothermal exploration, 1.2.3.4:shallow geothermal exploration, 3.4:Geochimical Biougra 10 km investigation. Q:Quaternary, M:Miocene, Og:Oligocene, S:Senonian, Tr:Turonian, C:Cenomanian, Pr:Portlandian, K:Kimmeridgian, Cal:Callovian, Ox:Oxfordian, Ba-To:Bathonian-Toarcien, L:Lias, Ts:Triasic, Pz:Paleozoïc, A:Aalenian, Do:Domerian, P-N:Paleogene-Neogene, H-Be:Hauterivian- Turonian visible fault Fault from electric Oil well Hydrogeological well Berriasian, D:Dogger, Ms-Eo:Maastrichtian-Eocene, Pl:Pliocene, IC:Infra-Cenomanian, Mp:Miocene South limit of Turonian deposit 200 Piezometric curve of Turonian aquifers post-nappe, Npr: Nappe pre-rifain Figure 2b: Piezometric map of Turonian aquifer. Figure 1: Simplified geological map of Morocco with the study zones and their hydrostratigraphical 3.1.2 Tadla basin logs. In the Tadla basin the aquifer is represented by the 3. HYDROSTRATIGRAPHICAL STUDY carbonate. The outcrops are limited to the Nord of Kasbat The basic data were mainly obtained from final well reports, Tadla-El Borouj. The tickness varies from 20m to 100m. from both oil and hydrogeologic research. Also some data The depth of the reservoir ranges from the outcrops to 500m have been acquired on the land (piezometrical level, chemical (Fig. 3a ). In the north part of Kasbat Tadla-El Borouj, the analysis of water, measure of temperature). These data hydrodynamic flow is from the North to the South of the proved useful for characterising the hot aquifers of Morocco. basin and to South-Ouest, but in the South of this limit the aquifer is deep and the groundwater flow is toward ENE- The hydrostratigraphical study (Fig.1) of each basin revealed WSW . The discharge zone is in the South-Ouest of El several potential reservoir layers in which the carbonate Brouj (Fig. 3b). The aquifer temperature and the salinity aquifer of Turonian (South-Western and Tadla basin) and varies respectively from 21°C to 47°C and from 530mg/l to Liasic (North-Western and North-Eastern basin) are the most 2530mg/l important hot water reservoirs in Morocco (Zarhloule, 1999, Zarhloule et al.2001). These areas are different geologically and hydrogeologically. +600

KT 3.1 Hydrogeological characterstics of the Turonian +400 aquifers EB FBS Atlasic +200 0 Domain 3.1.1 South-Western basin -200 BM -400 Turonian In the Agadir basin the aquifer is mainly limestone. The OZ -600 Paleozoïc +200 outcrops are limited to High-Atlas, Haffaia, Sidi-bourja, 0 Hydrogeological well Ouled bou Rbia, El Aaricha and Tagtrannat zones. The -200 15 km aquifer thickness ranges from 10m in the East to 120m in the KT: Kasba Tadla, EB: El Borouj, FBS: Fkih Ben Salah, BM: Beni Mellal, OZ, Ouled Zidouh. West. The depth of the aquifer varies from the outcrops in the south of the basin to 500 m in the East (Fig. 2a). The Figure. 3a. Structural map of Turonian aquifer. hydrodynamic flow is from the Est (outcrops zone) to the West of the basin, where the reservoir is deep and artesien N 720 15 km 720 (Ouled Teima, El-Klea and El gouna zones) (Fig. 2b). The 640 aquifer temperature and the salinity varies respectively from 560

22°C to 32°C and from 330 mg/l to 750 mg/l. 480 KT 460 E.B FBS 320 400 BM Turonian OZ Paleozoïc Hydrogeological well 400 400 Piezometric curve KT: Kasba Tadla, EB: El Borouj, FBS: Fkih Ben Salah, BM: Beni Mellal, OZ, Ouled Zidouh.

Figure. 3b. Piezometric map of Turonian aquifer.

2 Zarhloule et al.

3.2 Hydrogeological characterstics of the Liasic aquifers 1) for which few deep thermal data are avaible (North- Western basin, North-Eastern basin, South-Western basin,

3.2.1 North-Western part of Morocco Tadla basin). It has been launched to estimate the natural In this zone, the aquifer is mainly limestone. The outcrops geothermal gradient in these areas, to determine the principal are limited to the South of the basin. The tickness varies thermal anomalies, to identify the main thermal indices, and from 14 m to 370m. The deep of the aquifer ranges from to characterize the recharge, discharge and potential mixing outcrops to 1000m (Fig. 4a). The hydrodynamic flow is limits of the turonian and liasic aquifers (Zarhloule et al., from the South to the North in the Eastern part of the basin 1998, 2001). and to the West in the Western zone of the basin (Fig. 4b). The aquifer temperature and the salinity varies respectively The temperature data from depths between 15 and 500m of from 22°C to 55°C and from 132mg/l to 2334mg/l. 250 wells have been analysed. The temperature measurements were made at 5m depth intervals using South rifain-rides -1000 Fès portable thermistor probe equipment with 0.01°C resolution. -400 -200 The shallow temperature data allowed to establish a thermal 0 200 -200 400 profile for each investigated well, assumed to be in thermal Meknès 600 0 -200 0 800 equilibrium (Fig. 6). 200 0 400 600 800 200 Liasic N 24T0i 25 24 25 26 27 24 25 24 26 24 26 26 28 30 T(°C) 23 25 T(°C) 1000 Liasic hiatus 32 Permo-Triasic 10 Paleozoïc Midle Atlas 20 Fault 4 km WT Hydrogeological well (Liasic) Oil well Thermal spring -200 Structural curve 30 60 50 59 Figure 4a: Structural map of Liasic aquifer. 70 100 10 53 22 90 4 19 140 South rifain-rides 300 Fès 110 300 Z (m) Z (m) 600 400 500 53 : Apparent shallow geothermal gradient (C°/km), WT : Water table (m) 12 400 600 T0i: Interception temperature(°C) 600 450 650 500 700 700 Liasic N 800 900 Liasic hiatus Permo-Triasic Figure 6: Example of thermal profile. 1000 Paleozoïc Midle Atlas Fault 4 km Thermal behaviour is changing from an area to an another, Hydrogeological well (Liasic) Oil well Thermal spring 300 Piezometric curve from a well to another as well as within the same well. These differences in the Lateral and vertical temperature assessment Figure 4b: Piezometric map of Liasic aquifer. depend on several factors: geological and structural homogeneity within the same region, the lithology and its 3.2.2 North-Eastern part of Morocco degree of homogeneity within each well, the depth of water In this zone, the aquifer is mainly limestone. The outcrops are table and its temperature and the well location within the limited to Beni Snassen, High-Atlas, Midle-Atlas and the hydrodynamic frame. The temperature values of water range South of the basin. The tickness varies from 50 m to 1140m. from 18 to 55.5°C. The deep of the aquifer ranges from outcrops to 1370m. The hydrodynamic flow is from the South to the North of basin From a well to another, several main types of profiles have (Fig. 5). The aquifer temperature and the salinity varies been distinguished depending on whether the evolution V.S respectively from 20°C to 52°C and from 130mg/l to depth is increasing (Fig. 7a), steady (Fig. 7c) or decreasing 3000mg/l. (Fig. 7b). In the same well three main slope breaks in the termal profile have been noticed that are (Fig. 7d): G0 is the Liasic-Dogger Permo-Triasic thermal gradient between the surface and the limit of 400 Hydrogeological well 450 influence of surface effects (10m), G1 is the thermal Beni Drar (Liasic) 500 Piezometric curve gradient between the groundwater level and he bottom of the limit of influence of surface effects, G2 is the thermal Aïn Sfa 500 gradient between the groundwater level and the bottom of the well and GGSA is apparent shallow geothermal 550 gradient. Also an another gradient has been defined Gwater Oujda 600 that corresponds to the thermal gradient between the 700 groundwater level and the interception temperature (T0i). 650 N The cartography of some parametrizes (water temperatures 750 and GGSA) for each basin show that the recharge outcrops Horst Mountains 6 km zones of the turonian and lisaic aquifers are characterised by the high topography, high water potential, shallow cold water, low geothermal gradient and negative anomalies (Fig.8a-d). Figure 5b: Piezometric map of Liasic aquifer. The disharge zones are characterised by low topography, low piezometric level, high geothermal gradient, high water 4. SHALLOW GEOTHERMAL PROSPECTION IN temeprature with hot spring and positive anomalies (Fig. 9a- MOROCCO d). The shallow geothermal methods has ben used in many locations and has met with considerable succes in the past (Leshack and lewis 1983; Smith 1983; Sass et al., 1984; Ben Dhia et al., 1992).The shallow temperature measurements program has been undertaken in four zones in Morocco (Fig. 3 Zarhloule et al.

