PINSTECH-202 Investigation of Geothermal Fields in Himalayan Range in Pakistan Using Isotope and Chemical Techniques

PINSTECH-202

Investigation of Geothermal Fields in Himalayan Range in Pakistan Using Isotope and Chemical Techniques

Manzoor Ahmad Muhammad Raflq Sheikh WaheedAkram M. Azam Tasneem Naveed Iqbal Zahid Latif

Isotope Application Division Directorate of Technology Pakistan Institute of Nuclear Science and Technology P. O. Nilore, Islamabad. July, 2007 CONTENTS

1. INTRODUCTION 1 2. NORTHERN AREAS 1 2.1 Tectonic Setting 2 2.2 Geology and Thermal Manifestations 3 3. KOTLI 3 3.1 Geology and Regional Setting 3 3.2 Stratigraphy 4 3.2.1 Muzaffarabad Formation 4 3.2.2 Patala Formation 4 3.2.3 Margalla Hill Limestone 4 4. MATERIALS AND METHODS 5 5. RESULTS AND DISCUSSION 5 5.1 Hydrochemistry 6 5.1.1 Northern Areas 6 5.1.2 Kotli 6 5.2 Recharge Sources and Subsurface History 9 5.2.1 Tatta Pani and Tato 9 5.2.2 Mutazaabad Area 11 5.2.3 Kotli 16 5.3 Chemical Geothermometry 17 5.3.1 Murtazabad Area 17 5.3.2 Tatta Pani and Tato Fields ... 20 5.3.3 Kotli , 23 5.4 Isotope Geothermometry 23 6. CONCLUSIONS 24 ACKNOWLEDGMENTS 26 REFERENCES 27

] Abstract

There are many geothermal sites in Himalayan belt of Pakistan having low to high temperatures (boiling water). Isotopes and geochemical techniques were applied to investigate the origin, subsurface history and reservoir temperatures of geothermal fields at Tatta Pani and Tato lying along Main Mantle Thrust, Murtazabad along Main Karakoram Thrust and Kotli in the area of overlapping thrusts: Punjal Thrust, Main Boundary Thrust and the Himalaya Frontal Thrust. Discharge of the springs varies from 30 to 2000 liters per minute with the surface temperature from 47.3 to 92°C. Two sets of water samples were collected from these fields. The samples were analyzed for various isotopes (I80, 2H & 3H of water; 13C of dissolved inorganic carbon; 34S & ,sO of dissolved sulphates); and water chemistry. The thermal waters of the Northern Areas of Pakistan are generally neutral to slightly alkaline and have low dissolved contents. Sodium is the dominant cation in all the cases. In terms of anions, HC03 is dominating. Source of recharge is meteoric water (rains and/or snow-melt). The dominant process of cooling is conduction at Tatta Pani, Tato, and Murtazabad. Shallow groundwater is mixing with the thermal springs in different proportions at Murtazabad, while there is no mixing in the thermal waters of Tatta Pani and Tato. The equilibrium temperature of the thermal end-member at Murtazabad is in the range of 185- 225°C and the isochemical-mixing model based on the Na-K. and quartz 1S geothermometers estimates 227°C temperature. A 0(S04-H20) geothermometer indicates equilibrium temperatures (before mixing) above 185°C. The dissolved silica vs. enthalpy plot suggests heat losses through conduction from the original temperature about 245°C. The reservoir temperatures of Tatta Pani (100-130°C) determined by the Na-K, K-Mg and quartz geothermometers are in good ls agreement. A O(S04-H20) geothermometer indicates equilibrium temperatures around 150°C. For the Tato springs, the isotope and chemical geothermometers (except for the K-Mg) agree on equilibrium temperature of about 170-200°C. Thermal waters of Kotli are immature having meteoric origin. They are of sodium bicarbonate type. The thermal water seems to be young or significant component of fresh water is mixing. Reservoir temperatures estimated by K-Mg and Na-K- Ca-Mg thermometers have similar range (122-125°C). Geothermometer based on dissolved silica gives reservoir temperature about 100°C.

ii- Investigation of geothermal fields in Himalayan Range in Pakistan using isotope and chemical techniques

1. INTRODUCTION

Determination of origin, subsurface history including processes involved and residence time, and reservoir temperature are the major aspects in exploration of geothermal resources. During the last few decades, various geochemical and isotope techniques have been developed and extensively used for geothermal investigations [1-10], Most of the high enthalpy geothermal resources of the world are within seismic belts associated with zones of crustal weakness such as plate margins and centers of volcanic activity. A global seismic belt passes through Pakistan and the country has a long geological history of geotectonic events: Permocarboniferous volcanism (Panjal traps in Kashmir) as a result of rifting of Iran- Afghanistan micro-plates [11], Late Jurassic to Early Cretaceous rifting of the Indo-Pakistan Plate [12], widespread volcanism during Late Cretaceous (Deccan traps) attributed to the appearance of a "hot spot" in the region, emergence of a chain of volcanic islands along the margins of the Indo-Pakistan Plate [13-14], collision of India and Asia (Late Cretaceous- Paleocene) and the consequent Himalayan upheaval [12], and Neogene-Quaternary volcanism in the Chagai District (Koh-i-Sultan Volcano). This geotectonic framework suggests that Pakistan should not be lacking in commercially exploitable sources of geothermal energy. This view is further strengthened by the fairly extensive development of alteration zones and fumaroles in many regions of Pakistan, presence of a fairly large number of hot springs in different parts of the country, and indications of Quaternary volcanism.

In the Northern Areas of Pakistan, preliminary study of six geothermal fields were carried out within the frame work of IAEA Coordinated Research Programme for Africa, Asia and the Middle East on the Application of Isotope and Geochemical Techniques in Geothermal Exploration. Keeping in view the encouraging results of the study, Pakistan also participated in the IAEA/RCA Project RAS/8/092 "Investigating the Environment and Water Resources in Geothermal Areas" and investigated major geothermal fields viz. Murtazabad, Tatta Pani, Tato and Kotli of Himalayan Range in the country. About thirty-three hot springs were studied. Discharge of these springs ranges from 0.5 to 30 liters per second (L/s) and surface temperatures vary from 47.3 to 92°C. As shown in the plates, some of the springs discharge boiling water. Recharge sources and subsurface processes of the thermal reservoir were investigated and different geothermometers were applied to estimate the reservoir temperatures. The locations of these fields are shown in Fig. 1.

