Arabian Gold Licences

Detailed descriptions of the licences to follow.

Regional Geology

The Ishmas-Nabitah geological district includes two terranes, the eastern and western, which are separated by the north-trending Nabitah Fault Zone (NFZ). The eastern terrane, constituting part of the Malahah-Najran terrane, is composed of amphibolite and mylonite schist, originally a sequence of volcanic and volcaniclastic rocks of Halaban age (785 - 746 Ma), and an intrusion of monzogranite. The western terrane, constituting part of the Asir terrane, comprises Halaban age formations which include mafic volcanic rocks, ferruginous chert, carbonates and volcanic wacke. Some fine grained amphibolites is also present along with older plutonic rocks which include an extensive diabase sill complex and several gabbro intrusive.

Post-Nabitah plutonic rocks in the western terrane include quartz-diorite plutons, tonalite masses, dacite porphyry and quartz monzodiorite.

Three phases of faulting have been identified in the regional and can be defined as follows:

• Nabitah-age - closely related to the what is thought to be the actual suture zone. Characterised by steeply dipping faults, shear zones and mylonitic belts striking 5° west or east of north and commonly hosting elongate diapiric bodies of serpentinite. Parallel structures in the vicinity of the main suture zone are thought to be synchronous and related (Doebrich et al., 1988). This deformation was plastic in character and is more typical of deformation by compressional forces at depth.

• Transitional-age -- these are transitional between the Nabitah and Post-Nabitah (Najd) age structures in both orientation and deformation style. The lack of mylonitization and serpentinite emoplacement differentiates these structures from Nabitah structures of similar orientation.

• Post-Nabitah (Najd) age -- throughout the Arabian Shield, the Najd faulting event was characterised by elastic deformation of a brittle craton resulting in an extensive left-lateral wrench-fault system (Moore et al, 1979). In this region the event is manifested by a series of steeply dipping faults that offset both Nabitah and Transitional-age structures. This phase of deformation was more elastic in nature with brittle facture deformation and tensional features being characteristic of a shallower environment.

Economic Geology

There are over 30 gold occurrences within the district. These occurrences range in size from isolated surface exposures to large ancient workings with extensive tailings. Several phases of work have investigated these occurrences in the past (Worl, 1979; Doebrich et al., 1988) with several locations having resource potential. More critically the area as a whole has yet to be thoroughly investigated by modern exploration technologies giving great upside-potential for the discovery of significant resources.

Mineralisation occurrences in the Ishmas-Nabitah geological district can be generally grouped chronologically in association with the first and third phases of deformation described in the previous section:

• Nabitah-age type mineralisation is exemplified by auriferous quartz pods occupying faults and shear zones that originated during the Nabitah orogeny (synchronous with accretion and suturing). The faults characteristically strike within 5° west or east of north and contain either schist or mylonite. Quartz pods commonly exhibit crustification and vugs and can be as long as 65 m and as thick as 5 m. Slickensides are common on pod margins and sulphides are occasionally observed in the quartz (pyrite, galena, chalcopyrite). There is some variation in the style of alteration zones present adjacent to the veins, namely pyritic iron-carbonate or pyrite-sericite (White et al., 1988). The lack of proximal intrusive bodies suggests a deep-seated, distal source for the mineralising fluids. North American studies of analogous quartz-Au veins have proposed that fluids originated from deep circulation of meteoric water, from granulation of lower crustal material and from deep-seated isotopically heavy metasomatic fluids of unknown source.

• Post-Nabitah type mineralisation is mostly associated with quartz veins and fault breccias hosted in igneous intrusions. The strikes of the faults vary and comprise ferruginous fault breccias and argillized gouge. Quartz veins average 0.5 m in thickness and are continuous rather than podiform. Veins contain internal iron-oxide-coated parting surfaces but lack well developed crustification and vugs. Sulphides present in the quartz include pyrite, galena and chalcopyrite. Alteration adjacent to the quartz veins is mostly pyrite-sericite with a late carbonate overprint. Within the faults, gold and molybdenum are commonly enriched in the quartz veins with arsenic and copper generally concentrating in the adjacent fault breccias.

Regardless of the fluid origin, the basic elements of the ore-forming process are generally thought to be the same in the faults of both ages, with fluids leaching constituents from surrounding country rock, concentrating in permeable fracture zones and then precipitating quartz, gold and associated sulphides. The quartz body was dependent on the host rock and structure type (strike-slip or open) and gold precipitation was predominantly concentrated in the quartz with subsequent remobilisation and recrystallisation to adjacent fractured and sheared footwall and hanging wall contacts as a result of weathering (supported by iron-oxide-coated fracture surfaces, White et al., 1988).

References:

Doebrich, J.L., White, W.H., 1988, Geology of the Ishmas Gold District, Kingdom of Saudi Arabia: Saudi Arabian Directorate General of Mineral Resources Technical Report USGS-TR-08-1, 40p.

Moore, J.Mc., Al-Shanti, A.M., 1979, Structure and mineralization in the Najd Fault System, Saudi Arabia, Volume 2, Bulletin No.3 - Evolution and Mineralization of the Arabian-Nubian Shield, Institute of Applied Geology, King Abdulaziz University, Jeddah, pp17-28.

White, W.H., Doebrich, J.L., 1988, Gold deposits of the Ishmas district, Kingdom of Saudi Arabia: Saudi Arabian Directorate General of Mineral Resources Technical Report USGS-TR-07-5, 73p.

Worl, R.G., 1979, Gold deposits associated with the Jabal Ishmas-Wadi Tathlith Fault Zone, Volume 2, Bulletin No.3 - Evolution and Mineralization of the Arabian-Nubian Shield, Institute of Applied Geology, King Abdulaziz University, Jeddah, pp61-69.

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