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.
Location: Marsa Alam, Red Sea, Egypt.
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.
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