2. NORTHERN AREAS

The Northern Areas, located between the latitudes 35° 20' N to 36° 30' N and longitudes 74°E to 76°E, host the major geothermal fields of Pakistan. These areas are characterized by steep topography and U-shaped glaciated valleys, which are drained by the rivers Indus, Gilgit and Hunza, while the rivers Shigar, Shyok, Ishkuman and Yasin form the major tributaries to the main rivers. Important mountain ranges of the area are the Kailas, Rakaposhi, Masherbrum and Karakoram. Cold winters and warm and dry summers characterize the climate. June-August are the hot months during which mean maximum

1 temperature is about 30°C. Snowfall occurs during the cold months of December-February when minimum temperature goes several degrees below the freezing point. Rainfall is scanty.

^ Lahore »je QmVa / Ji<"«" I

•34*N»

^ /s

Fig. 1. Map showing major tectonic features of Himalayan range and study sites

2.1. Tectonic Setting

The geotectonic development of the Northern Areas of Pakistan during late Cretaceous to Cenozoic involved three tectonic elements, i.e.: the Indo-Pakistan shield and its northern sedimentary cover (Indian Mass), the rocks deposited on the southern part of the Eurasian Mass, and the Kohistan Island Arc Sequence [12]. From Archaean times, the Indian Sub-Continent was a part of Gondwanaland, which consisted of the continents of South America, Africa, Antarctica, Australia and India. A vast stretch of the Tethys Sea existed between the Indo-Australian part of Gondwanaland and the Eurasian Mass. About 130 million years ago, the Indian Ocean plate broke away from Gondwanaland and started drifting towards Eurasia with the simultaneous consumption of the Tethys Sea Plate in between [15]. As a result of subduction, the Kohistan Island Arc Sequence was produced to the north of the subduction zone. The first contact of this Island Arc was with the Indo- Pakistan plate that finally collided: with the Eurasian Mass. The Kohistan Island Arc Sequence is juxtaposed between the Indo-Pakistan plate and the Eurasian plate. A major thrust fault called the Main Mantle Thrust (MMT) separates the Indian Mass from the Kohistan Island Arc Sequence while another thrust fault called the Main Karakoram Thrust (MKT) marks the boundary between the Kohistan Island Arc Sequence and the Eurasian Mass. The geothermal manifestations under investigation lie along these faults, which are still active. A substantial amount of heat is presumably generated by frictional movement along these faults [16], However, these faults might simply act as uprising routes of deeply

2 circulating waters of possible meteoric origin, which become thermal because they come into contact with relatively hot rocks present at relevant depths. The major tectonic features of the Northern Areas of Pakistan along with the locations of geothermal fields are shown in Fig. 1.

2.2. Geology and Thermal Manifestations

The oldest rocks of the Indian Mass are the Salkhala Series, which are involved in the Nanga Parbat metamorphic rocks and constitute a substantial part of the massif. The main rock types are slate, phyllite, various types of schists, paragneisses, sandstone and quartzitic crystalline conglomerate, which are intruded by basic-to-acidic igneous rocks. The rocks constituting the Kohistari Island Arc Sequence consist of a thick series of calc-alkaline plutonic, volcanic and volcano-sedimentary rocks, Jurassic-Cretaceous in age [16]. The rocks of the Eurasian Mass north of MKT are late-Paleozoic metasedimentary rocks, mainly flysch (limestone- and shale-dominant), which are considered deep-sea sediments deposited by turbidity currents along the Eurasian plate margin in the northern Tethys geosyncline [15].

Tatta Pani springs flow from unconsolidated to semi-consolidated fluvial deposits or talus. Amphibolites fractured by the MMT constitute the hard rocks exposed around these geothermal manifestations. Tato spring emerges from semi-consolidated fluvial and moraine deposits. It lies about 1200 m above Tatta Pani springs. Murtazabad springs flow from a steep cliff that is made up of coarse-grained fluvial deposits. The hard rocks exposed around the manifestations are garnet-staurolite schist and lime-silicate marble of the Baltit Group, which is assigned to the lower Paleozoic to Precambrian age. The Karakoram Granodiorite Belt is located 15 km to the north of the manifestations. The manifestations at Murtazabad lie north of the MKT [16].

3. KOTLI

Kotli is located in Azad Jammu and Kashmir region (Long: 73° 54; and Lat: 33° 327). There are five hot springs in this field having surface temperature from 54 to 62°C. Two sets of water samples were collected and analyzed for environmental isotopes and water chemistry.

3.1. Geology and Regional Setting

The Kotli-Tattapani area is a part of the sub Himalayan mountain belt. The rocks of the area record tectonic history varying from Precambrian to Recent. The larger scale tectonic structure of the region is characterized by syntaxial band. As the study area lies in Hazara Kashmir syntenial belt, which is region of rapid uplift as, indicated by locally increased steam gradient [17] and regionally anomalous topography.

Hazara Kashmir syntanics consists of a series of overlapping thrusts. These thrusts are Punjal Thrust, Main Boundary Thrust and the Himalaya Frontal Thrust. The Murree Thrust corresponds to the Main Boundary Thrust in India. The Hazara Kashmir syntaxis is cut by the Jhelum left lateral slip fault. It terminates the Hazara Swat Foreland Fold and Kashmir Foreland Fold and thrust belt on the eastern limb in Azad Jammu & Kashmir [18].

3 3.2. Stratigraphy

The project area is a part of Kashmir foreland and thrust belt, which lies along the eastern limb of the Hazara Kashmir Syntaxis in sub Himalayas. The whole study area comprises sedimentary rocks ranging in age from Pre-Cambrian to recent. Pre-Cambrian to Cenozoic sequence is exposed in the area under study. The Pre-Cambrian Muzaffarabad formation overlie the Cenozoic rocks due to up lifting and erosions.

The stratigraphic sequence includes the Pre-Cambrian Muzaffarabad formation equivalent to Jammu limestone in occupied Kashmir and Muzaffarabad limestone near Muzaffarabad. Early Eocene Patala Formation and Lophant Margalla Hill Formation middle to late Eocene Miocene Murree Formation. The early Paleocene Nagri Formation, the Chingi Formation Middle Miocene, Dhok Pathan Formation and Mirpur conglomerates and quaternary alluvium. Two unconformities observed in the stratigraphic sequence first lies between Pre-Cambrian and Cenozoic and second below the quaternary alluvium of the area.

3.2.1. Muzaffarabad Formation;

The Muzaffarabad formation comprises shales, dolomites, cherty dolomites, chert bands, limestone and arenaceous limestone, stomalite and quartzite. The Muzaffarabad formation extends and exposed from Tattapani to Dandli area and further extension is towards Nikyal. Muzaffarabad formation can be divided into three units. Lower Part comprise grey to dull grey shales, arenacious limestone and dark limestone. The limestone is thinly bedded and fractured. The middle part comprises of dolomite, massive and thickly bedded cherty dolomite. In upper part fine to medium grained cherty dolomite and quartzite rocks are present. The thickness of formation is about 485 m. On the basis of stratigraphic correlation with early Cambrian Sirban Formation of the Abbottabad group and Amber Formation of Peshawar basin age can be assigned early Cambrian [19].

