Major Ionic Composition of Jizan Thermal Springs, Saudi Arabia

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1 Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 2 (1): Scholarlink Research Institute Journals, 2011 (ISSN: ) jeteas.scholarlinkresearch.org Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 2 (1): (ISSN: ) Major Ionic Composition of Jizan Thermal Springs, Saudi Arabia 1 M. T. Hussein and 2 Omer A. Loni 1 SGSRC, Department of geology, College of Sciences King Saud University, Riyadh, Saudi Arabia 2 KACST, King Abdulaziz City for Science and Technology, Riyadh, Saudi Arabia, Riyadh 11446, Saudi Arabia Corresponding Author: M. T. Hussein Abstract Jizan thermal springs are located in the southwestern part of Saudi Arabia. The springs flow through fractures within the Precambrian- Cambrian Arabian Shield rocks that occupy the eastern boundary of the Red Sea Plate boundary. The springs are characterized with temperatures that vary from 40 to 75 degrees Celsius. The groundwater in the area is subjected to sea water intrusion, mixing and dissolution of salts. Depletion of (Ca+Mg) and enrichment of ( a+k) in thermal waters is the result of an interaction of CO 2 with water and rocks. In fact, CO 2 -rich water facilitates Ca a exchange processes in feldspars and clay minerals. The thermal springs, having a lower (Cl+SO 4 )/HCO 3 ratio (0.38 to 0.56), higher ( a+k)/ (Ca+Mg) ratio (>4) and Cl>SO 4, are chemically distinct from the groundwater. The enrichment of a HCO 3 in thermal spring samples relative to groundwater could, therefore, be a residual feature caused by CaCO 3 precipitation at relatively high temperatures within the thermal circuits in which CO 2 tends to rise to the surface. Keywords: jizan thermal springs, feldspars, ionic composition, clay minerals I TRODUCTIO Geothermal Energy and geothermal reservoirs are getting increasing interest in recent years as an alternative of energy resources. Geothermal springs have always been important for spas and have medical benefits especially for dermatology diseases. Geothermal site is any source from which heat can be extracted through flow of water, steam or mud. Such a system requires deeply seated magmatic body. The Red Sea is considered as one of the most important and promising areas for geothermal energy. It is close to the continental-oceanic crust boundary at a depth of some 20 km. Jizan area is located in the southern end of the Red Sea. It is an integral part of the southern Arabian Shield which is known for its volcanic rocks and Quaternary- Recent tectonics associated with the Red Sea Rifting. In this area a number of springs occur with varying thermal degrees. This spring field extends across the borders into Yemen. Thus the area is considered to have a good potential for geothermal energy (Bazuhair et al, 1990). 65 groundwater samples were collected from dug wells in the area in addition to four thermal springs emerging in Jizan area and its neighborhood to define their major ionic composition, understand their circulation pattern and hydrochemical significance (Figure 1, Table 1). GEOLOGY OF THE STUDY AREA The general geology of the study area is summarized on figure (2). The Precambrian Basement Complex includes the Sabya Formation, the Baish Group and Halaban Group Sabya Formation The Sabiya Formation outcrops over about 40% of the exposed bedrock area in Jazan area and is exposed mainly in the mountainous region. Metasedimentary rocks of the Sabya Formation consist of quartzite, quartz pebble-conglomerate, argillite, limestone, dolomite and early basalt flows accompanied by intrusion of sills of hypabyssal gabbro. The formation is a highly complex group of schists which include several varieties of different mineral content. In the field it is difficult to identify contacts between one layer and the other. The presence of chlorite causes the green color in many rocks. Baish Group The Baish Group is the name for greenstones of metabasalt and diabase, exposed along the course of Wadi Baysh. In Jazan area they cover a narrow zone in the north eastern portion surrounding the upper embankments of Wadi Sabya and Wadi Qasi. Baish greenstones were described as locally pillow structured and spilitic where interbedded with the upper part of the Sabya Formation. Mapping at a large scale has shown that the Baish group consists of a thick sequence of basaltic flows and broken basalt intercalated with minor discontinuous beds of metagraywacke, metachert, schist and marble. Baish extrusive rocks consist of medium to thick basaltic flows, some of which are spilitic and pillow 190