T(°C) 30 a T(°C) b Figure 8c: Temperature distribution map of water of the 32 Liasic aquifer (South-Eastern basin: Oujda). 28 30

28 26 d

Z(m) Z(m) 26 24 0 40 80 120 020406010 30 50 70 30 T(°C) T(°C) GGSA G2 35 25 c KT T0i 35 FBS 20 d E.B 30 25 G0 G1 Water table 40 Atlasic Domain 40 35 BM Z(m) Te > 40 15 10 Z(m) 30 35 < Te < 40 0 20 60 100 020406080 100 25 OZ N 30 < Te < 35 25 < Te < 30 15 km Te < 25 Figure 7: Different types of geothermal gradient: a) Hydrogeological well Paleozoïc Turonian positive gradient; b) negative gradient; c) no KT: Kasba Tadla, EB: El Borouj, FBS: Fkih Ben Salah, BM: Beni Mellal, OZ:Ouled Zidouh. gradient; d) main slope breaks in the thermal profile. Figure 8d: Temperature distribution map of water of the Turonian aquifer (Tadla basin). a High-Atlas a High-Atlas 0 26 25 24

Bou Rbia El Gouna 24 25 35 0 Agadir 30 24 El Haffaia El Kléa 30 < Te < 32°C Agadir Od Teima 28 < Te < 30°C Atlantic 28 26 < Te < 28°C N GGSA > 35 °C/Km Ocean 30 24 24 < Te < 26°C 25 < GGSA < 35 °C/Km 26 Atlantic 25 25 0 10Km 20 40 GGSA > 40 C°/km Pre-rifain 20 < GGSA < 40 35 < Te < 40 b Pre-rifain b 40 25 < Te < 35 0 < GGSA < 20 Fes 40 Fes GGSA < 0 5 km Te < 25 35 0 25

Meknes Meknes 20 0 N 25 20 40 Midle Atlas 5 km Midle Atlas Hydrogeological well Thermal spring Southern limit of the Rif Hydrogeological well Thermal spring Southern limit of the Rif Figure 9b: Isovalue map of apparent shallow geothermal Figure 8b: Temperature distribution map of water of gradient (°C/km) (South-Western basin: the Liasic aquifer (South-Western basin: Saïss). Saïss). GGSA > 50 C°/km c N Beni Drar 50 30 < GGSA < 50 0 < GGSA < 30 30 30 Te > 30 c N Beni Drar 25 < Te < 30 NN Aïn Sfa Te < 25 30 Aïn Sfa 25 50 Oujda Algeria 30 50

Oujda 30 25 30

Mountain Horst 6 km Liasic wellPlio-quaternary well Liasic- Dogger Permo-Triasic

Mountain Horst 6 km Figure 9c: Isovalue map of apparent shallow geothermal Liasic wellPlio-quaternary well Liasic- Dogger Permo-Triasic gradient (°C/km) (South-Eastern basin: Oujda).

4 Zarhloule et al.

the origin-reservoir, to evaluate undergroud temperature and to determined the mixing shallow cold water with deep hot d water.

NN Nouthern part of Morocco Sebta Tanger 300 Km KT 20 30 E.B FBS 40 40 Oujda BM Rif 40 30 40 OZ GGSA > 40 N 20 30

35 m /K Figure 11: Map of shallow geothermal anomalies in °C 30 Morocco. 30

South rifin zones N Mio - Plio - Quaternary 25 Rharb Liasic Permo-Triasic 13 Paleozoïc 15 2 Rifan zone Rides South-rifan limit 10 km 7 Thermal water 3 20 5 1 2 14 8 11 Fes Depth (m) 4 12 10 9 15 Plain 0 100 200 300 400 500 of Saïss Meknes 16 Midlle Atlas Figure 10: Bottom shallow hydrogeological wells temperture V.S depth Figure 12a: Geological skech map of the North western The main thermal indices (Fig. 11) and the principal thermal of Morocco (Saïs basin) with location of anomalies coincide with the zones of turonian and Liasic simpling sites. aquifers. Also the water temperatures of the shallow aquifer is higher to the neighborhood of the artesianisme zones of the 5.1 Water chemistry deep aquifers that in the rest of the basins. What explians the Major (Na, K, Ca, Mg, HCO3, SO4 and CL) and minor existence of a groundwater flow from deep aquifer to shallow (SiO2, Li) components in solution (mg/l) are reporeted in one favoured by an abandant fracturation. Table 1.

5. GEOCHEMISTRY OF THERMAL SPRINGS IN We retained all the analysed springs with good ionic NORTHERN MOROCCO balance. From Table I it can be seen that PH varies from 6.9 to 7.9, temperature ranges from 22 to 54°C, salinity from The Northern Morocco basin is constituted by a lithological 0.13 to 27.6 g/l. From the North Western to the North succession from paleozoïc to Quaternary (Fig.1) and only the Liasic limestone aquifer is an importante Eastern part of Morocco, there are wide variations in these hydrogeothermic unit. The Numerous hot springs are know parametrs because for the same aquifer system there may be heterogeneity within a given reservoir and /or variation in in the North part of Morocco (Fig. 12a-b) (Lahrach et the upflow routes linking the reservoir to the surface al.1998, Zarhloule, 1999). (Zarhloule 1999, Lahrach et al.1998). The outcrops are limited to the Middle-Atlas (Saïss), the Northern and the Southern areas of Oujda. The aquiclude Based on the relative amount of major ions, The water classification has been made in Figure.13, using the consists of the Cretaceous to Tertiary sediments (schale). Langelier and Ludwing diagram (1996). The hot springs emanating from the limestone liasic aquifer, have been inventoried and analysed in order to characterize 5 Zarhloule et al.

