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Deep-seated slow slip and tremor (SST), including slow slip events, episodic tremor and slip, and low-frequency earthquakes, occur downdip of the seismogenic zone of numerous subduction megathrusts and plate boundary strike-slip faults. These events represent a fascinating and perplexing mode of fault failure that has greatly broadened our view of earthquake dynamics. In this contribution, we review constraints on SST deformation processes from both geophysical observations of active subduction zones and geological observations of exhumed field analogues. We first provide an overview of what has been learned about the environment, kinematics and dynamics of SST from geodetic and seismologic data. We then describe the materials, deformation mechanisms, and metamorphic and fluid pressure conditions that characterize exhumed rocks from SST source depths. Both the geophysical and geological records strongly suggest the importance of a fluid-rich and high fluid pressure habitat for the SST source region. Additionally, transient deformation features preserved in the rock record, involving combined frictional-viscous shear in regions of mixed lithology and near-lithostatic fluid pressures, may scale with the tremor component of SST. While several open questions remain, it is clear that improved constraints on the materials, environment, structure, and conditions of the plate interface from geophysical imaging and geologic observations will enhance model representations of the boundary conditions and geometry of the SST deformation process. This article is part of a discussion meeting issue ‘Understanding earthquakes using the geological record’.

Radiolarian discoveries indicate that deep-marine conditions prevailed in central Tibet from the early Middle Jurassic until well into the Early Cretaceous (late Hauterivian-early Aptian; 131-121 Ma) and help to constrain the temporal extent of oceanic conditions along the Bangong-Nujiang suture. These new fossils occur in chert or siliceous mudstone blocks associated with the Lagkor Tso ophiolitic melange. Basin inversion associated with closure of Mesotethys between the Qiangtang and Lhasa terranes was accompanied by melange formation and predated regionally widespread deposition of overlying shallow-marine late Aptian-Albian orbitolinid limestones.

Subduction interfaces exhibit various slip styles, including slow slip events (SSEs). We use a micromechanics‐based approach to calculate the effective rheology of a shear zone containing ellipsoidal amphibolite clasts deforming by dislocation creep within an interconnected linear‐viscous phyllosilicate‐dominated matrix. Frictional failure occurs if local stress exceeds Mohr‐Coulomb yield strength. At moderate fluid overpressure, mixed‐frictional‐viscous behavior emerges at ∼${\\sim} $ 350–560°^{\\circ}$ C, consistent with a broad zone of mixed fault slip behavior without requiring extreme fluid overpressures. Increasing stress in this transition zone promotes local frictional failure and raises bulk strain rate. If, however, the bulk strain rate increases by more than one order of magnitude, system‐wide frictional sliding becomes preferable. This strain rate increase is insufficient to explain the slip rates observed in geophysically detectable SSEs. Therefore, viscous matrix flow as modeled here cannot explain SSEs without either invoking dynamic weakening within a frictional‐viscous flow or a mechanism switch to dominantly frictional sliding. Plain Language Summary Subduction plate boundaries are locked near the Earth's surface and will release the stored energy as earthquakes. Subduction zones creep steadily and viscously at deeper depths where temperatures and pressures are high. At the depth of the transition from earthquakes to steady creep, episodic aseismic slip is often observed. Rocks from this region are mixtures of strong, fractured clasts surrounded by a weak matrix. The observations of exhumed rocks suggest that the episodic, aseismic slip may nucleate when local frictional failure occurs in strong clasts, but the surrounding weak matrix stops this failure from generating major earthquakes. However, it is unclear how much the small‐scale rock behavior could be linked to the large‐scale slip. We use a numerical model to simulate the interplay between frictional and viscous creep and calculate the overall behavior of the subduction zone plate boundary. We explore how the slip style changes with depth and determine the transition zone's depth/temperature range. In the transition zone, a small increase in stress or decrease in strength can lead to a change from pure viscous flow to frictional sliding. This study overcomes the scale challenge between the small‐scale features preserved on outcrops and the large‐scale geophysical observations. Key Points Frictional‐viscous flow in a two‐phase shear zone modeled by a multiscale approach occurs at ∼350–560°C with moderate fluid overpressure Stress loading and/or fluid pressure weakening can cause a switch from steady viscous creep to transient frictional slip Viscous creep modeled here can accommodate tectonic strain rates but not slow slip events without invoking a switch to frictional sliding