2 structured. The basalt is commonly sheared and this shearing has resulted in greenstone schist. The Baish Group occupies the center of a large northwest plunging syncline within the region. On the southeastern end of the syncline, the contact with the underlying Sabya Formation is conformable but commonly shows bedding plane shearing. Only a small portion of this formation is exposed in the study area. Halaban Group The Halaban Group is divided into two units: a metavolcanic unit and a metasedimentary unit. The metavolcanic unit consists of basalt flows, pillow lava, andesite, and dacite pyroclastic rocks. The metasedimentary unit consists of greywacke and siltstone probably derived from the older igneous rocks. Table 1: Groundwater and Spring Samples S. o. ph Temperature EC TDS a K Mg Ca Cl SO 4 HCO 3 W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W W S S S S

3 plutonic and hypabyssal rocks over a long span of time. The gabbros are believed to be contemporaneous with the Baish group. These gabbros are encountered as sheets between the older Sabya Formation to the east and the younger Quaternary sediments to the west. Foliated Granite This formation is very well exposed north of the study area at the ancient Harisi dam. A relatively small outcrop appears in the study area, in and around Suq Ayban. The rock consists of a sub-layered and weakly foliated granite. Veins, dikes and sills of leucocratic rock related to these foliated granites are commonly found in the Sabya Formation within the study area and also outside the boundary of the study area. Syenite The post-tectonic plutons that form Jabal Fayfa and Jabal Bani Malik are complex. Discordant bodies that range from syenite to monzogranite. Syenites are found only in Jabal Fayfa. The Bani Malik pluton is a complex mass of dark to medium-gray syenite intruded by light gray to white dikes, sills and irregular veins of granite or monzogranite. Large xenoliths and roof pendants of older rocks are present in the syenites. In hand specimen the rock is coarse grained and pink in color. The contact with other formations is sharp. Figure1. Location map of the main springs in study area including the regional geology The metasedimentary unit consists of greywacke and siltstone probably derived from the older igneous rocks. Volcanic rocks found north of the area have been dated as about 785 Ma to 745 Ma old, distinctly younger than the Baish Group. The metasedimentary rocks of Halaban group are exposed at the extreme eastern boundaries in the upper catchment of Damad. They consist of greywacke, pyritiferous slate. Carbonaceous slate, biotite schist, minor metaconglomerate, and imperfect beds of marble that are intruded by gabbro. Field observations of features such as bedding sequence indicate that these rocks were derived from siliceous marine sediments intercalated with basaltic flows and tuffs Intrusive Rocks The age of these formations range between Precambrian to early Cambrian: Gabbro and Diorite A large elongated body of gabbro crops out in a zone 6-7km wide in the study area. It extends from Wadi Damad in the south to Nakhlan in the north. It is thought to have been emplaced along with other Monzogranite Monzogranite is found in very limited in Jazan area. Rock types range from medium-gray quartz diorite to pale-red monzogranite. Outcrops take the form of large spheroid boulders. The cantact between monzogranite and the foliated rocks of the adjacent granodiorite and granite is transitional. A circular stock of very coarsely crystalline biotite monzogranite separated by a thin relic of highly metamorphosed schist is present near the southeastern edge of the Bani Malik pluton. Gabbro and Diabase Gabbro and Diabase sheeted dikes are exposed in a discontinuous band, 8km wide within the study area. Limited data indicate that the dikes were generally emplaced vertically and then rotated to their present positions. The oldest dikes dip about 60 NE and have been rotated approximately the same amount as the Wajid Sandstone blocks. The younger dikes cut older dikes as well as the sandstones. Paleozoic and Mesozoic rocks Wajid Sandstone Wajid Sandstone is present as erosion remnants of a continuous blanket of Nubian-type sandstone and is considered Cambrian and Ordovician in age. This sandstone rests unconformably on Proterozoic metamorphic and polutonic rocks and is para- 192

