Crystallographic control and texture inheritance during mylonitization of coarse grained quartz veins

Quartz veins within Rieserferner pluton underwent deformation during post-magmatic cooling at temperature around 450 \ub0C. Different crystallographic orientations of cm-sized quartz vein crystals conditioned the evolution of microstructures and crystallographic preferred orientations (CPO) during vein-parallel simple shear up to high shear strains (\u3b3 48 10). For \u3b3 b 2, crystals stretched to ribbons of variable aspect ratios. The highest aspect ratios resulted from {m}baN glide in ribbons with c-axis sub-parallel to the shear zone vorticity Y-axis. Ribbons with c-axis orthogonal to Y (XZ-type ribbons) were stronger and hardened more quickly: they show lower aspect ratios and \ufb01ne (grain size ~10\u201320 \u3bcm) recrystallization along sets of microshear zones (\u3bcSZs) exploiting crystallographic planes. Distortion of XZ-type ribbons and recrystallization preferentially exploited the slip systems with misorientation axis close to Y. New grains of \u3bcSZs initiated by subgrain rotation recrystallization (SGR) and thereupon achieved high angle misorientations by a concurrent process of heterogeneous rigid grain rotation around Y associated with the con\ufb01ned shear within the \u3bcSZ. Dauphin\ue9 twinning occurred pervasively, but did not play a dominant role on \u3bcSZ nucleation. Recrystallization became widespread at \u3b3 N 2 and pervasive at \u3b3 48 10. Ultramylonitic quartz veins are \ufb01ne grained (~10 \u3bcm, similar to new grains of \u3bcSZ) and show a CPO banding resulting in a bulk c-axis CPO with a Y-maximum, as part of a single girdle about orthogonal to the foliation, and orientations at the pole \ufb01gure periphery at moderate to high angle to the foliation. This bulk CPO derives from steady-state SGR associated with preferential activity, in the different CPO bands, of slip systems generating subgrain boundaries with misorientation axes close to Y. The CPO of individual recrystallized bands is largely inherited from the original crystallographic orientation of the ribbons (and therefore vein crystals) from which they derived. High strain and pervasive recrystallization were not enough to reset the initial crystallographic heterogeneity and this CPO memory is explained by the dominance of SGR. This contrast with experimental observation of a rapid erasure of a pristine CPO by cannibalism from grains with the most favourably oriented slip system under dominant grain boundary migration recrystallization

Structural evolution of a crustal‐scale seismogenic fault in a magmatic arc: The Bolfin Fault Zone (Atacama Fault System)

How major crustal-scale seismogenic faults nucleate and evolve in crystalline basements represents a long-standing, but poorly understood, issue in structural geology and fault mechanics. Here, we address the spatio-temporal evolution of the Bolfin Fault Zone (BFZ), a >40-km-long exhumed seismogenic splay fault of the 1000-km-long strike-slip Atacama Fault System. The BFZ has a sinuous fault trace across the Mesozoic magmatic arc of the Coastal Cordillera (Northern Chile) and formed during the oblique subduction of the Aluk plate beneath the South American plate. Seismic faulting occurred at 5–7 km depth and ≤ 300°C in a fluid-rich environment as recorded by extensive propylitic alteration and epidote-chlorite veining. Ancient (125–118 Ma) seismicity is attested by the widespread occurrence of pseudotachylytes. Field geologic surveys indicate nucleation of the BFZ on precursory geometrical anisotropies represented by magmatic foliation of plutons (northern and central segments) and andesitic dyke swarms (southern segment) within the heterogeneous crystalline basement. Seismic faulting exploited the segments of precursory anisotropies that were optimal to favorably oriented with respect to the long-term far-stress field associated with the oblique ancient subduction. The large-scale sinuous geometry of the BFZ resulted from the hard linkage of these anisotropy-pinned segments during fault growth

Percutaneous pericardiocentesis for pericardial effusion: predictors of mortality and outcomes