19 50 SO4 + Cl 0 Oujda 50 0 13 N Eastern Beni Snassen 5 km Algeria 1 C 23 18 35 38 Oujda 28 36 11 19 40 33 34 18 32 23

39 37 a 17 20 30 i N 27 21 r 5

28 3124 e 29 g

25 26 22 l 14 5 Km A 38 29 4 25 km Carbonate rocks (Mesozoic) 9 N Rifan unit 3 Mediterranean Sea Neogen and Quaternary 10 Mio-plio-quaternary volcanism 27 43 Thermal waters 44 41 47 42 Na + K 45 39 25 na Ca + Mg da 46 16 6 2 Keb Ahfir 15 n Berkane Algeria 20 B tai ntain 8 30 26 24 7 on n Mo 22 M asse 31 35 b n Sn Oujda 21 17 12 36 are Be G 37 33 A 40 Taourirt nes 34 t zo ors 0 50 Basin H Beni Mathar 0 HCO3 + CO3 50

47 43 42 Figure 13: Langelier-Ludwing diagram for the water 44 41 samples investigated. Taourirt 32 N 10 km 46 The hot waters can be grouped into Ca (Mg)-SO4 (Cl) (A) type waters with moderate salinity (<3g/l), Ca(Mg)-HCO3 Beni Methar NNN (B) type waters with low salinity (<700mg), and Na-Cl (C)

5 m type waters with a salinity that varied from 0.61mg/l to 45 27.6g/l. The C type waters showed a chemical composition

nearby to the Ca-Mg with the exception of springs N° 5,11,13 and 32 who have a high salinity. This can be due to Figure 12b: Geological skech map of the North Eastern the interaction of water with the different rocks principally of Morocco with location of simpling sites. evaporitic one. Table 1: Chemical composition of thermal waters from northern Morocco

TDS + + 2+ 2+ - - 2- N° Name T (°C) pH K mg/l Na Ca Mg Cl HCO SO SIO Li mg/l mg/l 3 4 2 1 A.H.du Zalagh 35.5 7.1 3850 32 1325 88 42 2066.1244 184.3 17.1 5 2 A. Anseur 24 7.3 510 9 70 68 21 78.1 280.6 111.9 10.3 1.2 3 A.Maaser 25 7 610 2 125 73 18 177.5 256.2 62.5 4 A. S. Trhat 26 6.9 840 4.6 198 34 28 277.2 305 139.9 15.4 1.7 5 M. Y. Outita 39 7.4 6230 37.8 1704.7 349.2 122.4 3735.9292.8 1139 24.8 7 6 A. El Beida 22 7.6 460 8.5 65 84 18 92.3 219.6 64.2 7 A. Es-Skhoun 25 7.5 440 1.9 51.1 74.8 24.8 87.3 283.6 34.5 18 8 A. H. My. Idriss31 7.2 2850 6.2 282.2 465 106.1 476.4 283.6 1379 12.8 5.2 9 A. Skhinat 33 7.1 1020 6 244 66 38 440.2 292.8 59 11.1 1.3 10 S. Harazem 35 7.3 710 3.8 150 62 36 312.4 256.2 14 9.4 1.7 11 My. Yacoub Fès54 7.2 23430 320 7900 1150 260 13668 219.6 28 30.8 60 12 A. Allah 45 7 450 1.3 50 50 48 71 335 67 11.1 0.4 13 M. Y. Tiouka 24 7.8 27610 143 10230 775 400 15365 756 328 16.3 5.3 14 A. S. Metmata 31 7.6 1120 3 300 50 36 525.4 317.2 36.2 10 15 A. H .Bou Draa 22.5 7.3 540 3.1 75 87.4 29.9 120 271.4 89.7 13 16 2527/15 38 7390 2 57 41 22 149.1 170.8 37.8 11.1 0.4 17 Camp. Rose 28 7.6 1005 2.6 37 60 66 152 329 62 13.2 18 Ben Kachour 51 7.2 2680 14 899 70 51 1391 311 181 26.4 0.1 19 1225 / 12 26 7.4 1040 13 335 14 34 362 133 102.8 13 0.1 20 2843 / 12 28 7.6 1010 2.3 53 61 55 220 154 90.5 10.2 21 2899 / 12 25.5 7.6 620 2.7 80 60 52 230 135 57.6 11.2 22 2933 / 12 27 7.6 650 3.3 55 85 53 230 130 117.7 14.3 23 2952/ 12 46.5 7.1 2960 18 920 114 52 1508 372 192 25.7 0.2 24 2431 / 12 30 6.9 695 1.8 72 70 59 181 353 48 15 25 2364 / 12 26.5 7.4 615 1.6 117 72 58 106 378 172 13.8 26 2363 / 12 28 7.4 700 2.1 69 76 58 135 402 52 12.3 27 Oued Nachef IV33 7.1 870 3 149 66 60 305 378 96 18 0.2 28 Champ de tir 29 7.5 2880 9.8 869 80 50 1363 323 96 16 0.2 29 1255 / 12 29 7.2 640 3.2 179 64 54 255 323 139 12.8 0.1 30 2311/ 12 28 7.1 580 1.7 74 76 56 142 366 33 12 31 1125/ 12 28 7.3 715 1.7 71 74 58 156 347 67 12.4 32 S. Gouttitir 49 7.3 9700 24.7 2472 870 169.2 4110.9 199 2146.11 34.6 33 Tercha 28 7.3 360 1.5 30 37 38 35 268 67.5 12.3 34 Fezzouane 37 7.9 340 1.1 22 70 36 28 292 19.5 15.3 35 Sidi Rahmoune 29 7.4 500 1.7 43 66 44 106 353 24.3 13.2 36 Aichoun 29 7.8 130 1.7 32 74 33 60 341 33.4 12.8 37 S. Aoulout 20.5 7.4 320 2.6 32 55 49 60 341 55.9 12.2 38 S. Kiss 27 7.1 780 45 330 104 52 610 281 176 17.3 39 1292 / 7 24 7.2 755 1.9 94 60 50 184 341 33 12 40 1267 / 7 34.5 7.9 395 0.7 18 60 44 24 378 33 20 0.1 41 22 / 18 26 7.1 870 2.3 162 86 49 273 286 124 13.6 42 62 / 18 27.5 7.2 630 2.8 135 56 62 266 274 76 12.6 43 159 / 18 26.5 7.7 860 2.5 142 56 44 220 268 48 13 44 170 / 18 27.5 7.1 1020 39.9 135 58 68 248 280 187 12.1 45 171 / 18 25 7.9 1740 5.9 219 170 94 433 225 470 12 46 188 / 18 26 7.3 1710 4.1 175 160 94 426 237 350 14 47 35 / 18 29 7.3 625 3 144 56 65 266 274 144 15

6 Zarhloule et al.

Table 2: Chemical geothermometry. Application in Northern of Morocco.