This study is focused on slide blocks including oceanic lavas associated with pelagic sediments within the eastern part of the Ankara Mélange. A detailed petrological characterization of the volcanic rocks and a detailed biochronological investigation of the associated radiolarian cherts in eight sections (east of Ankara) was carried out. The volcanic rocks are largely represented by basalts and minor ferrobasalts and trachytes. They show different geochemical affinities and overlapping ages including: (a) Late Jurassic – Early Cretaceous garnet-influenced MORB (middle late Oxfordian to late Kimmeridgian–early Tithonian and early–early late Tithonian; late Valanginian–early Barremian); (b) Early Cretaceous enriched-MORB (middle late Barremian–early early Aptian; Valanginian to middle Aptian–early Albian); (c) Middle Jurassic plume-type MORB (early–middle Bajocian to late Bathonian–early Callovian); (d) Late Jurassic – Early Cretaceous alkaline basalts (middle–late Oxfordian to late Kimmeridgian–early Tithonian; late Valanginian to late Hauterivian). All rock types show a clear garnet signature, as testified to by their high MREE/HREE (middle rare earth element/heavy rare earth element) ratios. The coexistence of chemically different rock types from Middle Jurassic to Early Cretaceous times suggests that they were formed in a mid-ocean ridge setting from partial melting of a highly heterogeneous mantle characterized by the extensive occurrence of OIB-metasomatized portions, which were likely inherited from Triassic mantle plume activity associated with the continental rift and opening of the Neotethys branch.

The Pulo do Lobo Zone, which crops out immediately north of the allochthonous South Portuguese Zone in southern Iberia, is classically interpreted as a polydeformed accretionary complex developed along the southern margin of the Gondwanan parautochthon (Ossa-Morena Zone), during the late Palaeozoic closure of the Rheic Ocean. This closure was a major event during the amalgamation of Pangaea. U-Pb laser ablation inductively coupled mass spectrometry dating of detrital zircons from late Palaeozoic Devono-Carboniferous clastic units in the South Portuguese Zone and Pulo do Lobo Zone yield contrasting age populations and attest to the exotic nature of both zones. Detrital zircons from the South Portuguese Zone display populations typical of detritus derived from either Gondwana (Ossa-Morena Zone), or peri-Gondwanan terranes. In contrast, rocks from the Pulo do Lobo Zone contain populations consistent with derivation from Baltica, Laurentia or recycled early Silurian deposits along the Laurentian margin. An example of one such deposit is the Southern Uplands terrane of the British Caledonides. Taken together, these data can be reconciled by a model involving tectonic transport of a crustal fragment that was laterally equivalent to the Southern Uplands terrane between the allochthonous South Portuguese Zone and Gondwana as a result of an early Devonian collision between an Iberian indenter with Laurussia.

The Central Asian Orogenic Belt (c. 1000-250 Ma) formed by accretion of island arcs, ophiolites, oceanic islands, seamounts, accretionary wedges, oceanic plateaux and microcontinents in a manner comparable with that of circum-Pacific Mesozoic-Cenozoic accretionary orogens. Palaeomagnetic and palaeofloral data indicate that early accretion (Vendian-Ordovician) took place when Baltica and Siberia were separated by a wide ocean. Island arcs and Precambrian microcontinents accreted to the active margins of the two continents or amalgamated in an oceanic setting (as in Kazakhstan) by roll-back and collision, forming a huge accretionary collage. The Palaeo-Asian Ocean closed in the Permian with formation of the Solonker suture. We evaluate contrasting tectonic models for the evolution of the orogenic belt. Current information provides little support for the main tenets of the one- or three-arc Kipchak model; current data suggest that an archipelago-type (Indonesian) model is more viable. Some diagnostic features of ridge-trench interaction are present in the Central Asian orogen (e.g. granites, adakites, boninites, near-trench magmatism, Alaskan-type mafic-ultramafic complexes, high-temperature metamorphic belts that prograde rapidly from low-grade belts, rhyolitic ash-fall tuffs). They offer a promising perspective for future investigations.

Galligan Francesca. A new manuscript of Li quatre livre des Reis. In: Romania, tome 138 n°551-552, 2020. pp. 447-452.

Melange cotton yarns possess unique attributes of aesthetics and comfort. The quality of melange yarn is largely influenced by fibre properties, spinning process, dyeing conditions and proportion of grey and dyed fibres. In this study, dyed and grey cotton fibre components were mixed at the blow room to produce melange yarns with three different shade depths. The aim of present work is to investigate the effect of raw material properties and process variables at different shade depths on the properties of cotton melange yarns. Box–Behnken experimental design was used to study effect of three factors: fineness of cotton, noil extraction% and shade depth% on properties of melange yarn. ANOVA analysis shows that there is significant effect of noil extraction and shade depth on all yarn properties. Fibre fineness also shows significant effect on unevenness, tensile, abrasion, yarn metal friction properties except breaking extension and hairiness. Better yarn quality with respect to yarn evenness, imperfections, hairiness, tenacity, breaking extension, yarn metal friction and yarn abrasion resistance RRI is achieved for lower shade depth melange yarn. The properties of melange yarn with higher noil extracted at comber stage are noticeably better in respect of tensile strength, elongation, hairiness, mass irregularity, imperfections and yarn abrasion resistance RRI.