4 conformably overlain by Mesozoic sandstone and limestone encountered south of the study area. In general the Wajid sandstone consists of tan to reddish brown, medium to coarse, sub angular to rounded, friable quartz grains weakly cemented by silica. Thin pebble conglomerate bands are present throughout the section, especially near the base. Thin, red, sandy shales and siltstones, present in the upper beds of Wajid sandstone, show the onset of marine conditions. The basal part of Wajid Sandstone is typically coarse-grained quartz sand. It is torrentially cross-bedded, weakly cemented with calcite, and contains conglomerate beds composed of pebbles of quartz and plutonic and metamorphic rock. In the three localities where the Wajid is encountered in the study area it is seen to be associated with deep vertical faulting. forces. Structurally the area is composed of two distinct units, the Pre-Cambrian elevated mountains and Quaternary deposits in the plains. Major structural movements of the Pre-Cambrian period caused a series of parallel thrust faults which are closely spaced with a broad symmetrical synclinorium in Jizan. This was followed by antithetic faulting in the area. Quaternary Rocks Basalt Quaternary alkali olivine basalt found between Wadi Jazan and Wadi Baish is believed to have erupted from various vent cones. The main cone is a vent ridge cone in the catchment of Wadi Jazan. However, two distinct isolated cones occur as well. These are Jabal Akwat Ash Sham to the north, and Akwat Al Yaman to the south. Wadi Nakhlan cuts its course between these volcanoes. The rock unit consists of basaltic bombs, lapilli and scoria. Alkali olivine basalt flows in the area have been dated in the interval 5 Ma to Recent. The unit consists of vesicular, fine grained, black to dark greenish gray basalt that contains small olivine phenocrysts. The original flow fractures of the basalt are preserved although commonly covered by a thin layer of sand or loess. Pillow lava structures are typical in Wadi Damad. Quaternary Sediments About half of the area is covered by Quaternary deposits ranging from eolian sands to alluvial terrace deposits. With respect to groundwater supply, these coastal plain sediments are the major units of interest because they comprise the only potential aquifer in the area. The alluvium is composed of inter-bedded clay and sands, silts, cobbles and gravels, which have good storage and conductive properties. They also make good farming soils, and large areas have been used for crop production for a long period of history. Structure The study area is located within a continental margin that is characterized by a series of north west trending structural belts which are bounded by west directed listric faults that were later modified during emplacement of plutonic rocks. Red Sea movements during the Tertiary reactivated these faults and resulted in a movement opposite to the direction of the faults in Precambrian basement. The area is in the active zone of rifting, and is subject to tensional Eolian Deposit Flood Plain Deposites Biotite Granite Sabya Formation (Metasedimentary and minar metavolcanic rocks) Amran formation (Limestone and Dolomitized Limestone Granophyer-In central massif and ring dike F a Dike Rock Alluvium Deposits (Gravel,Sand and Silt) AlKali- Olivine Layered Gabbro Granite and Granodiorite 193

Major structural movements took place in the Tertiary period due to rifting associated with spreading of the Red Sea (Coleman 1977, Coleman et al, 1977).

Later deep faulting caused the exposure of the Wajid sandstones and provided for basic magma to flow upwards and be emplaced as layered gabbro.