Na/Li Na/Li Na/K Na/K Na/K Na/K Na/K N° Na-K-CaNa-K-Ca Mg/Li Name T (°C)Qz Rof Qz ArnCal RofCal Arn L S H S Arn1 Arn2 Tr Mi Rof Mg 1 A.H.du Zalagh 35.5 58 44 25 29 164 220 84 119 73 119 119 133 34 72 2 A. Anseur 24 40 26 7 12 341 347 222 298 216 298 239.5 167.5 47 55.5 3 A.Maaser 25 61 91 49 91 98 88 67 4 A. S. Trhat 26 54 40 21.5 25 245 282 82 116 70 115.9 117 112 57 5 M. Y. Outita 39 72 59 40 43 171 226 79 113 68 113 115 123 44 56 6 A. El Beida 22 224300 218 300 241 165 67 7 A. Es-Skhoun 25 59.5 46 27 31 114 155.5 103 155.5 146 108 47 8 A. H. My. Idriss 31 48 34 15 19 353254 79 112 67 112 115 98 67.5 52 9 A. Skhinat 33 43 29 10 15 195 244 85 120 73 120 120 112 26 45 10 S. Harazem 35 37 23 4.5 9 280 306 87 122 76 122 122 108 27 51.5 11 My. Yacoub Fès 54 80.5 68 49 52 538272 118 161 107 161 150 165 69 88 12 A. Allah 45 43 28 10 15 237276 89 124 77 124 123.5 96 19 13 M. Y. Tiouka 24 56 42 23 27.5 456242 54.5 82 42 82 91.5 123 29 74.5 14 A. S. Metmata 31 39 25 6.5 11 39 63 26 63 76 84 15 A. H .Bou Draa 22.5 48 34 15 20 120 163 109 163 152 116 45 16 2527/15 38 42 29 10 15 223265 108 148 97 148 141 110 28 33 17 Camp. Rose 28 49 35 16 20 162 189 152 217 188 310 27.5 18 Ben Kachour 51 74 61.5 43 46 741 60 103 48 89 97 270 27 28 191225 / 12 26 48 34 16 20 4581 115 151 104 157 147 346 36 32 20 2843 / 12 28 40 26 7 12 123 158 112 167 155 279 22 21 2899 / 12 25.5 43 29 1015 105 143 94 145 139 270 20 22 2933 / 12 27 51 38 19 23 148 178 138 199 177 302 39 23 2952/ 12 46.5 73 60 41 45 3167 72 114 60 104 108 283 49 41 24 2431 / 12 30 53 39 21 25 86 126 75 121 121 243 15 25 2364 / 12 26.5 50 36 17 22 53 97 41 81 90 214 11.5 26 2363 / 12 28 46 32 14 18 99 137 87 136 133 255 20 27 Oued Nachef IV33 60 46 27 31 128166 74 115 62 106 110 246 14 39 28 Champ de tir 29 55 42 23 27 3469 44 89 32 70 82 244 25 41 29 1255 / 12 29 47 34 15 19 75112 67 109.5 55 98 103 242 15 28 30 2311/ 12 28 45 31.5 13 17 81 122 70 115 117 237 17 31 1125/ 12 28 46 33 14 18 84 124 72 118 119 239 16 32 S. Gouttitir 49 85 73 54 57 59 95 3983 26 63 76 232 84 62 33 Tercha 28 46 32 14 18 134 166.5 123 181 164 281.5 20 34 Fezzouane 37 54 40 21 25 134 166.5 123 181 164 265 35 35 Sidi Rahmoune 29 49 35 16 20 116 152 105 159 148.5 265 26 36 Aichoun 29 48 34 15 19 138 170 128 187 168 279 45 37 S. Aoulout 20.5 46 32 13 18 175 200 166 234 200 320 35 38 S. Kiss 27 58 45 26 30 229 241 223.5 307 245 455 131 39 1292 / 7 24 45 31.5 13 13 74 116 62 106 110 207 10 40 1267 / 7 34.5 63 50 31 35 260294 115 151 104 157 147.5 243 18 29 41 22 / 18 26 50 36 17 21 55 99 43 83 92 221 22 42 62 / 18 27.5 47 33 14 19 75 117 64 108 111 247 12 43 159 / 18 26.5 48 34 15 20 66 109 54 97 103 237 16 44 170 / 18 27.5 46 32 13 17 340 319 344 465 332 545 147 45 171 / 18 25 45 31.5 13 17 90.9 130 79 127 125.5 265 32 46 188 / 18 26 51 37 18 22 82.5 123 71 116.5 118 250 26 47 35 / 18 29 53 39 21 25 75.7 117 64 108 111 249 11

The application of the IIRG diagram (D’Amore et al.1983) The thermal waters are mainly Cl or HCO3-Ca and Mg. (Fig.14 ), show the same results gotten by the Langelier and The parameterize calculated (A, B, C, D, E, F) are reported Ludwing diagram. in Figure and Table . That shows that the thermal springs (1, 3, 4, 5, 9, 10, 11, 13, 14, 18, 19, 23, 27, 28, 29, 38, 41 and % INDICES 42) have a deep circulation in detrital layers , what shows 100 100 N°.12 N°.15, 16 100 N°.1, 3, 4, 5, 9, 11, 13 50 50 50 the influence of the evaporitic rock of the Triasic on the 0 0 0 chemical composition of the water. The springs and a -50 -50 -50 borholes (2, 6, 7, 12, 15, 16, 17, 20, 24, 25, 26, 30, 31, 33, -100 -100 -100 ABCD E F ABCF D E ABCF DE INDICES 33, 34, 35, 36, 37, 39, 40 and 43) have a limestone origin 100 100 100 N°. 2, 6, 7, 10 N°. 14 N°. 8 also revelead by the local geology near of the emergence 50 50 50

0 0 0 zones (36, 37 and 2). The points (21, 22, 44, 45, 46 and 47) -50 -50 -50 show that the waters circulated in the limestone resrvoir in -100 -100 -100 A CFDE ABCF D E ABCF DE B contact with a evaporitic rock of the Triasic. The thermal 100 100 100 N°. 17, 19, 20, 25, 26, 30. N°. 21, 24, 22. N°. 32. springs N°32 and 8 have a deep circulation with influence 50 50 50 0 0 0 of gypseous layers. -50 -50 -50 -100 ABCD EF -100 -100 ABC DEFABCDEF 5.2 Geothermometry 100 100 100 N°. 18, 19, 23, 27, 28, 29. N°. 45, 46. N°.41, 42, 43, 44, 47. 50 50 50 The following geothermometers were applied to estimate 0 0 0 -50 subsurface temperatures and the depth of the thermal -50 -50 -100 ABCDEF-100 -100 aquifers by using the geothermal gradient (Zarhloule, 1999, 100 ABCDEFABCDEF 100 N°. 38, 39. N°. 33, 34, 35, 36, 37, 40. Lahlou Mimi et al 1999): silica (Fournier et Rowe, 1966, 50 A: anhydritic rocks, B: Limestone 50 circulation, C: Deep circulation pro Arnorson et al., 1983), Na/K (Fournier, 1979, Truesdell, 0 0 within the cristalline basement, D: Marl-clay sediments, E: circulat 1976, Michard, 1979, Arnorson et al., 1983, Arnorson, -50 -50 limestone or sulphate reservoir, F: -100 -100 the increasing of cencentration of K A BCDEFAB CDEF 1983), Na-K-Ca ( Fournier and Truesdell, 1973), Na-K-Ca- Mg ( Fournier and Potter, 1979), Mg/Li (Kharaka and Figure 14: IIRG diagram for the water samples Mariner, 1986) and Na/Li (Fouillac and Michard, 1981). investigated. Table 2, shows the temperature estimates from the above geothermometers. Extreme values revealed by each are: 37

7 Zarhloule et al. to 85°C (QzRof), 23° to 73°C (Qz Arn), 7 to 54°C (cal Rof) 54°C. Also the gap between the measured and estimated and from 12 to 57°C (cal Arn). The mesaured températures temperatures (TQRof) are all positive (except N°12) and it are ranges from 20°C to 54°C. ranges from 2.4°C (n°10) to 36.4°C (n°32). On the other hand, several Tcal-Rof and Tcal-Arn are lower than Tm, for In order to evaluate the applicability of those which silica equilibrium seems to be in correspondence with geothermometers (Lahrach et al.1998, Zarhloule, 1999), the Quartz (Fig. 17). estimated values are plotted against the measured values(Tm). Figures 15a-i, show the plots of Tm versus alkaline geothermometers (TNa/K-Arn2, TNa/K-Tr, TNa/K- SIO2 (mg/l) Mi, TNa/K-Rof, TNa-K-Ca, TNa-K-Ca-Mg, TMg/Li, 60 TNa/Li high salinity and TNa/K low salinity).

