1 Metallogenic Characteristics of Some localities of gold mineralization Along Shear Zones of Elgaab, Dum el Tor and Sodri -Um Bader, (Sudan). Mohamed Osman ELGIZOULI 1, Badr El Din KHALIL 2 , Mohammed Y. ABEDELGALIL 2 1 Geological Research Authority of the Sudan, Khartoum, Sudan, orcid.org 0000-0002-7521-5685 2 Faculty of Petroleum and Minerals AlNileen University, Khartoum, Sudan Abstract The areas of study constitute the eastern sector of Saharan Meta-Craton which includes the western part of Bayuda Terrane and extend southwest to Sodri-Um Badir Shear Zones. The sector is dominated by metasediments, metavolcano-sedimentry series represented by chlorite schist, quartzite, calk-silicate and marble. Low- grade arc volcano-sedimentary sequence occurs as thin narrow bands and subjected to tectono-thermal events of Pan- African orogeny during Late-Proterozoic era (900 – 550 Ma.). All these rock sequences have been intruded by Syn-late orogenic granitoids and later by post-orogenic ring complex and felsic dykes. Those intrusions are thought to be the source of hydrothermal solutions that resulted in gold mineralization. Similar characteristics in geological, structures and geotectonic settings support the possibility of the extensions of gold mineralization between these shear zones. The comparison between the three gold mineralization zones reveals variations in minerals association, pathfinders, and grade of gold content. The result of this study define a new metallogenic province in the region west of the River Nile, which occupy a very large area covered by Phanerozoic sediments. Numerous mineral deposits of economic potentiality have been targeted along those shear zones and their fractures and faults. Among those potential deposits, five have been selected as targets for future gold exploration and evaluation. Key words: Shear, related, gold, mineralizations, in Sudan 1. Introduction The study area constitutes the eastern sector of Saharan Meta-Craton, which is bounded from northwest by Uweinat-Salima tectonic belt, from southwest by Rahib ophiolite Belt while southwestern boundary is the NE trending Wadi Hawar uplift. Central Africa Fault Zone with deep NE-SW faults extended through the southern part of the study area and from east area is bounded by the western margin of Bayuda desert (Fig. 1). The area is relatively flat and cover by thick Phanerozoic sediments. Field observations, geological mapping and geochemical investigations suggest that, those areas have similar litho-tectonic features, dominated by low grade meta-volcano-sedimentary sequences, which in North Kurdofan considered by Abdel Rahman et. al., (2006) as possible west continuation of the Upper Proterozoic Pan African Arabian Nubian Shield. The general NE-SW structural trend of the low-grade Pan-African rocks sequences was parallel to the dominant structural all over the Arabian Nubian shield. Gold mineralizations in Elgaab, Hamadi gold mine (Dum el Tor) and Gammama area of Sodri-Um Bader Shear Zones reveal similar characteristics in geological, structural and geotectonic settings. These characteristics support the possibility of the extensions of gold mineralization between these shear zones. A total of 266 samples (25 chips of quartz and rocks, 31 soil, and 190 trenches samples) have been collected and analyzed using Atomic Absorption Spectrometry (AAS) and X- Ray fluorescence (XRF) method. The artisanal gold mining mega-pits and trenches in Elgaab area has helped substantial investigations of the subsurface geology, beside description of the shapes, features and geometry of the ore body, lithological horizon bearing mineralization since there are no bores holes and geophysical survey conducted in the area. The main objective of the current study is to define the extensions of the gold mineralization along shear zones beneath thick cover of Phanerozoic sediments in the area of study. The result of this study is to define possible new metallogenic province in the region west of the river Nile. In the process, geological, geochemical and structural studies were carried out in the three shear zones. Bull. Min. Res. Exp. (2020) 163-? Bulletin of the Mineral Research and Exploration http://bulletin.mta.gov.tr BULLETIN OF THE CONTENTS Foreign Edition ISSN : 0026 - 4563 BULLETIN OF THE MINERAL RESEARCH AND EXPLORATION UNCORRECTED PROOF
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Metallogenic Characteristics of Some localities of gold mineralization Along Shear Zones of Elgaab, Dum el
Tor and Sodri -Um Bader, (Sudan).
