The Structural Evolution of the Hamisana Geodynamic Zone, Red Sea Region, NE Sudan

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1 American Journal of Earth Sciences 2015; 2(3): Published online May 30, 2015 ( The Structural Evolution of the Hamisana Geodynamic Zone, Red Sea Region, NE Sudan Abdalla E. M. Elsheikh, Khalid A. Elsayed Zeinelabdein, Elsheikh M. Abdel Rahman, Musab A. Eljah Faculty of Petroleum and Minerals, Al Neelain University, Khartoum, Sudan address (K. A. E. Zeinelabdein) To cite this article Abdalla E. M. Elsheikh, Khalid A. Elsayed Zeinelabdein, Elsheikh M. Abdel Rahman, Musab A. Eljah. The Structural Evolution of the Hamisana Geodynamic Zone, Red Sea Region, NE Sudan. American Journal of Earth Sciences. Vol. 2, No. 3, 2015, pp Abstract The study area lies in the Red Sea region of NE Sudan, which belongs to the Nubian Shield that originated during the Pan African Era. The Hamisana Shear Zone (HSZ) is a broad zone of cataclastic deformation in the Nubian Shield formed as prominent N-S trending major structure. The objective of this work is to recognize the structural manifestations through the remotely sensed data and field measurements for demarcation of the major structural styles and to study the structural evolution of the study area with respect to the tectonic events of the Nubian-Arabian Shield in NE Sudan. A set of four Landsat 7 ETM+ scenes (p172r45, p172r46, p173r45 and p173r46) has been mosaicked and subset to obtain a full coverage of the study area. Remote sensing data were supplemented by field observations and intense structural measurements. Ductile deformation has been obtained in macro- and meso-scales under different folding styles representing different deformation phases. In Landsat imagery, many folds are observed; where the N-S trending fold is the common folding direction, however, the NE-SW, NW-SE and E-W folding directions are also defined. The common types of faults in the study area are strike slip faults, where the dextral sense of movements is dominant. The extensional fractures are parallel to the greatest stress axis (σ 1 ) in NW-SE direction, the release fractures are in NE-SW normal to the acting stress (σ 3 ), where the shear fractures are in N-S and ENE direction parallel to the positive and negative shear arms (σ 2 s±), respectively. At least three episodes of tectonic events involving five phases of deformations are recognized. The first episode is represented by the formation of foliation (D1), followed by the strong collision between Haya and Gebeit terrains (D2) resulted in tight folding. The second episode is the collision of the mentioned arcs with Gabgaba terrain (D3). The third episode is represented by the open folding with E-W axis, and the reactivation of the N-S shear zone in the study area (HSZ) that represents the prominent structural feature in the area. The former HSZ represents a geodynamic zone, hereafter referred to as the Hamisana Geodynamic Zone (HGZ). This is evident by the crustal shortening, the presence of ophiolitic masses with the eastward younging of its lithologies opposite to the thrust direction. The intensive N-S shearing marks a significant cataclastic deformation. Keywords Structural Styles, Structural Evolution, Nubian-Arabian Shield, Hamisana Area, Red Sea Region, Sudan 1. Introduction The study area is located within the northwestern flanks of the Red Sea Hills in the Hamisana area, which forms a prominent physiographic feature in NE Sudan. It is considered as a part of Gebeit Al-Maadin Mining District, bounded by latitudes: N and longitudes: E (Fig.1). Topographically, the Hamisana area is characterized by undulating topographic surface and high relief rocky terrain that vary in height between m above sea level. Generally, the drainage pattern of the Red Sea hills is structurally controlled. Faults and folds produce rectangular drainage patterns where large batholiths produce radial patterns. Numerous khors and wadis dissect the rocky area. The region is characterized by a desert climate, where the rainfall ranges from 10 mm/y in the north to about 50 mm/y in the southern part, being restricted to the summer season between August and September. The summer is very hot with temperatures reach more than 40 C, while winter is dry and cold. Due to the influence of the climate, the vegetation cover is poor and sparse, where bushes and small trees are confined to the seasonal water courses [1].