350 Na/K Arn 2 350 500 Na/K Tr Na/K Mi y= -2x + 221 300 y= -1.8x + 200 300 y= -2x + 156 40 R=0.25 400 R=0.25 R=0.26 250 32 250 N=47 N=47 N=47 200 b 300 c 200 a 150 200 150 100 5 100 100 50

50 0 0 38 20 25 30 35 40 45 50 55 20 25 30 35 40 45 50 55 20 25 30 35 40 45 50 55 20 7 350 Na/K Rof 600 13 y= -2x + 189 Na-K-Ca 150 Na-K-Ca-Mg 300 500 y= -2x + 274 y= 0.5x + 22 R=0.26 d R=0.14 250 N=47 400 R=0.13 N=47 e 100 N=44 f 12 200 300

150 200 Tm (°C) 50 100 100 0 20406080 50 0 20 25 30 35 40 45 50 55 20 25 30 35 40 45 50 0 20 25 30 35 40 45 50 55 90 Mg/Li 350 Na/Li high salinity 600 Na/Li low salinity 80 y= 0.1x + 44 300 70 R=0.05 h 500 y= -1.6x + 259 Figure 17: Application of the silica gheothermometer. N=19 250 R=0.1 60 g 400 N19 i 50 200 y= 1.4x + 79 300 40 150 R=0.5 While the other springs especially for n°5, 7, 13, 32 and 38 200 30 100 N=19 20 100 show a good tendency to ward the chalcedony curve. The 50 10 20 25 30 35 40 45 50 55 0 0 deep reservoir temperatures cannot be lower than the spring 20 25 30 35 40 45 50 55 20 25 30 35 40 45 50 55 discharge temperatures, so the chalcedony temperatures Figure 15a-i: Plot of Tm Vs alkaline geothermometers. appear to be in error for the other springs. So, only the silica geothermometers quartz Rof and quartz Arnorsson seem to The wide spread of the geothermometer values reveal that give plausible values, except for the springs n° n°5, 7, 13, these temperatures can not be considered reliable. This 32 and 38 whose temperature is estimated better by could be explained by a strong possibility of a mixing chalcedony. The silica geothermometer used for the thermal between fresh and deep waters during upflow from the waters in North part of Morocco gave 81°C as a maximum reservoir to surface such mixing could greatly affect all the value (n°11). Similar estimates have also been obtained geothermometry. Also the water composition is greatly through application of the K-Na-Mg technique affected by the interaction with the evaporitic rocks that are (Giggenbach, 1988) summarized in the K/100-Na/1000- ubiquitous in the region. Mg1/2 ternary diagram of Figure 18. where the most of thermal springs are aligned towards the Mg corner, The silica geothermometers have been applied: quartz Rof suggesting very low K2/Mg deep temperatures that varying (TQRof ), quartz Arnorsson (TQArn), chalcedony-Rof between 60 and 100°C, what could be to explaine by the (Tcal-Rof) and chalcedony-Arnorsson (Tcal-Arn). Figure enormous dilution with the waters of shallow aquifers in the 16a-d, shows the plot of TQRof, TQArn, Tcal-Rof and Tcal-Arn against Tm, with the correlation coefficients of 67%. Na / 1000

TQz Rof (°C) T Qz Arn (°C) 90 80 y = 22.76 + 0.94x R= 0.67 N=47 y = 8.12+ 0.97x R= 0.67 N=47 80 70

70 60

60 50 full (a) (b) equilibrium line 50 40

40 30 ° * * Tm (°C) T m (°C) 0 * % 20 * 1 30 20 0 * 0 5 0 20 25 30 35 40 45 50 55 20 25 30 35 40 45 50 55 * * ° 60 60 y = -10.7+ 0.97x R= 0.67 N=47 y = -5.05+ 0.92x R= 0.67 N=47 * * 50 50 * T Cal Rof (°C) Tcal Arn (°C) * ° 0 * 13 40 40 0 3 * 11 * 30 30 * Partial equilibrium x (c) (d) 2 x dilution * 20 20 d 4 x ilu 0 1 ti 1 on 32 10 10

Tm (°C) ° 5 Tm (°C) ° 0

0 0 0 6 immature

20 25 30 35 40 45 50 55 4 1 20 25 30 35 40 45 50 55 2 waters

Figure 16a-d: Plot of Tm Vs silica geothermometers. K / 100 50 % Mg1/2 Temperature estimated by QRof are systematically higher Figure 18: Application of ternary diagram (Giggenbach, than for the other three. It ranges from 37 to 85°C for Qrof, 1988) showing relative cation concentrations 23 to 73°C for QArn, 7 to 54°C for Cal-Rof, 12 to 57°C for for thermal springs. Qcal-Arn. The mesured temperatures ranges from 20 to