3.2.2. Patala Formation:

In Kotli area, the Patala Formation usually overlies the bauxite and fire clays; however, at places it is directly underlain by the Sirban Formation. The absence of bauxite fire clays may probably be the result of their complete erosion in such localities before the deposition of Patala Formation. The formation is composed of Light brown, dark grey to black shales with subordinate (0.3m thick) interbedded limestone. Shales are generally silty and splintery, however, sandy shales have also been noticed as in Dandili. Lenticular good quality coal seams are found at two horizons within these shales. The lower horizon is near the contact of Patala Formation with bauxite-fire clay, whereas the upper horizon is approximately 15m above the lower horizon. Another important feature is the repetition of yellowish brown, ferruginous mudstones or muddy iron stone beds, which are 10-30cm in thickness. These occur nearly 22 m above the contact with bauxite. Good exposures of these beds have been found in Newal, Dhanwan and Dandili area. The thickness of formation is 43m in Nakial area and the age of the formation is Paleocene.

3.2.3. The Margala Hill Limestone:

The Margala Hill Limestone over lies the Patala Formation with a transitional contact. The formation is separated from Patala Formation on the basis of fauna, and higher proportion of limestone to shale. The formation is composed of grey, dark grey to black

4 limestone with subordinate greenish gray shales. The limestone is fine to medium grained, medium to thickly bedded, whereas the shales are silty and splintery in nature. Sill and dykes of basic composition have been observed in the many part of the Tattapani area. The main occurrences in the study area associated with dolomites near Tattapani. The formation is Eocene.

MATERIALS AND METHODS

Two sets of water samples from hot springs were collected for chemical analysis and determination of isotopes: 2H, ,80 & 3H (water), ,80 & 34S (sulphate), and 13C (TIC). Physico-chemical parameters such as temperature, pH and electrical conductivity (EC) were determined in the field. A total of seven sample aliquots were collected for each hot spring site for chemical and isotopic analyses. Where filtration was required, a 0.45 u.m pore diameter filter was used. The volume of the sample and treatment in the field for various analyses are given below.

Analysis Volume Treatment Anions (CI, HC03, S04) 1L Unfiltered, unpreserved Cations (Na, K, Ca, Mg) 250 mL Filtered, acidified with HN03 Silica 100 mL Filtered, diluted with deionized water (1:1) Stable isotopes: (180,2H) 500 mL Unfiltered, unpreserved ,3C (DIC) 100 mL Filtered and poisoned 18O^ , ^S34c (Sulphate/c ) 1L Filtered Tritium IL Unfiltered, unpreserved

Chemical analyses were carried out using: atomic absorption spectrophotometry for Na, K, Ca and Mg; UV-visible spectrophotometry for Si and SO4; titrimetry for HCO3; and ion selective electrode for CI [20]. The 5I80 value of the water was measured by mass spectrometer using the CO2 equilibration method [21]. For analysis of 81 O of dissolved sulphates, the sulphates were precipitated as BaS04 in the field [9]. The co-precipitated carbonate was removed by reacting with hydrochloric acid, and BaS04 was obtained in powder form. The BaS04 was reacted with graphite in a vacuum system to convert its total oxygen into CO2 [22] which was analyzed on the mass spectrometer for 834S. 5180 values of water and dissolved sulphate were analyzed relative to VSMOW with a standard error of ±0.1 %o. The tritium content of the samples was determined by liquid scintillation counting after electrolytic enrichment of the water samples with a standard error of ±1 TU [23].

RESULTS AND DISCUSSION

The discharge temperature of the hot springs of Tatta Pani and Tato varies from 48 to 89.5°C while that of the thermal waters of Murtazabad has a range from 47.3 to 92°C. One spring at Murtazabad (HS-10) and the Tato springs discharge almost boiling water with temperatures of 92°C and 89.5°C, respectively. All the thermal waters in the area are neutral to slightly alkaline. Considering both the samplings, the hot springs of Tatta Pani have pH values from 7.8 to 8.9 while those of Murtazabad have pH values in the range of 6.5 to 9.0 and Tato springs have pH about 9.0. The Tatta Pani hot springs have EC values in the range

5 of 860-1046 u,S/cm and Tato springs 1180-1261 |j,S/cm, whereas Murtazabad hot waters are relatively more saline (EC = 1833 to 2560 u^S/cm).

5.1.! Hydrochemistry

5.1.1. Northern Areas

The triangular plots for the major cations (Fig. 2) and anions (Fig. 3) are used to explain the chemical facies of thermal waters. Na is the dominant cation in all cases. The relative concentrations of the main anions show that these hot waters are HC03 type except two springs, which is S04 type. Therefore, these thermal waters are Na-HC03 type except one sample from Murtazabad, which is Na-S04. These Na-rich compositions are typical of comparatively evolved waters circulating mainly in gneissic and granitic rocks. In the thermal waters of Murtazabad area, HCO3 is the dominant anion and it ranges from 49 to 72% (meq/L) except HS-10 and HS-16, which are S04 type. Following, the varying HCO3/SO4 ratios of the Na-rich waters could be attributed to the relative importance of: (a) dissolution under oxidizing conditions of sulfide minerals, which brings about production of H2SO4, and subsequent neutralization of H2SO4 by reaction with silicates, mainly feldspars, vs. (b) H2C03-driven dissolution of silicates, mainly feldspars. The first process gives rise to Na- S04 waters, whereas Na-HC03 waters result from the second process which would be dominant in the present case. H2S smell is also noted in the thermal springs, so an input of S- bearing gases from below and subsequent oxidation of reduced-S species to sulfate, as observed in high-temperature geothermal areas [8, 24] could also explain the transition from HCO3 to SO4 waters. This evolution could also reflect dissolution of CaS04 accompanied by precipitation of CaC03, as hypothesized for the Tekke Hmam thermal springs, near Kizildere, Turkey [25]. At Murtazabad, however, this process seems unlikely due to the absence of evaporitic rocks. As discussed below, mixing of shallow water with the thermal springs in varying proportions also changes water chemistry. Although data for the shallow groundwater are not available, mixing trends indicate that it is likely to be relatively rich in Ca, Mg and HCO3.

At Tatta Pani geothermal field, all the thermal waters are Na-HC03 type having Na >90% and HCO3 varying from 45 to 60% with the second dominant anion as S04 (20-35%). The thermal water of Tato spring in the nearby, area also has Na-HC03 facies. All the Tatta Pani springs are located along a line in a zone about 1 km wide, and have almost the same total dissolved solids and no tritium (0 TU). It seems that the same thermal water splits into different paths during upward movement towards the surface.