Mohamed Osman ELGIZOULI1, Badr El Din KHALIL2, Mohammed Y. ABEDELGALIL2
1Geological Research Authority of the Sudan, Khartoum, Sudan, orcid.org 0000-0002-7521-5685 2Faculty of Petroleum and Minerals AlNileen University, Khartoum, Sudan
Abstract
The areas of study constitute the eastern sector of Saharan Meta-Craton which includes the western part of
Bayuda Terrane and extend southwest to Sodri-Um Badir Shear Zones. The sector is dominated by
metasediments, metavolcano-sedimentry series represented by chlorite schist, quartzite, calk-silicate and marble.
Low- grade arc volcano-sedimentary sequence occurs as thin narrow bands and subjected to tectono-thermal
events of Pan- African orogeny during Late-Proterozoic era (900 – 550 Ma.). All these rock sequences have
been intruded by Syn-late orogenic granitoids and later by post-orogenic ring complex and felsic dykes. Those
intrusions are thought to be the source of hydrothermal solutions that resulted in gold mineralization. Similar
characteristics in geological, structures and geotectonic settings support the possibility of the extensions of gold
mineralization between these shear zones. The comparison between the three gold mineralization zones reveals
variations in minerals association, pathfinders, and grade of gold content. The result of this study define a new
metallogenic province in the region west of the River Nile, which occupy a very large area covered by
Phanerozoic sediments. Numerous mineral deposits of economic potentiality have been targeted along those
shear zones and their fractures and faults. Among those potential deposits, five have been selected as targets for
future gold exploration and evaluation.
Key words: Shear, related, gold, mineralizations, in Sudan
1.
Introduction
The study area constitutes the eastern sector of Saharan Meta-Craton, which is bounded from northwest
by Uweinat-Salima tectonic belt, from southwest by Rahib ophiolite Belt while southwestern boundary is the NE
trending Wadi Hawar uplift. Central Africa Fault Zone with deep NE-SW faults extended through the southern
part of the study area and from east area is bounded by the western margin of Bayuda desert (Fig. 1). The area is
relatively flat and cover by thick Phanerozoic sediments. Field observations, geological mapping and
geochemical investigations suggest that, those areas have similar litho-tectonic features, dominated by low grade
meta-volcano-sedimentary sequences, which in North Kurdofan considered by Abdel Rahman et. al., (2006) as
possible west continuation of the Upper Proterozoic Pan African Arabian Nubian Shield. The general NE-SW
structural trend of the low-grade Pan-African rocks sequences was parallel to the dominant structural all over the
Arabian Nubian shield. Gold mineralizations in Elgaab, Hamadi gold mine (Dum el Tor) and Gammama area of
Sodri-Um Bader Shear Zones reveal similar characteristics in geological, structural and geotectonic settings.
These characteristics support the possibility of the extensions of gold mineralization between these shear zones.
A total of 266 samples (25 chips of quartz and rocks, 31 soil, and 190 trenches samples) have been
collected and analyzed using Atomic Absorption Spectrometry (AAS) and X- Ray fluorescence (XRF) method.
The artisanal gold mining mega-pits and trenches in Elgaab area has helped substantial investigations of the
subsurface geology, beside description of the shapes, features and geometry of the ore body, lithological horizon
bearing mineralization since there are no bores holes and geophysical survey conducted in the area.
The main objective of the current study is to define the extensions of the gold mineralization along shear
zones beneath thick cover of Phanerozoic sediments in the area of study. The result of this study is to define
possible new metallogenic province in the region west of the river Nile. In the process, geological, geochemical
and structural studies were carried out in the three shear zones.
Bull. Min. Res. Exp. (2020) 163-?
Bulletin of the Mineral Research and Exploration
http://bulletin.mta.gov.trB
UL
LE
TIN
OF T
HE
CONTENTS
Foreign Edition ISSN : 0026 - 4563
BULLETIN OF THE MINERAL RESEARCH AND EXPLORATION
UNCORRECTED PROOF
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2- Geological Setting
2.1 Lithology
The geology of the prospect areas were dominated by metasediments, metavolcano-sedimentry series
represented by chlorite schist, quartzite, calk-silicate and marble. Low- grade arc volcano-sedimentary sequence
occurs as thin narrow bands and subjected to tectono-thermal events of Pan- African orogeny during Late-
Proterozoic era (900 – 550 Ma.), resulted in low grade green-schist to lower amphibolite facies, with local high
grade gneiss inlier. All these rock sequences have been intruded by Syn-late orogenic granitoids mainly diorite
and later by post-orogenic ring complex and felsic dykes. The basement rocks of Northern Kurdofan consist of
high-grade and low-grade assemblage exposed in the foreland region of the Arabian-Nubian Shield west of the
Nile. Those assemblages are intruded by syn-orogenic granite and later by post-orogenic granite and dykes.