8 Zarhloule et al.

The depth of the thermal aquifers in the North part of comparison of all BHT with test temperatures (DST) that Morocco is gotten by the use of the deep geothermal are representive of the actual formation temperatures. In gradient calculated from the petroleum well that ranges order to establish the geothermal gradient of Morocco , the from 19 to 42°C/km (Zarhloule, 1999) and the deep area was subdivided into five hydrogeothermal basins (Fig. temperatures estimated from the geothermometers. The 1): north-eastern basin, north-western basin, Errachidia- depth of thermal aquifers ranges from 524m to 1700m. Boudnib basin, south-western basin and the tarfaya- laayoune-sahara basin. Each basin presents the same 5.3 Schematic and idealized hydrogeological model of geodynamical evolution and is characterised by its specific thermal waters in Northern Morocco. reservoirs and hydrodynamism. For each basin the petroleum well data have been processed. The objective was As shown in Figure 19, the outcropings zones of the Liasic to set a regional geothermal gradient map, and then to aquifer are characterized by shallow cold water and both compilate a geothermal gradient map of Morocco. from cold spring and hydrogeological wells are mainly Ca(Mg)-HCO3 type, resulting from great influence of carbonate rocks. The discharge zones are characterized by 6.1 Processing of temperature values shallow hot water. The hot springs are generaly Ca(Mg)- Temperature behaviour with depth is studied both for the SO4(Cl) or Na-Cl, resulting from infleunce of evaporitic rough BHT (Fig. 21a-g) and DST (Fig.22).. rocks. The midle of the basin shows a communication Southwestern basin of Morocco between the deep and the shallow aquifers and the waters 160 Northeastern basin of Morocco 160 Northwestern basin of Morocco 140 a 140 100 BHT (°C) BHT (°C) b 120 120 BHT (°C) are Ca(Mg)-SO4(Cl) or Ca(Mg)-HCO3. In this zone there is Tbht = 23z + 23 Tbht = 23z + 29 c r = 0.92 100 r = 0.79 100 N= 555 a high dilution of thermal water by the shallow aquifers. N = 53 60 80 80 Tbht = 18z + 29 60 60 r = 0.91 N = 298 Disharge zone 40 40 Depth (m) Thermal springs, high temparature Transtition area Recharge area Depth (m) Depth (m) Cold water S 20 N Ca (Mg)-SO4 (Cl) ou Na-Cl Medium temperature water 20 20 0 2000 4000 Low mixing water Ca (Mg)-SO4 (Cl) ou Ca (Mg)-HCO3 Ca (Mg)-HCO3 0 1000 2000 3000 4000 5000 0 1000 2000 3000 4000 5000 Deep of the reservoir 1700m as maxumum Hihg mixing water 140 Temperature estimated by geothermometer BHT (°C) BHT (°C) 80°C-100°C 90 d BHT (°C) 100 Errachidia-Boudnib- Tarfaya-Laayoune- f Tadla basin e Ouarzazatebasin 100 Sahara basin 70 Plio-Quternary Tufs and clay Alluvions Tbht = 19z + 32 60 Tbht = 25z + 17 (shallow aquifer) Calcareous 50 r = 0.95 r = 0.97 60 Tbht = 19z + 29 Cretaceaous Marl N = 16 N= 49 r = 0.92 Tertiary N= 155 Depth(m) Depth(m) Source froide Jurasic Limestone (deep aquifer) Depth (m) water flow Evaporitic rocks 30 20 20 0 500 1500 2500 Source chaude Permo-Triasic Basalte 0 500 1500 2500 3500 0 2000 4000 Forage artésien d'eau chaude Evaporitic rocks BHT (°C) Marl-Clay 140 g Paleozoïc Basement Morocco BHT: Bottum hole temperature (°C) r: correlation coefficient 100 N: number of temperture BHT z: depth (m) 60 Figure 19: Conceptuel model: relation between Tbht = 20z + 29 r = 0.90 topography, temperature, geochimestry 20 N = 1126 Depth (m) 0 and hydrodynamics. 0 2000 4000 6. DEEP GEOTHERMAL GRADIENT OF Figure 21: BHT vs depth for each basin MOROCCO: PETROLEUM DATA The least squares fitted straight line gave: For BHT(Fig. The aim of this study is to establish a geothermal gradient 21), T= az+Ts, where a is the slope of the straight line and map for the whole of Morocco, by using thermal data the average geothermal gradient measured in the mud, Ts is obtained from petroleum exploration wells. Both the the BHT at the surface and T is the BHT (°C) at any given corrected bottom-hole temperatures (BHT) and the drill- depth z(m). For Morocco the average geothermal gradient is stem test temperature (DST) were used to elaborate the 20°C/km. For the DST (Fig. 22), T=az+Ts, where a is the geothermal gradient map. A total of 410 wells provided averge geothermal gradient of DST, which could be the 1204 temperature values (1126 BHT and 78 DST) (Fig. 20). value nearest the true geothermal gradient, and Ts is the surface temperature, representing the mean annual 16° 14° 12° 10° 8° 6° 4° 2° Tanger Mediterranean sea temperature as indicated by climatic surveys. For Morocco ANS1 N LARA1 Melilla DHT1 IZA1 the geothermal gradient from DST is 24°C/km ATM1 Oujda MAO1 Rabat 34° 10 km Fès 140 DST (°C) a 120 DST (°C) DIR RR1 b 120 Errachidia-Boudnib- ESS1 KAT1 Southeastern basin NDK BHL1 Tadla 100 of Morocco Ouarzazatebasin Essaouira Errachidia 100 Colomb Bechar 32° 80 RH1 à 9 TAT1 10 km AF4 80 RJK1 OZ101 60 Tdst = 23z + 21 Tdst = 25z + 22.5 r = 0.97 r = 0.98 TGA1 40 60 Atlantic ocean Agadir N = 48 N = 14 30° 20 IFNI1 40 ZL1 Depth (m) Depth (m) MO4 AZ1 0 Iles canaries MO8 0 500 1500 2500 3500 0 1000 2000 3000 4000 Tarfaya 100 km 140 160 28° DST (°C) E1 TW7-1 DST (°C) 140 d Laayoune c EAN1 120 Corc1 Tarfaya-Laayoune- 120 Morocco Boujdour Bir Lahlou 100 Boukraa Smara2-17 Sahara basin 100 26° 80 Tdst=26z + 21 80 Tdst = 24z + 23 TW521 Guelta Zemmour r = 0.93 60 60 r = 0.92 TW561 N = 16 Bir Enzaran N = 78 40 24° 40 depth (m) Depth (m) 20 20 0 1000 2000 3000 4000 5000 0 1000 2000 3000 4000 5000 Figure 20: Location of petroleum wells used. Figure 22: DST vs depth for each basin

BHT were systematically corrected for mud circulation With DST values as references, it was possible to calculate ∆ cooling effects either by Horner technique when several the difference ( T) beween DST and BHT at the same depth temperature records are available at a given depth or by the for each value. Plotting the ∆T values with depth (Fig. 23a)

9 Zarhloule et al. gave a curve wich is used a correction abacus. Also, for the 6.2 Geothermal gradient map of each basin Northern part of Morocco, there is no DST values, the Corrected BHT and DST values for each well will be used application of the Horner plot method’s allowed us to to estimate theaverge geothermal grdaient to selected wells correct the BHT tempertures in this area (Fig. 23b). and thus to construct the geothermal gradient map for each hydrogeothermal basin and the compilation of the regional 14 8 ∆ t (°C) Southwestern basin ∆ 12 7 (t) maps allowed us to establish he geothermal gradient for the ∆(t)= 0.003z - 0.86 10 whole of Morocco. r = 0.98 6 8 N= 33 5 ∆(t)= 8.6*logz - 23 r = 0.95 In the North-Western part of Morocco (Fig. 24a) the deep 6 4 N= 9 geothermal gradient ranges from 26°C/km to 35°C/km . 4 3 Errachidia-Boudnib- 2 2 Ouarzazate basin Zones of relatively high geothermal gradient seem to z (m) 0 z (m) correspond to zones proved or supposed faults. Also the 0 1000 2000 3000 4000 5000 1000 2000 3000 4000 14 anomalies are related to deep hydrodynamic activities ∆ ∆ (t) (°C) Morocco (t) (°C) 12 (Zarhloule, 1999). 4 10 ∆(t)= 0.002z + 0.062 r = 0.85 The spatial distribution of geothermal gradients in the 8 N = 60 3 North-Eastern Morocco (Fig. 24b) could be related to the ∆(t) = 3.5logz-8.5 6 r = 0.93 4 hydrodynamic effects and the neotectonic associated to the 2 N = 18 2 recent volcanim. It ragnes from 15 to 42°C/km (Zarhloule, z(m) 1 Tarfaya-Laayoune- 0 1999). Sahara basin 0 1000 2000 3000 4000 5000 z(m) 6° 5° 0 N 0 1000 3000 5000 Sebta Figure 23a: ∆T vs depth Tanger Mediterranean Sea 160 Measured tempertures values 160 Extrapolated temperatures values BHT (°C) Larache BHT corrected (°C) BHT = 0.03z + 8.6 N 120 120 A r = 0.86 35° E N = 15 C O 26 C 80 80 I T BHTc = 0.035z + 4 N 28 A 30 40 40 r = 0.9 L 32 T N = 15 A 32 30 Depth (m) Depth (m) 0 0 34 Fes 0 500 1500 2500 3500 0 500 1500 2500 3500 Rabat 28 34° 26 28 Figure 23b: Application of Horner plot method’s. 100 km Thus, after correcting all the BHT values, we plotted 28 geothermal isogradient curve (°C/km), petroleum borhole coorected BHT and DST with depth (Fig. 24a-g). The least squares fitted straight line gave: T= az + Ts, where T is the Figure 24a: Geothermal gradient map of the North- undergroud temperature at any given depth z, a is the slope, representing the average geothermal gradient in the region western basin of Morocco. (28°C/k for north-eastern basin, 27°C/km for north-western N 4° 3° N basin, 28°C/km for Errachidia-ouarzazat-Boudnib basin, Mediterranean sea 21°C/km for the south-western basin, 21°C/km for the El Hoceima Melilla tarfaya-laayoune-sahara basin, 22°C/km for Tadla basin and 35° 23°C/km for the whole of Morocco) and Ts is the surface temperture. Oujda 42

