Arabian Gold Licences

Detailed descriptions of the licences to follow.

Geology

The Al Amar-Idsas fault is one of the most important geological-tectonic features of the eastern region of the Arabian Shield. The nature of the fault has long been the subject of widely varying interpretations, however, the apparent 'best-fit' model combines several of these interpretations with the early Neoproterozoic (850-550 Ma) terrane accretion model which is generally accepted for the overall formation of the Arabian-Nubian Shield. The Arabian Shield consists of deformed and metamorphosed volcanic and sedimentary rocks, which were deposited in volcanic arcs, sedimentary basins, half-grabens and other types of complex oceanic environments, and vast amount of granitic, dioritic and other igneous rock. These rocks were formed during a process of crustal accretion that starts with the collision and accretion of juvenile oceanic crust and possible continental microplates which resulted in the creation of new continental lithosphere about 40 - 45 km thick. By the end of the Precambrian, this crustal layer, which is subdivided into an upper section of volcanic, sedimentary, and igneous, mainly granitic, rocks, and a lower section of mainly mafic rocks, each about 20 km thick, was sutured between the cratons of West and East Gondwana.

The Al Amar-Idsas fault is interpreted as being an easterly dipping thrust fault with the eastern Ar Rayn terrane (comprising a meta-volcanic sequence, the Halaban Group, overlying a gneissic granodiorite basement) having been thrust over a back-arc basin derived accretionary prism (a predominantly meta-sedimentary sequence, the Abt Formation) which itself has been thrust over the western Ad Dawadimi sub-terrane (part of the larger accreted Afif terrane and similar in compositon to the Ar Rayn terrane).

The Halaban Group comprises two phases of igneous activity:

• The Meharga volcanics - an early phase of calc-alkali volcanic arc rocks derived from a westerly dipping subduction zone to the east of the Ar Rayn terrane; characterised by meta-basalt flows alternating with thick meta-andesitic flows.

• The Al Amar volcanics - a secondary phase of volcanic arc rocks, once more derived from the presence of the westerly dipping subduction zone; characterised by slightly metamorphosed andesitic flows alternating with thick altered rhyolitic volcanic and associated agglomerate, volcanic breccias, pyroclastic rocks and conglomerate.

Economic Geology

Proterozoic basement rocks are host to dominantly zinc-copper-gold mineralisation, the oxidised parts of which had most likely been prospected and mined probably as long ago as 2500 B.C. More recent evidence, in the form of ruined mining villages, pottery and charcoal from slags confirms, via C14 dating, that mining was occurring around 800 A.D. (Vaslet et al., 1983). Several mineral occurrences are known in the volcanic and sub-volcanic rocks of the Al Amar volcanic Group to which they are genetically related. Some are directly linked to the volcanism whilst others are associated with soda rhyolite protusions (the Al Amar deposit) or are segregations in sub-volcanic intrusions or are volcanosedimentary mineralisations that were modified by contact with silicic intrusions. The most notable mine is the Al Amar mine, being operated by Ma'aden. The Al Amar resources includes:

• North vein zone - 1.55Mt at 12.3 g/t Au, 6.16% Zn, 21.1 g/t Ag, 0.92 % Cu (Measured and Indicated)

• South vein zone - 3.0 Mt at 5.1 g/t Au (Inferred)

The mine is currently operating as an 'up/down-hole retreat-stoping' underground operation with production of approximately 200,000 t per year. Open pit potential exists but this would most likely require extensive evaluation (Source: Ma'aden website).

Other notable occurrences include:

Jabal Idsas - comprising segregated lenses of massive magnetitie occurring in gabbor, diorite and microdiorite near the contact with porphyritic and aphyric andesite of the Sidriyah formation which itself contains appreciable disseminated magnetite. Lenses are scattered over an area of 7 km2 and vary from 30 - 460 m in length and 0.5 to 15 m in thickness. Resources are quoted as 105 Mt at 18-20% Fe (Collenette et al., 1994).

Numerous veins of quartz and carbonate cut almost all the Proterozoic rock units. Ages of emplacement remain unclear but with an absence of deformation it would appear that most are related to the last epirogenic movements of the Najd fault system and more specifically to a late Proterozoic rejuvenation of the Al Amar-Idsas fault zone. Locally veins are weakly mineralised in lead, copper, gold and silver and were prospected in ancient times.

References:

Nawab, Z.A., 1979, Geology of the Al Amar - Idsas region of the Arabian Shield, Volume 2, Bulletin No.3 - Evolution and Mineralization of the Arabian-Nubian Shield, Institute of Applied Geology (King Abdulaziz University, Jeddah), pp29-39.

Vaslet, D., Manivit, J., Le Nindre, Y., Brosse, J., Fourniguet, J., Delfour, J., 1983, Explanatory notes to the Geologic Map of the Wadi Ar Rayn Quadrangle, Sheet 23H, to accompany Map GM-63 C, DMMR.