Abstract
The Tizert Cu-Ag deposit is the largest of a series of sediment-hosted copper deposits of the Anti-Atlas copper province in Morocco. Mineralized rocks in the deposit contain disseminated sulphides within a Late Ediacaran, dominantly siliciclastic sedimentary formation named the Basal Series. Isopach map of the Basal Series thickness shows that during the Late Ediacaran the area was composed of large subsiding zones separated by paleohighs. The ore-grade zones are well developed along basin margins adjacent to the basement paleohighs. These mineralized zones display a lateral sulphide zoning with central bornite-chalcocite zones grading outward to intermediate chalcopyrite and external pyrite zones. There is also a vertical sulphide zoning with evolution from bornite and chalcocite dominant mineralized rocks at the bottom to chalcopyrite and pyrite dominant mineralized rocks at the top of the lithostratigraphic succession. A second style of mineralization is represented by sulphide filled fractures and veins present in the Basal Series, as well as in the basement and the overlying dolomites. The similarity of the paragenetic sequences between the disseminated and the vein-hosted mineralization suggests that they may be related to the same mineralizing event, the disseminated style of mineralization being rapidly followed by the onset of the vein-style mineralization.
Highlights
Sediment-hosted stratiform copper deposits are widely distributed on earth and constitute an important source of copper at the global scale [1,2,3]
The early diagenetic view is suggested in cases where textures link early bacterial sulfate reduction with mineralization while the late diagenetic view is supported in cases where the ore zones are broadly transgressive relative to lithologies and the sulphide mineral paragenetic sequence exhibits textures documenting replacement of early diagenetic sulphides by late copper sulphides
This work is a contribution to the syngenetic versus epigenetic origin of the copper mineralization hosted by the terminal Neoproterozoic-Lower Cambrian sedimentary formations of the western Anti-Atlas, north of the West African Craton
Summary
Sediment-hosted stratiform copper deposits are widely distributed on earth and constitute an important source of copper at the global scale [1,2,3]. Active mines include the Tazalaght mine whose reserves are estimated to 260,000 t with 1.89% Cu [15], the Ouansimi mine whose reserves are estimated to 1,087,000 t with 2.63% Cu [16], and the Agjgal mine whose reserves are estimated to 5,000,000 t with 1% Cu and 20 g/t Ag [17], while others are presently closed (e.g., Talat N’ouaman, Assif Imider, and Cheikh Imi N’irifi deposits) These orebodies are hosted by Upper Neoproterozoic volcanic and volcaniclastic formations, for example, Alous [18] and Assif Imider [19] deposits, or by terminal Neoproterozoic clastic and carbonaceous sedimentary formations, for example, Tizert, Tiferki, and Talat N’ouaman deposits [14, 16, 20, 21]. An integration of the Tizert Cu deposit into the post-Pan-African tectonic evolution of the western AntiAtlas is presented
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