A traveller's guide to the geology of Everest (a traverse from Lukla to Everest)
Hochreiter, Rene Carlo
In this, Part 1 of a two-part MSc, the geology of the area between Lukla and Mount Everest is described. An outcome of the MSc is the production of a field guide to this area, presented as Part 2 of this thesis. The collision between India and Asia resulted in the Himalayan orogen, 3000 km in lateral extent, an elevated Tibetan Plateau and a crust of at least 60 km in thickness. The resulting crustal flow from under this region is in the direction of least resistance, eastwards towards the Pacific subduction zones, but there is also southwards flow towards the Indian subcontinent resulting in vertical complexity. This southwards extrusion of mid-crustal rocks through a mechanism termed channel flow explains the presence of Miocene leucogranite between Ordovician limestones comprising the summit of Everest, and granite gneiss underlying the exhumed granite. Rapid rates of denudation assisted the extrusion of crustal slabs between the South Tibetan Detachment (STD) and the Main Central Thrust (MCT). Low-grade metamorphic rocks of the Everest Series are juxtaposed across the STD with the underlying high-grade metamorphic rocks of the Greater Himalayan Sequence (GHS). The GHS rocks in turn, are juxtaposed across the MCT with the underlying low-grade Siwaliks. Everest Series schists record temperatures of between 600 °C and 650 °C, and pressure estimates for these rocks ranging from 2.9 ± 0.6 kbar to 6.2 ± 0.7 kbar, corresponding to burial depths of between 10 km and 20 km. The GHS experienced eclogite facies metamorphism with pressures of > 14 kbar (>45 km depth) before being exhumed to granulite facies conditions of 4-6 kbar and 700-800 °C. High-temperature metamorphism of the GHS has resulted in partial melting and melt segregation and ascent to form the High Himalayan Leucogranites, a number of granitic bodies that have accumulated near the top of the GHS. Intense erosion through the action of glaciers, rivers, landslides and earthquakes (as the 25th April 2015 magnitude 7.8, and 12th May 2015, of magnitude 7.3 earthquakes attest), balance uplift of the Himalaya.
A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2016.
Hochreiter, Rene Carlo (2016) A traveller's guide to the geology of Everest (a traverse from Lukla to Everest), University of Witwatersrand, Johannesburg, <http://wiredspace.wits.ac.za/handle/10539/21688>