5 Major structural movements took place in the Tertiary period due to rifting associated with spreading of the Red Sea (Coleman 1977, Coleman et al, 1977). The Paleozoic rocks were down-dropped and the Pre-Cambrian rocks were uplifted. Later deep faulting caused the exposure of the Wajid sandstones and provided for basic magma to flow upwards and be emplaced as layered gabbro. Three major sets of faults have been recorded in Jizan area (Figure 3). The first major set is parallel to the Red Sea; it strikes N 30 o W. Another set strikes N 60 o W, and a third set strikes N o E. The faults are very steep vertical faults with throws of more than 300 meters displacement. Several normal and strike slip faults were observed in the metamorphosed Sabiya Formation. Slight deformation of the granites is observed where coarse grained specimens show some alteration of the mafic minerals (biotite) due to local compression forces which might have been produced by movements associated with spreading Red Sea. The granites show some layering and foliation. No obvious shear zones were observed in the area, with the exception of the monzogranites where the orthoclase is crushed. The influence of faulting in the basement rocks is not apparent in the character, thickness and distribution of the alluvial sediments. The alluvium has been intruded by the volcanic cones of Jabal Akwat As Sham and Akwat Al Yaman where the thickness and continuity of the water bearing sediments has been disrupted. (b) (c) orose Diagram (b)circular Diagram Figure 3. Diagrams illustrating the main structural elements in the study area HYDROCHEMISTRY The ph and temperature of the groundwater samples and thermal springs were measured in the field using Karl-Kolb measurement unit. Chemical analyses were performed according to Standard Methods (APH/AWWA/WPCF, 1989). Activities of various ions and saturation indices for relevant minerals used in this paper were calculated for all water samples, using the AquaChem computer software. The TDS in the study area ranges between mg/l (well no. 26) to 5,567.9 mg/l (well no. 38), with standard deviation of 1,305.5 (Tables 1 and 2). The mean value of TDS is 2,353.5 mg/l indicating that most of the groundwater in the region is highly saline. The spatial distribution of TDS (Figure 4) shows a general increase towards the flow direction. The general increase of TDS is from the east towards the west. An anomalous area of relatively higher TDS value has been shown around well 47. Major ions The concentration of calcium in the study area varies from 100 mg/l upstream to 355 mg/l downstream, with a mean value of 190 mg/l. It increases from upstream to downstream, towards the sea, and in Al Khasawiah and Al Jawabrah areas. The concentration of magnesium ranges between 39 mg/l upstream and 450mg/L downstream. The spatial distribution of magnesium increases from upstream to downstream, towards the sea. The variation is lower in upstream and downstream areas. It is relatively higher in the middle of the Wadi, Al Eshwah and Al Kawamlah areas. The concentration of sodium ranges from 180 mg/l to 960 mg/l. It increases from upstream to downstream, towards the sea, as well as in Al Khasawiah and Al Jawabrah areas. Relatively higher values are located in middle of the Wadi. This may indicate that, the mid area of the Wadi is a transitional area. The concentration values of potassium are between 2.7 mg/l and 17 mg/l. The values rise from upstream to downstream, towards the sea; they are lower at the middle of the Wadi, and of higher values in the downstream. The bicarbonate ranges from 180mg/L (downstream to 308 mg/l (upstream). This distribution is opposite to those of previous elements (Na, K, Mg 2, Ca 2). This is associated with recharge waters coming from the upstream areas. This indicates that the water recharge or supply is higher in the upper valley than that of the lower valley. The sulphate distribution shows high values, which range between 500 mg/l and 1,400 mg/l. The value rises from upstream to downstream. Chloride values in the study area are generally high. It ranges from 190 mg/l to 2,100 mg/l, increasing from upstream to downstream (Figure 5). The enrichment of Cl and SO 4 in groundwater is generally either due to mixing of seawater or to dissolution of evaporite minerals present in sediments deposited under a marine environment. Since the surface temperature of the thermal springs ranges from 40 to 194