5.1.2. Kotli

Thermal waters of Kotli have low dissolved salts as indicated by their EC values ranging from 964 to 980|iS/cm. Surface temperature (54 to 62°C), EC and pH (6.6-6.9) values of all the thermal springs are close to each other, EC and pH values of a cold water sample from a nearby area are 821|j.S/cm and 7.8 respectively. Triangular diagrams of cations and anions (Fig. 4 and Fig. 5) indicate that bicarbonate is the dominant anion in all the samples whereas no single cation shows more than 50% concentration (based on meq/1). K has relatively more concentration followed by Na in all the cases. Hence these thermal waters areofK-Na-HC03type.

6 Legend CI + Tatta Pani-1$t o Murtazabad-lst D Surface Water • Tatta Pani-2nd * Murtazabad-2nd O Tatto-2nd

0 o.e / 0,2

\ .

%&*•*'«]? ** \ 0 1 HCO so, 0 0,6 0.8 1

Fig. 2. Triangular plot of main anions for thermal waters of the Northern Areas

A • Legend / • -*\ • + Tatta Pani-1st 0.2 A , \ o.e • TaLta Pani-2nd 0- Murtazabad-1sl it Murtazabad-2nd o Tatto^Znd u Surface Water

Fig. 3. Triangular plot of main cations for thermal waters of the Northern Areas Legend \ Thermal

River (J) Open Well

Fig. 4. Triangular plot of cations of Kotli area

Legend • Thermal m River e Open Well

so, 0

Fig. 5. Triangular plot of anions of Kotli area 5.2. Recharge Source and Subsurface History

5.2.1. Tatta Pani and Tato

Isotopic data can-well differentiate between the three possible types of origin of thermal water i.e. magmatic, oceanic and meteoric. Ranges of S180 and S2H of all the sampled geothermal manifestations of Tatta Pani are -11.3 to -10%o and -84.7 to -62.8%o respectively, while the5l80 and S2H ranges of Tato are -U.l to -10.6%o and-77.6 to -78%o. These data do not show the presence of any significant amount of magmatic water which generally has S180: +6 to +9%o and 52H: -40 to -80%o [26, 27]. The important feature of the fluids emerging from thermal manifestations is their low salt contents. The maximum EC is 1261 u.S/cm for Tato spring, while that of Tatta Pani ranges from 860 to 1046 (iS/cm. The CI content of Tatta Pani varies from 44 to 55 ppm, whereas Tato spring has relatively higher value of CI i.e. 102-111 ppm. Normally the oceans have 5,80 & 52H about 0%o (VSMOW), the salinity from 33500 to 37600 ppm and chloride about 19300 ppm [28]. The possibility of oceanic origin of the encountered thermal waters is ruled out by the absence of highly enriched 8I80, 52H, EC and CI values. So the origin of thermal waters is obviously meteoric.

There are three most important processes affecting the isotopic and chemical concentrations during upward movement of geothermal waters viz. steam separation due to adiabatic expansion of thermal fluids with decreasing pressure, dilution/mixing with shallow fresh waters and lsO shift due to rock-water interaction at higher temperatures [7]. The isotopic and chloride signatures of the geothermal fluids have been used to identify the prevailing processes. The tritium concentration of all the thermal springs is zero TU. Absence of tritium indicates that there is no contribution of fresh water recharged during last 50 years in the thermal water [28]. This evidence is sufficient to rule out the mixing process.

8 O vs. 52H of the first set and second set of samples have been plotted in Fig. 6 and Fig. 7 respectively with the following local meteoric water line (LMWL) determined by Hussain et al. [29] for the same area using the samples of snow-melt and river water instead of rain water which is usually in traces.

82H = (8±0.4)818O + (16.5±6) (r2 = 0.933, n = 24) (1)

All the data points for thermal waters of Tatta Pani reflecting varying degrees of enrichment in 180 and 2H contents lie below and close to the LMWL. Considering the extreme right point in Fig. 6, the scattered group follows the 180-shift trend otherwise it can also be considered evaporation trend. In the second set (Fig. 7) Tatta Pani samples clearly follow the 180-shift trend. In these cases the 1sO-shift is slightly more than l%o. The previous study carried out during early 1990s [30] indicated that the points of Tatta Pani springs in 5 0-S2H diagram31ying below the LMWL have slope of 5.6 and seem originating from a point at LMWL having isotopic contents similar to that of local meteoric water (5I80 = -12.3%o and 8 H = -81 %o). In Fig. 8 representing the combined plot of both the samplings, the scattered cluster seems dominantly due to 180-shift but the evaporation/steam separation process might also be playing significant role. The slight change in type of water and S180- 8 H indicates that there is significant change in the subsurface processes during the last decade. The correspondence of isotopic contents with the local meteoric water indicates a predominantly meteoric origin of geothermal discharges [7].

9 -50 • TP-1stset X TP-Cold Sp 2 18 -60 A Murtz-lst set LMWL: 8 H = 8.0 8 0 +16.5 + Murtz-Gold Sp -LMWL

-70

Q-18 Shift at TattaPani •SO

Mixing trend with shallow groundwater at Murtazabad -90 (slope: 15.6)

-100 -14.5 -13.5 -12.5 -11.5 -10.5 -9.5 8180(%o) Fig. 6. 2Hvs., lsO of first set of samples of Northern Areas

-50

A TP-2nd set • Tato 2 18 -60 X TP-ColdSp LMWL: 5 H «= 8.0 8 0 + 16.5^ o Murtz-2nd set + Murtz-Cold Sp -LMWL -70

-80 + 0-18 Shift at TattaPani and Tato

ixing trend with shallow groundwater at Murtazabad -90 (slope: 13.8)

-100 -14.5 -13.5 -12.5 -11.5 -10.5 -9.5 8180(%o) Fig. 7. Hvs. 18O of second set of samples of Northern Areas

10 Chloride of Tatta Pani samples has very short range (44-55 ppm) and it does not have any significant correlation with temperature (Fig. 9) and S,80 (Fig. 10), which indicates that there is no significant evaporation. Three samples of Tato falling on the straight horizontal line (Fig. 7) indicate purely lsO-shift up to 1.5%o, which is more than that determined by Manzoor et al. in a previous study [31]. Lack of tritium contents in the water samples from Tato show that nO detectable amount of fresh water is mixing with the thermal water.