2 American Journal of Earth Sciences 2015; 2(3): Tectonically, the study area is a part of the Nubian Shield of the northeast Africa. The Arabian-Nubian Shield is known to be one of the major orogenic belts formed during the Neoproterozoic assembly of the Greater Gondwana [2]. The Sudanese ophiolites are key elements in all models that concern the late Precambrian crustal development in the Arabian-Nubian Shield [3], [4]. The Onib - Sol Hamed ophiolite complex is one of the largest and best-preserved ophiolite yet described at the north Hamisana area in the Red Sea Hills of Sudan [5], [6]. It is supposed to be continuous and contemporaneous with the Yanbu suture of the Arabian Shield [7]. The Onib complex forms a 60 km arcuate belt which is flanked by volcano-sedimentary sequences of the Gebeit and the Gabgaba terranes from east and west, respectively. The structural style is characterized by SE verging isoclinal folds [1]. Fig. 1. Location map of the study area. The Hamisana Shear Zone (HSZ) is one of the largest basement structures in NE Africa, a broad zone of deformation approximately 50 km wide and at least 300 km long. It has been interpreted as a Precambrian suture, as a zone of strike-slip displacement, or as a zone of crustal shortening [8]. Vail [3] first appreciated the significance of the major N-S trending structure that is known as the HSZ. He demonstrated that the southern part of the HSZ is characterized by tabular bodies of greenschist facies volcanic rocks, gabbros, and serpentinites, all being affected by a pervasive N-S trending foliation and upright isoclinals folds. Hussein et al. [5] defined the southwestward extension of the Arabian Yanbu Suture, as a major N-S trending structure to the south (Sol Hammed-Abirketeib Shear Zone). Almond et al. [9] defined a further continuation of this suture to the south, and termed the entire structure the Sol- Hammed Suture (Fig. 2). The results of Rb-Sr and U-Pb zircon geochronological studies indicated that the northern part of the HSZ was thermally active during the Pan-African event until 550 Ma ago [8]. The timing of activity in the HSZ is Ma, being younger than collisional suturing and terrain assembly in the Arabian-Nubian Shield, but is similar to the Ma Najd Fault System of Egypt and Arabia [8]. Geochemical investigations on igneous stratification gross suggest that the cumulate units are younger to the east [1] indicating thrusting. The objective of this work is to recognize the structural manifestations through the remotely sensed data and field measurements to understand the structural evolution of the southern Hamisana area with respect to the tectonic events of the Nubian-Arabian Shield in northeast Sudan. 2. Data Types The area is a rocky terrain which is characterized by arid

54 Abdalla E. M. Elsheikh et al.: The Structural Evolution of the Hamisana Geodynamic Zone, Red Sea Region, NE Sudan environment and well rock exposures.

Accordingly, a set of four Landsat 7 ETM+ scenes (p172r45, p172r46, p173r45 and p173r46) has been utilized during the present study.

Remote sensing data have been supplemented by field observations and numerous measurements of structural elements where available.

Methodology The methods are planned in order to achieve the abovementioned objectives of the study. Those include office work, field work and laboratory analysis.

In the prefield stage, Landsat ETM+ images were digitally processed in order to obtain a full coverage of the study area and produce more appealing images suitable for geological interpretation.

3 54 Abdalla E. M. Elsheikh et al.: The Structural Evolution of the Hamisana Geodynamic Zone, Red Sea Region, NE Sudan environment and well rock exposures. Therefore, remote sensing can be utilized with high degree of success in such conditions. Accordingly, a set of four Landsat 7 ETM+ scenes (p172r45, p172r46, p173r45 and p173r46) has been utilized during the present study. These imageries were mosaicked and subset to obtain a full coverage of the study area. Remote sensing data have been supplemented by field observations and numerous measurements of structural elements where available. Published and unpublished literature about the development of the ANS constitutes valuable information for the present investigations. 3. Methodology The methods are planned in order to achieve the abovementioned objectives of the study. Those include office work, field work and laboratory analysis. Office work has been conducted in two stages, pre- and post-field work. In the prefield stage, Landsat ETM+ images were digitally processed in order to obtain a full coverage of the study area and produce more appealing images suitable for geological interpretation. This has been conducted utilizing image mosaicking, sub-setting, false color compositing, spatial filtering and image transformations, with special emphasis on the spatial enhancements ([10]-[12]). The post-field stage includes the different types of analyses and interpretations of data measured in the field. GIS data integration was conducted to combine the geological and structural field data. The field work was conducted by the support of Orshab Mining Co. and Al Neelain University, by which a two-week field trip was conducted to the study area. The work was devoted to investigate the major aspects of geology and the structural setting of the area that to a large extent control the mineralization and the groundwater occurrences in the area studied. The results of the structural measurements were manipulated, projected and analyzed employing the appropriate software to recognize the structural styles and evolution in the area. 4. Results and Discussions The term deformation is defined as the process whereby physical changes are produced in the material as a result of the action of applied forces [13]. Many structural processes span thousands to millions of years. Most structural data describe the final product of some deformation history, ductile deformation occurs when rocks flow under the influence of stress. The opposite, discontinuous deformation or brittle deformation, occurs when rocks break or fractured [14]. Field observations of deformed rocks and their structures represent the most direct and important source to understanding the natural expression of the rock material toward the acting force. The structural analysis depends on some basic geometric and dynamic analyses. The geometric analysis of the structures includes the shape, geographic orientation, size and geometric relation between the main structure and the related smaller-scale structures, which is very useful to represent orientation data. Stereographic projection is used to interpret both the orientation and geometry of a structure. Both strain and kinematics expressions are a result of the accumulation and release of stress. Dynamic analysis thus explores the connection between stress and the structures or strains that can be observed in the crust [15] Ductile Deformations Ductile deformation (folds) in the study area was found in macro- and meso-scales under different folding styles representing different deformation phases. Many folds are observed in Landsat imagery, in which the N-S trending fold is the common folding direction. However, the NE-SW, NW- SE and E-W folding directions are also present (Fig. 3). During the field survey many types of folding are recognized representing many phase of deformations. Different folding styles are observed including tight up right isoclinal, overturned, recumbent and open folds; in addition to mushroom structure and poly deformed rocks (Plate 1). Upright isoclinal fold (N-NW) Overturned fold (NE)

