Characterization of Aliwal North Hotspring in the Eastern Cape Province of South Africa, Using Magnetic, Electromagnetic and Radiometric Methods
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IOSR Journal of Engineering (IOSRJEN) www.iosrjen.org ISSN (e): 2250-3021, ISSN (p): 2278-8719 Vol. 04, Issue 12 (December 2014), ||V3|| PP 43-58 Characterization of Aliwal North Hotspring in the Eastern Cape Province of South Africa, using Magnetic, Electromagnetic and Radiometric Methods C. Baiyegunhi1, N. W. Mupandawana1, T. L. Oloniniyi2and O. Gwavava1 1Department of Geology, Faculty of Science and Agriculture, University of Fort Hare, Private Bag X1314, Alice, 5700, Eastern Cape Province, South Africa 2Department of Geology and Mining, Faculty of Natural and Applied Sciences, Nasarawa State University, Keffi, Nasarawa State, Nigeria ABSTRACT Magnetic, electromagnetic and radiometric survey were conductedalong two profilelines that traverses Aliwal North spa using two G-859SX portable cesium vapor magnetometer, EM34-3 terrain conductivity meter and a RS-125 spectrometer, respectively. This was undertaken in order to characterise Aliwal North hot spring by revealing magnetic signatures, buried conductive bodies and determine the concentration/relative abundance of radioactive elements, like U, K and Th (in cpm, ppm and %). The magnetic result reveal signature with amplitude of about 0.4 nT,which is inferred to be a real feature extending to depth. The EM result showsmajor anomaly in the southeastern part of the studyarea. This anomaly is associated with rocks with highconductivity and occurring to a depth of about 30 m through which the highly mineralized hot water could have migrated to the surface. There is no traceable recent volcanic activity in the area and due to the deep seated faults in the survey site, it was inferred that Aliwal thermal spring is of meteoric origin and the source of the heat is due to the deep circulation along the major fault zones. The radiometric result reveals that thorium is the most abundant radioelements with concentration that isless than the world average hazardous threshold (7.4 ppm).The concentration of the radioactive elements is relatively low and acceptable for groundwater; however it could be harmful to humans’health, as well as animals when exposed to the radiation or consumed over a long period of time. Keywords: Magnetic, electromagnetic, radiometric, hot spring, groundwater, Aliwal North I. INTRODUCTION Groundwater is the major source of water in the Republic of South Africa especially in water-scarce area such as Aliwal North where people fetch or get water from groundwater discharge points (springs). A total of about 74 hot springs are known in South Africa (Figure 1; Table 1) cutting across the entire the country (Yibaset al., 2011). The occurrences of these hot springs are not restricted to a particular geology but they are usually seen in locations that has high rainfall as well as existence of deep crustal faulting. Yibaset al.(2011) stated that, no exploration boreholes have been drilled in South Africa for the purpose of determining origin, geothermal heat flow, and sourceas well as the circulation pattern of the source of heat. However,geothermal heat flow has been measured from some boreholes that were drilled for other purposes. Presently, the maximum measured surface temperature of the hot springs is seen at the Siloam hot spring which is about 70 . Thus there is low possibility of generating electricity from hydrothermal source; however, research is still ongoing to determine the possible alternative means of power generation. International organization of Scientific Research 43 | P a g e Characterization Of Aliwal North Hotspring In The Eastern Cape Province Of South Africa, Using Magnetic, Figure1Map showing location of hot springs in the South Africa, neotectonic fault and the Eastern Cape northern neotectonic belt (Madi, 2014). Table 1 Distribution of hot springs and Boreholes per Province (Olivier et al., 2008) Kent, 1949 Boekstein, 1998; Hoole, 2001 Province Springs BHs Total Developed Western Cape 14 1 15 9 Northern Cape 4 - 4 1 Eastern Cape 10 3 13 2 KwaZulu-Natal 5 - 5 4 Free State 4 4 8 4 North-West - - - 1 Mpumalanga 13 - 13 3 Gauteng 1 - 1 1 Limpopo 23 1 24 10 Total 74 9 83 35 Aliwal North hot spring is associated with fractured and fault zones (Figure 1) through which the dolerite dykes (groundwater localizers) intruded the sandstones of the Tarkastad Subgroup at about 180 Ma. The spring is not well developed, it has a temperature of about 37 and mostly used for washing clothes, bathing and medicinal purposes to cure rheumatism and other related diseases (Hartnady, 2005).Hobday (1978) emphasized on the need of detailed geophysical investigations of contacts between the lithological subdivisions of the Karoo Supergroup in order to characterize