Pericardial effusion can dangerously precipitate patient’s hemodynamic stability and requires prompt intervention in case of tamponade. We investigated potential predictors of in-hospital mortality, a composite outcome of in-hospital mortality, pericardiocentesis-related complications, and the need for emergency cardiac surgery and all-cause mortality in patients undergoing percutaneous pericardiocentesis. This is an observational, retrospective, single-center study on patients undergoing percutaneous pericardiocentesis (2010–2019). We enrolled 81 consecutive patients. Median age was 71.4 years (interquartile range [IQR] 58.1–78.1 years) and 51 (63%) were male. Most of the pericardiocentesis were performed in an urgency setting (76.5%) for cardiac tamponade (77.8%). The most common etiology was idiopathic (33.3%) followed by neoplastic (22.2%). In-hospital mortality was 14.8% while mortality during follow-up (mean 17.1 months) was 44.4%. Only hemodynamic instability (i.e., cardiogenic shock, hypotension refractory to fluid challenge therapy and inotropes) was associated with in-hospital mortality at the univariate analysis (odds ratio [OR] 7.2; 95% confidence interval [CI] 1.76–29.4). Non-neoplastic/non-idiopathic etiology and hemodynamic instability were associated with the composite outcome of in-hospital mortality, need for emergency cardiac surgery, or pericardiocentesis-related complications (OR 5.75, 95% CI 1.65–20.01, and OR 5.81, 95% CI 2.11–15.97, respectively). Multivariate Cox regression analysis adjusted for possible confounding variables (age, coronary artery disease, and hemodynamic instability) showed that neoplastic etiology was independently associated with medium-term mortality (hazard ratio [HR] 4.05, 95% CI 1.45–11.36). In a real-world population treated with pericardiocentesis for pericardial effusion, in-hospital adverse outcomes and medium-term mortality are consistent, in particular for patients presenting with hemodynamic instability or neoplastic pericardial effusion

Controls on early‐rift geometry: new perspectives from the Bilila‐Mtakataka fault, Malawi

We use the ~110 km long Bilila‐Mtakataka fault in the amagmatic southern East African Rift, Malawi, to investigate the controls on early‐rift geometry at the scale of a major border fault. Morphological variations along the 14±8 m high scarp define six 10‐40 km long segments, which are either foliation parallel, or oblique to both foliation and the current regional extension direction. As the scarp is neither consistently parallel to foliation, nor well oriented for the current regional extension direction, we suggest the segmented surface expression is related to the local reactivation of well oriented weak shallow fabrics above a broadly continuous structure at depth. Using a geometrical model, the geometry of the best‐fitting subsurface structure is consistent with the local strain field from recent seismicity. In conclusion, within this early‐rift, pre‐existing weaknesses only locally control border fault geometry at subsurface

The management of acute venous thromboembolism in clinical practice. Results from the European PREFER in VTE Registry

Venous thromboembolism (VTE) is a significant cause of morbidity and mortality in Europe. Data from real-world registries are necessary, as clinical trials do not represent the full spectrum of VTE patients seen in clinical practice. We aimed to document the epidemiology, management and outcomes of VTE using data from a large, observational database. PREFER in VTE was an international, non-interventional disease registry conducted between January 2013 and July 2015 in primary and secondary care across seven European countries. Consecutive patients with acute VTE were documented and followed up over 12 months. PREFER in VTE included 3,455 patients with a mean age of 60.8 ± 17.0 years. Overall, 53.0 % were male. The majority of patients were assessed in the hospital setting as inpatients or outpatients (78.5 %). The diagnosis was deep-vein thrombosis (DVT) in 59.5 % and pulmonary embolism (PE) in 40.5 %. The most common comorbidities were the various types of cardiovascular disease (excluding hypertension; 45.5 %), hypertension (42.3 %) and dyslipidaemia (21.1 %). Following the index VTE, a large proportion of patients received initial therapy with heparin (73.2 %), almost half received a vitamin K antagonist (48.7 %) and nearly a quarter received a DOAC (24.5 %). Almost a quarter of all presentations were for recurrent VTE, with >80 % of previous episodes having occurred more than 12 months prior to baseline. In conclusion, PREFER in VTE has provided contemporary insights into VTE patients and their real-world management, including their baseline characteristics, risk factors, disease history, symptoms and signs, initial therapy and outcomes

Extrinsic Anisotropy of Two-Phase Newtonian Aggregates: Fabric Characterization and Parameterization

Rocks of the Earth's crust and mantle commonly consist of different minerals with contrasting mechanical properties. During progressive, high-temperature (ductile) deformation, these rocks develop extrinsic mechanical anisotropy linked to strain partitioning between different minerals, amount of accumulated strain, and bulk strain geometry. Extrinsic anisotropy plays an important role in a wide range of geodynamic processes up to the scale of mantle convection. However, the evolution of grain- and rock-scale fabrics causing this anisotropy cannot be directly simulated in large-scale numerical simulations. For two-phase aggregates–a good rheological approximation of most Earth's rocks–we propose a method to indirectly approximate the extrinsic viscous anisotropy by combining (a) 3D mechanical models of rock fabrics, and (b) analytical effective medium theories. Our results confirm that weak inclusions induce substantial weakening by forming a network of weak thin layers with limited lateral connectivity. Consequently, even when the inclusion phase is extremely weak, structural weakening is not larger than 30–60%, less than in previous estimates. On the other hand, the presence of strong inclusions does not have a profound impact on the effective strength of the aggregate, and lineated fabrics only develop at relatively low viscosity contrasts. When rigid inclusions become clogged, however, the aggregate viscosity can increase over the theoretical upper bound. We show that the modeled grain-scale fabrics can be parameterized as a function of the bulk deformation and material phase properties and combined with analytical solutions to approximate the anisotropic viscous tensor