200 140 BHTc (°C) Northeastern basin BHTc(°C) BHTc (°C) a DST(°C) 160 b 38 150 North western basin South western c Taza T = 28z + 19 100 34 r = 0.85 basin N = 54 100 34° T = 21z + 28 30 80 60 T = 27z + 25 r = 0.95 50 r = 0.94 N = 346 26 N = 556 20 z (m) z (m) z (m) 0 0 0 0 2000 4000 0 1000 2000 3000 4000 5000 0 2000 4000 26 22 140 140 BHTc (°C) BHTc (°C) BHTc (°C) 90 DST (°C) DST (°C) f Tadla basin d 100 Errachidia-Boudnib- e 100 Ouarzazate basin 30 70 33° T = 22z + 31 60 T = 21z + 28 18 r = 0.96 T= 28z + 16 60 r = 0.93 50 N = 16 r = 0.98 N = 63 N = 171 20 20 Tarfaya-Laayoune- z(m) z (m) Sahara basin z (m) 100 km 30 0 0 0 1000 2000 3000 0 1000 2000 3000 4000 0 2000 4000 200 BHTc and DST (°C) g 18 geothermal isogradient curve (°C/km), Petroleum well BHTc: corrected BHT(°C) 150 Morocco DST: drill steam temperature z: depth (m) 100 r: correlation coefficient Figure 24b: Geothermal gradient map of the North- N: number of temperatures T = 23z + 28 T: Temperture 50 r = 0.92 Eastern basin of Morocco. N = 1205 z (m) 0 1000 3000 5000 In the South-Western basin (Fig. 24c), the higher geothermal gradient observed in the center could be the Figure 24: Corrected temperature vs de consequence of proximity to the Tidsi diapir, given the high thermal conductivity of evaporitic rocks (Zarhloule et al., 1998). Also the anormal geothermal gradient is related to

10 Zarhloule et al. the deep hydodynamic effects (oxfordian reservoirs) The regional distribution of geothermal gradients in the (Zarhloule, 1994). In the South of the basin, the geothermal Errachidia-Ouarzazate- basin (Fig. 24e) shows that gradient is related to the basement faulting. the relatively high geothermal gradients could be related to subsidence and the basement proximity, respectively, in Turonian N Jurassic the south-eastern and southern sectors in the basin Triasic (diapir) 10 km Permian (Zarhloule, 1999). Petroleum well Fault Fault 21 N 5° 3° N 25 isogradient curve (°C/ km) High-atlas

19 28 26 22 17 N 20 Errachidia

23 28 24 Safi 31° 30 ntic 21 26 Atla Senonian Paleozoïc South-atlasic fault 32° Petroleum borehole Kourati Mountain's geothermal isogradient 30° 30 curve (°C /km) 30 km Oean Hadid Mountain's Figure 24e: Geothermal gradient map of the Errachidia- 21 23 Ouarzazate-Boudnibe basin. Essaouira 21 25 23 25 27 25 21 For the whole of Morocco (Fig. 25) the geothermal gradient 27 varies from 15 to 42°C/km. A distinction can easily be made 29 25 27 29 23 between zones of high geothermal gradient (>30°C/km) and 27 21 others of low geothermal gradient (<30°C/km). The major part of the region is characterized by low gradient ranging Ihchech Mountain's from 20 to 30°C/km. The areas of high gradient marked in 31° Amsitene Mountain's 23 the regional maps (Fig. 24a-e) are in the geothermal 27 gradient map of Morocco (Fig. 25). The isogradient curves

25 dispaly several main directions where the geothermal anomalies are related to deeper hydrodynamic, recent 21 29 31 tectonic, volcanism or to elevation of the Moho (Zarhloule, 1999, 2003). Agadir

33 27 16° 14° 12° 10° 8° 6° 4° 2° 29 Sebta Tanger MIDITERRANEAN SEA 31 N 25 Anti-Atlas LAR.A1 Melilla 10° 9° 35 Oujda 30 30 30 Kénitra Fès 34°

Figure 24c: Geothermal gradient map of the South- Azemmour 30 25 Azrou Western basin of Morocco. 25 20 Tadla Algeria 30 25 25 Errachidia Essaouira 32° The Tarfaya-Laayoune-Sahara basin (Fig. 24d) presents two Marrakech25 25 20 30 30 domains with a relative high geothermal gradient: the on- Agadir Ouarzazat shore domain characterized by a great fault basement of 20 ATLANTIC OCEAN 30 N65 to N70 direction revealed by geophysics, and the off 30° 25 shore domain where the Miocene volcanoes of the Canary 30 Islands contribute to increased geothermal gradients 30 30 (Zarhloule, 1999). Tarfaya 28° 25 Laayoun

16° 10° Boujdour 20 32 30 26 28 24 26° 29° 28 26 34 Deep Geothermal gradient GG. (°C/km) CANARIAS 26 32 Guelta Zemmour GG > 35 24 Dakhla 30 < GG < 35 32 Bir Enzaran Tarfaya Tindouf 30 25 < GG < 30 24 24 2 0 < GG < 25 0 100 km ATLANTIC 26 2 0 < GG Laayoune 22 Deep geothermal anomalies Boujdour Samara 20 OCEAN 26

N 22 Figure 25: Geothermal gradient map of Morocco. 25° 24 Dakhla 7. SYNTHETIC GEOTHERMAL APPROACH AND CONCLUSION. Geothermal studies of sedimentary basin have revealed lateral as well as vertical variations in the temperature fields. These 100 km N variations are commonly interpreted as resulting from thermal Petroleum borehole conductivity heterogeneities or local variations in basement heat 20 MAURITANIE geothermal isogradient curve (°C/km) flow. Variations many also result from groundwater flow systems. The movement of water in deep aquifers can significantly perturb Figure 24d: Geothermal gradient map of Tarfaya- the local underground temperature distribution in sedimentary Laayoune-Sahara basin. basins (Zarhloule, 1994).

