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Recent Submissions
Researching Back Internet Governance: Towards a Critical Internet Governance?
Rosa, Fernanda R. (2025-04-15)
Evidence of Dislocation Mixed Climb in Quartz From the Main Central and Moine Thrusts: An Electron Tomography Study
Weidner, Timmo; Mussi, Alexandre; Castelnau, Olivier; Kronenberg, Andreas; Law, Richard D.; Cordier, Patrick (American Geophysical Union, 2024-07)
In this study we apply electron tomography to characterize 3D dislocation microstructures in two quartz mylonite specimens from the Moine and Main Central Thrusts, both of which accommodated displacements by dislocation creep in the presence of water. Both specimens show dislocation activity with dislocation densities of the order of 3–4 × 1012 m−2 and evidence of recovery from the presence of subgrain boundaries. 〈a〉 slip occurs predominantly on pyramidal and prismatic planes (〈a〉 basal glide is not active). [c] Glide is not significant. On the other hand, we observe a very high level of activation of 〈c + a〉 glide on the (Formula presented.), (Formula presented.), (Formula presented.) (n = 1,2) and even (Formula presented.) planes. Approximately 60% of all dislocations show evidence of climb with a predominance of mixed climb, a deformation mechanism characterized by dislocations moving in a plane intermediate between the glide and the climb planes. This atypical mode of deformation demonstrates comparable glide and climb efficiency under natural deformation conditions. It promotes dislocation glide in planes not expected for the quartz structure, probably by inhibiting lattice friction. Our quantitative characterization of the microstructure enables us to assess the strain that dislocations can generate. We show that glide systems indicated by the observed dislocations are sufficient to accommodate any arbitrary 3D strain by themselves. Although historically dislocation glide has been regarded as being primarily responsible for producing strain, activation of climb can also directly contribute to the finite strain. On the basis of this characterization, we propose a numerical modeling approach for attempting to characterize the local stress state that gave rise to the observed microstructure.
The making of Mt Everest: channel flow and low-angle normal faults in the compressional Himalayan orogen
Searle, Mike; Cottle, John; Jessup, Micah; Law, Richard D. (Geological Society of London, 2025-01-06)
Mt Everest (8849 m) spans the Greater Himalayan Sequence metamorphic rocks and the base of the unmetamorphosed Tethyan sedimentary rocks in the Nepal–South Tibet Himalaya. Two north-dipping, low-angle normal faults cut the massif: the upper Qomolangma Detachment placing Ordovician sedimentary rocks above Everest Series greenschist–amphibolite facies rocks; and the lower Lhotse Detachment placing Everest Series schists above sillimanite gneisses, migmatites and leucogranites. The two faults merge northwards into one large ductile shear zone (the South Tibetan Detachment). Pressure–temperature constraints and structural restoration show that the South Tibetan Detachment acted as a passive roof fault during extrusion of the footwall. At least 120 km of southward flow of the footwall rocks occurred during the Miocene, resulting in the exhumation of rocks that were buried to 5.5 kbar (c. 18–22 km depth) below the detachment, juxtaposing them against hanging wall rocks that are essentially unmetamorphosed. The low-angle normal faults were operative during north–south convergence and reflect the exhumation of a locked passive roof fault, unrelated to any crustal extensional processes. U–(Th)–Pb dating of peraluminous leucogranites exposed on Mt Everest (21–20 Ma), Nuptse (c. 19–18 Ma) and along the Rongbuk valley (15.6–15.4 Ma) show that ductile extrusion occurred during the Early Miocene, with brittle faulting at <15.4 Ma during exhumation.
The timing and significance of mid-crustal shearing and exhumation of amphibolite-facies rocks along the Great Glen Fault Zone, Scotland
Law, Richard D.; Thigpen, J. Ryan; Mako, Calvin A.; Kylander-Clark, Andrew; Caddick, Mark J.; Moore, Lowell R.; Becker, Cassandra; Holdsworth, Robert E.; Strachan, Robin A.; Leslie, A. Graham (Geological Society of London, 2025-07-07)
The Rosemarkie Inlier lies on the NW side of the Great Glen Fault Zone (GGFZ) and is composed of foliated and lineated Archean orthogneisses and Moine metasedimentary rocks. The mylonitic foliation strikes NE–SW (parallel to the GGFZ), dips steeply SE and contains a gently to moderately plunging mineral lineation. Microstructural and quartz c-axis fabric analyses indicate that oblique sinistral shearing occurred under amphibolite-facies conditions. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses on monazite rims in the gneisses yielded 206Pb/238U ages of 401.8 ± 4.8 Ma (including 2 (Formula presented.) uncertainty and a propagated additional 1% external uncertainty). Similar deformation and recrystallization temperatures indicated by quartz fabrics (610°C) and monazite–xenotime thermometry (616 ± 25°C), respectively, in the gneisses suggest that ductile sinistral shearing was ongoing at c. 402 Ma. The c. 402 Ma rim age is the youngest monazite age recorded in the Northern Highland Terrane (NHT) and indicates that sinistral shearing at mid-crustal levels was ongoing along the GGFZ in Lower Devonian (Emsian, 407–393 Ma) times when the thrust sheets of the NHT to the NW had already been exhumed. The Rosemarkie basement rocks are unconformably overlain by Middle Devonian (Eifelian, 393–387 Ma) sedimentary rocks, indicating time-averaged exhumation rates of c. 1.75 mm a−1 between 402 and c. 390 Ma, assuming a geothermal gradient of 30°C km−1.
Critical environmental communication framework
Bhatti, Shumaila; Ramasubramanian, Srividya; Feldpausch-Parker, Andrea; Takahashi, Bruno; Kristiansen, Silje (Taylor & Francis, 2025-10-21)
This study develops a Critical Environmental Communication (CEC) framework to assess the landscape of Environmental Communication research and to what extent and in which ways critical and justice-oriented perspectives are included. The CEC framework consists of four interconnected themes: (a) Marginalized Ecocultural Identities, (b) Context and Scale, (c) Power and Agency, and (d) Justice, Equity, Diversity, Access, and Inclusion (JEDAI). Using this framework in a bibliometric analysis examining 1,297 Environmental Communication publications, we assess the occurrence of these themes in the scholarship. Our analysis found that Marginalized Ecocultural Identities, and Context and Scale were most frequently occurring, while Power and Agency, and JEDAI occurred less frequently. These findings suggest research directions to create a more inclusive research agenda for Environmental Communication scholarship.