4 American Journal of Earth Sciences 2015; 2(3): Recumbent fold (NW-SE) Open fold (E-W) Mushroom structure (NE, NW) Poly deformed rocks Plate 1. The common folding styles in the Hamisana area. Fig. 2. Tectonic image map of northeast Sudan.

5 56 Abdalla E. M. Elsheikh et al.: The Structural Evolution of the Hamisana Geodynamic Zone, Red Sea Region, NE Sudan Fig. 3. Structural map of the study area. (a) (b) Fig. 4. Equal area projection, (a) projection of common fold axes, the major trend is in N-S direction with minor others directions refer to minor folds. (b), projection of the dip with common dip direction to east and west.

American Journal of Earth Sciences 2015; 2(3): 52-60 57 These different folding styles were originated as a result of different tectonic events by the effects of the paleo-stress on rock materials

$SW normal to the acting stress (σ 3 ), where the shear fractures are in N-S and ENE-WSW direction parallel to the positive and negative shear arms (σs±), respectively in stress ellipsoid.$ $The observed fractures in the area are release, extensional and shear fractures, which were classified according to stress-strain ellipsoid (Fig. 6).$

6 American Journal of Earth Sciences 2015; 2(3): These different folding styles were originated as a result of different tectonic events by the effects of the paleo-stress on rock materials under different prevailing conditions. The structural measurements including foliation plains and folds axes orientations have been manipulated in rose diagram and stereonet projection (Figs. 4 and 5). These figures illustrate at least four folding orientation; namely: the NNW-SSE isoclinal folds, NE-SW folds, NW-SE folds and E-W open folding systems (see also Plate 1). SW normal to the acting stress (σ 3 ), where the shear fractures are in N-S and ENE-WSW direction parallel to the positive and negative shear arms (σs±), respectively in stress ellipsoid. The observed fractures in the area are release, extensional and shear fractures, which were classified according to stress-strain ellipsoid (Fig. 6). From the satellite images, field observations and structural measurements a general structural map of the study area has been created to manifest the common ductile and brittle deformations (Fig. 3) Structural Evolution of the Study Area Fig. 5. Stereonet projection showing the NNW, NE, NW and E-W folding axes Brittle Deformations Brittle deformation occurs under conditions where plastic deformation mechanisms are negligible and the rupture strength of the rock exceeds the plastic limit. Brittle structures dominate shallow crustal levels; it can also form in strong and dry zones in the lower crust and mantle. Brittle deformation tends to be extremely localized and result in structures that significantly weaken the upper crust [16], [14]. The fractures are generally classified into: open fractures including extensional, tensional and release fractures and the closed fractures represented by the two shear fractures, positive and negative arms [15]. The common type of faults in the study area is the strike slip faults. They are found with dextral or sinistral sense of movements. Z and S sigmoidal structures occur in abundance within the area, from which the sense of movement can be identified. The two arms of shearing can be delineated and the active one can easily be recognized. Z structures (dextral movements) are common, where S structures (sinistral movements) are less abundant (Plate 2). Accordingly, the active shear arm in the Hamisana area is the positive one of the Pan-African Orogeny that led to translational shearing. The extensional fractures are parallel to the greatest stress axis (σ 1 ) in NW-SE direction, the release fractures are in NE- The structural study has been conducted in the southern Hamisana area with the aim of collecting and manipulating the measurements of dip and strike for foliation and shearing planes to decipher the different phases of deformation. The measurements of foliations trends and dip are presented in a rose diagram (Fig. 4a). From the interpretation of this diagram, the general trend of the foliations in the area is in the N S direction with dip either to the east or west (Fig. 4b). The common fold axes trend is N-S direction with minor others directions. The stereonet projection indicates at least three phases of deformation, appear in the projection as folding in the NE SW trend, which is refolded in NNW- SSE and in E W directions (Fig. 5). Based on Rose diagram, stereonet projection and field checks, there are at least five phases of deformations: D1 is the formation of foliations; D2 is upright tight folding in NE-SW; D3 is the NNW-SSE folding; D4 is the open refolding in E-W; D5 is the reactivation of the N-S shearing that represents the dominant structural features in the area. According to the present studies in this part of the Nubian Shield, there are at least three episodes of tectonic events involving the above-mentioned phases of deformation. The first episode is the collision between old island arcs (soft collision) represented by the formation of foliations D1, followed by the strong event of collision between Haya and Gebeit terrains caused by SE-NW directional force that produced the NE sutures such as Nakasib suture zone [17] and the manifestation of N-S shear zone. The second episode is the collision of the mentioned arcs with Gabgaba terrain, resulting in the tight isoclinal upright fold in NNW, SSE (D3) regarded as a post collisional accretion [2]. A third episode is represented by the open folding with E-W axis, followed by reactivation of the common N-S shear zone (HSZ), which represents the last tectonic phase in the area. The outcome of the present study revealed that the former Hamisana Shear Zone (HSZ), represents a geodynamic zone, hereafter referred to as the Hamisana Geodynamic Zone (HGZ). This is evident by the crustal shortening represented by the existence of tight isoclinal folds as a result of strong collision during the ductile phase of deformation. The presence of ophiolitic masses within the area indicates thrusting of oceanic crust, as inferred from the eastward younging of ophiolitic lithologies opposite to the thrust direction [1]. The intensive N-S shearing marks a significant