11 Zarhloule et al.

In sedimentary basins of Morocco, the treatment and the Fouillac, C., and Michard, G.: Sodium/Lithium ratio in compilation of geological, geophysical and hydro-geothermal data water applied geothermometry of geothermal allowed the construction of a conceptual model showing the reservoirs. Geothermics, 10, 55-77, 1981. relationships between topography, hydrodynamism, chemistry and temperature of the all hot aquifers in Morocco (Fig. 26). Fournier, R.O.: A revised equation for the Na/K geothermometer. Ress.Coun.Tran, 3, 221-224, 1979. Potential mixing zone Discharge zone Recharge zone T(°c) T(°c) T(°c) Z(m) Z(m) Z (m) Fournier, R.O., and Potter, R.W.: Magnesium correction to Meduim Apparent shallow geothermal gradient (GGSA) Higher GGSA Low to negative GGSA Medium mesured temperature of water (Tm) (24-29°C) High Tm (30-54°C) Low Tm (< 23°C) High dilution of thermal waters Only the silica geothermometrs seem to Infiltration of meteoric Water the chemical geothermometer. Geochimica Cold area give a plausible values. Alimentation Low dilution of the thermal waters Cold area Cosmochimica Acta, 43, 1543-1550, 1979. High temperature of the reservoir. It's depend of deep geothermal gradient Alimentation Transition area Zone of thermal anomalies and shallow indices Hot area "mixing" Fournier, R.O., and Rowe, J.J.: Estimation of underground * + temperatures from the silica content of water from hot springs and west steam wells. American Journal of Sciences, 264, 685-697, 1966.

Fournier, R.O., and Truesdell, A.H.: An empirical Na-K- Aquiclude Ca geothermometer for naturel waters. Geochimica Plio-quaternary aquifer

Aquiclude Cosmochimica Acta, 37, 1255-1275, 1973.

Deep aquifer (hot water) T(°c) + * Well in the artesia zones Plio-quaternary well Thermal spring Z(m) shallow thermal profil Giggenbach, W.F.: Geothermal solute equilibria; derivation of Na-K-Mg-Ca geoindicators. Geochimica Cosmochimica Acta, 52, 2749-2765, 1988. Figure 26.Conceptual model of circulation of hot water of the different aquifers in Morocco: Kharaka, Y.K and Mariner, R.H.: Chemical relationship between hydrodynamism, geothermometers and their application to formation temperature, chemistry and topography waters from sedimentary basins. Proceedings, (schematic section). Thermal History of Sedimetary Basins, Spriga-Verlag, The recharge zones are characterized by shallow cold water, New York, pp. 99-117. (1989). low apparent geothermal gradient, negative anomalies and high topography. The waters are mainly HCO3-Ca-Mg type, Lahlou Mimi, A., Zarhloule, Y., Bouri, S., Ouda, B., resulting from the great influence of carbonate rocks. Lahrach, A., Ben Aabidat, L., and Ben Dhia, H.: Géochimie des eaux chaudes et prospection The discharge zones are characterized by shallow hot water, hydrothermale au Maghreb (NW): Caractérisation du high apparent geothermal gradient, positive anomalies and réservoir d'origine et indices thermiques. Bulletin de low topography. The hot springs are generaly Ca (Mg)-SO4 Liaison Scientifique Afro-Québécoise, canada, II, 89- (Cl) or Ca (Mg)-HCO3 type, resulting from the main 104, 1999. influence of evaporitic rocks. Lahrach, A., Zarhloule, Y., Ben Aabidat, L., Bouri, S., Ben The middle of the basin shows a low apparent geothermal Dhia, H., Khattach, D., Boughriba, M., El Mandour, A., gradient. However, the communication between the deep and and Jebrane, R.: Géochimie des eaux chaudes et the shallow aquifers found expression in a potentiel mixing prospection géothermique de surface au Maroc zone, with a hot water and a high apparent geothermal septentrional: caractérisation du réservoir d'origine et gradient. indices thermiques. Revue Hydrogéologie, BRGM, , 3, 7-23, 1998. In general the shallow geothermal gradient is high near hot springs. Hot springs represent discharge from deep reservoir, Leschak L.A., and Lewis, J.E.: Geothermal prospecting with and upward moving growndwater flow. The upward moving shallow-temperature surveys. Geophysics, 48, 975-996, water may come from the centre of the basin and the 1983. discharge zone may be related to the hydrologic limit of the aquifer or to the existence of faults or fractures. Michard, G.: Geothermomètres chimiques. Bulletin, BRGM, Sect. III, 2, 183-189. 1979.

REFERENCES Sass, T.H., Lawyer, L.A., and Munroe, R.J.: Aheat flow Arnorsson, S.: Chemical equilibria in Icelandic geothermal reconnaissance of southeastern Alaska. Can. Jour. systems-implication for chemical geothermometry Earth Sciences, 22, 416-421, 1984. investigations. Geothermics, 12, 119-128, 1983. Smith, C.: Thermal hydrology and heat flow of Beowawe Arnorsson, S., Gunnlaugsson, E., and Svavarsson, H.: The geothermal area, Nevada. Geophysics 48, 5, 618-626, element of geothermal waters in Iceland III chemical 1983. geothermometry in geothermal investigations. Geochimica. Cosmochimica Acta, 47, 567-577. 1983. Truesdell, A.H.: Geochimical techniques in exploration. Proceedings, 2th U.N. Symposium on development and Ben Dhia, H., Jones, F.W., Meddeb, N., Lucazeau, F., and Use of Geothermal Resources, San Francisco 1, Liii- Bouri, S.: Shallow geothermal studies in Tunisia, Ixiii, Summary of Section III (1976). comparison with deep subsuraface information. Geothermics, 21, 4, 503-517, 1992. Zarhloule, Y.: Potentialités hydrogéothermiques du bassin d'Essaouira-Agadir (Maroc). Doctorat de Spécialité. D’Amore, F., Scandifio, G., Panichi, C.: Some observation Ecole Nationale d’Ingénieurs de Sfax sfax, Tunisie. on the chemical classification of ground waters. 240pp. 1994 Geothermics, 12, 141-148, 1983.

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Zarhloule, Y. : Les Potentialités géothermiques du Maroc: (Maroc). Journal of African Earth Sciences 27, 71-85, Approche intégrée par les températures profondes et 1998. indices de surface. Doctorat d’Etat es sciences. Faculty of Sciences, Oujda, Maroc, 153pp, 1999. Zarhloule, Y., Lahrach, A., Ben Aabidat, L., Khattach, D., Bouri, S., Boukdir, A,. and Ben Dhia, H.: La Zarhloule, Y. : La carte du gradient Géothermique du prospection géothermique de surface au Maroc: Maroc, submitted to Bulletin de l’Institut scientifique, hydrodynamisme, anomalies géothermiques et indices Section Sciences de la Terre, Rabat Maroc, 2004. de surface. Journal of African Earth Sciences, 32, 851- 867, 2001. Zarhloule, Y.: Overview of geothermal activities in Morocco, Proceedings, International Geothermal Conference, Zarhloule, Y., Lahrach, A., Khattach, D., Beni Akhy, R., and Mutiple integrated uses of geothermal ressources, Ben Dhia, H.: Geothermal Gradient Map of the South Reykjavik 14-17 september, Iceland, 1-8 (2003). Western Morocco Basin. Bulletin of The Moroccan Association Of Petroleum Geologists. 3/99 , 10-12, Zarhloule, Y., Lahrach, A., Ben Aabidat, L., Bouri, S., Ben 1999. Dhia, H., and Khattach, D.: Anomalies géothermiques de surface et hydrodynamisme dans le bassin d'Agadir

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