In a geothermal system, 834S of sulphates with a magmatic origin ranges between 0 to 2%o CDT (Canyon Diablo Troilite) whereas S34S of modern oceanic sulphates is about +20%o [32]. Isotopic composition of sulphates derived from different sources is summarized in Fig. 11. The 634S values of sulphates of Tatta Pani hot springs are clustered in a small range of 18 +11.8 to +13.5%o, while the 8 0(S04) ranges from +0.3 to +2.4%o. It shows that the sulphates are neither of magmatic origin nor of modem oceanic origin. Position of the data points in Fig. 11 suggests that sulphates are resulting from mixing of two sources i. e. dissolution of marine and terrestrial evaporites with major contribution from the second source.

5.2.2. MurtazabadArea

Ranges of S,80 and 52H of all the sampled geothermal manifestations are -12.9 to -11.6%o and -98.8 to -81.5%o respectively. The electrical conductivity (EC) varies from 1833 to 2560 uS/cm while the CI content is 27 to 42 ppm (CI content of 192 ppm for Sample No. HS-10 is rejected). These data do not show the presence of any significant amount of magmatic or oceanic water as discussed earlier [24, 26],

5180 vs. 52H has been plotted in Figure 6 and Fig. 7 for the first and second sets, while the Fig. 8 depicts the combined data. All the points form a trend below the LMWL. Departure of these points from LMWL may be due to rock interaction, evaporation or mixing processes [7]. These plots not only confirm the mixing process but also give insight into the history of thermal waters. All the thermal waters plot below the LMWL forming the trend lines of slopes 15.6 for the first set and 13.8 for the second set, which intersect the LMWL at the points having compositions of 5lsO: -12.1%o, 82H: -81%o and 8180: -11.5%o, 82H: -76%o respectively. The end-point in the second set is exactly similar to the average 5lsO and 52H values of snow (i.e. -11.6 & -76%o) collected from Murtazabad terrace and the trend is similar to that found earlier [31], Due to location being at relatively low altitude, the snow of the local area is isotopically enriched as compared to general meteoric water, which originates from precipitation at higher altitudes and drained by rivers (5I80 = -13.8%o,52H = -94%o). The isotope indices of cold spring (5180: -11.6%o, 52H: -81%o) emerging from he Murtazabad terrace fall in the range of above-mentioned endpoints, therefore, it may be considered as the representative of the shallow groundwater (end-mixing component) of this area. Variation in the slopes and shift in the mixing trends (Fig. 8) might have resulted from the changes in subsurface conditions due to series of earthquakes in the second quarter of 2003. Changes in surface temperature, discharges and locations of the springs were also observed. Negative correlation of 8180 with CI (Fig. 12) indicates mixing with shallow groundwater having low CI content and relatively more enriched in l80, and rules out the dominance of steam separation/evaporation process [33], The cold spring, which represents

11 -50 • TP-1stset h TP-2nd set m Tato X TP-ColdSp 2 18 •60 LMWL:5 H = 8.0 5 0 + 16.5 & Murtz-1st set o Murtz-2rid set + Murtz-Cold Sp -LMWL -70

65 X to -80

-90

-100 -14.5 -13.5 -12.5 -11.5 -10.5 -9.5 5180 ( %„)

Fig. 8. 2Hvs. ,80 of both the sets of samples of Northern Areas (Tatta Pani, Tato and Murtazabad)

100 • 1st Set • 2nd Set 90 - i 1 •

O 80- • a. • • • % • E * i 1 • • • S. 70 m 4 t • • 60

50 1 1 —i ' 42 44 46 48 50 52 54 CI (ppm)

Fig. 9. Chloride vs. temperature of thermal waters of Tatta Pani, Northern Areas

12 54 ' • •

52 • '

50 • E • & 48 . • •

• • 46 - * 1st Sampling

I. • 2nd Sampling 44 • •

42 1 1 1 —I •: "—' 1 i i -11.5 -11.3 -11.1 -10.9 -10.7 -10.5 -10.3 -10.1

5"0 Fig. 10. Chloride vs. ,80 of thermal waters of Tatta Pani, Northern Areas

25 Devonian to Cenozoic Lower Triassic 20 ( V \ \ * Atmospheric S04 15 ft, ^

i O10 X CO J o Modem x marine S0 " Tertiary O 5 -l X. 4 vO Magmatic and

hydrothermal S04

o Tatta Pani x k. Murtazabad Terrestrial evaporites xKotly

-10 -15 -5 15 25 35 45 ,34, 5"SofS04(%o)

Fig. 11. Source of sulphates in Himalayan geothermal springs with the help of 5'341 ScDrfSOj) and 6JSOVSMOW(S04) ranges in various origins of dissolved sulphates in groundwater

13 the shallow groundwater, has highest concentrations of Ca, Mg and HC03 indicating dissolution of dolomite. Negative correlations of chloride with Mg (Fig. 13) and Ca (Fig. 14) confirm the dominance of mixing process during movement of the thermal water towards the ground surface. Different proportion of fresh water sets the different isotopic and chemical concentrations of thermal waters flowing through various paths.

Although, mixing of the thermal water with shallow groundwater is confirmed, but it does not cause significant cooling because there is no correlation of their surface temperature with 5,sO and chloride in both the samplings. It means that cooling of the thermal water is not mainly due to mixing of shallow cold groundwater, while the steam separation process is already ruled out. Therefore, the dominant process of cooling is conduction prior to mixing of shallow water.

The 5;34 Sc values of sulphates of hot springs being in the range of +8.4 to +13.2%o show that the sulphates are neither of magmatic origin nor of modern oceanic origin as explained in the case of Tatta Pani. Relatively low values of 534S indicate that the major contribution of sulphates is derived from reduced sulphur compounds such as sulphide minerals and/or organic sulphides [26], Sulphide minerals are exposed at some places along 1S the cliff of Murtazabad terrace. The 5 0(S04) of hot springs varies from -2.9 to +1.3%o 34 which is plotted against 5 S(S04) in Fig. 11 showing ranges of these parameters for different origins of sulphates [28]. Locations of data points in the terrestrial zone except one, which is also very near to this zone, confirms the terrestrial source of sulphates.