Fractures and shear zones were intruded by dykes of intermediate to acidic composition such as quartz porphyry,
dacite and trachyte.
Figure 1: Location Map of Area of Study
2.2 Geotectonic and Local Structures
The extension of Delgo – Atmur Suture east of the Nile, were represented by NNE Elgaab shear zone,
which possible extends up to Sodri – Um Badir shear zones in North Kurdofan. While Dum el Tor Sheer zone
which represent the western extension of the Red Sea- Oko Shear Zone of Nakasib Suture into east Bayuda
Desert, and possibly continue westwards. The rifting between East Sahara /Halfa and Bayuda /Kurmut eastern
terranes began prior to 750 Ma and could have started as early as 830 Ma (Kuster and Liegeois, 2001). Then
followed by sea floor spreading and ocean basin formation. Suturing of the terranes was initiated at around
720Ma, and it was probably completed by 700Ma (Stern et al., 1994). The Basin closure driven by N-S
shortening and collision between Halfa and Bayuda/ Kurmut terranes started at southeastern part of the Halfa
UNCORRECTED PROOF
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Figure 2: Geological map of the areas of study
Terrane probably around 750Ma (Abdelsalam et al.,1995). The obduction of Atmur-Delgo ophiolite took place
~702 Ma. (Harms et al., 1994), and the peak metamorphism were believed to occur at around the same time.
Collision between Bayuda/Kurmut and Halfa Terranes was associated with progressive deformation, granitoid
UNCORRECTED PROOF
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intrusions and metamorphism that continued until 650Ma. These granitoid intrusions were believed to be the
source of hydrothermal solution that initiated emplacement of gold mineralization. Data from Jebel Rahib
ophiolite within Rahib belt indicates that an ocean was present at ~740Ma until its closure at ~707 Ma. (Harms
et al., 1994). Multi-phase deformations have affected the basement rocks in the study areas. A pair of anticline
–syncline overturn fold system is recognized in the mapped area. The fold show NE-SW trending axial plane.
The NNE normal faults also affected the area. Other set of E-W trending fault represent by second order
drainage pattern, cutting lithological units and displaced the NE-SW trending lineament. The study area was
traversed by major shear zone trending NE and extend several hundred kilometers parallel to Dam El Tor Shear
zone, suggested earlier as western extension to Sodri- Um Badir shear zone of Northern Kurdofan by (Abdel
Rahman and Elmahi J. E. 2006). The central part of the shear zone in the area characterized by the present of
extensive quartz veins, which are embedded into a high shear acidic to intermediate meta-volcanic as well as
basic meta-volcanic and meta-sediment in Hamadi gold mine area.
However, more than five phase of deformation have affected the Hamadi gold mine East Bayuda area.
The first phase of deformation is a bedding plane Schistosity which is correspondent to first phase of
deformation. The second generation as folds overturn. Dextral shearing is the dominant one, reflected in
chevron fold Z- shaped fold, which in dimension vary From centimeters to hundred meters. This shearing gave
rise to quartz boundinage manifested by third phase of deformation. (Pinch and swelling). Similarly in Elgaab
gold mineralization zone exposed subsurface structures in artisanal gold mining mega pits, shows that at least
five phases of deformations have affected the area and represented by: D1; stress pressure (convergent)
explain by arrow, D2 folding, followed by D3; faults along fold axial-plane (3), then followed after by D4;
shears fabrics. D5 correspond to tension gashes (5). Those complex fabrics we believed to have facilitated the bath-ways to pregnant hydrothermal solutions to deposit the gold along shear zones (Plate 1-A).
Figure 3: The tectonic map of North and central Sudan modify after tectonic and Structural map of Sudan
(2016) and Rose- geo (2018) tectonic map of Sudan.
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Plate (1): A: a vertical section across artisanal gold mining mega-pits illustrates the subsurface structural