A Proterozoic Lacustrine Interlude from the Zambian Copperbelt

Evidence for participation of microbial mats in the deposition of the siliciclastic ‘ore formation’ in the Copperbelt of Zambia

“…Secondly, a ''silt/fine sand facies assemblage" consisting of thinly laminated siltstones and argillites and including layers of massive siltstone are interpreted as storm deposits within an otherwise low-energy environment. According to Clemmey (1978), this facies assemblage was deposited in the subtidal and intertidal zones under permanently subaqueous conditions during transgressions. From alternations of the two facies assemblages in the 'ore formation', Clemmey (1978) reconstructed five depositional cycles (Fig.…”

“…According to Clemmey (1978), this facies assemblage was deposited in the subtidal and intertidal zones under permanently subaqueous conditions during transgressions. From alternations of the two facies assemblages in the 'ore formation', Clemmey (1978) reconstructed five depositional cycles (Fig. 4) which are recognized over most of the Copperbelt and up to Katanga.…”

“…We selected this locality because (i) open pits generally expose more and larger bedding surfaces than underground workings and subtle sedimentary structures are usually better recognized on slightly weathered than on fresh surfaces; (ii) the intertidal/supratidal facies of the 'ore formation' is most promising for the development and preservation of microbial signatures, if compared with modern peritidal siliciclastic settings; (iii) lithostratigraphy and sedimentology of the succession have been well documented by Clemmey (1978); (iv) the same author has described from the succession some peculiar sedimentary structures and has furthermore related a specific type of ''wispy" lamination developed in some of the sediments to selective ''algal" binding in siliciclastic sediment.…”

“…Still further to the southwest, the depocentre ore-shale argillites grade into more dolomitic rocks (Mendelsohn, 1961). The great majority of orebodies are located in the intertidal/supratidal zone that is characterized by progradations/retrogradations and deposition of siltstone and argillite at transgressive stages, whereas precipitation of dolomite and anhydrite at regressive stages and subaerial exposure (Clemmey, 1978).…”

Non-cylindrical parasitic folding and strain partitioning during the Pan-African Lufilian orogeny in the Chambishi-Nkana Basin, Central African Copperbelt

“…The most important is a massive white, occasionally siliceous dolomite, intensely studied by other authors (Bard and Jordaan 1963;Clemmey 1974Clemmey , 1978Annels 1989;Croaker 2011). These studies and other Bull et al, 2011) have found that massive dolomite bodies are associated with so-called subeconomic barren gaps in the COM and always lies on inferred basement palaeohighs.…”