45 • IstSampling • 2nd Sampling »\ • • 40

• E • D. - & 35 v •

30 • •

25 —1—: -1 1 —1 -^ -13.0 -12.8 -12.6 -12.4 -12.2 -12.0 5180

Fig. 12, Negative correlation of Chloride with, O of thermal waters at Murtazabad, Northern Areas due to mixing of shallow groundwater having enriched O and low chloride

14 100 • 1st Sampling • • • ^v • 2nd Sampling 80

E CL 60 • Q. *— 2 40

\^ • 20 • rJ 1 1 1 1 r —5—,— 25 27 29 31 33 35 37 39 41 43 45

CI (ppm)

Fig. 13. Increase in Mg content of thermal waters due to mixing of shallow groundwater with relatively high Mg and low CI at Murtazabad, Northern Areas

80 • 1st Sampling 70 • 2nd Sampling 60

50 ? Q. & 40 CD O 30 20

0 —i— —,— —r- 25 27 29 33 35 37 39 43 45 31 41 CI (ppm)

Fig. 14. Increase in Ca content of thermal waters due to mixing of shallow groundwater with relatively high Ca and low CI at Murtazabad, Northern Areas

15 5.2.3. Kotli (Kashmir)

Chemical parameters of the thermal springs plotted in Schoeller diagram (Fig. 15) indicate that all the waters are very similar having same origin and subsurface history. The CI values of thermal waters vary from 41 to 53 ppm. Ranges of 5180 and 52H of all the sampled geothermal manifestations of Kotli are -6.49 to -6.19%o and -41 to -38%o respectively. These data indicate that thermal waters are not of magmatic or oceanic origin. So the origin of thermal waters is obviously meteoric. All the data points lie below and close to LMWL in 5180-52H diagram (Fig. 16); Their 5,80 and 52H are more depleted than that of the river water, which show that the thermal waters are recharged at higher altitude. Tritium of thermal springs varies from 7 to 8 TU, while that of river water and open well is 15 TU and 17 TU. Using the temporal input of tritium in this region and Multis Model (combining piston flow and exponential models) [34], the mean residence time comes out to be 35-40 years.

The 534S values of sulphates of hot springs have a narrow range (-2.5 to +4.9%o) which shows that the sulphates are neither of magmatic origin nor of modern oceanic origin as explained above. Relatively low values of 8 4S indicate that the sulphats is derived from reduced sulphur compounds such as sulphide minerals and/or organic sulphides. The 5180(S04) of hot springs varies widely from -3.6 to +13.6%o. Isotopic composition of sulphates from this area is plotted in Fig. 11 which shows that mixing of sulphates from magmatic origin and those resulting from reduced sulphur compounds is taking place.

Parameters

Fig. 15. Schoeller Diagram of thermal springs of Kotli area

16 0 • Thermal Sp. -5 8ZH = 8.0 51B0 + 14 0 River -10 Open Well -15 A LMWL ? -20 •I -25 -30 -35 -40 -45 -6 -5 -4 -3 -2 5180(%o)

Fig. 16. Isotopic (2H and'sO) composition of geothermal springs, shallow groundwater and river in Kotli area

5.3. Chemical Geothermometry

Various chemical geothermometers like Na-K, K-Mg, Na-K-Ca, Na-K-Ca-Mg and quartz geothermometers were used to estimate reservoir temperatures. The following equations were used and calculated temperatures (°C) are given in Table I, II and III.

TNa_K = {1217/[1.483 + log(Na/K)]}-273.15 [35] (2)

TNa-K = {933/[0.993+log(Na/K)]}-273.15] [4] (3)

TNa-K = {1178 /[1.470+log(Na/K)]}- 273.15 [36] (4)

TNa-K= {1390/ [1.70+ log (Na/K)]}-273.15 [8] (5)

2 TK-Mg ={4410/ [14.0- log (K /Mg)]}- 273.15 [8] (6)

= 05 TK.ca {1930/(2.92+]og(K/Ca )} -273.15 [5] (7)

Twa-K-Ca = {1647/[log(Na/K)+p log(Caa5/Na)+2.24}-273.15] [37] (8)

2 TNa-K-Mg={ 11140/(61og(Na/K)+log(Mg/Na )-log(Mg/Na2)+44.67)}-273.15 [8] (9)

2 TNa-K-Ca-Mg={16000/(31og(Na/K)+31og(Ca/Na )+18.3)}-273.15 [38] (10)

Tquartz= {1309 / [5.19-log (Si02)]}-273.15 [2] (11)

5.3.1. MurtazabadArea

Reservoir temperatures of Murtazabad thermal waters as determined by above mentioned chemical geothermometers vary very widely. Generally, the Na-K temperatures are higher than that of Na-K-Ca, Na-K-Ca-Mg and quartz temperatures. The mixing of

17 shallow groundwater brings about changes in water chemistry that have a remarkable influence on chemical geothermometers. Therefore, the mixing process was modeled by means of the isochemical method [39]. Three geothennometers i.e. the Na-K [35], the K-Mg [8] and the quartz [2] described by Equations No. 2, 6 and 11 respectively are more reliable. First, the concentrations of Na, K, Mg and Si02 involved in the these geothermometers were regressed with CI and the following linear equations were obtained (sample HS-10 was excluded from the calculation, since it is boiled water):

CNa= 15.144 Cci-206.757 (12) CK = 0.432 CC| + 24.232 (13) CM8 = -4.403 Cci + 193.33 (14) CSio2= H-768 Cci-64.534 (15)

Inserting the above functions (Equations 12 to 15) in the Na-K, K-Mg, and quartz geothermometers (Equations 2, 6 and 11), the following T(C1) functions were obtained for Murtazabad area:

TNa_K = {1217/[1.48 + log (15.14 Cci -206.75) - log (0.43 Cc, + 24.23)]} -273 (16) TK-Mg = {4410/[14 -2 log (0.43 CCi + 24.23) + log (r4.403 CCi + 193.33)]}-273 (17) Tquartz = {1309/[5.19 - log (11.76 CCi - 64.53)]} - 273 (18)

Table I: Reservoir temperatures (°C) of thermal springs of Northern Areas by various chemical geothermometers (First sampling, March 2002)

Surface Na-K-Ca Na-K Na-K Na-K Na-K Na-K-Ca- Si02 Sample Code Temp. (Eq. 8) (Eq- 3) (Eq. 4) (Eq. 5) (Eq. 6) Mg(Eq. 10) (Eq. 11) Tatta Pani HS-1 65 202 110 116 99 130 129 HS-2b 70 205 104 110 93 124 128 HS-2c 65 139 106 112 96 127 107 HS-3 48 186 109 115 99 130 120 HS-4 74 244 117 122 106 137 139 HS-5 77 201 92 99 113 124 HS-6 87 111 117 101 132 HS-7 69.4 180 105 119 119 HS-8 74 268 144 148 132 163 154 Murtazabad HS-9 74 135 231 228 217 245 108 HS-10 92 270 197 197 184 214 136 HS-11 58 HS-11A 58 142 239 236 226 253 112 HS-1 IB 60 149 236 233 222 250 114 HS-12 86.5 254 209 208 196 225 133 HS-13 68 230 195 196 183 212 132 HS-14 61 218 212 211 199 227 133 Table II: Reservoir temperatures (°C) of thermal springs of Northern Areas by various chemical geothermometers (Second sampling, March 2004)