7 58 Abdalla E. M. Elsheikh et al.: The Structural Evolution of the Hamisana Geodynamic Zone, Red Sea Region, NE Sudan cataclastic deformation. The obtained results reinforce that the Hamisana is a Geodynamic zone involving both ductile and brittle deformations. Fig. 6. The classified fractures in the study area, related to the common Pan-African collision direction in NW-SE using stress strain ellipsoids. Plate 2. Z, S structures and sigmoidal features in the area.

8 American Journal of Earth Sciences 2015; 2(3): Conclusions The Hamisana Shear Zone (HSZ) is a broad zone of deformation which considered as one of the largest basement structures in NE Africa. The present work has been undertaken to recognize the structural manifestations through the remotely sensed data and field measurements to understand the structural evolution of the study area with respect to the tectonic events of the Nubian-Arabian Shield in northeastern Sudan. Ductile deformation (folds) has been obtained in macroand meso-scales under different folding styles representing different deformation phases. In Landsat imagery, many folds are observed; where the N-S trending fold is the common folding direction, however, the NE-SW, NW-SE and E-W folding directions are also defined. Many types of folding are found representing many phases of deformations reflected in different folding including; tight up right isoclinal, overturned, recumbent and open folds. The common types of faults in the study area are strike slip faults, where the dextral sense of movements are dominant. The tectonic fractures are classified according to stress-strain ellipsoid. The extensional fractures are parallel to the greatest stress axis (σ 1 ) in NW-SE direction, the release fractures are in NE-SW normal to the acting stress (σ 3 ), where the shear fractures are in N-S and ENE direction parallel to the positive and negative shear arms (σ 2 s±), respectively. There are at least three episodes of tectonic events including five phases of deformations. The first episode is represented by the formation of foliations (D1), followed by the strong collision between Haya and Gebeit terrains (D2). The second episode is the collision of the mentioned arcs with Gabgaba terrain (D3). The third episode is represented by the open folding with E-W axis, and the reactivation of the N-S shear zone in the study area (HSZ) that represents the prominent structural feature in the area. The former HSZ represents a geodynamic zone, hereafter referred to as the Hamisana Geodynamic Zone (HGZ). This is evident by the crustal shortening represented by the existence of tight isoclinal folds as a result of strong collision during the ductile phase of deformation. The presence of ophiolitic masses within the area indicates thrusting of oceanic crust, as inferred from the eastward younging of ophiolitic lithologies opposite to the thrust direction. The intensive N-S shearing marks a significant cataclastic deformation. Acknowledgment This work was supported by the Orshab Minning Co. Ltd and Al Neelain University, Sudan to all we acknowledge and appreciate their support. References [1] Abdel Rahman, E. M. (1993). Geochemical and geotectonic controls of the metallogenic evolution of selected ophiolite complexes from the Sudan. Berliner GeowissAbh. (A), 145, 175Pp, Berlin (FU-Berlin). [2] Stern, R.J. (1994). Arc assembly and continental collision in the NeoproterozoicEastAfrican Orogeny: implication for the consolidation of Gondwanaland. Annual Review, Earth Planetary Science. 