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Selection of dam type for Luapula hydropower site at Mumbotuta site CX
Published in Jean-Pierre Tournier, Tony Bennett, Johanne Bibeau, Sustainable and Safe Dams Around the World, 2019
M Simainga, R Mukuka, M Muamba, L Engendjo
In the Mumbotuta Falls the Kundelungu outcrop consists of the Psammite and Rudite formation of which evidently only a Psammite (sandstone) development is represented in the area in question. Minor shale phases are thought to occur in the Psammite formation at Mumbotuta. Well to the north shales and carbonate rocks (limestones) form a significant part of the outcrop. Shoals occur to the south-east (upstream) of the dam center line, but downstream of the concrete cofferdam the water is very deep. The geology is similar to the upstream areas designated site M in various studies: The geology comprises fine grained sandstone interlayered by laminated siltstones in beds up to 1 m thick, but with a third rock type – a coarser-grained sandstone - also in evidence. From borehole CXI which is situated very close to the center-line the succession can be seen to be made up of very fine-grained sandstone giving way in places to the laminated siltstone in beds of up to 1 m in thickness. Thicker sequences of laminated siltstone occur near the top and bottom of the succession, but in total it does not exceed about 30% of the full thickness proved in the borehole.
Structure and topology of a brittle-ductile fault swarm at Crawford Knob, Franz Josef, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2023
Susan Ellis, Matthew Hill, Timothy A. Little
The fault swarm deforms Alpine Schist consisting mainly of biotite-grade quartzofeldspathic metagreywacke (psammite or meta-sandstone) with subordinate meta-argillite (pelite). Rocks intermediate in texture and colour between psammite and pelite (referred to here as semi pelite/psammite), laminated schist (alternating bands of pelite and psammite < 5 cm thick), strongly veined pelite (pelite that has been intruded by numerous quartz veins to make up 20–50% of the rock), and large (10’s of cm in diameter) quartz masses are also present. The dominant foliation in the schist strikes northeast at a mean azimuth of ∼045° and dips, on average, very steeply (80° or more) to the southeast. A recent paleogeothermometric transect of the Alpine Schist that includes the Franz-Josef Glacier indicates that biotite zone rocks near Crawford Knob experienced peak metamorphic temperatures of ∼400–524°C within ∼2 km to the SE of the ∼1 km-wide brittle-ductile fault swarm, and 525–536°C within 2 km to the NW of the swarm (Beyssac et al. 2016). As pointed out by these authors, these paleotemperature estimates relate to the steeply dipping, biotite-grade, peak-metamorphic fabric that is termed ‘S3’ by Little et al. (2002). The S3 Mesozoic foliation also deforms a pervasive set of 1–5 cm-thick quartz veins that mostly strike north and dip east at a moderate angle (Wightman and Little 2007), and crenulates an older, higher-strain foliation of shallower dip (known as ‘S2’), that is typically subparallel to relict bedding and was later cut and offset in the Neogene by the brittle-ductile faults at temperatures of 400–530°C (Wightman 2005; Wightman and Little 2007; Grigull et al. 2012, see below).