Surface Na-K-Ca Na-K Na-K Na-K Na-K Na-K-Mg Si0 Sample Code 2 Temp. (Eq. 8) (Eq. 3) (Eq. 4) (Eq. 5) (Eq. 6) (Eq. 9) (Eq. 11) Tatta Pani HS-1 68.4 137 126 131 115 146 165 115 HS-1A 61.4 121 129 134 118 149 177 HS-2A 72.9 127 119 124 108 139 158 HS-2B 70.8 124 121 126 110 141 170 117 HS-4 53.8 114 144 148 132 163 173 127 HS-5 78.8 121 123 128 112 143 172 122 HS-6 87.5 144 141 145 129 160 183 122 HS-7 71.4 109 117 122 106 137 174 117 HS-8 76.6 146 134 138 123 154 176 119 HS-15 70.3 112 122 127 111 142 174 117 HS-16TP 63.9 128 119 124 108 139 165 120 HS-17 66.4 158 117 122 106 137 154 112 HS-18 78.8 no 116 122 105 137 158 119 HS-19 72.2 161 147 151 136 166 185 115 Tato HS-18 89.4 181 183 169 199 294 189 HS-18A 88.3 176 178 164 194 315 HS-18B 89.5 168 171 156 187 292

Murtazabad HS-9 59.6 228 271 265 257 282 103 199 HS-10 73 184 242 238 228 256 111 203 HS-10A 66.1 168 233 230 219 247 113 HS-11 83 325 227 225 213 242 92 229 HS-11A 71.2 224 279 272 264 289 102 HS-11C 69.1 215 264 258 250 275 104 HS-12 88.9 127 245 241 231 258 112 156 HS-13 53.9 170 235 232 221 249 110 236 HS-13A 47.3 174 224 222 211 239 109 HS-14 59 185 245 242 232 259 110 231 HS-16MD 75.3 132 252 248 238 265 111 186

Table III: Reservoir temperatures (°C) of thermal springs of Kotli (Kashmir) by various chemical geothermometers

Surface Sample Na-K-Ca Na-K-Ca K-Ca K-Mg Na-K-Ca-Mg Si0 Temp. 2 TP-1 62.4 213 132 168 124 125 92 TP-2 62.5 206 138 171 125 122 91 TP-3 63.1 214 135 169 125 124 90 TP-4 59 206 144 174 124 122 92 TP-5 54.3 213 135 168 123 125 92

19 The Na-K, K-Mg and quartz temperatures were calculated for varying CI concentrations. Temperatures estimated by K-Mg are much lower (7I-105°C) because Mg has been increased drastically by mixing of shallow groundwater. Therefore, temperatures estimated by the other two geothermometers are plotted against CI (Fig. 17). Both the functions converge and after crossing they again diverge indicating the equilibrium temperature 227°C. The reservoir temperatures estimated by different geothermometers are also shown in Table II and Table III for comparison.

The geothermal reservoir temperature was also estimated using the Na-K-Mg05 triangular diagram (Fig. 18). In this plot, full equilibrium curve (FEC) is drawn using the Na- K geothermometer of Arnorsson et al. [38] and the K-Mg geothermometer of Giggenbach [8]. This approach was adopted in order to take into account the possible uncertainties of the Na-K geothermometer. Both the sets of Murtazabad samples are found spread along two alignments starting from the Mg05 vertex and pointing towards the full equilibrium region. As discussed above, the equilibrium of the thermal water is disturbed due to mixing of cold shallow groundwater having high Mg content, which seems to be responsible for shifting the data points away from the FEC. Assuming very low Mg content in the original thermal water component and extrapolating the trend lines towards FEC, the reservoir temperatures are estimated to be 185°C (1st sampling) and 220°C (2nd sampling). This range is in close agreement with the range (185-200°C) estimated in the previous study [40].

Using the procedure published by Truesdell and Fournier [1], dissolved silica was plotted versus enthalpy (in terms of temperature in °C) for the geothermal manifestations (Fig. 19). In case of Murtazabad, the data points are scattered along a line, which is almost vertical and does not originate from the quartz solubility curve. It shows mixing of shallow fresh water with the thermal water after lowering of temperature by conduction, which supports the above finding that the thermal water is cooled mainly by conduction process. Assuming the conductive cooling, the temperature of hot water corresponding to highest content of silica with maximum steam loss comes out to be 240°C.

5.3.2. Tatta Pani and Tato Fields

In the first set of samples, the Na-K and Na-K-Ca-Mg geothermometers agree on the temperature range of 100-150°C with few exceptions, while the Na-K-Ca geothermometer give higher temperature (up to 270°C). In the second set of samples, the Na-K, Na-K-Ca and quartz geothermometers indicate 100-150°C temperature but Na-K-Mg geothermometer shows slightly higher range (150-185°C). In the dissolved silica vs. temperature (°C) plot (Fig. 19) the data points of Tatta Pani are clustered along a horizontal line showing cooling by conduction. It originates from the quartz solubility! curve at the temperature of about 110°C.

The reservoir temperature of the Tato springs is estimated in the range of 180 to 202°C by Na-K, Na-K-Ca and quartz geothermometers, whereas Na-K-Mg geothermometer shows quite higher temperature (about 300°C). In the Na-K-Mg0 triangular diagram (Fig. 18), most of the thermal waters of Tatta Pani plot between Mg vertex and FEC, indicating a reservoir temperature from 100 to 125°C. The sample from Tato plots in partial equilibrium zone along the line of 150°C temperature.

20 i3U - _0_ Temp.(Na-K)

270 OX. —A—Temp.(Si02)

190

170 :—i ' —I 1 1 1 1 1 25 27 29 31 33 35 37 39 41 43

Chloride (ppm)

Fig. 17. Estimation of reservoir temperature when shallow groundwater mixes with geothermal water at Murtazabad - use of iso-chemical model by plotting Na-K and quartz temperatures as functions of CI vs. CI content of thermal waters

Legend D T-Pani 1st T-Pani 2nd M-abad 1st M-abad 2nd Tatto-2nd Point of intersection of equal temp, lines

0.6 0.4 K/100

Fig. 18. Evaluation of Na-K-Mg temperatures of thermal waters of Murtazabad, Northern Areas

21 900 • Murtazabad Max. steam loss 800- • Tatta Pani • Tato E ^600 Quartz solubility £ 500 HMO0

0 50 100 150 200 250 300 350 400 Temp. (°C)

Fig. 19. Dissolved silica vs. enthalpy plot of Murtazabad thermal waters

Legend J V- i • Point of intersection of equal temp, lines 0.8 / \ \ 0.2 *• Kotli ,/ioo \

Fig. 20. Evaluation of Na-K-Mg temperatures of thermal waters of Kotli area 5.3.3. Kotli (Kashmir)

Various chemical geothermometers as described above were applied to determine the reservoir temperatures of the geothermal manifestations. However Na-K geothermometer did not yield any meaningful results. Temperatures estimated by remaining thermometers are given in Table III. The results indicate that K-Mg and Na-K-Ca-Mg thermometers give similar temperature (122-125°C), while Na-K-Ca (132-144°C) and K-Ca (206-214°C) thermometers give higher estimates. SiC>2 geothermometer estimates relatively low temperature (90-92°C).

