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Jabal Sayid |
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Saudi Arabia |
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Cu Zn Au
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Super Porphyry Cu and Au
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The Jabal Sayid volcanic hosted stockwork and massive sulphide (VHMS) copper - zinc deposit is located approximately 120 km south-east of Medina (Al Madinah) in central western Saudi Arabia (#Location: 23° 51' 2"N, 40° 56' 29"E).
The deposit comprises at least four steeply plunging lenses within Neoproterozoic volcanic hosts of the Arabian-Nubian Shield.
The Arabian section of the Neoproterozoic Arabian-Nubian Shield and overlying Palaeozoic to Cenozoic Platform lie between the Nubian section of the same Shield to the south-west (separated by the Red Sea) and the more recent Alpine-Himalayan (Tethyan) Zagros mountains to the north-east. The Arabian-Nubian Shield is part of the much larger East African Orogen that extends throughout Eastern Africa and constituted the core of the Neoproterozoic Gondwana super-continent. The exposed, trapezoidal-shaped, 1500 x 500 km Arabian section of the shield, which forms the western half of Saudi Arabia (and extends into Yemen to the south and Jordan to the north), is largely composed of the high grade metamorphic roots of a Neoproterozoic (860 to 540 Ma) complex of continent margin magmatic arc volcanics (750 to 685 Ma), successor basin sediments (632 to 620 Ma) and post-orogenic intrusives (659 to 601 Ma). Older interspersed Paleoproterozoic to Mesoarchaean rocks are also known in the east of the shield. The Arabian section of the shield is bounded to the west by the Cenozoic Red Sea rift valley and its coastal plain (Tihama), and to the north and east by Phanerozoic platformal sedimentary rocks.
The Arabian-Nubian Shield is composed of a series of terranes, separated by suture zones. The terranes in the west are compose of oceanic arc suites, while the eastern terranes may have some continental affinity. The suture zones separating the individual terranes are characterised by highly deformed ophiolite complexes composed of distinctive mafic and ultramafic rocks. The three SW-NE trending suture zones in the west (the Ad Damm, Bi'r Umq and Yanbu) represent the fusing of the 850 to 700 Ma western island arcs of the Midyan, Hijaz, Jeddah and Asir terranes. Further to the east, the NNW-SSE Nabitah suture represents a probable major continental collision event between these three terranes, which together constitute the Western Oceanic terranes and the Afif and other smaller terranes of the Eastern Oceanic terranes in the east. These terranes were progressively amalgamated between 715 and 630 Ma. Following amalgamation, deformation and the intrusion of igneous rocks continued.
The development of seas within the orogenic belt associated with subsequent collapse and extension of the orogen resulted in the deposition of thick sequences of shallow-water to terrestrial sedimentary and the extrusion of mainly rhyolitic volcanic rocks, and coeval granitic rocks between 640 and 570 Ga. Toward the end of this magmatic episode, basaltic and intermediate lavas were interbedded with sediments in continental basins that had resulted from movement along the NW- to NNW-trending transcurrent faults of the Najd wrench-fault system that operated from about 640 to 550 Ma which displaced segments of the orogen to the northwest. These episodes marked the accretion of the Arabian portion of Gondwana during the Pan-African tectonic event.
For more detail of the setting, tectonics and geology of the Arabian-Nubian Shield see the separate Arabian Nubian Shield Overview and the Central Arabian Gold and Base Metal Region records.
The Jabal Sayad deposit lies within the northeastern corner of the Jiddah Terrane, one of the Western Oceanic terranes, and is located immediately to the south of, or within, the Biir Umq Suture zone, just to the west of the Nabitah Mobile Belt. The hosts consist of stretched and sheared volcanic, sedimentary and plutonic rocks that are tightly to isoclinally folded about north-trending axes and cut by a great number of north-trending brittle-ductile shear zones.
The Jabal Sayid VHMS copper-zinc deposit is hosted by ~800 Ma felsic metavolcanic rocks in the upper part of the Sayid Formation, the lower felsic unit of the Al Arj Group that dips steeply to the northwest and forms the northwestern flank of a NNE trending anticline. The Al Arj Formation is interpreted to unconformably underlie the 785 to 775 Ma Mahd Group that hosts the Mahd Ad'Dahab. Both are intruded by the 780 to 760 Ma Hufayriyah Complex which comprises irregular plutons of tonalite. The principal hosts are rhyolitic volcanic, sub-volcanic and pyroclastic rocks with intercalated layers of jasper. They are overlain by a volcano-sedimentary unit composed of conglomerate, sandstone and pelitic rocks containing pyrite, which is in turn, overlain by a unit of andesitic rocks. The tuffaceous rocks of the deposit footwall are typically chloritised and contain more pyrite than the hanging-wall tuffs.
Four sulphide bodies are known, confined within a north-easterly 200 to 700 m wide corridor which can be traced over a 1.2 km length. Deposit 1 is exposed as the conspicuous 'Main Gossan'. To the northeast, this gossan is displaced 400 m to the east by the major dextral, ENE-trending, strike-slip East Valley Fault, to form the Northeast Gossan. Drilling below this gossan encountered the blind Deposit 2, which appears to be unrelated to the gossan. The surface expression of Deposit 4 is a number of discontinuous outcrops of chert. Small pyritic bodies to the west of deposits 2 and 4 comprise Deposit 3.
