Copper–Gold–Sulphide Mineralization Associated with Late Precambrian Volcanic Ring Structures, Southern Sinai, Egypt (original) (raw)
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The Kid Group is one of the fewexposures of Neoproterozoicmetavolcano-sedimentary rocks in the basement of southern Sinai in the northernmost Arabian–Nubian Shield. It is divided into the mostly metamorphosed volcaniclastic Melhaq and siliciclastic Um Zariq formations in the north and the mostly volcanic Heib and Tarr formations in the south. The Heib, Tarr, and Melhaq formations reflect an intense episode of igneous activity and immature clastic deposition associated with core-complex formation during Ediacaran time, but Um Zariq metasediments are relicts of an older (Cryogenian) sedimentary sequence. The latter yielded detrital zircons with concordant ages as young as 647±12 Ma,whichmay indicate that the protolith ofUmZariq schistwas deposited after ~647 Ma but 19 concordant zircons gave a 206Pb/238U weighted mean age of 813±6 Ma, which may represent themaximumdepositional age of this unit. In contrast, a cluster of 11 concordant detrital zircons from the Melhaq Formation yield a weighted mean 206Pb/238U age of 615±6 Ma. Zircons from Heib Formation rhyolite clast define a 206Pb/238U weighted mean age of 609±5 Ma, which is taken to approximate the age of Heib and Tarr formation volcanism. Intrusive syenogranite sample fromWadi Kid yields a 206Pb/238Uweighted mean age of 604±5 Ma. These constraints indicate that shallow-dipping mylonites formed between 615±6 Ma and 604±5 Ma. Geochemical data for volcanic samples from the Melhaq and Heib formations and the granites show continuous major and trace element variations corresponding to those expected from fractional crystallization. The rocks are enriched in large ion lithophile and light rare earth elements, with negative Nb anomalies. These reflectmagmas generated by melting of subduction-modified lithospheric mantle, an inference that is further supported by εNd(t)=+2.1 to+5.5. Thismantle source obtained its trace element characteristics by interaction with fluids and melts from subducting oceanic crust during the Late Cryogenian time, prior to terminal collision between fragments of East and West Gondwana at ~630 Ma. Positive εNd(t) values and the absence of pre-Ediacaran zircons in all but Um Zariq metasediments indicate minor interaction with Cryogenian and older crust. A model of extensional collapse following continental collision, controlled mainly by lithospheric delamination and slab break-off is suggested for the origin of the post-collision volcanics and granites at Wadi Kid. No evidence of pre-Neoproterozoic sources was found. Kid Group Ediacaran volcanic rocks are compositionally and chronologically similar to the Dokhan Volcanics of NE Egypt, which may be stratigraphic equivalents.
Euro-Mediterranean Journal for Environmental Integration, 2024
The Hamama metavolcanics and their sulfide deposits are an important part of the Neoproterozoic Shadli bimodal metavolcanics in the central Eastern Desert (CED) of Egypt and recently became a promising target for gold exploration in Egypt. Semi-massive to massive sulfide deposits occur in quartz-carbonate exhalite and as disseminated grains in metabasalt and metadacite. The Hamama prospect comprises polymetallic bimodal-mafic-type volcanogenic massive sulfide (VMS) deposits, particularly Zn-Cu-Ag-Au VMS deposits. Polybasite is a silver-bearing sulfosalt (65.17-71.81 wt% Ag). Arsenic-bearing framboidal pyrite is the main host of the precious metals (Au and Ag contents reach up to 0.12 wt% and up to 0.55 wt%, respectively). The arsenic-rich fluids likely promoted gold and silver accumulation in framboidal pyrite, which is hosted in the quartz-carbonate exhalite. This exhalite may have acted as a cap rock preventing the dissipation of the metal-rich hydrothermal fluids. Gold-and silver-bearing sulfides were possibly formed in a back-arc basin, which is considered as a suitable environment for VMS formation. The dominance of Zn and Ag reveals that the Hamama VMS deposits were generated at low temperature and a shallow water depth during rifting of the intra-oceanic island arc. Supergene processes formed secondary copper deposits in the upper part of the exhalite. Gold and silver are also accumulated in the gossan zone that is formed by low-temperature oxidized fluids. The factors controlling precious metal mineralization in the CED of Egypt are possibly related to the composition of the host rock and the hydrothermal fluid beside shear zones that act as channels for fluid circulation in an extensional tectonic setting.
Gondwana Research
SHRIMP U–Pb dating reveals that the hypabyssal Katerina Ring Complex formed over a ~ 9 Ma interval. The first rocks that formed were the alkaline to peralkaline granitoids that form the wall and the roof cap of the Ring Dike, emplaced at 602 ± 8 Ma and 602 ± 4 Ma respectively. These were closely followed by the Isbaiya calc-alkaline quartz-monzonites at 599 ± 3 Ma, and by the main Katerina pluton at 596 ± 3 Ma. The pluton is composed of A-type metaluminous fluorite-bearing granites that contain one inherited Archean zircon (~ 3.2 Ga). The Katerina magmatic cycle ended with the intrusion of another peralkaline body in the ring interior at 593 ± 2 Ma; this body forms the summit of Gebel Musa (Mount Sinai). The Ring Dike encloses older rocks such as the 844 ± 4 Ma Moneiga quartz-diorites and the 622 ± 3 Ma Rutig volcanic rocks. The conglomerates interbedded with these contain boulders of granites with ages of 735 ± 6 Ma and 748 ± 11 Ma. Outcrops of igneous rocks with these ages are cur...
Genesis and evolution of the Hamama volcanic massive sulphide deposits, Egypt
IOP Conference Series: Materials Science and Engineering, 2019
Hamama Zn-Pb-Cu VMS deposits are hosted along the contact of bimodal metavolcanic sequence and their volcaniclastics in association with quartz-carbonate matrix. Ore forming process include multi-stage steps. 3D interpolation of drill hole database shows that the ore body was affected by multidirectional faults and fracture zones, that later were occupied by carbonates. The origin of carbonates is approached using a C and O isotopic compositions in whole-rock samples. The isotopic data revealed signs of both hydrothermal-sedimentary and hydrothermal-metasomatic processes. The primary gold and sulphide minerals were deposited from exhalations, forming massive sulphide ore then the tectonic processes due to the emergence of two successive phases of granitoids followed by the of post-tectonic dykes provided war to the introduction of carbonates that changed the configuration of the ore deposit and affected its grade. Later diagenetic and metasomatic processes resulted in enrichment of ...