Ti distribution in quartz across a heterogeneous shear zone within a granodiorite: The effect of deformation mechanism and strain on Ti resetting

The study of a heterogeneous ductile shear zone that developed at ~ 500 \ub0C and 0.2 GPa during post-magmatic cooling of a granodiorite has allowed the effect of strain and recrystallization on Ti re-equilibration of quartz to be assessed. Understanding this effect is critical for applying Ti-in-quartz thermobarometry to mylonites. Differently strained quartz across the shear zone shows a heterogeneous distribution of Ti concentrations ([Ti]) (measured by Secondary Ion Mass Spectrometry, SIMS) ranging between 2 and 45 ppm. Quartz cathodoluminescence (CL) is proven by spectral analysis to be correlated with [Ti], allowing CL images to be calibrated as Ti maps using SIMS measurements. Coarse-grained weakly deformed domains consist of magmatic quartz extensively recrystallized by grain boundary migration (GBM) and mostly (65\u201375% area) contain 20\u201338 ppm Ti. Resetting to lower [Ti] occurred locally: (i) in haloes surrounding titanite and biotite inclusions ([Ti] as low as 6 ppm); (ii) along grain boundaries; and (iii) towards the interface of quartz domains with other mineral domains. With increasing strain, quartz underwent progressive grain size reduction and developed a bimodal microstructure with elongate grains (> 100's \u3bcm long) surrounded by mantles of new grains (10\u201330 \u3bcm in size) recrystallized by subgrain rotation (SGR). Dynamic recrystallization by SGR, associated with prism slip, became increasingly dominant over GBM as strain increased towards the shear zone core. Significant resetting of Ti in quartz only occurred in high strain domains (at shear strain \u3b3 probably >> 10) in the shear zone core where fine recrystallization amounts to 50\u201360% by area and coarser cores are strongly sub-structured. These domains are not compositionally homogeneous and still show a range of [Ti] mostly between 2 and 10 ppm. In all strain facies of the shear zone quartz-filled pressure shadows associated with feldspar show an almost constant [Ti] of ~ 2 ppm. The pristine Ti content of the magmatic quartz mylonitized in the shear zone core is therefore significantly reset and converges \u201casymptotically\u201d towards the \u201cequilibrium\u201d 2 ppm [Ti] shown by new quartz precipitated in pressure shadows. It is inferred that extensive recrystallization by SGR and repeated cycles of dislocation creep and rearrangement provided fluid access to quartz grain interiors, promoting chemical buffering and leading to partial re-equilibration to low [Ti]. These observations imply limitations on the use of the Ti-in-quartz thermobarometry to constrain ambient conditions of ductile deformation

Influence of Deformation and Fluids on Ti Exchange in Natural Quartz

Using a combination of microstructural, spectroscopic, and geochemical analyses, we investigate how subgrain rotation recrystallization and fluid migration affect Ti concentration [Ti] in naturally deformed quartz veins from the Prijakt Nappe (Austroalpine Unit, Eastern Alps). These coarse-grained quartz veins, that formed at amphibolite facies conditions, were overprinted by lower greenschist facies deformation to different degrees. During the overprint, subgrain rotation recrystallization was dominant during progressive deformation to ultramylonitic stages. The initial [Ti] (3.0–4.7 ppm) and cathodoluminescence (CL) signature of the vein crystals decrease during deformation mainly depending on the availability of fluids across the microstructure. The amount of strain played a subordinate role in resetting to lower [Ti] and corresponding darker CL shades. Using a microstructurally controlled analysis we find that the most complete re-equilibration in recrystallized aggregates ([Ti] of 0.2–0.6 p.m.) occurred (a) in strain shadows around quartz porphyroclasts, acting as fluid sinks, and (b) in localized microshear zones that channelized fluid percolation. [Ti] resetting is mainly observed along wetted high angle boundaries (misorientation angle >10–15°), with partial [Ti] resetting observed along dry low angle boundaries (<10–15°). This study shows for the first time that pure subgrain rotation recrystallization in combination with dissolution-precipitation under retrograde condition provide microstructural domains suitable for the application of titanium-in-quartz geothermobarometry at deformation temperatures down to 300–350°C