Three styles of mineralisation are recognised, namely:
i). massive fine-grained sulphides, which are poor in copper but rich in zinc, and are found at deposits 1 and 4, occurring as tabular to lenticular bodies of >40 to 50% sulphide that consist of a fine-grained, very variable assemblage of pyrite, sphalerite and chalcopyrite, subordinate pyrrhotite, magnetite, galena and tetrahedrite, with rare arsenopyrite and cassiterite;
ii). copper-rich stockwork stringer ores which are zinc-poor, and are found at deposits 2 and 4 and comprise blebs and ramifying thin veins and disseminations of chalcopyrite, pyrrhotite and lesser pyrite and minor associated sphalerite, pyrrhotite and various tellurides. This zone is characterised by strong chloritisation and silicification of host volcanic rocks;
iii). sulphide breccia, which is relatively rich in copper, being characterised by late coarse-grained chalcopyrite, and occurs at Deposit 1. It is variably overprinted by veins, veinlets, blebs and disseminations of chalcopyrite with lesser pyrite.
Galena and magnetite are generally rare, while tellurides can only be seen under the microscope. Precious metal values are of the order of <0.5 ppm Au and 30-50 ppm Ag in the massive sulphides and 0.1 ppm Au and 10 ppm Ag in the stockwork.
Deposit 4 is the largest and consists of a vertical stockwork of pyrite and chalcopyrite veinlets accompanied by disseminated sulphides in a sub-volcanic dome of variably chloritised quartz porphyritic rhyolite. The stockwork is stratigraphically overlain about 300 m below surface by a 10 m thick lens of massive pyrite and pyrrhotite showing pronounced clastic textures, and by a 22 m thick unit of jasper. The massive sulphide and jasper were evidently deposited under subaqueous conditions, as was the succeeding rhyolitic crystal lithic tuff. The deposit extends from ~200 m to ~800 m below the surface and is open at depth.
Details of the individual ore lenses, including resources and dimensions as follows:
Deposit 1 - is characterised by a steeply plunging massive pyrite breccia body with disseminated chalcopyrite and spalerite. The deposit extends for over 400 metres down plunge with a width of around 100 m and is open at depth.
JORC resources in 2007 (Citadel Resources) include:
Indicated Resource - 1.85 Mt @ 1.61% Cu, 1.44% Zn;
Inferred Resource is 4.64 Mt @ 1.53% Cu, 1.29% Zn.
Alternatively, the deposit comprises non-JORC resources of:
Massive sulphide copper ore - 4.1 Mt @ 1.9% Cu, 1.3% Zn;
Massive sulphide zinc ore - 6.9 Mt @ 0.4% Cu, 2.0% Zn;
Deposit 2 - consists of a reasonably coherent body of stringer-style chalcopyrite with lesser massive sulphide hosted by chloritised, silicic volcanic rocks, that extends down plunge for >300 m, by ~100 m wide.
JORC resources in 2007 (Citadel Resources) include:
Indicated Resource - 3.27 Mt @ 2.23% Cu;
Inferred Resources - 3.33 Mt @ 1.67% Cu.
Alternatively, the deposit comprises non-JORC resources of:
Stringer copper ore - 8.8 Mt @ 1.7% Cu, including,
A high grade zone of - 6.4 Mt @ 2.1% Cu.
Deposit 4 - hosts the bulk of the mineralisation and is principally chalcopyrite stringer mineralisation with an associated west facing pyritic Cu-Zn lode not incuded in the resource. The deposit extends down plunge for >600 m, by ~350 m wide;
JORC resources in 2007 (Citadel Resources) include:
Indicated Resource - 9.83 Mt @ 2.03% Cu;
Inferred Resource is 23.26 Mt @ 1.71% Cu.
Alternatively, the deposit comprises non-JORC resources of:
Stringer copper ore - 43.2 Mt @ 1.6% Cu, including,
A high grade zone of - 25 Mt @ 2.3% Cu.
Massive sulphide zinc ore - 11 Mt @ 0.5% Cu, 2.3% Zn.
Total Resource in the three deposits - 46.1865 Mt @ 1.79% Cu.
Total JORC compliant resource estimates as at February, 2008 (Citadel Resources) were 74 Mt of ore, including:
Stockwork ore - 52 Mt @ 1.6% Cu, including 31 Mt @ 2.2% Cu
Massive sulphide copper ore - 4 Mt @ 1.9% Cu, 1.3% Zn;
Massive sulphide zinc ore - 18 Mt @ @ 2.2% Zn and 0.4% Cu
The resource does not include the oxide gold caps or the gold contained within the copper sulphides.
Total NI 43-101 compliant Ore Reserve and Mineral Resource estimates 31 December 2018 (Ma'aden Annual Report, 2018) were:
Remaining Proved + Probable Ore Reserves - 27.11 Mt @ 2.39% Cu, 0.35 g/t Au (cut-off 1.4% Cu), plus,
Remaining Measured + Indicated + Inferred Mineral Resources - 6.17 Mt @ 1.92% Cu, 1.45 g/t Au (cut-off 1.4% Cu).
The Jabal Sayid mine was commissioned in 2015, followed shortly after by the first comercial production.
Much of the information detailed above has been drawn from reports, ASX releases and website entries of Citadel Resources Group Limited and Equinox Minerals Limited.
The most recent source geological information used to prepare this decription was dated: 2007.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Jabal Sayid
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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