The geothermal reservoir temperature using the Na-K-Mg05 triangular diagram (Fig. 20) is not conclusive. The Kotli thermal water samples are located along the x-axis towards the Mg vertex.

5.4. Isotope Geothermometry

Although several isotope exchange reactions can be used as indicators of subsurface equilibrium temperature, the exchange of lsO between dissolved sulphates and water is often the most useful because isotope equilibrium can be attained in a reasonable lapse of time 18 depending on temperature and pH [28, 41]. The A 0(S04-H20) geothermometer is based on the oxygen isotope exchange reaction:

l6 ,8 16 ,8 16 S 04 + H2 0 <^>S 03 0 + H2 0 (18)

The reservoir temperatures were calculated using the relationship of Mizutani and Rafter [42]

6 2 1000 In aS04-H20 = 2.88 xl0 T" -4.1 (19) where

,8 ,8 a = [1000 + 5 0(S04)] / [1000 + 5 0(H20)]

18 The results of A 0(S04-H20) geothermometer [42] are graphically displayed in the ,8 ,8 5 0(S04) vs. 5 0(H20) diagram (Fig. 21) in which relevant isotherms from 50 to 250°C are also shown. Samples from Murtazabad are somewhat scattered. This scatter might be attributed, at least in part, to mixing, but the occurrence of other interfering processes cannot be ruled out. However, the isotope equilibrium temperatures range from 130 - 185°C . In the diagram (Fig. 21), the Tatta Pani samples plot around the 150°C isotherm or somewhat above it, indicating equilibrium temperatures in agreement with most of the chemical geothermometers but slightly higher than the range suggested by Na-K-Mg05 geothermometer (75-120°C). This discrepancy might be due to the fact that the oxygen isotope ( O) exchange between dissolved S04 and H20 becomes sluggish at low ,8 temperatures and high pH values [7, 43]. The enrichment in 5 0(H20) due to steam separation can also cause an overestimation of equilibrium temperature. In the same figure, ,8 the Tato spring shows the A 0(S04-H20) temperature close to 170°C, which agrees with most of the chemical geothermometers.

23 2 13 Isotope geothermometers [7] based on the analysis of 5 H and 8 C in H20 vapours, H2, CH4, and C02 gases were applied to three samples collected from Tatta Pani, Tato and 2 l3 Murtazabad. The A H(CH4-H2) and A C(C02 -CH4) geothermometers give very high reservoir temperatures in the range of 500-900°C, may be due to non- equilibrium conditions. Especially, the 13C equilibrium reaction is very slow at low temperatures as the 6 experimentally determined reaction half-life of C02-CH4 geothermometer at 300°C is 10 years [44].

15 - J 10 _ ....„.; : Tatta Pani | 100°C— o Murtazabad I w 5 0 O # 150 C- O ' * • r-*-x 200°C- A ___250°C - -5 (jatcT^)

-10 -14 -13 -12 -11 -10

18 8 0 of H20 (%o)

8 ls ,8 Fig 21. A' 0(S04-H20) geothermometer based on O(S04) and 0(H20) of geothermal springs of Northern Areas

CONCLUSIONS

On the basis of hydrochemical and isotopic data, the following conclusions are drawn.

> The thermal waters of the Northern Areas of Pakistan are generally neutral to slightly alkaline and have low dissolved contents. Sodium is the dominant cation in all the cases. In terms of anions, HC03 is dominating.

> Source of recharge is meteoric water (rains and/or snowmelt at higher altitude). The dominant process of cooling is conduction at Tatta Pani, Tato, and Murtazabad. Shallow groundwater is mixing with the thermal springs in different proportions at Murtazabad, while there is no mixing in the thermal waters of Tatta Pani and Tato.

At Murtazabad the equilibrium temperature of the thermal end-member is in the range 185-225°C. The isochemical-mixing model based on Na-K and quartz ,8 geothermometers estimates 227°C temperature. The A 0(S04-H20) geothermometer indicates equilibrium temperatures (before mixing) above 185°C. The dissolved silica vs. enthalpy model suggests heat losses through conduction and reservoir temperature of245°C.

24 > The thermal waters of Tatta Pani and Tato are not mixing with shallow groundwater. The reservoir temperatures determined by the Na-K, K-Mg, quartz and Na-K-Mg05 triangular diagram geothermometers are in good agreement in the range of 100- 1S 150°C. The A 0(S04-H20) geothermometer indicates equilibrium temperatures around 150°C. For the Tato springs, the isotope and chemical geothermometers (except K-Mg) agree on an equilibrium temperature of about 170-200°C.

> Thermal waters of Kotli have meteoric origin. They are of sodium bicarbonate type. The thermal water seems to be young or significant component of fresh water is mixing. The reservoir temperatures given by K-Mg and Na-K-Ca-Mg thermometers are similar (122-125°C). Geothermometer based on dissolved silica gives reservoir temperature about 100°C.

25 ACKNOWLEDGMENTS

The present study was carried out under the IAEA/RCA Project RAS/8/092 "Investigating the Environment and Water Resources in Geothermal Areas". Cooperation of the Agency for sponsoring meetings, workshops and trainings, and providing financial support in the form of supply of consumables, minor equipment and analytical service for gas isotopes is thankfully acknowledged. Special thanks are due to Mr. Z. Pang, Technical Officer for his cooperation and guidance in the investigations. The authors express their gratitude to Mr, P. Dias, RCA Coordinator, Mr. C. R. Aleta, Ex RCA Coordinator, Project Officer and the supporting staff at the Agency for their cooperation in administrative matters.

The authors would like to express their gratitude to PAEC authorities, especially Dr. Mustanser Jehangir, Director General PINSTECH and Dr. Riffat Mahmood Qureshi, Head Isotope Application Division for providing infrastructure and financial support for the research work. The efforts of M/S Mubarik Ali, Muhammad Rafique, Muhammad Fazil, M Islam Pasha, Mumtaz Khan, Imtiaz Ahmad, Bashir Ahmad, Muhammad Zamir and Amjad Ali for various sample analyses are appreciated.

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