6 Latitude (deci.deg.) 75 C, it could be concluded that their feeding water circulates through the geologic members before emerging at the surface. Depletion of (Ca+Mg) and enrichment of (Na+K) in thermal waters may be the result of an interaction of CO 2 with water and rocks. In fact, CO 2 -rich water facilitates Ca Na exchange processes in feldspars and clay minerals (Drever, 1982). The thermal springs, having a lower (Cl+SO 4 )/HCO 3 ratio (0.38 to 0.56), higher (Na+K)/ (Ca+Mg) ratio (>4) and Cl>SO 4, are chemically distinct from the groundwater. Figure 6 is based on chemical equilibrium (Giggenbach, 1986, Giggenbach, 1988), shows the relationship between the cation concentrations of natural solutions and possible sources of ions such as crust (simple isochemical dissolution of crustal rocks), seawater and water rock interaction resulting in secondary crystallization at different temperatures (full equilibrium line). The thermal springs cluster suggests that their chemical composition resulted from a simple crustal dissolution process. It also excludes mixing with present-day seawater. The hypothesis for this simple crustal dissolution is further supported by using the activities of the cations and discharge temperatures. The Na/K ratio in the geothermal discharges is inversely proportional to the temperature due to cation exchange reactions between coexisting feldspars (White, 1957; Orville, 1963; Waring, 1965). The enrichment of Na HCO 3 in thermal spring samples relative to groundwater could, therefore, be a residual feature caused by CaCO 3 precipitation at relatively high temperatures within the thermal circuits in which CO 2 tends to rise to the surface Figure 4. Total Dissolved Solids Distribution in the study area Longitude (deci.deg.) Latitude (deci.deg.) Figure 5. Chloride ion Distribution in the study area 20 K* Giggenbach Triangle Na* Logitude (deci.deg.) ABC C DEF GHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABA Mg Legend Legend A S1 B S2 C S3 D S4 E W1 F W10 G W11 H W12 I W13 J W14 K W15 Figure 6. Giggenbach Triangle for Jizan Springs. 195

7 ACK OWLEDGME T The authors would like to express their acknowledgment to Dr. Faisal Kamal Zaidi for revising the manuscript. CO CLUSIO S Thermal Springs in Jizan area are part of the thermal field at the edge of the Red Sea tectonic plate boundary. The springs temperatures range between 40 and 70 degrees Celsius. Its discharge vary from 1-20 l/m. The ionic constituents are relatively rich in sodium and bicarbonate ions, compared to the groundwater in the study area which is relatively rich in sodium, chloride and sulphate ions. The springs are depleted in (Ca+Mg) ions and enriched in (Na+K) ions. This is possibly the result of interaction of CO 2 with water and rocks The enrichment of Na HCO 3 in thermal spring samples relative to groundwater is possibly a residual feature caused by CaCO 3 precipitation at relatively high temperatures within the thermal circuits in which CO 2 tends to rise to the surface. Orville, P.M., Alkali ion exchange between vapour and feldspar phases. American Journal of Science 261, Waring, G.A Thermal Springs of the United States and Other Countries of the World A Summary. U.S. Geological Survey, Prof. Paper 492. White, D.E., Magmatic, connate and metamorphic waters. Bulletin of the Geological Society of America 69, REFERE CES APH/AWWA/WPCF. 1989, Standard Methods for the Examination of Water, WasteWater, American Public Health Association, Washington, DC. Bazuhair, A. S., Hamza, M. S, Hussein, M. T. and Nouri, M An Investigation of Springs water In Saudi Arabia. Unpublished Report 409/111, King abdulaziz University, Jeddah, Saudi Arabia. Coelman, R., Geologic Background of the Red Sea. Mineral Resources Bulletin 22,DGMR, Jeddah, Saudi Arabia. Coleman,R.,G., Fleck,R.J., Headge,C.E.and Ghent.E.D., The Volcanic rocks of the Southwest Saudi Arabia and the opening of the Red Sea. Mineral Resources Bulletin 22,DGMR, Jeddah, Saudi Arabia. Directorate General of Mineral resources (1985) Geological Maps GM 77 C and GM 104 C. DGMR, Jeddah, Saudi Arabia. Drever, J.J., The Geochemistry of Natural Waters. Prentice Hall, Englewood Cliffs, pp Giggenbach, W.F., Graphical techniques for the evaluation of water rock interaction conditions by use of Na, K, Mg and Ca contents of discharge waters. In: Proc. 8th New Zealand Geothermal Workshop, pp Giggenbach, W.F., Geothermal solute equilibria; derivation of Na K Mg Ca geoindicators. Geochim. Cosmochim. Acta 52,

As compaction and cementation of these sediments eventually occur, which area will become siltstone? A) A B) B C) C D) D

As compaction and cementation of these sediments eventually occur, which area will become siltstone? A) A B) B C) C D) D 1. A student obtains a cup of quartz sand from a beach. A saltwater solution is poured into the sand and allowed to evaporate. The mineral residue from the saltwater solution cements the sand grains together,