Egypt

Egypt

Al Sukari Gold Mine

Al Sukari Gold Mine

Location: Marsa Alam, Red Sea, Egypt.

Products: Gold.

Owner: Centamin.

Geology of the Sukari gold mine area

The mine occurs within a Late Neoproterozoic granitoid (Arslan 1989; Harraz 1991) that intruded older volcanosedimentary successions and an ophiolitic assemblage, both known as Wadi Ghadir me´lange (El Sharkawi and El Bayoumi 1979). The volcanosedimentary succession is composed of andesites, dacites, rhyodacites, tuffs and pyroclastics. Magmatic rocks are of calc-alkaline affinity (Akaad et al. 1995) and were formed in an island-arc setting (El Gaby et al. 1990). The dismembered ophiolitic succession is represented by a serpentinite at the base, followed upwards by a metagabbro-diorite complex and sheeted dykes. Metagabbro-diorite rocks and serpentinites form lenticular bodies (1–3 km2) as well as small bodies occur conformably scattered in the volcanosedimentary arc assemblage (Harraz 1991). All rocks are weakly metamorphosed (lower greenschist metamorphic facies), intensely sheared and transformed into various schists along shear zones. Mineralized quartz veins and talc-carbonate veinlets are common.

The fresh rock is leucocratic, coarse-grained and pink in color. It has a heterogeneous mineralogical composition and ranges from monzogranite to granodiorite with dominant quartz, plagioclase and potash feldspars and less abundant biotite. The Sukari granitoid has a trondhjemitic affinity (Arslan 1989) and belongs to the ‘‘Younger Granite Suite’’ of Akaad and Nowier (1980).

Harraz (1991) argued for a transitional tectonic environment between within-plate, volcanic-arc and syncollision granite fields. The age of the Sukari granitoid body is poorly constrained (630–580 Ma, Harraz 1991) but documents Late Pan-African magmatic activity in the area.

In the vicinity of shear zones the granite is foliated, elsewhere, however, it has sharp intrusive contacts against the older rocks. Along those shear zones serpentinite and andesite is altered to listvenite rock (Khalaf and Oweiss 1993) that attains up to 70 m in thickness and extends for several kilometers. At the intersection of the two shear zones, where the gold mineralization is concentrated, the Sukari granite is almost completely altered and transected by a large amount of quartz veins.

Type of Deposit & Mineralization

The vein-type deposit is hosted in Late Neoproterozoic granite that intruded island-arc and ophiolite rock assemblages. The vein-forming process is related to overall late Pan-African shear and extension tectonics. At Sukari, bulk NE– SW strike-slip deformation was accommodated by a local flower structure and extensional faults with veins that formed initially at conditions of about 300 C and 1.5–2 kbar. Gold is associated with sulfides in quartz veins and in alteration zones. Pyrite and arsenopyrite dominate the sulfide ore beside minor sphalerite, chalcopyrite and galena. Gold occurs in three distinct positions: (1) anhedral grains (GI) at the contact between As-rich zones within the arsenian pyrite; (2) randomly distributed anhedral grains (GII) and along cracks in arsenian pyrite and arsenopyrite, and (3) large gold grains (GIII) interstitial to fine-grained pyrite and arsenopyrite.

Fluid inclusion studies yield minimum veinformation temperatures and pressures between 96 and 188 _C, 210 and 1,890 bar, respectively, which is in the range of epi- to mesothermal hydrothermal ore deposits. The structural evolution of the area suggests a longterm, cyclic process of repeated veining and leaching followed by sealing, initiated by the intrusion of granodiorite. This cyclic process explains the mineralogical features and is responsible for the predicted gold reserves of the Sukari deposits. A characteristic feature of the Sukari gold mineralization is the co-precipitation of gold and arsenic in pyrite and arsenopyrite.

How the Gold is Extracted

Thousands of pounds of explosives, trucks and shovels as large as a house, and massive grinding machines that can reduce hard rocks to dust are involved in the extraction process. In this way, Gold is extracted from one of the largest open-air mines on the planet. The raw material excavated from the terraces in the mine contains gold and arsenic in pyrite and arsenopyrite is a distinct feature of the gold mineralisation at Sukari.

It is the Only Open pit mine in Egypt.