22/ [3] Vail, J. R. (1985). Pan-African (late Precambrian) tectonic terrains and the reconstructions of the Arabian-Nubian Shield. Geology, 13, [4] Kröner, A., Greiling, R., Reischmann, T., Hussein, I.M., Stern, R.J., Durr,S., Kruger, J. and Zimmer, M. (1987). Pan-African crustal evolution in the Nubian segment of the northeast Africa. In: kroner, A (ed), proterozoic lithospheric evolution. Amer. Geophs. Union, Geodynamics Series, 17, , Washington. [5] Hussein, I. M., Kröner, A. and Durr, St. (1984). WadiOnib-a dismembered Pan- African ophiolite in the Red Sea Hills of Sudan. Bull. Fac. Earth Sci., King Abdulaziz Univ., Jeddah, 6, , Jeddah. [6] Kröner, A. (1985). Ophiolites and the evolution of tectonic boundaries in the late Proterozoic Arabian-Nubian Shield of northeast Africa and Arabia.- Precambrian Res., 27, , Amsterdam. [7] Stoeser, D. B. and Camp, V. E. (1985). Pan-African micro plate accretion of the Arabian Shield.- Geol. Soc. Am. Bull., 96, , Baltimore. [8] Stern, R. J., Manton, W. I., Kröner, A., Reischman, T. and Hussein. I. M. (1989). Rb-Sr and U-Pb geochronology constraints on Late Precambrian crustal evolution in Northeast Sudan.- 28th Int. Geol. Congr. Washington, D. C., July , Abstrcts, 3, , Washington. [9] Almond, D. C., Kheir, O. M., and Poole, S. (1984). Alkaline basalt volcanic in northern Sudan: a composition of the Bayuda and Gadaref areas. Jour. Afr. Earth Sci. 2, 3, [10] Gupta, R. P. (2003). Remote Sensing Geology. 2nd ed. Springer-Verlag, Berlin Heidelberg, Germany. [11] Lillesand, T.M., and Kiefer, R.W. (2000). Remote Sensing and Image interpretation. 4 thed., John Wiley & Sons Ltd, New York, USA. [12] List, F. K. (1993). Fundamental of digital image processing for geologic applications. in: F.K. List and P. Bankwitz (eds),- proceed of the 4th United Nations / CDG Int. training course on remote sensing application to geological science, Potsdam & Berlin,-Berliner Geowiss.Adh., D, 5, 7-29, Berlin. [13] Park, R. G. (1997). foundation of structural geology, third edition, pp Printed in Chapman & Hall. [14] Williams, M.E. and Artoni, A., (1997). Progressive evolution of a fault-related fold pair from growth strata geometries. SantLloreq de Morunys, SE Pyrenees. Journal of Structural Geology,Vol. 19, Nos 34, pp. 413 to 441, 1997, Elsevier Science Publisher.

9 60 Abdalla E. M. Elsheikh et al.: The Structural Evolution of the Hamisana Geodynamic Zone, Red Sea Region, NE Sudan [15] Twiss, R.J. and Moores, E.M.; (1992). Structural geology.pp. 534.Freeman and company. [16] Cruikshank, K., Zhao, G., and Johnson, A., M., (1991). Duplex structures connecting fault segments in Entrada Sandstone. Journal of Structural Geology, Volume 13, Issue 10, 1991, Pages [17] Almond, D.C. and Ahmed, F. (1987). Ductile shear zones on northern Red Sea Hills, Sudan and their implication for crustal collision. Geological Journal, 22,

KEYWORDS: Remote sensing, GIS, Structural analysis, Geophysics, Groundwater, Hamisana, Red Sea Hills, Sudan.

KEYWORDS: Remote sensing, GIS, Structural analysis, Geophysics, Groundwater, Hamisana, Red Sea Hills, Sudan. The use of Remote Sensing and GIS Techniques as a Guide to Other Geological Methods for Groundwater Investigations in Hamisana Basement Terrains, Red Sea Hills, NE Sudan Abdalla E.M. Elsheikh, Khalid A.