and ascertain the origin of the thermal springs in the Karoo Supergroup. International organization of Scientific Research 44 | P a g e Characterization Of Aliwal North Hotspring In The Eastern Cape Province Of South Africa, Using Magnetic, Recently, many of these contacts between the lithological subdivisions have been studied and documented but some areas such as Ecca – Beaufort contact, Beaufort–Molteno contact, and Burgersdorp– Molteno contact are still understudied or difficult to characterise in terms of origin and associated geological structures of the thermal springs. The Molteno-Burgersdorp contact is believed to be defined by an unconformity in which the deposition is preceded by an erosional period but Visseret al. (1984) proposed that the Molteno – Burgersdorp contact is conformable, but no absolute date is known for the Burgersdorp and the Molteno Formations.Aliwal North hot spring serves as a target for groundwater exploration, which makes Aliwal North to be regarded as a potential source of groundwater since no detailed geophysical surveys have been carried out previously in Aliwal North, the occurrence and movement of groundwater is unpredictable or complicated.Therefore, it is very important to characterize Aliwal North spa as exploration targets using the magnetic, electromagnetic and radiometric. 1.1 Location of the study area Aliwal North spa is located in the town of Aliwal North which lies on the border between the Free State and Eastern Cape Province of South Africa.The studyarea extends from longitudes 26o 42′ 52″E to 26o 43′ 06″ E and latitudes 30o 42′ 49″ S to 30o 42′ 50″ S(Figure 2). The town covers an area of about 169580 km2 with a population of 6,906,200 people and geographically situated between the Western Cape and KwaZulu-Natal province, the northern part leads to Bloemfontein through the General Hertzog Bridge and to the south-west, the Kramberg raises to about 2,000 m above the sea level (Hartnady, 1985). The climatic condition of the Eastern Cape is a mixture of the climatic condition of the Western Cape and KwaZulu-Natal, it which get very wet gradually from the west to the east part of the province (Hartnady, 1985). Figure 2Geological map showing the study area (Catuneanuand Elango, 2001). 1.2 General background Aliwal North belongs to the Tarkastad Subgroup in the Beaufort Group which is a fluvial environment (Figure 2; Table 2). The Beaufort Group is stratigraphically subdivided into the Adelaide and the Tarkastad Subgroups (Johnson, 1976; Tordiffe, 1978; Visser and Dukas, 1979; SACS, 1980; Catuneanu and Elango, 2001). The Adelaide Subgroup forms the lower part of the Beaufort Group and consists of the Koonap, Middleton and Balfour Formations. The Tarkastad Subgroup where the study area belongs; forms the upper part International organization of Scientific Research 45 | P a g e Characterization Of Aliwal North Hotspring In The Eastern Cape Province Of South Africa, Using Magnetic, of the Beaufort Group and consists of the Katberg and Burgersdorp Formations which are restricted to the southern margins of the Karoo Basin from south of Queenstown to north of Aliwal North (Rubidge, 1995; Hancox and Rubidge, 2001). Table 2 Lithostratigraphy of the Beaufort Group in the Eastern Cape Province of South Africa (After, Johnson et al., 2006). GROUP SUBGROUP FORMATION MEMBER LITHOLOGY DEPOSITIONAL ENVIRONMENT Burgersdorp Mudstone, Sandstone, Shale Tarkastad Katberg Sandstone, Mudstone, Shale Fluvial Palingkloof Mudstone, Sandstone, Shale Elandsberg Sandstone, Siltstone Beaufort Balfour Barberskrans Sandstone, Khaki Shale Adelaide Daggaboersnek Shale, Sandstone, Siltstone Oudeberg Sandstone, Khaki Shale Middleton Shale, Sandstone, Mudstone Transitional Koonap Sandstone, (Deltaic) Mudstone The Koonap Formation consists of alternating sequence of sandstone and mudstone. It is the base of the Adelaide Subgroup in the lower vicinity of the Beaufort Group and has lithological variation similar to those of the overlying Middleton and Balfour Formations. It has a total thickness of about 1300 m (Johnson, 1976; SACS, 1980). The Middleton Formation has a maximum thickness of about 1500 m and consists predominantly of mudstone with subordinate shale and sandstone (Johnson, 1976). It is essentially a non-marine and siliciclastic succession that was deposited in meandering rivers and their extensive environments (flood plains, lakes and ponds). The lithology of the overlying Balfour Formation is dominated by sandstone interbedded with mudstones and it represent a fully succession of Late Permian - Early Triassic age. The total thickness of up to 2150 m was measured around the Fort Beaufort area (Johnson, 1976; SACS, 1980), but Visser and Dukas (1979), working further west of the study area measured about 650 m, thus indicating thickening towards the south east. Generally, the prevailing climatic